* [PATCH v2 1/2] x86/shstk: support via prctl
@ 2026-08-12 17:19 Bill Roberts
2026-08-12 17:19 ` [PATCH v2 2/2] selftests/x86: add generic prctl shadow stack test Bill Roberts
0 siblings, 1 reply; 6+ messages in thread
From: Bill Roberts @ 2026-08-12 17:19 UTC (permalink / raw)
To: H. Peter Anvin, Albert Ou, Alexandre Ghiti, Borislav Petkov,
Dave Hansen, Ingo Molnar, Palmer Dabbelt, Paul Walmsley,
rick.p.edgecombe, Shuah Khan, Thomas Gleixner, x86
Cc: bpf, linux-kernel, linux-kselftest, linux-riscv, Bill Roberts
Historically, managing the user-space shadow stack state on x86 has
been handled exclusively through the arch_prctl() interface via the
ARCH_SHSTK_* operations. However, other architectures (such as arm64 and
riscv) do not implement arch_prctl() and instead utilize the newer,
arch-agnostic, prctl() interface (i.e. PR_GET_SHADOW_STACK_STATUS and
PR_SET_SHADOW_STACK_STATUS).
To provide language runtimes, toolchains, and libc implementations with a
consistent, cross-architecture interface for managing control-flow
integrity, wire up the generic shadow stack prctl handlers for x86.
Map the generic PR_SHADOW_STACK_ENABLE, PR_SHADOW_STACK_DISABLE, and
PR_SHADOW_STACK_LOCK operations onto the underlying x86 internal CET helper
routines. This allows portable userspace applications to toggle or query
shadow stack states without relying on architecture-specific system calls,
while maintaining backward compatibility with existing arch_prctl() calls.
Signed-off-by: Bill Roberts <bill.roberts@arm.com>
---
arch/x86/kernel/shstk.c | 37 +++++++++++++++++++++++++++++++++++++
1 file changed, 37 insertions(+)
diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c
index 0ca64900192f..c34ba3701dd0 100644
--- a/arch/x86/kernel/shstk.c
+++ b/arch/x86/kernel/shstk.c
@@ -18,6 +18,7 @@
#include <linux/sizes.h>
#include <linux/user.h>
#include <linux/syscalls.h>
+#include <linux/prctl.h>
#include <asm/msr.h>
#include <asm/fpu/xstate.h>
#include <asm/fpu/types.h>
@@ -630,3 +631,39 @@ bool shstk_is_enabled(void)
{
return features_enabled(ARCH_SHSTK_SHSTK);
}
+
+#define PR_SHADOW_STACK_SUPPORTED_STATUS_MASK \
+ (PR_SHADOW_STACK_ENABLE | PR_SHADOW_STACK_WRITE | PR_SHADOW_STACK_PUSH)
+
+/* Handles the generic prctl interface for PR_SET_SHADOW_STACK_STATUS and its feature bits */
+int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status)
+{
+ int rc;
+
+ if (status & ~PR_SHADOW_STACK_SUPPORTED_STATUS_MASK)
+ return -EINVAL;
+
+ /* x86 arch_prctl is single bit at a time, so handle these one at time */
+ if (!status & PR_SHADOW_STACK_ENABLE)
+ return shstk_prctl(t, ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
+
+ rc = shstk_prctl(t, ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK);
+ if (rc)
+ return rc;
+
+ if (status & PR_SHADOW_STACK_WRITE)
+ return shstk_prctl(t, ARCH_SHSTK_ENABLE, ARCH_SHSTK_WRSS);
+
+ return shstk_prctl(t, ARCH_SHSTK_DISABLE, ARCH_SHSTK_WRSS);
+}
+
+/* Handles the generic prctl interface for PR_LOCK_SHADOW_STACK_STATUS and its feature bits */
+int arch_lock_shadow_stack_status(struct task_struct *t, unsigned long status)
+{
+ return shstk_prctl(t, ARCH_SHSTK_LOCK, status);
+}
+
+int arch_get_shadow_stack_status(struct task_struct *t, unsigned long __user *status)
+{
+ return shstk_prctl(t, ARCH_SHSTK_STATUS, (unsigned long)status);
+}
--
2.55.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* [PATCH v2 2/2] selftests/x86: add generic prctl shadow stack test
2026-08-12 17:19 [PATCH v2 1/2] x86/shstk: support via prctl Bill Roberts
@ 2026-08-12 17:19 ` Bill Roberts
2026-08-12 18:03 ` Bill Roberts
0 siblings, 1 reply; 6+ messages in thread
From: Bill Roberts @ 2026-08-12 17:19 UTC (permalink / raw)
To: H. Peter Anvin, Albert Ou, Alexandre Ghiti, Borislav Petkov,
Dave Hansen, Ingo Molnar, Palmer Dabbelt, Paul Walmsley,
rick.p.edgecombe, Shuah Khan, Thomas Gleixner, x86
Cc: bpf, linux-kernel, linux-kselftest, linux-riscv, Bill Roberts
Run the same test suite for arch_prctl, against prctl, to ensure
consisteny and correctness between the interfaces.
Signed-off-by: Bill Roberts <bill.roberts@arm.com>
---
tools/testing/selftests/x86/Makefile | 5 +-
tools/testing/selftests/x86/shadow_stack.c | 1205 +++++++++++++++++
tools/testing/selftests/x86/shadow_stack.h | 14 +
.../testing/selftests/x86/test_shadow_stack.c | 1167 +---------------
.../selftests/x86/test_shadow_stack_prctl.c | 12 +
5 files changed, 1242 insertions(+), 1161 deletions(-)
create mode 100644 tools/testing/selftests/x86/shadow_stack.c
create mode 100644 tools/testing/selftests/x86/shadow_stack.h
create mode 100644 tools/testing/selftests/x86/test_shadow_stack_prctl.c
diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 434065215d12..8748e2f4a915 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -19,7 +19,8 @@ TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
vdso_restorer
TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip syscall_numbering \
- corrupt_xstate_header amx lam test_shadow_stack avx apx
+ corrupt_xstate_header amx lam test_shadow_stack avx apx \
+ test_shadow_stack_prctl
# Some selftests require 32bit support enabled also on 64bit systems
TARGETS_C_32BIT_NEEDED := ldt_gdt ptrace_syscall
@@ -138,3 +139,5 @@ $(OUTPUT)/avx_64: CFLAGS += -mno-avx -mno-avx512f
$(OUTPUT)/amx_64: EXTRA_FILES += xstate.c
$(OUTPUT)/avx_64: EXTRA_FILES += xstate.c
$(OUTPUT)/apx_64: EXTRA_FILES += xstate.c
+$(OUTPUT)/test_shadow_stack_64: EXTRA_FILES += shadow_stack.c
+$(OUTPUT)/test_shadow_stack_prctl_64: EXTRA_FILES += shadow_stack.c
diff --git a/tools/testing/selftests/x86/shadow_stack.c b/tools/testing/selftests/x86/shadow_stack.c
new file mode 100644
index 000000000000..a375c4ff7a6a
--- /dev/null
+++ b/tools/testing/selftests/x86/shadow_stack.c
@@ -0,0 +1,1205 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+
+#include <sys/syscall.h>
+#include <asm/mman.h>
+#include <sys/mman.h>
+#include <sys/stat.h>
+#include <sys/wait.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <x86intrin.h>
+#include <asm/prctl.h>
+#include <sys/prctl.h>
+#include <stdint.h>
+#include <signal.h>
+#include <pthread.h>
+#include <sys/ioctl.h>
+#include <linux/userfaultfd.h>
+#include <setjmp.h>
+#include <sys/ptrace.h>
+#include <sys/signal.h>
+#include <linux/elf.h>
+#include <linux/perf_event.h>
+
+#include "shadow_stack.h"
+
+/*
+ * Define the ABI defines if needed, so people can run the tests
+ * without building the headers.
+ */
+#ifndef __NR_map_shadow_stack
+#define __NR_map_shadow_stack 453
+
+#define SHADOW_STACK_SET_TOKEN (1ULL << 0)
+
+#define ARCH_SHSTK_ENABLE 0x5001
+#define ARCH_SHSTK_DISABLE 0x5002
+#define ARCH_SHSTK_LOCK 0x5003
+#define ARCH_SHSTK_UNLOCK 0x5004
+#define ARCH_SHSTK_STATUS 0x5005
+
+#define ARCH_SHSTK_SHSTK (1ULL << 0)
+#define ARCH_SHSTK_WRSS (1ULL << 1)
+
+#define NT_X86_SHSTK 0x204
+#endif
+
+#define SS_SIZE 0x200000
+#define PAGE_SIZE 0x1000
+
+void write_shstk(unsigned long *addr, unsigned long val)
+{
+ asm volatile("wrssq %[val], (%[addr])\n"
+ : "=m" (addr)
+ : [addr] "r" (addr), [val] "r" (val));
+}
+
+static inline unsigned long __attribute__((always_inline)) get_ssp(void)
+{
+ unsigned long ret = 0;
+
+ asm volatile("xor %0, %0; rdsspq %0" : "=r" (ret));
+ return ret;
+}
+
+/*
+ * For use in inline enablement of shadow stack.
+ *
+ * The program can't return from the point where shadow stack gets enabled
+ * because there will be no address on the shadow stack. So it can't use
+ * syscall() for enablement, since it is a function.
+ *
+ * Based on code from nolibc.h. Keep a copy here because this can't pull in all
+ * of nolibc.h.
+ */
+#define ARCH_PRCTL(arg1, arg2) \
+({ \
+ long _ret; \
+ register long _num asm("eax") = __NR_arch_prctl; \
+ register long _arg1 asm("rdi") = (long)(arg1); \
+ register long _arg2 asm("rsi") = (long)(arg2); \
+ \
+ asm volatile ( \
+ "syscall\n" \
+ : "=a"(_ret) \
+ : "r"(_arg1), "r"(_arg2), \
+ "0"(_num) \
+ : "rcx", "r11", "memory", "cc" \
+ ); \
+ _ret; \
+})
+
+#define PRCTL(option, arg2, arg3, arg4, arg5) \
+({ \
+ long _ret; \
+ register long _num asm("rax") = __NR_prctl; \
+ register long _arg1 asm("rdi") = (long)(option); \
+ register long _arg2 asm("rsi") = (long)(arg2); \
+ register long _arg3 asm("rdx") = (long)(arg3); \
+ register long _arg4 asm("r10") = (long)(arg4); \
+ register long _arg5 asm("r8") = (long)(arg5); \
+ \
+ asm volatile ( \
+ "syscall" \
+ : "=a"(_ret) \
+ : "0"(_num), \
+ "r"(_arg1), "r"(_arg2), "r"(_arg3), \
+ "r"(_arg4), "r"(_arg5) \
+ : "rcx", "r11", "memory", "cc" \
+ ); \
+ _ret; \
+})
+
+#define SHADOW_STACK_DISABLE(which_test) \
+ ((which_test) == SHADOW_STACK_TEST_ARCH_PRCTL ? \
+ ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK) : \
+ PRCTL(PR_SET_SHADOW_STACK_STATUS, 0, 0, 0, 0))
+
+#define SHADOW_STACK_ENABLE(which_test) \
+ ((which_test) == SHADOW_STACK_TEST_ARCH_PRCTL ? \
+ ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK) : \
+ PRCTL(PR_SET_SHADOW_STACK_STATUS, PR_SHADOW_STACK_ENABLE, 0, 0, 0))
+
+#define SHADOW_STACK_ENABLE_WRITE(which_test) \
+ ((which_test) == SHADOW_STACK_TEST_ARCH_PRCTL ? \
+ ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_WRSS) : \
+ PRCTL(PR_SET_SHADOW_STACK_STATUS, \
+ PR_SHADOW_STACK_ENABLE|PR_SHADOW_STACK_WRITE, 0, 0, 0))
+
+void *create_shstk(void *addr)
+{
+ return (void *)syscall(__NR_map_shadow_stack, addr, SS_SIZE, SHADOW_STACK_SET_TOKEN);
+}
+
+void *create_normal_mem(void *addr)
+{
+ return mmap(addr, SS_SIZE, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
+}
+
+void free_shstk(void *shstk)
+{
+ munmap(shstk, SS_SIZE);
+}
+
+int reset_shstk(void *shstk)
+{
+ return madvise(shstk, SS_SIZE, MADV_DONTNEED);
+}
+
+void try_shstk(unsigned long new_ssp)
+{
+ unsigned long ssp;
+
+ printf("[INFO]\tnew_ssp = %lx, *new_ssp = %lx\n",
+ new_ssp, *((unsigned long *)new_ssp));
+
+ ssp = get_ssp();
+ printf("[INFO]\tchanging ssp from %lx to %lx\n", ssp, new_ssp);
+
+ asm volatile("rstorssp (%0)\n":: "r" (new_ssp));
+ asm volatile("saveprevssp");
+ printf("[INFO]\tssp is now %lx\n", get_ssp());
+
+ /* Switch back to original shadow stack */
+ ssp -= 8;
+ asm volatile("rstorssp (%0)\n":: "r" (ssp));
+ asm volatile("saveprevssp");
+}
+
+int test_shstk_pivot(void)
+{
+ void *shstk = create_shstk(0);
+
+ if (shstk == MAP_FAILED) {
+ printf("[FAIL]\tError creating shadow stack: %d\n", errno);
+ return 1;
+ }
+ try_shstk((unsigned long)shstk + SS_SIZE - 8);
+ free_shstk(shstk);
+
+ printf("[OK]\tShadow stack pivot\n");
+ return 0;
+}
+
+int test_shstk_faults(void)
+{
+ unsigned long *shstk = create_shstk(0);
+
+ /* Read shadow stack, test if it's zero to not get read optimized out */
+ if (*shstk != 0)
+ goto err;
+
+ /* Wrss memory that was already read. */
+ write_shstk(shstk, 1);
+ if (*shstk != 1)
+ goto err;
+
+ /* Page out memory, so we can wrss it again. */
+ if (reset_shstk((void *)shstk))
+ goto err;
+
+ write_shstk(shstk, 1);
+ if (*shstk != 1)
+ goto err;
+
+ printf("[OK]\tShadow stack faults\n");
+ return 0;
+
+err:
+ return 1;
+}
+
+unsigned long saved_ssp;
+unsigned long saved_ssp_val;
+volatile bool segv_triggered;
+
+void __attribute__((noinline)) violate_ss(void)
+{
+ saved_ssp = get_ssp();
+ saved_ssp_val = *(unsigned long *)saved_ssp;
+
+ /* Corrupt shadow stack */
+ printf("[INFO]\tCorrupting shadow stack\n");
+ write_shstk((void *)saved_ssp, 0);
+}
+
+void segv_handler(int signum, siginfo_t *si, void *uc)
+{
+ printf("[INFO]\tGenerated shadow stack violation successfully\n");
+
+ segv_triggered = true;
+
+ /* Fix shadow stack */
+ write_shstk((void *)saved_ssp, saved_ssp_val);
+}
+
+int test_shstk_violation(void)
+{
+ struct sigaction sa = {};
+
+ sa.sa_sigaction = segv_handler;
+ sa.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSEGV, &sa, NULL))
+ return 1;
+
+ segv_triggered = false;
+
+ /* Make sure segv_triggered is set before violate_ss() */
+ asm volatile("" : : : "memory");
+
+ violate_ss();
+
+ signal(SIGSEGV, SIG_DFL);
+
+ printf("[OK]\tShadow stack violation test\n");
+
+ return !segv_triggered;
+}
+
+/* Gup test state */
+#define MAGIC_VAL 0x12345678
+bool is_shstk_access;
+void *shstk_ptr;
+int fd;
+
+void reset_test_shstk(void *addr)
+{
+ if (shstk_ptr)
+ free_shstk(shstk_ptr);
+ shstk_ptr = create_shstk(addr);
+}
+
+void test_access_fix_handler(int signum, siginfo_t *si, void *uc)
+{
+ printf("[INFO]\tViolation from %s\n", is_shstk_access ? "shstk access" : "normal write");
+
+ segv_triggered = true;
+
+ /* Fix shadow stack */
+ if (is_shstk_access) {
+ reset_test_shstk(shstk_ptr);
+ return;
+ }
+
+ free_shstk(shstk_ptr);
+ create_normal_mem(shstk_ptr);
+}
+
+bool test_shstk_access(void *ptr)
+{
+ is_shstk_access = true;
+ segv_triggered = false;
+ write_shstk(ptr, MAGIC_VAL);
+
+ asm volatile("" : : : "memory");
+
+ return segv_triggered;
+}
+
+bool test_write_access(void *ptr)
+{
+ is_shstk_access = false;
+ segv_triggered = false;
+ *(unsigned long *)ptr = MAGIC_VAL;
+
+ asm volatile("" : : : "memory");
+
+ return segv_triggered;
+}
+
+bool gup_write(void *ptr)
+{
+ unsigned long val;
+
+ lseek(fd, (unsigned long)ptr, SEEK_SET);
+ if (write(fd, &val, sizeof(val)) < 0)
+ return 1;
+
+ return 0;
+}
+
+bool gup_read(void *ptr)
+{
+ unsigned long val;
+
+ lseek(fd, (unsigned long)ptr, SEEK_SET);
+ if (read(fd, &val, sizeof(val)) < 0)
+ return 1;
+
+ return 0;
+}
+
+int test_gup(void)
+{
+ struct sigaction sa = {};
+ int status;
+ pid_t pid;
+
+ sa.sa_sigaction = test_access_fix_handler;
+ sa.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSEGV, &sa, NULL))
+ return 1;
+
+ segv_triggered = false;
+
+ fd = open("/proc/self/mem", O_RDWR);
+ if (fd == -1)
+ return 1;
+
+ reset_test_shstk(0);
+ if (gup_read(shstk_ptr))
+ return 1;
+ if (test_shstk_access(shstk_ptr))
+ return 1;
+ printf("[INFO]\tGup read -> shstk access success\n");
+
+ reset_test_shstk(0);
+ if (gup_write(shstk_ptr))
+ return 1;
+ if (test_shstk_access(shstk_ptr))
+ return 1;
+ printf("[INFO]\tGup write -> shstk access success\n");
+
+ reset_test_shstk(0);
+ if (gup_read(shstk_ptr))
+ return 1;
+ if (!test_write_access(shstk_ptr))
+ return 1;
+ printf("[INFO]\tGup read -> write access success\n");
+
+ reset_test_shstk(0);
+ if (gup_write(shstk_ptr))
+ return 1;
+ if (!test_write_access(shstk_ptr))
+ return 1;
+ printf("[INFO]\tGup write -> write access success\n");
+
+ close(fd);
+
+ /* COW/gup test */
+ reset_test_shstk(0);
+ pid = fork();
+ if (!pid) {
+ fd = open("/proc/self/mem", O_RDWR);
+ if (fd == -1)
+ exit(1);
+
+ if (gup_write(shstk_ptr)) {
+ close(fd);
+ exit(1);
+ }
+ close(fd);
+ exit(0);
+ }
+ waitpid(pid, &status, 0);
+ if (WEXITSTATUS(status)) {
+ printf("[FAIL]\tWrite in child failed\n");
+ return 1;
+ }
+ if (*(unsigned long *)shstk_ptr == MAGIC_VAL) {
+ printf("[FAIL]\tWrite in child wrote through to shared memory\n");
+ return 1;
+ }
+
+ printf("[INFO]\tCow gup write -> write access success\n");
+
+ free_shstk(shstk_ptr);
+
+ signal(SIGSEGV, SIG_DFL);
+
+ printf("[OK]\tShadow gup test\n");
+
+ return 0;
+}
+
+int test_mprotect(void)
+{
+ struct sigaction sa = {};
+
+ sa.sa_sigaction = test_access_fix_handler;
+ sa.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSEGV, &sa, NULL))
+ return 1;
+
+ segv_triggered = false;
+
+ /* mprotect a shadow stack as read only */
+ reset_test_shstk(0);
+ if (mprotect(shstk_ptr, SS_SIZE, PROT_READ) < 0) {
+ printf("[FAIL]\tmprotect(PROT_READ) failed\n");
+ return 1;
+ }
+
+ /* try to wrss it and fail */
+ if (!test_shstk_access(shstk_ptr)) {
+ printf("[FAIL]\tShadow stack access to read-only memory succeeded\n");
+ return 1;
+ }
+
+ /*
+ * The shadow stack was reset above to resolve the fault, make the new one
+ * read-only.
+ */
+ if (mprotect(shstk_ptr, SS_SIZE, PROT_READ) < 0) {
+ printf("[FAIL]\tmprotect(PROT_READ) failed\n");
+ return 1;
+ }
+
+ /* then back to writable */
+ if (mprotect(shstk_ptr, SS_SIZE, PROT_WRITE | PROT_READ) < 0) {
+ printf("[FAIL]\tmprotect(PROT_WRITE) failed\n");
+ return 1;
+ }
+
+ /* then wrss to it and succeed */
+ if (test_shstk_access(shstk_ptr)) {
+ printf("[FAIL]\tShadow stack access to mprotect() writable memory failed\n");
+ return 1;
+ }
+
+ free_shstk(shstk_ptr);
+
+ signal(SIGSEGV, SIG_DFL);
+
+ printf("[OK]\tmprotect() test\n");
+
+ return 0;
+}
+
+char zero[4096];
+
+static void *uffd_thread(void *arg)
+{
+ struct uffdio_copy req;
+ int uffd = *(int *)arg;
+ struct uffd_msg msg;
+ int ret;
+
+ while (1) {
+ ret = read(uffd, &msg, sizeof(msg));
+ if (ret > 0)
+ break;
+ else if (errno == EAGAIN)
+ continue;
+ return (void *)1;
+ }
+
+ req.dst = msg.arg.pagefault.address;
+ req.src = (__u64)zero;
+ req.len = 4096;
+ req.mode = 0;
+
+ if (ioctl(uffd, UFFDIO_COPY, &req))
+ return (void *)1;
+
+ return (void *)0;
+}
+
+int test_userfaultfd(void)
+{
+ struct uffdio_register uffdio_register;
+ struct uffdio_api uffdio_api;
+ struct sigaction sa = {};
+ pthread_t thread;
+ void *res;
+ int uffd;
+
+ sa.sa_sigaction = test_access_fix_handler;
+ sa.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSEGV, &sa, NULL))
+ return 1;
+
+ uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
+ if (uffd < 0) {
+ printf("[SKIP]\tUserfaultfd unavailable.\n");
+ return 0;
+ }
+
+ reset_test_shstk(0);
+
+ uffdio_api.api = UFFD_API;
+ uffdio_api.features = 0;
+ if (ioctl(uffd, UFFDIO_API, &uffdio_api))
+ goto err;
+
+ uffdio_register.range.start = (__u64)shstk_ptr;
+ uffdio_register.range.len = 4096;
+ uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
+ if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+ goto err;
+
+ if (pthread_create(&thread, NULL, &uffd_thread, &uffd))
+ goto err;
+
+ reset_shstk(shstk_ptr);
+ test_shstk_access(shstk_ptr);
+
+ if (pthread_join(thread, &res))
+ goto err;
+
+ if (test_shstk_access(shstk_ptr))
+ goto err;
+
+ free_shstk(shstk_ptr);
+
+ signal(SIGSEGV, SIG_DFL);
+
+ if (!res)
+ printf("[OK]\tUserfaultfd test\n");
+ return !!res;
+err:
+ free_shstk(shstk_ptr);
+ close(uffd);
+ signal(SIGSEGV, SIG_DFL);
+ return 1;
+}
+
+/* Simple linked list for keeping track of mappings in test_guard_gap() */
+struct node {
+ struct node *next;
+ void *mapping;
+};
+
+/*
+ * This tests whether mmap will place other mappings in a shadow stack's guard
+ * gap. The steps are:
+ * 1. Finds an empty place by mapping and unmapping something.
+ * 2. Map a shadow stack in the middle of the known empty area.
+ * 3. Map a bunch of PAGE_SIZE mappings. These will use the search down
+ * direction, filling any gaps until it encounters the shadow stack's
+ * guard gap.
+ * 4. When a mapping lands below the shadow stack from step 2, then all
+ * of the above gaps are filled. The search down algorithm will have
+ * looked at the shadow stack gaps.
+ * 5. See if it landed in the gap.
+ */
+int test_guard_gap_other_gaps(void)
+{
+ void *free_area, *shstk, *test_map = (void *)0xFFFFFFFFFFFFFFFF;
+ struct node *head = NULL, *cur;
+
+ free_area = mmap(0, SS_SIZE * 3, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ munmap(free_area, SS_SIZE * 3);
+
+ shstk = create_shstk(free_area + SS_SIZE);
+ if (shstk == MAP_FAILED)
+ return 1;
+
+ while (test_map > shstk) {
+ test_map = mmap(0, PAGE_SIZE, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (test_map == MAP_FAILED)
+ return 1;
+ cur = malloc(sizeof(*cur));
+ cur->mapping = test_map;
+
+ cur->next = head;
+ head = cur;
+ }
+
+ while (head) {
+ cur = head;
+ head = cur->next;
+ munmap(cur->mapping, PAGE_SIZE);
+ free(cur);
+ }
+
+ free_shstk(shstk);
+
+ if (shstk - test_map - PAGE_SIZE != PAGE_SIZE)
+ return 1;
+
+ printf("[OK]\tGuard gap test, other mapping's gaps\n");
+
+ return 0;
+}
+
+/* Tests respecting the guard gap of the mapping getting placed */
+int test_guard_gap_new_mappings_gaps(void)
+{
+ void *free_area, *shstk_start, *test_map = (void *)0xFFFFFFFFFFFFFFFF;
+ struct node *head = NULL, *cur;
+ int ret = 0;
+
+ free_area = mmap(0, PAGE_SIZE * 4, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ munmap(free_area, PAGE_SIZE * 4);
+
+ /* Test letting map_shadow_stack find a free space */
+ shstk_start = mmap(free_area, PAGE_SIZE, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+ if (shstk_start == MAP_FAILED || shstk_start != free_area)
+ return 1;
+
+ while (test_map > shstk_start) {
+ test_map = (void *)syscall(__NR_map_shadow_stack, 0, PAGE_SIZE, 0);
+ if (test_map == MAP_FAILED) {
+ printf("[INFO]\tmap_shadow_stack MAP_FAILED\n");
+ ret = 1;
+ break;
+ }
+
+ cur = malloc(sizeof(*cur));
+ cur->mapping = test_map;
+
+ cur->next = head;
+ head = cur;
+
+ if (test_map == free_area + PAGE_SIZE) {
+ printf("[INFO]\tNew mapping has other mapping in guard gap!\n");
+ ret = 1;
+ break;
+ }
+ }
+
+ while (head) {
+ cur = head;
+ head = cur->next;
+ munmap(cur->mapping, PAGE_SIZE);
+ free(cur);
+ }
+
+ munmap(shstk_start, PAGE_SIZE);
+
+ if (!ret)
+ printf("[OK]\tGuard gap test, placement mapping's gaps\n");
+
+ return ret;
+}
+
+/*
+ * Too complicated to pull it out of the 32 bit header, but also get the
+ * 64 bit one needed above. Just define a copy here.
+ */
+#define __NR_compat_sigaction 67
+
+/*
+ * Call 32 bit signal handler to get 32 bit signals ABI. Make sure
+ * to push the registers that will get clobbered.
+ */
+int sigaction32(int signum, const struct sigaction *restrict act,
+ struct sigaction *restrict oldact)
+{
+ register long syscall_reg asm("eax") = __NR_compat_sigaction;
+ register long signum_reg asm("ebx") = signum;
+ register long act_reg asm("ecx") = (long)act;
+ register long oldact_reg asm("edx") = (long)oldact;
+ int ret = 0;
+
+ asm volatile ("int $0x80;"
+ : "=a"(ret), "=m"(oldact)
+ : "r"(syscall_reg), "r"(signum_reg), "r"(act_reg),
+ "r"(oldact_reg)
+ : "r8", "r9", "r10", "r11"
+ );
+
+ return ret;
+}
+
+sigjmp_buf jmp_buffer;
+enum shadow_stack_test _which_test;
+void segv_gp_handler(int signum, siginfo_t *si, void *uc)
+{
+ segv_triggered = true;
+
+ /*
+ * To work with old glibc, this can't rely on siglongjmp working with
+ * shadow stack enabled, so disable shadow stack before siglongjmp().
+ */
+ SHADOW_STACK_DISABLE(_which_test);
+ siglongjmp(jmp_buffer, -1);
+}
+
+/*
+ * Transition to 32 bit mode and check that a #GP triggers a segfault.
+ */
+int test_32bit(void)
+{
+ struct sigaction sa = {};
+ struct sigaction *sa32;
+
+ /* Create sigaction in 32 bit address range */
+ sa32 = mmap(0, 4096, PROT_READ | PROT_WRITE,
+ MAP_32BIT | MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
+ sa32->sa_flags = SA_SIGINFO;
+
+ sa.sa_sigaction = segv_gp_handler;
+ sa.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSEGV, &sa, NULL))
+ return 1;
+
+
+ segv_triggered = false;
+
+ /* Make sure segv_triggered is set before triggering the #GP */
+ asm volatile("" : : : "memory");
+
+ /*
+ * Set handler to somewhere in 32 bit address space
+ */
+ sa32->sa_handler = (void *)sa32;
+ if (sigaction32(SIGUSR1, sa32, NULL))
+ return 1;
+
+ if (!sigsetjmp(jmp_buffer, 1))
+ raise(SIGUSR1);
+
+ if (segv_triggered)
+ printf("[OK]\t32 bit test\n");
+
+ return !segv_triggered;
+}
+
+static int parse_uint_from_file(const char *file, const char *fmt)
+{
+ int err, ret;
+ FILE *f;
+
+ f = fopen(file, "re");
+ if (!f) {
+ err = -errno;
+ printf("failed to open '%s': %d\n", file, err);
+ return err;
+ }
+ err = fscanf(f, fmt, &ret);
+ if (err != 1) {
+ err = err == EOF ? -EIO : -errno;
+ printf("failed to parse '%s': %d\n", file, err);
+ fclose(f);
+ return err;
+ }
+ fclose(f);
+ return ret;
+}
+
+static int determine_uprobe_perf_type(void)
+{
+ const char *file = "/sys/bus/event_source/devices/uprobe/type";
+
+ return parse_uint_from_file(file, "%d\n");
+}
+
+static int determine_uprobe_retprobe_bit(void)
+{
+ const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";
+
+ return parse_uint_from_file(file, "config:%d\n");
+}
+
+static ssize_t get_uprobe_offset(const void *addr)
+{
+ size_t start, end, base;
+ char buf[256];
+ bool found = false;
+ FILE *f;
+
+ f = fopen("/proc/self/maps", "r");
+ if (!f)
+ return -errno;
+
+ while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &base) == 4) {
+ if (buf[2] == 'x' && (uintptr_t)addr >= start && (uintptr_t)addr < end) {
+ found = true;
+ break;
+ }
+ }
+
+ fclose(f);
+
+ if (!found)
+ return -ESRCH;
+
+ return (uintptr_t)addr - start + base;
+}
+
+static __attribute__((noinline)) void uretprobe_trigger(void)
+{
+ asm volatile ("");
+}
+
+/*
+ * This test setups return uprobe, which is sensitive to shadow stack
+ * (crashes without extra fix). After executing the uretprobe we fail
+ * the test if we receive SIGSEGV, no crash means we're good.
+ *
+ * Helper functions above borrowed from bpf selftests.
+ */
+static int test_uretprobe(enum shadow_stack_test which_test)
+{
+ const size_t attr_sz = sizeof(struct perf_event_attr);
+ const char *file = "/proc/self/exe";
+ int bit, fd = 0, type, err = 1;
+ struct perf_event_attr attr;
+ struct sigaction sa = {};
+ ssize_t offset;
+
+ type = determine_uprobe_perf_type();
+ if (type < 0) {
+ if (type == -ENOENT)
+ printf("[SKIP]\tUretprobe test, uprobes are not available\n");
+ return 0;
+ }
+
+ offset = get_uprobe_offset(uretprobe_trigger);
+ if (offset < 0)
+ return 1;
+
+ bit = determine_uprobe_retprobe_bit();
+ if (bit < 0)
+ return 1;
+
+ sa.sa_sigaction = segv_gp_handler;
+ sa.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSEGV, &sa, NULL))
+ return 1;
+
+ /* Setup return uprobe through perf event interface. */
+ memset(&attr, 0, attr_sz);
+ attr.size = attr_sz;
+ attr.type = type;
+ attr.config = 1 << bit;
+ attr.config1 = (__u64) (unsigned long) file;
+ attr.config2 = offset;
+
+ fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,
+ -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
+ if (fd < 0)
+ goto out;
+
+ if (sigsetjmp(jmp_buffer, 1))
+ goto out;
+
+ SHADOW_STACK_ENABLE(which_test);
+
+ /*
+ * This either segfaults and goes through sigsetjmp above
+ * or succeeds and we're good.
+ */
+ uretprobe_trigger();
+
+ printf("[OK]\tUretprobe test\n");
+ err = 0;
+
+out:
+ SHADOW_STACK_DISABLE(which_test);
+ signal(SIGSEGV, SIG_DFL);
+ if (fd)
+ close(fd);
+ return err;
+}
+
+/* Keep the CALL first so the function address is exactly the probed CALL. */
+extern void uprobe_call_trigger(void);
+asm (".pushsection .text\n"
+ ".global uprobe_call_target\n"
+ ".type uprobe_call_target, @function\n"
+ "uprobe_call_target:\n"
+ " ret\n"
+ ".size uprobe_call_target, .-uprobe_call_target\n"
+
+ ".global uprobe_call_trigger\n"
+ ".type uprobe_call_trigger, @function\n"
+ "uprobe_call_trigger:\n"
+ " call uprobe_call_target\n"
+ " ret\n"
+ ".size uprobe_call_trigger, .-uprobe_call_trigger\n"
+ ".popsection\n"
+);
+
+/* If CALL emulation misses the shadow stack update, this exits via SIGSEGV. */
+static int test_uprobe_call(enum shadow_stack_test which_test)
+{
+ const size_t attr_sz = sizeof(struct perf_event_attr);
+ const char *file = "/proc/self/exe";
+ int fd = -1, type, err = 1;
+ struct perf_event_attr attr;
+ struct sigaction sa = {};
+ ssize_t offset;
+
+ type = determine_uprobe_perf_type();
+ if (type < 0) {
+ if (type == -ENOENT)
+ printf("[SKIP]\tUprobe on CALL test, uprobes are not available\n");
+ return 0;
+ }
+
+ offset = get_uprobe_offset(uprobe_call_trigger);
+ if (offset < 0)
+ return 1;
+
+ sa.sa_sigaction = segv_gp_handler;
+ sa.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSEGV, &sa, NULL))
+ return 1;
+
+ /* Setup entry uprobe through perf event interface. */
+ memset(&attr, 0, attr_sz);
+ attr.size = attr_sz;
+ attr.type = type;
+ attr.config = 0;
+ attr.config1 = (__u64)(unsigned long)file;
+ attr.config2 = offset;
+
+ fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,
+ -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
+ if (fd < 0)
+ goto out;
+
+ if (sigsetjmp(jmp_buffer, 1))
+ goto out;
+
+ if (SHADOW_STACK_ENABLE(which_test))
+ goto out;
+
+ /*
+ * This either segfaults and goes through sigsetjmp above
+ * or succeeds and we're good.
+ */
+ uprobe_call_trigger();
+
+ printf("[OK]\tUprobe on CALL test\n");
+ err = 0;
+
+out:
+ SHADOW_STACK_DISABLE(which_test);
+ signal(SIGSEGV, SIG_DFL);
+ if (fd >= 0)
+ close(fd);
+ return err;
+}
+
+void segv_handler_ptrace(int signum, siginfo_t *si, void *uc)
+{
+ /* The SSP adjustment caused a segfault. */
+ exit(0);
+}
+
+int test_ptrace(void)
+{
+ unsigned long saved_ssp, ssp = 0;
+ struct sigaction sa = {};
+ struct iovec iov;
+ int status;
+ int pid;
+
+ iov.iov_base = &ssp;
+ iov.iov_len = sizeof(ssp);
+
+ pid = fork();
+ if (!pid) {
+ ssp = get_ssp();
+
+ sa.sa_sigaction = segv_handler_ptrace;
+ sa.sa_flags = SA_SIGINFO;
+ if (sigaction(SIGSEGV, &sa, NULL))
+ return 1;
+
+ ptrace(PTRACE_TRACEME, NULL, NULL, NULL);
+ /*
+ * The parent will tweak the SSP and return from this function
+ * will #CP.
+ */
+ raise(SIGTRAP);
+
+ exit(1);
+ }
+
+ while (waitpid(pid, &status, 0) != -1 && WSTOPSIG(status) != SIGTRAP);
+
+ if (ptrace(PTRACE_GETREGSET, pid, NT_X86_SHSTK, &iov)) {
+ printf("[INFO]\tFailed to PTRACE_GETREGS\n");
+ goto out_kill;
+ }
+
+ if (!ssp) {
+ printf("[INFO]\tPtrace child SSP was 0\n");
+ goto out_kill;
+ }
+
+ saved_ssp = ssp;
+
+ iov.iov_len = 0;
+ if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
+ printf("[INFO]\tToo small size accepted via PTRACE_SETREGS\n");
+ goto out_kill;
+ }
+
+ iov.iov_len = sizeof(ssp) + 1;
+ if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
+ printf("[INFO]\tToo large size accepted via PTRACE_SETREGS\n");
+ goto out_kill;
+ }
+
+ ssp += 1;
+ if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
+ printf("[INFO]\tUnaligned SSP written via PTRACE_SETREGS\n");
+ goto out_kill;
+ }
+
+ ssp = 0xFFFFFFFFFFFF0000;
+ if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
+ printf("[INFO]\tKernel range SSP written via PTRACE_SETREGS\n");
+ goto out_kill;
+ }
+
+ /*
+ * Tweak the SSP so the child with #CP when it resumes and returns
+ * from raise()
+ */
+ ssp = saved_ssp + 8;
+ iov.iov_len = sizeof(ssp);
+ if (ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
+ printf("[INFO]\tFailed to PTRACE_SETREGS\n");
+ goto out_kill;
+ }
+
+ if (ptrace(PTRACE_DETACH, pid, NULL, NULL)) {
+ printf("[INFO]\tFailed to PTRACE_DETACH\n");
+ goto out_kill;
+ }
+
+ waitpid(pid, &status, 0);
+ if (WEXITSTATUS(status))
+ return 1;
+
+ printf("[OK]\tPtrace test\n");
+ return 0;
+
+out_kill:
+ kill(pid, SIGKILL);
+ return 1;
+}
+
+#if (__GNUC__ < 8) || (__GNUC__ == 8 && __GNUC_MINOR__ < 5)
+int shadow_stack_run_tests(enum shadow_stack_test unused)
+{
+ printf("[SKIP]\tCompiler does not support CET.\n");
+ return 0;
+}
+#else
+int shadow_stack_run_tests(enum shadow_stack_test which_test)
+{
+ int ret = 0;
+
+ if (SHADOW_STACK_ENABLE(which_test)) {
+ printf("[SKIP]\tCould not enable Shadow stack\n");
+ return 1;
+ }
+
+ if (SHADOW_STACK_DISABLE(which_test)) {
+ ret = 1;
+ printf("[FAIL]\tDisabling shadow stack failed\n");
+ }
+
+ if (SHADOW_STACK_ENABLE(which_test)) {
+ printf("[SKIP]\tCould not re-enable Shadow stack\n");
+ return 1;
+ }
+
+ if (SHADOW_STACK_ENABLE_WRITE(which_test)) {
+ printf("[SKIP]\tCould not enable WRSS\n");
+ ret = 1;
+ goto out;
+ }
+
+ /* Should have succeeded if here, but this is a test, so double check. */
+ if (!get_ssp()) {
+ printf("[FAIL]\tShadow stack disabled\n");
+ return 1;
+ }
+
+ if (test_shstk_pivot()) {
+ ret = 1;
+ printf("[FAIL]\tShadow stack pivot\n");
+ goto out;
+ }
+
+ if (test_shstk_faults()) {
+ ret = 1;
+ printf("[FAIL]\tShadow stack fault test\n");
+ goto out;
+ }
+
+ if (test_shstk_violation()) {
+ ret = 1;
+ printf("[FAIL]\tShadow stack violation test\n");
+ goto out;
+ }
+
+ if (test_gup()) {
+ ret = 1;
+ printf("[FAIL]\tShadow shadow stack gup\n");
+ goto out;
+ }
+
+ if (test_mprotect()) {
+ ret = 1;
+ printf("[FAIL]\tShadow shadow mprotect test\n");
+ goto out;
+ }
+
+ if (test_userfaultfd()) {
+ ret = 1;
+ printf("[FAIL]\tUserfaultfd test\n");
+ goto out;
+ }
+
+ if (test_guard_gap_other_gaps()) {
+ ret = 1;
+ printf("[FAIL]\tGuard gap test, other mappings' gaps\n");
+ goto out;
+ }
+
+ if (test_guard_gap_new_mappings_gaps()) {
+ ret = 1;
+ printf("[FAIL]\tGuard gap test, placement mapping's gaps\n");
+ goto out;
+ }
+
+ if (test_ptrace()) {
+ ret = 1;
+ printf("[FAIL]\tptrace test\n");
+ }
+
+ if (test_32bit()) {
+ ret = 1;
+ printf("[FAIL]\t32 bit test\n");
+ goto out;
+ }
+
+ if (test_uretprobe(which_test)) {
+ ret = 1;
+ printf("[FAIL]\turetprobe test\n");
+ goto out;
+ }
+
+ if (test_uprobe_call(which_test)) {
+ ret = 1;
+ printf("[FAIL]\tuprobe on CALL test\n");
+ goto out;
+ }
+
+ return ret;
+
+out:
+ /*
+ * Disable shadow stack before the function returns, or there will be a
+ * shadow stack violation.
+ */
+ if (SHADOW_STACK_DISABLE(which_test)) {
+ ret = 1;
+ printf("[FAIL]\tDisabling shadow stack failed\n");
+ }
+
+ return ret;
+}
+#endif
diff --git a/tools/testing/selftests/x86/shadow_stack.h b/tools/testing/selftests/x86/shadow_stack.h
new file mode 100644
index 000000000000..d36a44df7387
--- /dev/null
+++ b/tools/testing/selftests/x86/shadow_stack.h
@@ -0,0 +1,14 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef TOOLS_TESTING_SELFTESTS_X86_SHADOW_STACK_H_
+#define TOOLS_TESTING_SELFTESTS_X86_SHADOW_STACK_H_
+
+enum shadow_stack_test {
+ SHADOW_STACK_TEST_ARCH_PRCTL,
+ SHADOW_STACK_TEST_PRCTL,
+ SHADOW_STACK_TEST_COUNT,
+};
+
+int shadow_stack_run_tests(enum shadow_stack_test which_test);
+
+#endif /* TOOLS_TESTING_SELFTESTS_X86_SHADOW_STACK_H_ */
diff --git a/tools/testing/selftests/x86/test_shadow_stack.c b/tools/testing/selftests/x86/test_shadow_stack.c
index 3d6ca33edba4..d89c04623001 100644
--- a/tools/testing/selftests/x86/test_shadow_stack.c
+++ b/tools/testing/selftests/x86/test_shadow_stack.c
@@ -1,1174 +1,21 @@
// SPDX-License-Identifier: GPL-2.0
+
/*
* This program test's basic kernel shadow stack support. It enables shadow
* stack manual via the arch_prctl(), instead of relying on glibc. It's
* Makefile doesn't compile with shadow stack support, so it doesn't rely on
* any particular glibc. As a result it can't do any operations that require
* special glibc shadow stack support (longjmp(), swapcontext(), etc). Just
- * stick to the basics and hope the compiler doesn't do anything strange.
+ * stick to the basics and hope the compiler doesn't do anything strange. It
+ * uses the x86 specific interface for ARCH_PCTL, whereas
+ * test_shadow_stack_prctl.c uses the generic PRCTL interface mixed with x86
+ * specific code.
*/
-
#define _GNU_SOURCE
-#include <sys/syscall.h>
-#include <asm/mman.h>
-#include <sys/mman.h>
-#include <sys/stat.h>
-#include <sys/wait.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <fcntl.h>
-#include <unistd.h>
-#include <string.h>
-#include <errno.h>
-#include <stdbool.h>
-#include <x86intrin.h>
-#include <asm/prctl.h>
-#include <sys/prctl.h>
-#include <stdint.h>
-#include <signal.h>
-#include <pthread.h>
-#include <sys/ioctl.h>
-#include <linux/userfaultfd.h>
-#include <setjmp.h>
-#include <sys/ptrace.h>
-#include <sys/signal.h>
-#include <linux/elf.h>
-#include <linux/perf_event.h>
-
-/*
- * Define the ABI defines if needed, so people can run the tests
- * without building the headers.
- */
-#ifndef __NR_map_shadow_stack
-#define __NR_map_shadow_stack 453
-
-#define SHADOW_STACK_SET_TOKEN (1ULL << 0)
-
-#define ARCH_SHSTK_ENABLE 0x5001
-#define ARCH_SHSTK_DISABLE 0x5002
-#define ARCH_SHSTK_LOCK 0x5003
-#define ARCH_SHSTK_UNLOCK 0x5004
-#define ARCH_SHSTK_STATUS 0x5005
-
-#define ARCH_SHSTK_SHSTK (1ULL << 0)
-#define ARCH_SHSTK_WRSS (1ULL << 1)
-
-#define NT_X86_SHSTK 0x204
-#endif
-
-#define SS_SIZE 0x200000
-#define PAGE_SIZE 0x1000
-
-#if (__GNUC__ < 8) || (__GNUC__ == 8 && __GNUC_MINOR__ < 5)
-int main(int argc, char *argv[])
-{
- printf("[SKIP]\tCompiler does not support CET.\n");
- return 0;
-}
-#else
-void write_shstk(unsigned long *addr, unsigned long val)
-{
- asm volatile("wrssq %[val], (%[addr])\n"
- : "=m" (addr)
- : [addr] "r" (addr), [val] "r" (val));
-}
-
-static inline unsigned long __attribute__((always_inline)) get_ssp(void)
-{
- unsigned long ret = 0;
-
- asm volatile("xor %0, %0; rdsspq %0" : "=r" (ret));
- return ret;
-}
-
-/*
- * For use in inline enablement of shadow stack.
- *
- * The program can't return from the point where shadow stack gets enabled
- * because there will be no address on the shadow stack. So it can't use
- * syscall() for enablement, since it is a function.
- *
- * Based on code from nolibc.h. Keep a copy here because this can't pull in all
- * of nolibc.h.
- */
-#define ARCH_PRCTL(arg1, arg2) \
-({ \
- long _ret; \
- register long _num asm("eax") = __NR_arch_prctl; \
- register long _arg1 asm("rdi") = (long)(arg1); \
- register long _arg2 asm("rsi") = (long)(arg2); \
- \
- asm volatile ( \
- "syscall\n" \
- : "=a"(_ret) \
- : "r"(_arg1), "r"(_arg2), \
- "0"(_num) \
- : "rcx", "r11", "memory", "cc" \
- ); \
- _ret; \
-})
-
-void *create_shstk(void *addr)
-{
- return (void *)syscall(__NR_map_shadow_stack, addr, SS_SIZE, SHADOW_STACK_SET_TOKEN);
-}
-
-void *create_normal_mem(void *addr)
-{
- return mmap(addr, SS_SIZE, PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
-}
-
-void free_shstk(void *shstk)
-{
- munmap(shstk, SS_SIZE);
-}
-
-int reset_shstk(void *shstk)
-{
- return madvise(shstk, SS_SIZE, MADV_DONTNEED);
-}
-
-void try_shstk(unsigned long new_ssp)
-{
- unsigned long ssp;
-
- printf("[INFO]\tnew_ssp = %lx, *new_ssp = %lx\n",
- new_ssp, *((unsigned long *)new_ssp));
-
- ssp = get_ssp();
- printf("[INFO]\tchanging ssp from %lx to %lx\n", ssp, new_ssp);
-
- asm volatile("rstorssp (%0)\n":: "r" (new_ssp));
- asm volatile("saveprevssp");
- printf("[INFO]\tssp is now %lx\n", get_ssp());
-
- /* Switch back to original shadow stack */
- ssp -= 8;
- asm volatile("rstorssp (%0)\n":: "r" (ssp));
- asm volatile("saveprevssp");
-}
-
-int test_shstk_pivot(void)
-{
- void *shstk = create_shstk(0);
-
- if (shstk == MAP_FAILED) {
- printf("[FAIL]\tError creating shadow stack: %d\n", errno);
- return 1;
- }
- try_shstk((unsigned long)shstk + SS_SIZE - 8);
- free_shstk(shstk);
-
- printf("[OK]\tShadow stack pivot\n");
- return 0;
-}
-
-int test_shstk_faults(void)
-{
- unsigned long *shstk = create_shstk(0);
-
- /* Read shadow stack, test if it's zero to not get read optimized out */
- if (*shstk != 0)
- goto err;
-
- /* Wrss memory that was already read. */
- write_shstk(shstk, 1);
- if (*shstk != 1)
- goto err;
-
- /* Page out memory, so we can wrss it again. */
- if (reset_shstk((void *)shstk))
- goto err;
-
- write_shstk(shstk, 1);
- if (*shstk != 1)
- goto err;
-
- printf("[OK]\tShadow stack faults\n");
- return 0;
-
-err:
- return 1;
-}
-
-unsigned long saved_ssp;
-unsigned long saved_ssp_val;
-volatile bool segv_triggered;
-
-void __attribute__((noinline)) violate_ss(void)
-{
- saved_ssp = get_ssp();
- saved_ssp_val = *(unsigned long *)saved_ssp;
-
- /* Corrupt shadow stack */
- printf("[INFO]\tCorrupting shadow stack\n");
- write_shstk((void *)saved_ssp, 0);
-}
-
-void segv_handler(int signum, siginfo_t *si, void *uc)
-{
- printf("[INFO]\tGenerated shadow stack violation successfully\n");
-
- segv_triggered = true;
-
- /* Fix shadow stack */
- write_shstk((void *)saved_ssp, saved_ssp_val);
-}
-
-int test_shstk_violation(void)
-{
- struct sigaction sa = {};
-
- sa.sa_sigaction = segv_handler;
- sa.sa_flags = SA_SIGINFO;
- if (sigaction(SIGSEGV, &sa, NULL))
- return 1;
-
- segv_triggered = false;
-
- /* Make sure segv_triggered is set before violate_ss() */
- asm volatile("" : : : "memory");
-
- violate_ss();
-
- signal(SIGSEGV, SIG_DFL);
-
- printf("[OK]\tShadow stack violation test\n");
-
- return !segv_triggered;
-}
-
-/* Gup test state */
-#define MAGIC_VAL 0x12345678
-bool is_shstk_access;
-void *shstk_ptr;
-int fd;
-
-void reset_test_shstk(void *addr)
-{
- if (shstk_ptr)
- free_shstk(shstk_ptr);
- shstk_ptr = create_shstk(addr);
-}
-
-void test_access_fix_handler(int signum, siginfo_t *si, void *uc)
-{
- printf("[INFO]\tViolation from %s\n", is_shstk_access ? "shstk access" : "normal write");
-
- segv_triggered = true;
-
- /* Fix shadow stack */
- if (is_shstk_access) {
- reset_test_shstk(shstk_ptr);
- return;
- }
-
- free_shstk(shstk_ptr);
- create_normal_mem(shstk_ptr);
-}
-
-bool test_shstk_access(void *ptr)
-{
- is_shstk_access = true;
- segv_triggered = false;
- write_shstk(ptr, MAGIC_VAL);
-
- asm volatile("" : : : "memory");
-
- return segv_triggered;
-}
-
-bool test_write_access(void *ptr)
-{
- is_shstk_access = false;
- segv_triggered = false;
- *(unsigned long *)ptr = MAGIC_VAL;
-
- asm volatile("" : : : "memory");
-
- return segv_triggered;
-}
-
-bool gup_write(void *ptr)
-{
- unsigned long val;
-
- lseek(fd, (unsigned long)ptr, SEEK_SET);
- if (write(fd, &val, sizeof(val)) < 0)
- return 1;
-
- return 0;
-}
-
-bool gup_read(void *ptr)
-{
- unsigned long val;
-
- lseek(fd, (unsigned long)ptr, SEEK_SET);
- if (read(fd, &val, sizeof(val)) < 0)
- return 1;
-
- return 0;
-}
-
-int test_gup(void)
-{
- struct sigaction sa = {};
- int status;
- pid_t pid;
-
- sa.sa_sigaction = test_access_fix_handler;
- sa.sa_flags = SA_SIGINFO;
- if (sigaction(SIGSEGV, &sa, NULL))
- return 1;
-
- segv_triggered = false;
-
- fd = open("/proc/self/mem", O_RDWR);
- if (fd == -1)
- return 1;
-
- reset_test_shstk(0);
- if (gup_read(shstk_ptr))
- return 1;
- if (test_shstk_access(shstk_ptr))
- return 1;
- printf("[INFO]\tGup read -> shstk access success\n");
-
- reset_test_shstk(0);
- if (gup_write(shstk_ptr))
- return 1;
- if (test_shstk_access(shstk_ptr))
- return 1;
- printf("[INFO]\tGup write -> shstk access success\n");
-
- reset_test_shstk(0);
- if (gup_read(shstk_ptr))
- return 1;
- if (!test_write_access(shstk_ptr))
- return 1;
- printf("[INFO]\tGup read -> write access success\n");
-
- reset_test_shstk(0);
- if (gup_write(shstk_ptr))
- return 1;
- if (!test_write_access(shstk_ptr))
- return 1;
- printf("[INFO]\tGup write -> write access success\n");
-
- close(fd);
-
- /* COW/gup test */
- reset_test_shstk(0);
- pid = fork();
- if (!pid) {
- fd = open("/proc/self/mem", O_RDWR);
- if (fd == -1)
- exit(1);
-
- if (gup_write(shstk_ptr)) {
- close(fd);
- exit(1);
- }
- close(fd);
- exit(0);
- }
- waitpid(pid, &status, 0);
- if (WEXITSTATUS(status)) {
- printf("[FAIL]\tWrite in child failed\n");
- return 1;
- }
- if (*(unsigned long *)shstk_ptr == MAGIC_VAL) {
- printf("[FAIL]\tWrite in child wrote through to shared memory\n");
- return 1;
- }
-
- printf("[INFO]\tCow gup write -> write access success\n");
-
- free_shstk(shstk_ptr);
-
- signal(SIGSEGV, SIG_DFL);
-
- printf("[OK]\tShadow gup test\n");
-
- return 0;
-}
-
-int test_mprotect(void)
-{
- struct sigaction sa = {};
-
- sa.sa_sigaction = test_access_fix_handler;
- sa.sa_flags = SA_SIGINFO;
- if (sigaction(SIGSEGV, &sa, NULL))
- return 1;
-
- segv_triggered = false;
-
- /* mprotect a shadow stack as read only */
- reset_test_shstk(0);
- if (mprotect(shstk_ptr, SS_SIZE, PROT_READ) < 0) {
- printf("[FAIL]\tmprotect(PROT_READ) failed\n");
- return 1;
- }
-
- /* try to wrss it and fail */
- if (!test_shstk_access(shstk_ptr)) {
- printf("[FAIL]\tShadow stack access to read-only memory succeeded\n");
- return 1;
- }
-
- /*
- * The shadow stack was reset above to resolve the fault, make the new one
- * read-only.
- */
- if (mprotect(shstk_ptr, SS_SIZE, PROT_READ) < 0) {
- printf("[FAIL]\tmprotect(PROT_READ) failed\n");
- return 1;
- }
-
- /* then back to writable */
- if (mprotect(shstk_ptr, SS_SIZE, PROT_WRITE | PROT_READ) < 0) {
- printf("[FAIL]\tmprotect(PROT_WRITE) failed\n");
- return 1;
- }
-
- /* then wrss to it and succeed */
- if (test_shstk_access(shstk_ptr)) {
- printf("[FAIL]\tShadow stack access to mprotect() writable memory failed\n");
- return 1;
- }
-
- free_shstk(shstk_ptr);
-
- signal(SIGSEGV, SIG_DFL);
-
- printf("[OK]\tmprotect() test\n");
-
- return 0;
-}
-
-char zero[4096];
-
-static void *uffd_thread(void *arg)
-{
- struct uffdio_copy req;
- int uffd = *(int *)arg;
- struct uffd_msg msg;
- int ret;
-
- while (1) {
- ret = read(uffd, &msg, sizeof(msg));
- if (ret > 0)
- break;
- else if (errno == EAGAIN)
- continue;
- return (void *)1;
- }
-
- req.dst = msg.arg.pagefault.address;
- req.src = (__u64)zero;
- req.len = 4096;
- req.mode = 0;
-
- if (ioctl(uffd, UFFDIO_COPY, &req))
- return (void *)1;
-
- return (void *)0;
-}
-
-int test_userfaultfd(void)
-{
- struct uffdio_register uffdio_register;
- struct uffdio_api uffdio_api;
- struct sigaction sa = {};
- pthread_t thread;
- void *res;
- int uffd;
-
- sa.sa_sigaction = test_access_fix_handler;
- sa.sa_flags = SA_SIGINFO;
- if (sigaction(SIGSEGV, &sa, NULL))
- return 1;
-
- uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
- if (uffd < 0) {
- printf("[SKIP]\tUserfaultfd unavailable.\n");
- return 0;
- }
-
- reset_test_shstk(0);
-
- uffdio_api.api = UFFD_API;
- uffdio_api.features = 0;
- if (ioctl(uffd, UFFDIO_API, &uffdio_api))
- goto err;
-
- uffdio_register.range.start = (__u64)shstk_ptr;
- uffdio_register.range.len = 4096;
- uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
- if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
- goto err;
-
- if (pthread_create(&thread, NULL, &uffd_thread, &uffd))
- goto err;
-
- reset_shstk(shstk_ptr);
- test_shstk_access(shstk_ptr);
-
- if (pthread_join(thread, &res))
- goto err;
-
- if (test_shstk_access(shstk_ptr))
- goto err;
-
- free_shstk(shstk_ptr);
-
- signal(SIGSEGV, SIG_DFL);
-
- if (!res)
- printf("[OK]\tUserfaultfd test\n");
- return !!res;
-err:
- free_shstk(shstk_ptr);
- close(uffd);
- signal(SIGSEGV, SIG_DFL);
- return 1;
-}
-
-/* Simple linked list for keeping track of mappings in test_guard_gap() */
-struct node {
- struct node *next;
- void *mapping;
-};
-
-/*
- * This tests whether mmap will place other mappings in a shadow stack's guard
- * gap. The steps are:
- * 1. Finds an empty place by mapping and unmapping something.
- * 2. Map a shadow stack in the middle of the known empty area.
- * 3. Map a bunch of PAGE_SIZE mappings. These will use the search down
- * direction, filling any gaps until it encounters the shadow stack's
- * guard gap.
- * 4. When a mapping lands below the shadow stack from step 2, then all
- * of the above gaps are filled. The search down algorithm will have
- * looked at the shadow stack gaps.
- * 5. See if it landed in the gap.
- */
-int test_guard_gap_other_gaps(void)
-{
- void *free_area, *shstk, *test_map = (void *)0xFFFFFFFFFFFFFFFF;
- struct node *head = NULL, *cur;
-
- free_area = mmap(0, SS_SIZE * 3, PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
- munmap(free_area, SS_SIZE * 3);
-
- shstk = create_shstk(free_area + SS_SIZE);
- if (shstk == MAP_FAILED)
- return 1;
-
- while (test_map > shstk) {
- test_map = mmap(0, PAGE_SIZE, PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
- if (test_map == MAP_FAILED)
- return 1;
- cur = malloc(sizeof(*cur));
- cur->mapping = test_map;
-
- cur->next = head;
- head = cur;
- }
-
- while (head) {
- cur = head;
- head = cur->next;
- munmap(cur->mapping, PAGE_SIZE);
- free(cur);
- }
-
- free_shstk(shstk);
-
- if (shstk - test_map - PAGE_SIZE != PAGE_SIZE)
- return 1;
-
- printf("[OK]\tGuard gap test, other mapping's gaps\n");
-
- return 0;
-}
-
-/* Tests respecting the guard gap of the mapping getting placed */
-int test_guard_gap_new_mappings_gaps(void)
-{
- void *free_area, *shstk_start, *test_map = (void *)0xFFFFFFFFFFFFFFFF;
- struct node *head = NULL, *cur;
- int ret = 0;
-
- free_area = mmap(0, PAGE_SIZE * 4, PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
- munmap(free_area, PAGE_SIZE * 4);
-
- /* Test letting map_shadow_stack find a free space */
- shstk_start = mmap(free_area, PAGE_SIZE, PROT_READ | PROT_WRITE,
- MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
- if (shstk_start == MAP_FAILED || shstk_start != free_area)
- return 1;
-
- while (test_map > shstk_start) {
- test_map = (void *)syscall(__NR_map_shadow_stack, 0, PAGE_SIZE, 0);
- if (test_map == MAP_FAILED) {
- printf("[INFO]\tmap_shadow_stack MAP_FAILED\n");
- ret = 1;
- break;
- }
-
- cur = malloc(sizeof(*cur));
- cur->mapping = test_map;
-
- cur->next = head;
- head = cur;
-
- if (test_map == free_area + PAGE_SIZE) {
- printf("[INFO]\tNew mapping has other mapping in guard gap!\n");
- ret = 1;
- break;
- }
- }
-
- while (head) {
- cur = head;
- head = cur->next;
- munmap(cur->mapping, PAGE_SIZE);
- free(cur);
- }
-
- munmap(shstk_start, PAGE_SIZE);
-
- if (!ret)
- printf("[OK]\tGuard gap test, placement mapping's gaps\n");
-
- return ret;
-}
-
-/*
- * Too complicated to pull it out of the 32 bit header, but also get the
- * 64 bit one needed above. Just define a copy here.
- */
-#define __NR_compat_sigaction 67
-
-/*
- * Call 32 bit signal handler to get 32 bit signals ABI. Make sure
- * to push the registers that will get clobbered.
- */
-int sigaction32(int signum, const struct sigaction *restrict act,
- struct sigaction *restrict oldact)
-{
- register long syscall_reg asm("eax") = __NR_compat_sigaction;
- register long signum_reg asm("ebx") = signum;
- register long act_reg asm("ecx") = (long)act;
- register long oldact_reg asm("edx") = (long)oldact;
- int ret = 0;
-
- asm volatile ("int $0x80;"
- : "=a"(ret), "=m"(oldact)
- : "r"(syscall_reg), "r"(signum_reg), "r"(act_reg),
- "r"(oldact_reg)
- : "r8", "r9", "r10", "r11"
- );
-
- return ret;
-}
-
-sigjmp_buf jmp_buffer;
-
-void segv_gp_handler(int signum, siginfo_t *si, void *uc)
-{
- segv_triggered = true;
-
- /*
- * To work with old glibc, this can't rely on siglongjmp working with
- * shadow stack enabled, so disable shadow stack before siglongjmp().
- */
- ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
- siglongjmp(jmp_buffer, -1);
-}
-
-/*
- * Transition to 32 bit mode and check that a #GP triggers a segfault.
- */
-int test_32bit(void)
-{
- struct sigaction sa = {};
- struct sigaction *sa32;
-
- /* Create sigaction in 32 bit address range */
- sa32 = mmap(0, 4096, PROT_READ | PROT_WRITE,
- MAP_32BIT | MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
- sa32->sa_flags = SA_SIGINFO;
-
- sa.sa_sigaction = segv_gp_handler;
- sa.sa_flags = SA_SIGINFO;
- if (sigaction(SIGSEGV, &sa, NULL))
- return 1;
-
-
- segv_triggered = false;
-
- /* Make sure segv_triggered is set before triggering the #GP */
- asm volatile("" : : : "memory");
-
- /*
- * Set handler to somewhere in 32 bit address space
- */
- sa32->sa_handler = (void *)sa32;
- if (sigaction32(SIGUSR1, sa32, NULL))
- return 1;
-
- if (!sigsetjmp(jmp_buffer, 1))
- raise(SIGUSR1);
-
- if (segv_triggered)
- printf("[OK]\t32 bit test\n");
-
- return !segv_triggered;
-}
-
-static int parse_uint_from_file(const char *file, const char *fmt)
-{
- int err, ret;
- FILE *f;
-
- f = fopen(file, "re");
- if (!f) {
- err = -errno;
- printf("failed to open '%s': %d\n", file, err);
- return err;
- }
- err = fscanf(f, fmt, &ret);
- if (err != 1) {
- err = err == EOF ? -EIO : -errno;
- printf("failed to parse '%s': %d\n", file, err);
- fclose(f);
- return err;
- }
- fclose(f);
- return ret;
-}
-
-static int determine_uprobe_perf_type(void)
-{
- const char *file = "/sys/bus/event_source/devices/uprobe/type";
-
- return parse_uint_from_file(file, "%d\n");
-}
-
-static int determine_uprobe_retprobe_bit(void)
-{
- const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";
-
- return parse_uint_from_file(file, "config:%d\n");
-}
-
-static ssize_t get_uprobe_offset(const void *addr)
-{
- size_t start, end, base;
- char buf[256];
- bool found = false;
- FILE *f;
-
- f = fopen("/proc/self/maps", "r");
- if (!f)
- return -errno;
-
- while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &base) == 4) {
- if (buf[2] == 'x' && (uintptr_t)addr >= start && (uintptr_t)addr < end) {
- found = true;
- break;
- }
- }
-
- fclose(f);
-
- if (!found)
- return -ESRCH;
-
- return (uintptr_t)addr - start + base;
-}
-
-static __attribute__((noinline)) void uretprobe_trigger(void)
-{
- asm volatile ("");
-}
-
-/*
- * This test setups return uprobe, which is sensitive to shadow stack
- * (crashes without extra fix). After executing the uretprobe we fail
- * the test if we receive SIGSEGV, no crash means we're good.
- *
- * Helper functions above borrowed from bpf selftests.
- */
-static int test_uretprobe(void)
-{
- const size_t attr_sz = sizeof(struct perf_event_attr);
- const char *file = "/proc/self/exe";
- int bit, fd = 0, type, err = 1;
- struct perf_event_attr attr;
- struct sigaction sa = {};
- ssize_t offset;
-
- type = determine_uprobe_perf_type();
- if (type < 0) {
- if (type == -ENOENT)
- printf("[SKIP]\tUretprobe test, uprobes are not available\n");
- return 0;
- }
-
- offset = get_uprobe_offset(uretprobe_trigger);
- if (offset < 0)
- return 1;
-
- bit = determine_uprobe_retprobe_bit();
- if (bit < 0)
- return 1;
-
- sa.sa_sigaction = segv_gp_handler;
- sa.sa_flags = SA_SIGINFO;
- if (sigaction(SIGSEGV, &sa, NULL))
- return 1;
-
- /* Setup return uprobe through perf event interface. */
- memset(&attr, 0, attr_sz);
- attr.size = attr_sz;
- attr.type = type;
- attr.config = 1 << bit;
- attr.config1 = (__u64) (unsigned long) file;
- attr.config2 = offset;
-
- fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,
- -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
- if (fd < 0)
- goto out;
-
- if (sigsetjmp(jmp_buffer, 1))
- goto out;
-
- ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK);
-
- /*
- * This either segfaults and goes through sigsetjmp above
- * or succeeds and we're good.
- */
- uretprobe_trigger();
-
- printf("[OK]\tUretprobe test\n");
- err = 0;
-
-out:
- ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
- signal(SIGSEGV, SIG_DFL);
- if (fd)
- close(fd);
- return err;
-}
-
-/* Keep the CALL first so the function address is exactly the probed CALL. */
-extern void uprobe_call_trigger(void);
-asm (".pushsection .text\n"
- ".global uprobe_call_target\n"
- ".type uprobe_call_target, @function\n"
- "uprobe_call_target:\n"
- " ret\n"
- ".size uprobe_call_target, .-uprobe_call_target\n"
-
- ".global uprobe_call_trigger\n"
- ".type uprobe_call_trigger, @function\n"
- "uprobe_call_trigger:\n"
- " call uprobe_call_target\n"
- " ret\n"
- ".size uprobe_call_trigger, .-uprobe_call_trigger\n"
- ".popsection\n"
-);
-
-/* If CALL emulation misses the shadow stack update, this exits via SIGSEGV. */
-static int test_uprobe_call(void)
-{
- const size_t attr_sz = sizeof(struct perf_event_attr);
- const char *file = "/proc/self/exe";
- int fd = -1, type, err = 1;
- struct perf_event_attr attr;
- struct sigaction sa = {};
- ssize_t offset;
-
- type = determine_uprobe_perf_type();
- if (type < 0) {
- if (type == -ENOENT)
- printf("[SKIP]\tUprobe on CALL test, uprobes are not available\n");
- return 0;
- }
-
- offset = get_uprobe_offset(uprobe_call_trigger);
- if (offset < 0)
- return 1;
-
- sa.sa_sigaction = segv_gp_handler;
- sa.sa_flags = SA_SIGINFO;
- if (sigaction(SIGSEGV, &sa, NULL))
- return 1;
-
- /* Setup entry uprobe through perf event interface. */
- memset(&attr, 0, attr_sz);
- attr.size = attr_sz;
- attr.type = type;
- attr.config = 0;
- attr.config1 = (__u64)(unsigned long)file;
- attr.config2 = offset;
-
- fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,
- -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
- if (fd < 0)
- goto out;
-
- if (sigsetjmp(jmp_buffer, 1))
- goto out;
-
- if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK))
- goto out;
-
- /*
- * This either segfaults and goes through sigsetjmp above
- * or succeeds and we're good.
- */
- uprobe_call_trigger();
-
- printf("[OK]\tUprobe on CALL test\n");
- err = 0;
-
-out:
- ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
- signal(SIGSEGV, SIG_DFL);
- if (fd >= 0)
- close(fd);
- return err;
-}
-
-void segv_handler_ptrace(int signum, siginfo_t *si, void *uc)
-{
- /* The SSP adjustment caused a segfault. */
- exit(0);
-}
-
-int test_ptrace(void)
-{
- unsigned long saved_ssp, ssp = 0;
- struct sigaction sa= {};
- struct iovec iov;
- int status;
- int pid;
-
- iov.iov_base = &ssp;
- iov.iov_len = sizeof(ssp);
-
- pid = fork();
- if (!pid) {
- ssp = get_ssp();
-
- sa.sa_sigaction = segv_handler_ptrace;
- sa.sa_flags = SA_SIGINFO;
- if (sigaction(SIGSEGV, &sa, NULL))
- return 1;
-
- ptrace(PTRACE_TRACEME, NULL, NULL, NULL);
- /*
- * The parent will tweak the SSP and return from this function
- * will #CP.
- */
- raise(SIGTRAP);
-
- exit(1);
- }
-
- while (waitpid(pid, &status, 0) != -1 && WSTOPSIG(status) != SIGTRAP);
-
- if (ptrace(PTRACE_GETREGSET, pid, NT_X86_SHSTK, &iov)) {
- printf("[INFO]\tFailed to PTRACE_GETREGS\n");
- goto out_kill;
- }
-
- if (!ssp) {
- printf("[INFO]\tPtrace child SSP was 0\n");
- goto out_kill;
- }
-
- saved_ssp = ssp;
-
- iov.iov_len = 0;
- if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
- printf("[INFO]\tToo small size accepted via PTRACE_SETREGS\n");
- goto out_kill;
- }
-
- iov.iov_len = sizeof(ssp) + 1;
- if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
- printf("[INFO]\tToo large size accepted via PTRACE_SETREGS\n");
- goto out_kill;
- }
-
- ssp += 1;
- if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
- printf("[INFO]\tUnaligned SSP written via PTRACE_SETREGS\n");
- goto out_kill;
- }
-
- ssp = 0xFFFFFFFFFFFF0000;
- if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
- printf("[INFO]\tKernel range SSP written via PTRACE_SETREGS\n");
- goto out_kill;
- }
-
- /*
- * Tweak the SSP so the child with #CP when it resumes and returns
- * from raise()
- */
- ssp = saved_ssp + 8;
- iov.iov_len = sizeof(ssp);
- if (ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
- printf("[INFO]\tFailed to PTRACE_SETREGS\n");
- goto out_kill;
- }
-
- if (ptrace(PTRACE_DETACH, pid, NULL, NULL)) {
- printf("[INFO]\tFailed to PTRACE_DETACH\n");
- goto out_kill;
- }
-
- waitpid(pid, &status, 0);
- if (WEXITSTATUS(status))
- return 1;
-
- printf("[OK]\tPtrace test\n");
- return 0;
-
-out_kill:
- kill(pid, SIGKILL);
- return 1;
-}
+#include "shadow_stack.h"
int main(int argc, char *argv[])
{
- int ret = 0;
-
- if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK)) {
- printf("[SKIP]\tCould not enable Shadow stack\n");
- return 1;
- }
-
- if (ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK)) {
- ret = 1;
- printf("[FAIL]\tDisabling shadow stack failed\n");
- }
-
- if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK)) {
- printf("[SKIP]\tCould not re-enable Shadow stack\n");
- return 1;
- }
-
- if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_WRSS)) {
- printf("[SKIP]\tCould not enable WRSS\n");
- ret = 1;
- goto out;
- }
-
- /* Should have succeeded if here, but this is a test, so double check. */
- if (!get_ssp()) {
- printf("[FAIL]\tShadow stack disabled\n");
- return 1;
- }
-
- if (test_shstk_pivot()) {
- ret = 1;
- printf("[FAIL]\tShadow stack pivot\n");
- goto out;
- }
-
- if (test_shstk_faults()) {
- ret = 1;
- printf("[FAIL]\tShadow stack fault test\n");
- goto out;
- }
-
- if (test_shstk_violation()) {
- ret = 1;
- printf("[FAIL]\tShadow stack violation test\n");
- goto out;
- }
-
- if (test_gup()) {
- ret = 1;
- printf("[FAIL]\tShadow shadow stack gup\n");
- goto out;
- }
-
- if (test_mprotect()) {
- ret = 1;
- printf("[FAIL]\tShadow shadow mprotect test\n");
- goto out;
- }
-
- if (test_userfaultfd()) {
- ret = 1;
- printf("[FAIL]\tUserfaultfd test\n");
- goto out;
- }
-
- if (test_guard_gap_other_gaps()) {
- ret = 1;
- printf("[FAIL]\tGuard gap test, other mappings' gaps\n");
- goto out;
- }
-
- if (test_guard_gap_new_mappings_gaps()) {
- ret = 1;
- printf("[FAIL]\tGuard gap test, placement mapping's gaps\n");
- goto out;
- }
-
- if (test_ptrace()) {
- ret = 1;
- printf("[FAIL]\tptrace test\n");
- }
-
- if (test_32bit()) {
- ret = 1;
- printf("[FAIL]\t32 bit test\n");
- goto out;
- }
-
- if (test_uretprobe()) {
- ret = 1;
- printf("[FAIL]\turetprobe test\n");
- goto out;
- }
-
- if (test_uprobe_call()) {
- ret = 1;
- printf("[FAIL]\tuprobe on CALL test\n");
- goto out;
- }
-
- return ret;
-
-out:
- /*
- * Disable shadow stack before the function returns, or there will be a
- * shadow stack violation.
- */
- if (ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK)) {
- ret = 1;
- printf("[FAIL]\tDisabling shadow stack failed\n");
- }
-
- return ret;
+ return shadow_stack_run_tests(SHADOW_STACK_TEST_ARCH_PRCTL);
}
-#endif
diff --git a/tools/testing/selftests/x86/test_shadow_stack_prctl.c b/tools/testing/selftests/x86/test_shadow_stack_prctl.c
new file mode 100644
index 000000000000..4641a3b1ca03
--- /dev/null
+++ b/tools/testing/selftests/x86/test_shadow_stack_prctl.c
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0
+
+/*
+ * Same as test_shadow_stack.c but uses the PRCTL interface
+ * instead of ARCH_PRCTL.
+ */
+#include "shadow_stack.h"
+
+int main(int argc, char *argv[])
+{
+ return shadow_stack_run_tests(SHADOW_STACK_TEST_PRCTL);
+}
--
2.55.0
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] selftests/x86: add generic prctl shadow stack test
2026-08-12 17:19 ` [PATCH v2 2/2] selftests/x86: add generic prctl shadow stack test Bill Roberts
@ 2026-08-12 18:03 ` Bill Roberts
2026-08-12 18:30 ` Edgecombe, Rick P
0 siblings, 1 reply; 6+ messages in thread
From: Bill Roberts @ 2026-08-12 18:03 UTC (permalink / raw)
To: H. Peter Anvin, Albert Ou, Alexandre Ghiti, Borislav Petkov,
Dave Hansen, Ingo Molnar, Palmer Dabbelt, Paul Walmsley,
rick.p.edgecombe, Shuah Khan, Thomas Gleixner, x86
Cc: bpf, linux-kernel, linux-kselftest, linux-riscv
On 8/12/26 12:19 PM, Bill Roberts wrote:
> Run the same test suite for arch_prctl, against prctl, to ensure
> consisteny and correctness between the interfaces.
>
> Signed-off-by: Bill Roberts <bill.roberts@arm.com>
> ---
> tools/testing/selftests/x86/Makefile | 5 +-
> tools/testing/selftests/x86/shadow_stack.c | 1205 +++++++++++++++++
> tools/testing/selftests/x86/shadow_stack.h | 14 +
> .../testing/selftests/x86/test_shadow_stack.c | 1167 +---------------
> .../selftests/x86/test_shadow_stack_prctl.c | 12 +
> 5 files changed, 1242 insertions(+), 1161 deletions(-)
> create mode 100644 tools/testing/selftests/x86/shadow_stack.c
> create mode 100644 tools/testing/selftests/x86/shadow_stack.h
> create mode 100644 tools/testing/selftests/x86/test_shadow_stack_prctl.c
>
> diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
> index 434065215d12..8748e2f4a915 100644
> --- a/tools/testing/selftests/x86/Makefile
> +++ b/tools/testing/selftests/x86/Makefile
> @@ -19,7 +19,8 @@ TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \
> test_FCMOV test_FCOMI test_FISTTP \
> vdso_restorer
> TARGETS_C_64BIT_ONLY := fsgsbase sysret_rip syscall_numbering \
> - corrupt_xstate_header amx lam test_shadow_stack avx apx
> + corrupt_xstate_header amx lam test_shadow_stack avx apx \
> + test_shadow_stack_prctl
> # Some selftests require 32bit support enabled also on 64bit systems
> TARGETS_C_32BIT_NEEDED := ldt_gdt ptrace_syscall
>
> @@ -138,3 +139,5 @@ $(OUTPUT)/avx_64: CFLAGS += -mno-avx -mno-avx512f
> $(OUTPUT)/amx_64: EXTRA_FILES += xstate.c
> $(OUTPUT)/avx_64: EXTRA_FILES += xstate.c
> $(OUTPUT)/apx_64: EXTRA_FILES += xstate.c
> +$(OUTPUT)/test_shadow_stack_64: EXTRA_FILES += shadow_stack.c
> +$(OUTPUT)/test_shadow_stack_prctl_64: EXTRA_FILES += shadow_stack.c
> diff --git a/tools/testing/selftests/x86/shadow_stack.c b/tools/testing/selftests/x86/shadow_stack.c
> new file mode 100644
> index 000000000000..a375c4ff7a6a
> --- /dev/null
> +++ b/tools/testing/selftests/x86/shadow_stack.c
> @@ -0,0 +1,1205 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#define _GNU_SOURCE
> +
> +#include <sys/syscall.h>
> +#include <asm/mman.h>
> +#include <sys/mman.h>
> +#include <sys/stat.h>
> +#include <sys/wait.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <fcntl.h>
> +#include <unistd.h>
> +#include <string.h>
> +#include <errno.h>
> +#include <stdbool.h>
> +#include <x86intrin.h>
> +#include <asm/prctl.h>
> +#include <sys/prctl.h>
> +#include <stdint.h>
> +#include <signal.h>
> +#include <pthread.h>
> +#include <sys/ioctl.h>
> +#include <linux/userfaultfd.h>
> +#include <setjmp.h>
> +#include <sys/ptrace.h>
> +#include <sys/signal.h>
> +#include <linux/elf.h>
> +#include <linux/perf_event.h>
> +
> +#include "shadow_stack.h"
> +
> +/*
> + * Define the ABI defines if needed, so people can run the tests
> + * without building the headers.
> + */
> +#ifndef __NR_map_shadow_stack
> +#define __NR_map_shadow_stack 453
> +
> +#define SHADOW_STACK_SET_TOKEN (1ULL << 0)
> +
> +#define ARCH_SHSTK_ENABLE 0x5001
> +#define ARCH_SHSTK_DISABLE 0x5002
> +#define ARCH_SHSTK_LOCK 0x5003
> +#define ARCH_SHSTK_UNLOCK 0x5004
> +#define ARCH_SHSTK_STATUS 0x5005
> +
> +#define ARCH_SHSTK_SHSTK (1ULL << 0)
> +#define ARCH_SHSTK_WRSS (1ULL << 1)
> +
> +#define NT_X86_SHSTK 0x204
> +#endif
> +
> +#define SS_SIZE 0x200000
> +#define PAGE_SIZE 0x1000
> +
> +void write_shstk(unsigned long *addr, unsigned long val)
> +{
> + asm volatile("wrssq %[val], (%[addr])\n"
> + : "=m" (addr)
> + : [addr] "r" (addr), [val] "r" (val));
> +}
> +
> +static inline unsigned long __attribute__((always_inline)) get_ssp(void)
> +{
> + unsigned long ret = 0;
> +
> + asm volatile("xor %0, %0; rdsspq %0" : "=r" (ret));
> + return ret;
> +}
> +
> +/*
> + * For use in inline enablement of shadow stack.
> + *
> + * The program can't return from the point where shadow stack gets enabled
> + * because there will be no address on the shadow stack. So it can't use
> + * syscall() for enablement, since it is a function.
> + *
> + * Based on code from nolibc.h. Keep a copy here because this can't pull in all
> + * of nolibc.h.
> + */
> +#define ARCH_PRCTL(arg1, arg2) \
> +({ \
> + long _ret; \
> + register long _num asm("eax") = __NR_arch_prctl; \
> + register long _arg1 asm("rdi") = (long)(arg1); \
> + register long _arg2 asm("rsi") = (long)(arg2); \
> + \
> + asm volatile ( \
> + "syscall\n" \
> + : "=a"(_ret) \
> + : "r"(_arg1), "r"(_arg2), \
> + "0"(_num) \
> + : "rcx", "r11", "memory", "cc" \
> + ); \
> + _ret; \
> +})
> +
> +#define PRCTL(option, arg2, arg3, arg4, arg5) \
> +({ \
> + long _ret; \
> + register long _num asm("rax") = __NR_prctl; \
> + register long _arg1 asm("rdi") = (long)(option); \
> + register long _arg2 asm("rsi") = (long)(arg2); \
> + register long _arg3 asm("rdx") = (long)(arg3); \
> + register long _arg4 asm("r10") = (long)(arg4); \
> + register long _arg5 asm("r8") = (long)(arg5); \
> + \
> + asm volatile ( \
> + "syscall" \
> + : "=a"(_ret) \
> + : "0"(_num), \
> + "r"(_arg1), "r"(_arg2), "r"(_arg3), \
> + "r"(_arg4), "r"(_arg5) \
> + : "rcx", "r11", "memory", "cc" \
> + ); \
> + _ret; \
> +})
> +
> +#define SHADOW_STACK_DISABLE(which_test) \
> + ((which_test) == SHADOW_STACK_TEST_ARCH_PRCTL ? \
> + ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK) : \
> + PRCTL(PR_SET_SHADOW_STACK_STATUS, 0, 0, 0, 0))
> +
> +#define SHADOW_STACK_ENABLE(which_test) \
> + ((which_test) == SHADOW_STACK_TEST_ARCH_PRCTL ? \
> + ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK) : \
> + PRCTL(PR_SET_SHADOW_STACK_STATUS, PR_SHADOW_STACK_ENABLE, 0, 0, 0))
> +
> +#define SHADOW_STACK_ENABLE_WRITE(which_test) \
> + ((which_test) == SHADOW_STACK_TEST_ARCH_PRCTL ? \
> + ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_WRSS) : \
> + PRCTL(PR_SET_SHADOW_STACK_STATUS, \
> + PR_SHADOW_STACK_ENABLE|PR_SHADOW_STACK_WRITE, 0, 0, 0))
> +
> +void *create_shstk(void *addr)
> +{
> + return (void *)syscall(__NR_map_shadow_stack, addr, SS_SIZE, SHADOW_STACK_SET_TOKEN);
> +}
> +
> +void *create_normal_mem(void *addr)
> +{
> + return mmap(addr, SS_SIZE, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
> +}
> +
> +void free_shstk(void *shstk)
> +{
> + munmap(shstk, SS_SIZE);
> +}
> +
> +int reset_shstk(void *shstk)
> +{
> + return madvise(shstk, SS_SIZE, MADV_DONTNEED);
> +}
> +
> +void try_shstk(unsigned long new_ssp)
> +{
> + unsigned long ssp;
> +
> + printf("[INFO]\tnew_ssp = %lx, *new_ssp = %lx\n",
> + new_ssp, *((unsigned long *)new_ssp));
> +
> + ssp = get_ssp();
> + printf("[INFO]\tchanging ssp from %lx to %lx\n", ssp, new_ssp);
> +
> + asm volatile("rstorssp (%0)\n":: "r" (new_ssp));
> + asm volatile("saveprevssp");
> + printf("[INFO]\tssp is now %lx\n", get_ssp());
> +
> + /* Switch back to original shadow stack */
> + ssp -= 8;
> + asm volatile("rstorssp (%0)\n":: "r" (ssp));
> + asm volatile("saveprevssp");
> +}
> +
> +int test_shstk_pivot(void)
> +{
> + void *shstk = create_shstk(0);
> +
> + if (shstk == MAP_FAILED) {
> + printf("[FAIL]\tError creating shadow stack: %d\n", errno);
> + return 1;
> + }
> + try_shstk((unsigned long)shstk + SS_SIZE - 8);
> + free_shstk(shstk);
> +
> + printf("[OK]\tShadow stack pivot\n");
> + return 0;
> +}
> +
> +int test_shstk_faults(void)
> +{
> + unsigned long *shstk = create_shstk(0);
> +
> + /* Read shadow stack, test if it's zero to not get read optimized out */
> + if (*shstk != 0)
> + goto err;
> +
> + /* Wrss memory that was already read. */
> + write_shstk(shstk, 1);
> + if (*shstk != 1)
> + goto err;
> +
> + /* Page out memory, so we can wrss it again. */
> + if (reset_shstk((void *)shstk))
> + goto err;
> +
> + write_shstk(shstk, 1);
> + if (*shstk != 1)
> + goto err;
> +
> + printf("[OK]\tShadow stack faults\n");
> + return 0;
> +
> +err:
> + return 1;
> +}
> +
> +unsigned long saved_ssp;
> +unsigned long saved_ssp_val;
> +volatile bool segv_triggered;
> +
> +void __attribute__((noinline)) violate_ss(void)
> +{
> + saved_ssp = get_ssp();
> + saved_ssp_val = *(unsigned long *)saved_ssp;
> +
> + /* Corrupt shadow stack */
> + printf("[INFO]\tCorrupting shadow stack\n");
> + write_shstk((void *)saved_ssp, 0);
> +}
> +
> +void segv_handler(int signum, siginfo_t *si, void *uc)
> +{
> + printf("[INFO]\tGenerated shadow stack violation successfully\n");
> +
> + segv_triggered = true;
> +
> + /* Fix shadow stack */
> + write_shstk((void *)saved_ssp, saved_ssp_val);
> +}
> +
> +int test_shstk_violation(void)
> +{
> + struct sigaction sa = {};
> +
> + sa.sa_sigaction = segv_handler;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL))
> + return 1;
> +
> + segv_triggered = false;
> +
> + /* Make sure segv_triggered is set before violate_ss() */
> + asm volatile("" : : : "memory");
> +
> + violate_ss();
> +
> + signal(SIGSEGV, SIG_DFL);
> +
> + printf("[OK]\tShadow stack violation test\n");
> +
> + return !segv_triggered;
> +}
> +
> +/* Gup test state */
> +#define MAGIC_VAL 0x12345678
> +bool is_shstk_access;
> +void *shstk_ptr;
> +int fd;
> +
> +void reset_test_shstk(void *addr)
> +{
> + if (shstk_ptr)
> + free_shstk(shstk_ptr);
> + shstk_ptr = create_shstk(addr);
> +}
> +
> +void test_access_fix_handler(int signum, siginfo_t *si, void *uc)
> +{
> + printf("[INFO]\tViolation from %s\n", is_shstk_access ? "shstk access" : "normal write");
> +
> + segv_triggered = true;
> +
> + /* Fix shadow stack */
> + if (is_shstk_access) {
> + reset_test_shstk(shstk_ptr);
> + return;
> + }
> +
> + free_shstk(shstk_ptr);
> + create_normal_mem(shstk_ptr);
> +}
> +
> +bool test_shstk_access(void *ptr)
> +{
> + is_shstk_access = true;
> + segv_triggered = false;
> + write_shstk(ptr, MAGIC_VAL);
> +
> + asm volatile("" : : : "memory");
> +
> + return segv_triggered;
> +}
> +
> +bool test_write_access(void *ptr)
> +{
> + is_shstk_access = false;
> + segv_triggered = false;
> + *(unsigned long *)ptr = MAGIC_VAL;
> +
> + asm volatile("" : : : "memory");
> +
> + return segv_triggered;
> +}
> +
> +bool gup_write(void *ptr)
> +{
> + unsigned long val;
> +
> + lseek(fd, (unsigned long)ptr, SEEK_SET);
> + if (write(fd, &val, sizeof(val)) < 0)
> + return 1;
> +
> + return 0;
> +}
> +
> +bool gup_read(void *ptr)
> +{
> + unsigned long val;
> +
> + lseek(fd, (unsigned long)ptr, SEEK_SET);
> + if (read(fd, &val, sizeof(val)) < 0)
> + return 1;
> +
> + return 0;
> +}
> +
> +int test_gup(void)
> +{
> + struct sigaction sa = {};
> + int status;
> + pid_t pid;
> +
> + sa.sa_sigaction = test_access_fix_handler;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL))
> + return 1;
> +
> + segv_triggered = false;
> +
> + fd = open("/proc/self/mem", O_RDWR);
> + if (fd == -1)
> + return 1;
> +
> + reset_test_shstk(0);
> + if (gup_read(shstk_ptr))
> + return 1;
> + if (test_shstk_access(shstk_ptr))
> + return 1;
> + printf("[INFO]\tGup read -> shstk access success\n");
> +
> + reset_test_shstk(0);
> + if (gup_write(shstk_ptr))
> + return 1;
> + if (test_shstk_access(shstk_ptr))
> + return 1;
> + printf("[INFO]\tGup write -> shstk access success\n");
> +
> + reset_test_shstk(0);
> + if (gup_read(shstk_ptr))
> + return 1;
> + if (!test_write_access(shstk_ptr))
> + return 1;
> + printf("[INFO]\tGup read -> write access success\n");
> +
> + reset_test_shstk(0);
> + if (gup_write(shstk_ptr))
> + return 1;
> + if (!test_write_access(shstk_ptr))
> + return 1;
> + printf("[INFO]\tGup write -> write access success\n");
> +
> + close(fd);
> +
> + /* COW/gup test */
> + reset_test_shstk(0);
> + pid = fork();
> + if (!pid) {
> + fd = open("/proc/self/mem", O_RDWR);
> + if (fd == -1)
> + exit(1);
> +
> + if (gup_write(shstk_ptr)) {
> + close(fd);
> + exit(1);
> + }
> + close(fd);
> + exit(0);
> + }
> + waitpid(pid, &status, 0);
> + if (WEXITSTATUS(status)) {
> + printf("[FAIL]\tWrite in child failed\n");
> + return 1;
> + }
> + if (*(unsigned long *)shstk_ptr == MAGIC_VAL) {
> + printf("[FAIL]\tWrite in child wrote through to shared memory\n");
> + return 1;
> + }
> +
> + printf("[INFO]\tCow gup write -> write access success\n");
> +
> + free_shstk(shstk_ptr);
> +
> + signal(SIGSEGV, SIG_DFL);
> +
> + printf("[OK]\tShadow gup test\n");
> +
> + return 0;
> +}
> +
> +int test_mprotect(void)
> +{
> + struct sigaction sa = {};
> +
> + sa.sa_sigaction = test_access_fix_handler;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL))
> + return 1;
> +
> + segv_triggered = false;
> +
> + /* mprotect a shadow stack as read only */
> + reset_test_shstk(0);
> + if (mprotect(shstk_ptr, SS_SIZE, PROT_READ) < 0) {
> + printf("[FAIL]\tmprotect(PROT_READ) failed\n");
> + return 1;
> + }
> +
> + /* try to wrss it and fail */
> + if (!test_shstk_access(shstk_ptr)) {
> + printf("[FAIL]\tShadow stack access to read-only memory succeeded\n");
> + return 1;
> + }
> +
> + /*
> + * The shadow stack was reset above to resolve the fault, make the new one
> + * read-only.
> + */
> + if (mprotect(shstk_ptr, SS_SIZE, PROT_READ) < 0) {
> + printf("[FAIL]\tmprotect(PROT_READ) failed\n");
> + return 1;
> + }
> +
> + /* then back to writable */
> + if (mprotect(shstk_ptr, SS_SIZE, PROT_WRITE | PROT_READ) < 0) {
> + printf("[FAIL]\tmprotect(PROT_WRITE) failed\n");
> + return 1;
> + }
> +
> + /* then wrss to it and succeed */
> + if (test_shstk_access(shstk_ptr)) {
> + printf("[FAIL]\tShadow stack access to mprotect() writable memory failed\n");
> + return 1;
> + }
> +
> + free_shstk(shstk_ptr);
> +
> + signal(SIGSEGV, SIG_DFL);
> +
> + printf("[OK]\tmprotect() test\n");
> +
> + return 0;
> +}
> +
> +char zero[4096];
> +
> +static void *uffd_thread(void *arg)
> +{
> + struct uffdio_copy req;
> + int uffd = *(int *)arg;
> + struct uffd_msg msg;
> + int ret;
> +
> + while (1) {
> + ret = read(uffd, &msg, sizeof(msg));
> + if (ret > 0)
> + break;
> + else if (errno == EAGAIN)
> + continue;
> + return (void *)1;
> + }
> +
> + req.dst = msg.arg.pagefault.address;
> + req.src = (__u64)zero;
> + req.len = 4096;
> + req.mode = 0;
> +
> + if (ioctl(uffd, UFFDIO_COPY, &req))
> + return (void *)1;
> +
> + return (void *)0;
> +}
> +
> +int test_userfaultfd(void)
> +{
> + struct uffdio_register uffdio_register;
> + struct uffdio_api uffdio_api;
> + struct sigaction sa = {};
> + pthread_t thread;
> + void *res;
> + int uffd;
> +
> + sa.sa_sigaction = test_access_fix_handler;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL))
> + return 1;
> +
> + uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
> + if (uffd < 0) {
> + printf("[SKIP]\tUserfaultfd unavailable.\n");
> + return 0;
> + }
> +
> + reset_test_shstk(0);
> +
> + uffdio_api.api = UFFD_API;
> + uffdio_api.features = 0;
> + if (ioctl(uffd, UFFDIO_API, &uffdio_api))
> + goto err;
> +
> + uffdio_register.range.start = (__u64)shstk_ptr;
> + uffdio_register.range.len = 4096;
> + uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
> + if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
> + goto err;
> +
> + if (pthread_create(&thread, NULL, &uffd_thread, &uffd))
> + goto err;
> +
> + reset_shstk(shstk_ptr);
> + test_shstk_access(shstk_ptr);
> +
> + if (pthread_join(thread, &res))
> + goto err;
> +
> + if (test_shstk_access(shstk_ptr))
> + goto err;
> +
> + free_shstk(shstk_ptr);
> +
> + signal(SIGSEGV, SIG_DFL);
> +
> + if (!res)
> + printf("[OK]\tUserfaultfd test\n");
> + return !!res;
> +err:
> + free_shstk(shstk_ptr);
> + close(uffd);
> + signal(SIGSEGV, SIG_DFL);
> + return 1;
> +}
> +
> +/* Simple linked list for keeping track of mappings in test_guard_gap() */
> +struct node {
> + struct node *next;
> + void *mapping;
> +};
> +
> +/*
> + * This tests whether mmap will place other mappings in a shadow stack's guard
> + * gap. The steps are:
> + * 1. Finds an empty place by mapping and unmapping something.
> + * 2. Map a shadow stack in the middle of the known empty area.
> + * 3. Map a bunch of PAGE_SIZE mappings. These will use the search down
> + * direction, filling any gaps until it encounters the shadow stack's
> + * guard gap.
> + * 4. When a mapping lands below the shadow stack from step 2, then all
> + * of the above gaps are filled. The search down algorithm will have
> + * looked at the shadow stack gaps.
> + * 5. See if it landed in the gap.
> + */
> +int test_guard_gap_other_gaps(void)
> +{
> + void *free_area, *shstk, *test_map = (void *)0xFFFFFFFFFFFFFFFF;
> + struct node *head = NULL, *cur;
> +
> + free_area = mmap(0, SS_SIZE * 3, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + munmap(free_area, SS_SIZE * 3);
> +
> + shstk = create_shstk(free_area + SS_SIZE);
> + if (shstk == MAP_FAILED)
> + return 1;
> +
> + while (test_map > shstk) {
> + test_map = mmap(0, PAGE_SIZE, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + if (test_map == MAP_FAILED)
> + return 1;
> + cur = malloc(sizeof(*cur));
> + cur->mapping = test_map;
> +
> + cur->next = head;
> + head = cur;
> + }
> +
> + while (head) {
> + cur = head;
> + head = cur->next;
> + munmap(cur->mapping, PAGE_SIZE);
> + free(cur);
> + }
> +
> + free_shstk(shstk);
> +
> + if (shstk - test_map - PAGE_SIZE != PAGE_SIZE)
> + return 1;
> +
> + printf("[OK]\tGuard gap test, other mapping's gaps\n");
> +
> + return 0;
> +}
> +
> +/* Tests respecting the guard gap of the mapping getting placed */
> +int test_guard_gap_new_mappings_gaps(void)
> +{
> + void *free_area, *shstk_start, *test_map = (void *)0xFFFFFFFFFFFFFFFF;
> + struct node *head = NULL, *cur;
> + int ret = 0;
> +
> + free_area = mmap(0, PAGE_SIZE * 4, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + munmap(free_area, PAGE_SIZE * 4);
> +
> + /* Test letting map_shadow_stack find a free space */
> + shstk_start = mmap(free_area, PAGE_SIZE, PROT_READ | PROT_WRITE,
> + MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> + if (shstk_start == MAP_FAILED || shstk_start != free_area)
> + return 1;
> +
> + while (test_map > shstk_start) {
> + test_map = (void *)syscall(__NR_map_shadow_stack, 0, PAGE_SIZE, 0);
> + if (test_map == MAP_FAILED) {
> + printf("[INFO]\tmap_shadow_stack MAP_FAILED\n");
> + ret = 1;
> + break;
> + }
> +
> + cur = malloc(sizeof(*cur));
> + cur->mapping = test_map;
> +
> + cur->next = head;
> + head = cur;
> +
> + if (test_map == free_area + PAGE_SIZE) {
> + printf("[INFO]\tNew mapping has other mapping in guard gap!\n");
> + ret = 1;
> + break;
> + }
> + }
> +
> + while (head) {
> + cur = head;
> + head = cur->next;
> + munmap(cur->mapping, PAGE_SIZE);
> + free(cur);
> + }
> +
> + munmap(shstk_start, PAGE_SIZE);
> +
> + if (!ret)
> + printf("[OK]\tGuard gap test, placement mapping's gaps\n");
> +
> + return ret;
> +}
> +
> +/*
> + * Too complicated to pull it out of the 32 bit header, but also get the
> + * 64 bit one needed above. Just define a copy here.
> + */
> +#define __NR_compat_sigaction 67
> +
> +/*
> + * Call 32 bit signal handler to get 32 bit signals ABI. Make sure
> + * to push the registers that will get clobbered.
> + */
> +int sigaction32(int signum, const struct sigaction *restrict act,
> + struct sigaction *restrict oldact)
> +{
> + register long syscall_reg asm("eax") = __NR_compat_sigaction;
> + register long signum_reg asm("ebx") = signum;
> + register long act_reg asm("ecx") = (long)act;
> + register long oldact_reg asm("edx") = (long)oldact;
> + int ret = 0;
> +
> + asm volatile ("int $0x80;"
> + : "=a"(ret), "=m"(oldact)
> + : "r"(syscall_reg), "r"(signum_reg), "r"(act_reg),
> + "r"(oldact_reg)
> + : "r8", "r9", "r10", "r11"
> + );
> +
> + return ret;
> +}
> +
> +sigjmp_buf jmp_buffer;
> +enum shadow_stack_test _which_test;
> +void segv_gp_handler(int signum, siginfo_t *si, void *uc)
> +{
> + segv_triggered = true;
> +
> + /*
> + * To work with old glibc, this can't rely on siglongjmp working with
> + * shadow stack enabled, so disable shadow stack before siglongjmp().
> + */
> + SHADOW_STACK_DISABLE(_which_test);
> + siglongjmp(jmp_buffer, -1);
> +}
> +
> +/*
> + * Transition to 32 bit mode and check that a #GP triggers a segfault.
> + */
> +int test_32bit(void)
> +{
> + struct sigaction sa = {};
> + struct sigaction *sa32;
> +
> + /* Create sigaction in 32 bit address range */
> + sa32 = mmap(0, 4096, PROT_READ | PROT_WRITE,
> + MAP_32BIT | MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
> + sa32->sa_flags = SA_SIGINFO;
> +
> + sa.sa_sigaction = segv_gp_handler;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL))
> + return 1;
> +
> +
> + segv_triggered = false;
> +
> + /* Make sure segv_triggered is set before triggering the #GP */
> + asm volatile("" : : : "memory");
> +
> + /*
> + * Set handler to somewhere in 32 bit address space
> + */
> + sa32->sa_handler = (void *)sa32;
> + if (sigaction32(SIGUSR1, sa32, NULL))
> + return 1;
> +
> + if (!sigsetjmp(jmp_buffer, 1))
> + raise(SIGUSR1);
> +
> + if (segv_triggered)
> + printf("[OK]\t32 bit test\n");
> +
> + return !segv_triggered;
> +}
> +
> +static int parse_uint_from_file(const char *file, const char *fmt)
> +{
> + int err, ret;
> + FILE *f;
> +
> + f = fopen(file, "re");
> + if (!f) {
> + err = -errno;
> + printf("failed to open '%s': %d\n", file, err);
> + return err;
> + }
> + err = fscanf(f, fmt, &ret);
> + if (err != 1) {
> + err = err == EOF ? -EIO : -errno;
> + printf("failed to parse '%s': %d\n", file, err);
> + fclose(f);
> + return err;
> + }
> + fclose(f);
> + return ret;
> +}
> +
> +static int determine_uprobe_perf_type(void)
> +{
> + const char *file = "/sys/bus/event_source/devices/uprobe/type";
> +
> + return parse_uint_from_file(file, "%d\n");
> +}
> +
> +static int determine_uprobe_retprobe_bit(void)
> +{
> + const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";
> +
> + return parse_uint_from_file(file, "config:%d\n");
> +}
> +
> +static ssize_t get_uprobe_offset(const void *addr)
> +{
> + size_t start, end, base;
> + char buf[256];
> + bool found = false;
> + FILE *f;
> +
> + f = fopen("/proc/self/maps", "r");
> + if (!f)
> + return -errno;
> +
> + while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &base) == 4) {
> + if (buf[2] == 'x' && (uintptr_t)addr >= start && (uintptr_t)addr < end) {
> + found = true;
> + break;
> + }
> + }
> +
> + fclose(f);
> +
> + if (!found)
> + return -ESRCH;
> +
> + return (uintptr_t)addr - start + base;
> +}
> +
> +static __attribute__((noinline)) void uretprobe_trigger(void)
> +{
> + asm volatile ("");
> +}
> +
> +/*
> + * This test setups return uprobe, which is sensitive to shadow stack
> + * (crashes without extra fix). After executing the uretprobe we fail
> + * the test if we receive SIGSEGV, no crash means we're good.
> + *
> + * Helper functions above borrowed from bpf selftests.
> + */
> +static int test_uretprobe(enum shadow_stack_test which_test)
> +{
> + const size_t attr_sz = sizeof(struct perf_event_attr);
> + const char *file = "/proc/self/exe";
> + int bit, fd = 0, type, err = 1;
> + struct perf_event_attr attr;
> + struct sigaction sa = {};
> + ssize_t offset;
> +
> + type = determine_uprobe_perf_type();
> + if (type < 0) {
> + if (type == -ENOENT)
> + printf("[SKIP]\tUretprobe test, uprobes are not available\n");
> + return 0;
> + }
> +
> + offset = get_uprobe_offset(uretprobe_trigger);
> + if (offset < 0)
> + return 1;
> +
> + bit = determine_uprobe_retprobe_bit();
> + if (bit < 0)
> + return 1;
> +
> + sa.sa_sigaction = segv_gp_handler;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL))
> + return 1;
> +
> + /* Setup return uprobe through perf event interface. */
> + memset(&attr, 0, attr_sz);
> + attr.size = attr_sz;
> + attr.type = type;
> + attr.config = 1 << bit;
> + attr.config1 = (__u64) (unsigned long) file;
> + attr.config2 = offset;
> +
> + fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,
> + -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
> + if (fd < 0)
> + goto out;
> +
> + if (sigsetjmp(jmp_buffer, 1))
> + goto out;
> +
> + SHADOW_STACK_ENABLE(which_test);
> +
> + /*
> + * This either segfaults and goes through sigsetjmp above
> + * or succeeds and we're good.
> + */
> + uretprobe_trigger();
> +
> + printf("[OK]\tUretprobe test\n");
> + err = 0;
> +
> +out:
> + SHADOW_STACK_DISABLE(which_test);
> + signal(SIGSEGV, SIG_DFL);
> + if (fd)
> + close(fd);
> + return err;
> +}
> +
> +/* Keep the CALL first so the function address is exactly the probed CALL. */
> +extern void uprobe_call_trigger(void);
> +asm (".pushsection .text\n"
> + ".global uprobe_call_target\n"
> + ".type uprobe_call_target, @function\n"
> + "uprobe_call_target:\n"
> + " ret\n"
> + ".size uprobe_call_target, .-uprobe_call_target\n"
> +
> + ".global uprobe_call_trigger\n"
> + ".type uprobe_call_trigger, @function\n"
> + "uprobe_call_trigger:\n"
> + " call uprobe_call_target\n"
> + " ret\n"
> + ".size uprobe_call_trigger, .-uprobe_call_trigger\n"
> + ".popsection\n"
> +);
> +
> +/* If CALL emulation misses the shadow stack update, this exits via SIGSEGV. */
> +static int test_uprobe_call(enum shadow_stack_test which_test)
> +{
> + const size_t attr_sz = sizeof(struct perf_event_attr);
> + const char *file = "/proc/self/exe";
> + int fd = -1, type, err = 1;
> + struct perf_event_attr attr;
> + struct sigaction sa = {};
> + ssize_t offset;
> +
> + type = determine_uprobe_perf_type();
> + if (type < 0) {
> + if (type == -ENOENT)
> + printf("[SKIP]\tUprobe on CALL test, uprobes are not available\n");
> + return 0;
> + }
> +
> + offset = get_uprobe_offset(uprobe_call_trigger);
> + if (offset < 0)
> + return 1;
> +
> + sa.sa_sigaction = segv_gp_handler;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL))
> + return 1;
> +
> + /* Setup entry uprobe through perf event interface. */
> + memset(&attr, 0, attr_sz);
> + attr.size = attr_sz;
> + attr.type = type;
> + attr.config = 0;
> + attr.config1 = (__u64)(unsigned long)file;
> + attr.config2 = offset;
> +
> + fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,
> + -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
> + if (fd < 0)
> + goto out;
> +
> + if (sigsetjmp(jmp_buffer, 1))
> + goto out;
> +
> + if (SHADOW_STACK_ENABLE(which_test))
> + goto out;
> +
> + /*
> + * This either segfaults and goes through sigsetjmp above
> + * or succeeds and we're good.
> + */
> + uprobe_call_trigger();
> +
> + printf("[OK]\tUprobe on CALL test\n");
> + err = 0;
> +
> +out:
> + SHADOW_STACK_DISABLE(which_test);
> + signal(SIGSEGV, SIG_DFL);
> + if (fd >= 0)
> + close(fd);
> + return err;
> +}
> +
> +void segv_handler_ptrace(int signum, siginfo_t *si, void *uc)
> +{
> + /* The SSP adjustment caused a segfault. */
> + exit(0);
> +}
> +
> +int test_ptrace(void)
> +{
> + unsigned long saved_ssp, ssp = 0;
> + struct sigaction sa = {};
> + struct iovec iov;
> + int status;
> + int pid;
> +
> + iov.iov_base = &ssp;
> + iov.iov_len = sizeof(ssp);
> +
> + pid = fork();
> + if (!pid) {
> + ssp = get_ssp();
> +
> + sa.sa_sigaction = segv_handler_ptrace;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL))
> + return 1;
> +
> + ptrace(PTRACE_TRACEME, NULL, NULL, NULL);
> + /*
> + * The parent will tweak the SSP and return from this function
> + * will #CP.
> + */
> + raise(SIGTRAP);
> +
> + exit(1);
> + }
> +
> + while (waitpid(pid, &status, 0) != -1 && WSTOPSIG(status) != SIGTRAP);
> +
> + if (ptrace(PTRACE_GETREGSET, pid, NT_X86_SHSTK, &iov)) {
> + printf("[INFO]\tFailed to PTRACE_GETREGS\n");
> + goto out_kill;
> + }
> +
> + if (!ssp) {
> + printf("[INFO]\tPtrace child SSP was 0\n");
> + goto out_kill;
> + }
> +
> + saved_ssp = ssp;
> +
> + iov.iov_len = 0;
> + if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> + printf("[INFO]\tToo small size accepted via PTRACE_SETREGS\n");
> + goto out_kill;
> + }
> +
> + iov.iov_len = sizeof(ssp) + 1;
> + if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> + printf("[INFO]\tToo large size accepted via PTRACE_SETREGS\n");
> + goto out_kill;
> + }
> +
> + ssp += 1;
> + if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> + printf("[INFO]\tUnaligned SSP written via PTRACE_SETREGS\n");
> + goto out_kill;
> + }
> +
> + ssp = 0xFFFFFFFFFFFF0000;
> + if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> + printf("[INFO]\tKernel range SSP written via PTRACE_SETREGS\n");
> + goto out_kill;
> + }
> +
> + /*
> + * Tweak the SSP so the child with #CP when it resumes and returns
> + * from raise()
> + */
> + ssp = saved_ssp + 8;
> + iov.iov_len = sizeof(ssp);
> + if (ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> + printf("[INFO]\tFailed to PTRACE_SETREGS\n");
> + goto out_kill;
> + }
> +
> + if (ptrace(PTRACE_DETACH, pid, NULL, NULL)) {
> + printf("[INFO]\tFailed to PTRACE_DETACH\n");
> + goto out_kill;
> + }
> +
> + waitpid(pid, &status, 0);
> + if (WEXITSTATUS(status))
> + return 1;
> +
> + printf("[OK]\tPtrace test\n");
> + return 0;
> +
> +out_kill:
> + kill(pid, SIGKILL);
> + return 1;
> +}
> +
> +#if (__GNUC__ < 8) || (__GNUC__ == 8 && __GNUC_MINOR__ < 5)
> +int shadow_stack_run_tests(enum shadow_stack_test unused)
> +{
> + printf("[SKIP]\tCompiler does not support CET.\n");
> + return 0;
> +}
> +#else
> +int shadow_stack_run_tests(enum shadow_stack_test which_test)
> +{
> + int ret = 0;
> +
> + if (SHADOW_STACK_ENABLE(which_test)) {
> + printf("[SKIP]\tCould not enable Shadow stack\n");
> + return 1;
> + }
> +
> + if (SHADOW_STACK_DISABLE(which_test)) {
> + ret = 1;
> + printf("[FAIL]\tDisabling shadow stack failed\n");
> + }
> +
> + if (SHADOW_STACK_ENABLE(which_test)) {
> + printf("[SKIP]\tCould not re-enable Shadow stack\n");
> + return 1;
> + }
> +
> + if (SHADOW_STACK_ENABLE_WRITE(which_test)) {
> + printf("[SKIP]\tCould not enable WRSS\n");
> + ret = 1;
> + goto out;
> + }
> +
> + /* Should have succeeded if here, but this is a test, so double check. */
> + if (!get_ssp()) {
> + printf("[FAIL]\tShadow stack disabled\n");
> + return 1;
> + }
> +
> + if (test_shstk_pivot()) {
> + ret = 1;
> + printf("[FAIL]\tShadow stack pivot\n");
> + goto out;
> + }
> +
> + if (test_shstk_faults()) {
> + ret = 1;
> + printf("[FAIL]\tShadow stack fault test\n");
> + goto out;
> + }
> +
> + if (test_shstk_violation()) {
> + ret = 1;
> + printf("[FAIL]\tShadow stack violation test\n");
> + goto out;
> + }
> +
> + if (test_gup()) {
> + ret = 1;
> + printf("[FAIL]\tShadow shadow stack gup\n");
> + goto out;
> + }
> +
> + if (test_mprotect()) {
> + ret = 1;
> + printf("[FAIL]\tShadow shadow mprotect test\n");
> + goto out;
> + }
> +
> + if (test_userfaultfd()) {
> + ret = 1;
> + printf("[FAIL]\tUserfaultfd test\n");
> + goto out;
> + }
> +
> + if (test_guard_gap_other_gaps()) {
> + ret = 1;
> + printf("[FAIL]\tGuard gap test, other mappings' gaps\n");
> + goto out;
> + }
> +
> + if (test_guard_gap_new_mappings_gaps()) {
> + ret = 1;
> + printf("[FAIL]\tGuard gap test, placement mapping's gaps\n");
> + goto out;
> + }
> +
> + if (test_ptrace()) {
> + ret = 1;
> + printf("[FAIL]\tptrace test\n");
> + }
> +
> + if (test_32bit()) {
> + ret = 1;
> + printf("[FAIL]\t32 bit test\n");
> + goto out;
> + }
> +
> + if (test_uretprobe(which_test)) {
> + ret = 1;
> + printf("[FAIL]\turetprobe test\n");
> + goto out;
> + }
> +
> + if (test_uprobe_call(which_test)) {
> + ret = 1;
> + printf("[FAIL]\tuprobe on CALL test\n");
> + goto out;
> + }
> +
> + return ret;
> +
> +out:
> + /*
> + * Disable shadow stack before the function returns, or there will be a
> + * shadow stack violation.
> + */
> + if (SHADOW_STACK_DISABLE(which_test)) {
> + ret = 1;
> + printf("[FAIL]\tDisabling shadow stack failed\n");
> + }
> +
> + return ret;
> +}
> +#endif
> diff --git a/tools/testing/selftests/x86/shadow_stack.h b/tools/testing/selftests/x86/shadow_stack.h
> new file mode 100644
> index 000000000000..d36a44df7387
> --- /dev/null
> +++ b/tools/testing/selftests/x86/shadow_stack.h
> @@ -0,0 +1,14 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#ifndef TOOLS_TESTING_SELFTESTS_X86_SHADOW_STACK_H_
> +#define TOOLS_TESTING_SELFTESTS_X86_SHADOW_STACK_H_
> +
> +enum shadow_stack_test {
> + SHADOW_STACK_TEST_ARCH_PRCTL,
> + SHADOW_STACK_TEST_PRCTL,
> + SHADOW_STACK_TEST_COUNT,
> +};
> +
> +int shadow_stack_run_tests(enum shadow_stack_test which_test);
> +
> +#endif /* TOOLS_TESTING_SELFTESTS_X86_SHADOW_STACK_H_ */
> diff --git a/tools/testing/selftests/x86/test_shadow_stack.c b/tools/testing/selftests/x86/test_shadow_stack.c
> index 3d6ca33edba4..d89c04623001 100644
> --- a/tools/testing/selftests/x86/test_shadow_stack.c
> +++ b/tools/testing/selftests/x86/test_shadow_stack.c
> @@ -1,1174 +1,21 @@
> // SPDX-License-Identifier: GPL-2.0
> +
> /*
> * This program test's basic kernel shadow stack support. It enables shadow
> * stack manual via the arch_prctl(), instead of relying on glibc. It's
> * Makefile doesn't compile with shadow stack support, so it doesn't rely on
> * any particular glibc. As a result it can't do any operations that require
> * special glibc shadow stack support (longjmp(), swapcontext(), etc). Just
> - * stick to the basics and hope the compiler doesn't do anything strange.
> + * stick to the basics and hope the compiler doesn't do anything strange. It
> + * uses the x86 specific interface for ARCH_PCTL, whereas
> + * test_shadow_stack_prctl.c uses the generic PRCTL interface mixed with x86
> + * specific code.
> */
> -
> #define _GNU_SOURCE
>
> -#include <sys/syscall.h>
> -#include <asm/mman.h>
> -#include <sys/mman.h>
> -#include <sys/stat.h>
> -#include <sys/wait.h>
> -#include <stdio.h>
> -#include <stdlib.h>
> -#include <fcntl.h>
> -#include <unistd.h>
> -#include <string.h>
> -#include <errno.h>
> -#include <stdbool.h>
> -#include <x86intrin.h>
> -#include <asm/prctl.h>
> -#include <sys/prctl.h>
> -#include <stdint.h>
> -#include <signal.h>
> -#include <pthread.h>
> -#include <sys/ioctl.h>
> -#include <linux/userfaultfd.h>
> -#include <setjmp.h>
> -#include <sys/ptrace.h>
> -#include <sys/signal.h>
> -#include <linux/elf.h>
> -#include <linux/perf_event.h>
> -
> -/*
> - * Define the ABI defines if needed, so people can run the tests
> - * without building the headers.
> - */
> -#ifndef __NR_map_shadow_stack
> -#define __NR_map_shadow_stack 453
> -
> -#define SHADOW_STACK_SET_TOKEN (1ULL << 0)
> -
> -#define ARCH_SHSTK_ENABLE 0x5001
> -#define ARCH_SHSTK_DISABLE 0x5002
> -#define ARCH_SHSTK_LOCK 0x5003
> -#define ARCH_SHSTK_UNLOCK 0x5004
> -#define ARCH_SHSTK_STATUS 0x5005
> -
> -#define ARCH_SHSTK_SHSTK (1ULL << 0)
> -#define ARCH_SHSTK_WRSS (1ULL << 1)
> -
> -#define NT_X86_SHSTK 0x204
> -#endif
> -
> -#define SS_SIZE 0x200000
> -#define PAGE_SIZE 0x1000
> -
> -#if (__GNUC__ < 8) || (__GNUC__ == 8 && __GNUC_MINOR__ < 5)
> -int main(int argc, char *argv[])
> -{
> - printf("[SKIP]\tCompiler does not support CET.\n");
> - return 0;
> -}
> -#else
> -void write_shstk(unsigned long *addr, unsigned long val)
> -{
> - asm volatile("wrssq %[val], (%[addr])\n"
> - : "=m" (addr)
> - : [addr] "r" (addr), [val] "r" (val));
> -}
> -
> -static inline unsigned long __attribute__((always_inline)) get_ssp(void)
> -{
> - unsigned long ret = 0;
> -
> - asm volatile("xor %0, %0; rdsspq %0" : "=r" (ret));
> - return ret;
> -}
> -
> -/*
> - * For use in inline enablement of shadow stack.
> - *
> - * The program can't return from the point where shadow stack gets enabled
> - * because there will be no address on the shadow stack. So it can't use
> - * syscall() for enablement, since it is a function.
> - *
> - * Based on code from nolibc.h. Keep a copy here because this can't pull in all
> - * of nolibc.h.
> - */
> -#define ARCH_PRCTL(arg1, arg2) \
> -({ \
> - long _ret; \
> - register long _num asm("eax") = __NR_arch_prctl; \
> - register long _arg1 asm("rdi") = (long)(arg1); \
> - register long _arg2 asm("rsi") = (long)(arg2); \
> - \
> - asm volatile ( \
> - "syscall\n" \
> - : "=a"(_ret) \
> - : "r"(_arg1), "r"(_arg2), \
> - "0"(_num) \
> - : "rcx", "r11", "memory", "cc" \
> - ); \
> - _ret; \
> -})
> -
> -void *create_shstk(void *addr)
> -{
> - return (void *)syscall(__NR_map_shadow_stack, addr, SS_SIZE, SHADOW_STACK_SET_TOKEN);
> -}
> -
> -void *create_normal_mem(void *addr)
> -{
> - return mmap(addr, SS_SIZE, PROT_READ | PROT_WRITE,
> - MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
> -}
> -
> -void free_shstk(void *shstk)
> -{
> - munmap(shstk, SS_SIZE);
> -}
> -
> -int reset_shstk(void *shstk)
> -{
> - return madvise(shstk, SS_SIZE, MADV_DONTNEED);
> -}
> -
> -void try_shstk(unsigned long new_ssp)
> -{
> - unsigned long ssp;
> -
> - printf("[INFO]\tnew_ssp = %lx, *new_ssp = %lx\n",
> - new_ssp, *((unsigned long *)new_ssp));
> -
> - ssp = get_ssp();
> - printf("[INFO]\tchanging ssp from %lx to %lx\n", ssp, new_ssp);
> -
> - asm volatile("rstorssp (%0)\n":: "r" (new_ssp));
> - asm volatile("saveprevssp");
> - printf("[INFO]\tssp is now %lx\n", get_ssp());
> -
> - /* Switch back to original shadow stack */
> - ssp -= 8;
> - asm volatile("rstorssp (%0)\n":: "r" (ssp));
> - asm volatile("saveprevssp");
> -}
> -
> -int test_shstk_pivot(void)
> -{
> - void *shstk = create_shstk(0);
> -
> - if (shstk == MAP_FAILED) {
> - printf("[FAIL]\tError creating shadow stack: %d\n", errno);
> - return 1;
> - }
> - try_shstk((unsigned long)shstk + SS_SIZE - 8);
> - free_shstk(shstk);
> -
> - printf("[OK]\tShadow stack pivot\n");
> - return 0;
> -}
> -
> -int test_shstk_faults(void)
> -{
> - unsigned long *shstk = create_shstk(0);
> -
> - /* Read shadow stack, test if it's zero to not get read optimized out */
> - if (*shstk != 0)
> - goto err;
> -
> - /* Wrss memory that was already read. */
> - write_shstk(shstk, 1);
> - if (*shstk != 1)
> - goto err;
> -
> - /* Page out memory, so we can wrss it again. */
> - if (reset_shstk((void *)shstk))
> - goto err;
> -
> - write_shstk(shstk, 1);
> - if (*shstk != 1)
> - goto err;
> -
> - printf("[OK]\tShadow stack faults\n");
> - return 0;
> -
> -err:
> - return 1;
> -}
> -
> -unsigned long saved_ssp;
> -unsigned long saved_ssp_val;
> -volatile bool segv_triggered;
> -
> -void __attribute__((noinline)) violate_ss(void)
> -{
> - saved_ssp = get_ssp();
> - saved_ssp_val = *(unsigned long *)saved_ssp;
> -
> - /* Corrupt shadow stack */
> - printf("[INFO]\tCorrupting shadow stack\n");
> - write_shstk((void *)saved_ssp, 0);
> -}
> -
> -void segv_handler(int signum, siginfo_t *si, void *uc)
> -{
> - printf("[INFO]\tGenerated shadow stack violation successfully\n");
> -
> - segv_triggered = true;
> -
> - /* Fix shadow stack */
> - write_shstk((void *)saved_ssp, saved_ssp_val);
> -}
> -
> -int test_shstk_violation(void)
> -{
> - struct sigaction sa = {};
> -
> - sa.sa_sigaction = segv_handler;
> - sa.sa_flags = SA_SIGINFO;
> - if (sigaction(SIGSEGV, &sa, NULL))
> - return 1;
> -
> - segv_triggered = false;
> -
> - /* Make sure segv_triggered is set before violate_ss() */
> - asm volatile("" : : : "memory");
> -
> - violate_ss();
> -
> - signal(SIGSEGV, SIG_DFL);
> -
> - printf("[OK]\tShadow stack violation test\n");
> -
> - return !segv_triggered;
> -}
> -
> -/* Gup test state */
> -#define MAGIC_VAL 0x12345678
> -bool is_shstk_access;
> -void *shstk_ptr;
> -int fd;
> -
> -void reset_test_shstk(void *addr)
> -{
> - if (shstk_ptr)
> - free_shstk(shstk_ptr);
> - shstk_ptr = create_shstk(addr);
> -}
> -
> -void test_access_fix_handler(int signum, siginfo_t *si, void *uc)
> -{
> - printf("[INFO]\tViolation from %s\n", is_shstk_access ? "shstk access" : "normal write");
> -
> - segv_triggered = true;
> -
> - /* Fix shadow stack */
> - if (is_shstk_access) {
> - reset_test_shstk(shstk_ptr);
> - return;
> - }
> -
> - free_shstk(shstk_ptr);
> - create_normal_mem(shstk_ptr);
> -}
> -
> -bool test_shstk_access(void *ptr)
> -{
> - is_shstk_access = true;
> - segv_triggered = false;
> - write_shstk(ptr, MAGIC_VAL);
> -
> - asm volatile("" : : : "memory");
> -
> - return segv_triggered;
> -}
> -
> -bool test_write_access(void *ptr)
> -{
> - is_shstk_access = false;
> - segv_triggered = false;
> - *(unsigned long *)ptr = MAGIC_VAL;
> -
> - asm volatile("" : : : "memory");
> -
> - return segv_triggered;
> -}
> -
> -bool gup_write(void *ptr)
> -{
> - unsigned long val;
> -
> - lseek(fd, (unsigned long)ptr, SEEK_SET);
> - if (write(fd, &val, sizeof(val)) < 0)
> - return 1;
> -
> - return 0;
> -}
> -
> -bool gup_read(void *ptr)
> -{
> - unsigned long val;
> -
> - lseek(fd, (unsigned long)ptr, SEEK_SET);
> - if (read(fd, &val, sizeof(val)) < 0)
> - return 1;
> -
> - return 0;
> -}
> -
> -int test_gup(void)
> -{
> - struct sigaction sa = {};
> - int status;
> - pid_t pid;
> -
> - sa.sa_sigaction = test_access_fix_handler;
> - sa.sa_flags = SA_SIGINFO;
> - if (sigaction(SIGSEGV, &sa, NULL))
> - return 1;
> -
> - segv_triggered = false;
> -
> - fd = open("/proc/self/mem", O_RDWR);
> - if (fd == -1)
> - return 1;
> -
> - reset_test_shstk(0);
> - if (gup_read(shstk_ptr))
> - return 1;
> - if (test_shstk_access(shstk_ptr))
> - return 1;
> - printf("[INFO]\tGup read -> shstk access success\n");
> -
> - reset_test_shstk(0);
> - if (gup_write(shstk_ptr))
> - return 1;
> - if (test_shstk_access(shstk_ptr))
> - return 1;
> - printf("[INFO]\tGup write -> shstk access success\n");
> -
> - reset_test_shstk(0);
> - if (gup_read(shstk_ptr))
> - return 1;
> - if (!test_write_access(shstk_ptr))
> - return 1;
> - printf("[INFO]\tGup read -> write access success\n");
> -
> - reset_test_shstk(0);
> - if (gup_write(shstk_ptr))
> - return 1;
> - if (!test_write_access(shstk_ptr))
> - return 1;
> - printf("[INFO]\tGup write -> write access success\n");
> -
> - close(fd);
> -
> - /* COW/gup test */
> - reset_test_shstk(0);
> - pid = fork();
> - if (!pid) {
> - fd = open("/proc/self/mem", O_RDWR);
> - if (fd == -1)
> - exit(1);
> -
> - if (gup_write(shstk_ptr)) {
> - close(fd);
> - exit(1);
> - }
> - close(fd);
> - exit(0);
> - }
> - waitpid(pid, &status, 0);
> - if (WEXITSTATUS(status)) {
> - printf("[FAIL]\tWrite in child failed\n");
> - return 1;
> - }
> - if (*(unsigned long *)shstk_ptr == MAGIC_VAL) {
> - printf("[FAIL]\tWrite in child wrote through to shared memory\n");
> - return 1;
> - }
> -
> - printf("[INFO]\tCow gup write -> write access success\n");
> -
> - free_shstk(shstk_ptr);
> -
> - signal(SIGSEGV, SIG_DFL);
> -
> - printf("[OK]\tShadow gup test\n");
> -
> - return 0;
> -}
> -
> -int test_mprotect(void)
> -{
> - struct sigaction sa = {};
> -
> - sa.sa_sigaction = test_access_fix_handler;
> - sa.sa_flags = SA_SIGINFO;
> - if (sigaction(SIGSEGV, &sa, NULL))
> - return 1;
> -
> - segv_triggered = false;
> -
> - /* mprotect a shadow stack as read only */
> - reset_test_shstk(0);
> - if (mprotect(shstk_ptr, SS_SIZE, PROT_READ) < 0) {
> - printf("[FAIL]\tmprotect(PROT_READ) failed\n");
> - return 1;
> - }
> -
> - /* try to wrss it and fail */
> - if (!test_shstk_access(shstk_ptr)) {
> - printf("[FAIL]\tShadow stack access to read-only memory succeeded\n");
> - return 1;
> - }
> -
> - /*
> - * The shadow stack was reset above to resolve the fault, make the new one
> - * read-only.
> - */
> - if (mprotect(shstk_ptr, SS_SIZE, PROT_READ) < 0) {
> - printf("[FAIL]\tmprotect(PROT_READ) failed\n");
> - return 1;
> - }
> -
> - /* then back to writable */
> - if (mprotect(shstk_ptr, SS_SIZE, PROT_WRITE | PROT_READ) < 0) {
> - printf("[FAIL]\tmprotect(PROT_WRITE) failed\n");
> - return 1;
> - }
> -
> - /* then wrss to it and succeed */
> - if (test_shstk_access(shstk_ptr)) {
> - printf("[FAIL]\tShadow stack access to mprotect() writable memory failed\n");
> - return 1;
> - }
> -
> - free_shstk(shstk_ptr);
> -
> - signal(SIGSEGV, SIG_DFL);
> -
> - printf("[OK]\tmprotect() test\n");
> -
> - return 0;
> -}
> -
> -char zero[4096];
> -
> -static void *uffd_thread(void *arg)
> -{
> - struct uffdio_copy req;
> - int uffd = *(int *)arg;
> - struct uffd_msg msg;
> - int ret;
> -
> - while (1) {
> - ret = read(uffd, &msg, sizeof(msg));
> - if (ret > 0)
> - break;
> - else if (errno == EAGAIN)
> - continue;
> - return (void *)1;
> - }
> -
> - req.dst = msg.arg.pagefault.address;
> - req.src = (__u64)zero;
> - req.len = 4096;
> - req.mode = 0;
> -
> - if (ioctl(uffd, UFFDIO_COPY, &req))
> - return (void *)1;
> -
> - return (void *)0;
> -}
> -
> -int test_userfaultfd(void)
> -{
> - struct uffdio_register uffdio_register;
> - struct uffdio_api uffdio_api;
> - struct sigaction sa = {};
> - pthread_t thread;
> - void *res;
> - int uffd;
> -
> - sa.sa_sigaction = test_access_fix_handler;
> - sa.sa_flags = SA_SIGINFO;
> - if (sigaction(SIGSEGV, &sa, NULL))
> - return 1;
> -
> - uffd = syscall(__NR_userfaultfd, O_CLOEXEC | O_NONBLOCK);
> - if (uffd < 0) {
> - printf("[SKIP]\tUserfaultfd unavailable.\n");
> - return 0;
> - }
> -
> - reset_test_shstk(0);
> -
> - uffdio_api.api = UFFD_API;
> - uffdio_api.features = 0;
> - if (ioctl(uffd, UFFDIO_API, &uffdio_api))
> - goto err;
> -
> - uffdio_register.range.start = (__u64)shstk_ptr;
> - uffdio_register.range.len = 4096;
> - uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
> - if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
> - goto err;
> -
> - if (pthread_create(&thread, NULL, &uffd_thread, &uffd))
> - goto err;
> -
> - reset_shstk(shstk_ptr);
> - test_shstk_access(shstk_ptr);
> -
> - if (pthread_join(thread, &res))
> - goto err;
> -
> - if (test_shstk_access(shstk_ptr))
> - goto err;
> -
> - free_shstk(shstk_ptr);
> -
> - signal(SIGSEGV, SIG_DFL);
> -
> - if (!res)
> - printf("[OK]\tUserfaultfd test\n");
> - return !!res;
> -err:
> - free_shstk(shstk_ptr);
> - close(uffd);
> - signal(SIGSEGV, SIG_DFL);
> - return 1;
> -}
> -
> -/* Simple linked list for keeping track of mappings in test_guard_gap() */
> -struct node {
> - struct node *next;
> - void *mapping;
> -};
> -
> -/*
> - * This tests whether mmap will place other mappings in a shadow stack's guard
> - * gap. The steps are:
> - * 1. Finds an empty place by mapping and unmapping something.
> - * 2. Map a shadow stack in the middle of the known empty area.
> - * 3. Map a bunch of PAGE_SIZE mappings. These will use the search down
> - * direction, filling any gaps until it encounters the shadow stack's
> - * guard gap.
> - * 4. When a mapping lands below the shadow stack from step 2, then all
> - * of the above gaps are filled. The search down algorithm will have
> - * looked at the shadow stack gaps.
> - * 5. See if it landed in the gap.
> - */
> -int test_guard_gap_other_gaps(void)
> -{
> - void *free_area, *shstk, *test_map = (void *)0xFFFFFFFFFFFFFFFF;
> - struct node *head = NULL, *cur;
> -
> - free_area = mmap(0, SS_SIZE * 3, PROT_READ | PROT_WRITE,
> - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> - munmap(free_area, SS_SIZE * 3);
> -
> - shstk = create_shstk(free_area + SS_SIZE);
> - if (shstk == MAP_FAILED)
> - return 1;
> -
> - while (test_map > shstk) {
> - test_map = mmap(0, PAGE_SIZE, PROT_READ | PROT_WRITE,
> - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> - if (test_map == MAP_FAILED)
> - return 1;
> - cur = malloc(sizeof(*cur));
> - cur->mapping = test_map;
> -
> - cur->next = head;
> - head = cur;
> - }
> -
> - while (head) {
> - cur = head;
> - head = cur->next;
> - munmap(cur->mapping, PAGE_SIZE);
> - free(cur);
> - }
> -
> - free_shstk(shstk);
> -
> - if (shstk - test_map - PAGE_SIZE != PAGE_SIZE)
> - return 1;
> -
> - printf("[OK]\tGuard gap test, other mapping's gaps\n");
> -
> - return 0;
> -}
> -
> -/* Tests respecting the guard gap of the mapping getting placed */
> -int test_guard_gap_new_mappings_gaps(void)
> -{
> - void *free_area, *shstk_start, *test_map = (void *)0xFFFFFFFFFFFFFFFF;
> - struct node *head = NULL, *cur;
> - int ret = 0;
> -
> - free_area = mmap(0, PAGE_SIZE * 4, PROT_READ | PROT_WRITE,
> - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> - munmap(free_area, PAGE_SIZE * 4);
> -
> - /* Test letting map_shadow_stack find a free space */
> - shstk_start = mmap(free_area, PAGE_SIZE, PROT_READ | PROT_WRITE,
> - MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
> - if (shstk_start == MAP_FAILED || shstk_start != free_area)
> - return 1;
> -
> - while (test_map > shstk_start) {
> - test_map = (void *)syscall(__NR_map_shadow_stack, 0, PAGE_SIZE, 0);
> - if (test_map == MAP_FAILED) {
> - printf("[INFO]\tmap_shadow_stack MAP_FAILED\n");
> - ret = 1;
> - break;
> - }
> -
> - cur = malloc(sizeof(*cur));
> - cur->mapping = test_map;
> -
> - cur->next = head;
> - head = cur;
> -
> - if (test_map == free_area + PAGE_SIZE) {
> - printf("[INFO]\tNew mapping has other mapping in guard gap!\n");
> - ret = 1;
> - break;
> - }
> - }
> -
> - while (head) {
> - cur = head;
> - head = cur->next;
> - munmap(cur->mapping, PAGE_SIZE);
> - free(cur);
> - }
> -
> - munmap(shstk_start, PAGE_SIZE);
> -
> - if (!ret)
> - printf("[OK]\tGuard gap test, placement mapping's gaps\n");
> -
> - return ret;
> -}
> -
> -/*
> - * Too complicated to pull it out of the 32 bit header, but also get the
> - * 64 bit one needed above. Just define a copy here.
> - */
> -#define __NR_compat_sigaction 67
> -
> -/*
> - * Call 32 bit signal handler to get 32 bit signals ABI. Make sure
> - * to push the registers that will get clobbered.
> - */
> -int sigaction32(int signum, const struct sigaction *restrict act,
> - struct sigaction *restrict oldact)
> -{
> - register long syscall_reg asm("eax") = __NR_compat_sigaction;
> - register long signum_reg asm("ebx") = signum;
> - register long act_reg asm("ecx") = (long)act;
> - register long oldact_reg asm("edx") = (long)oldact;
> - int ret = 0;
> -
> - asm volatile ("int $0x80;"
> - : "=a"(ret), "=m"(oldact)
> - : "r"(syscall_reg), "r"(signum_reg), "r"(act_reg),
> - "r"(oldact_reg)
> - : "r8", "r9", "r10", "r11"
> - );
> -
> - return ret;
> -}
> -
> -sigjmp_buf jmp_buffer;
> -
> -void segv_gp_handler(int signum, siginfo_t *si, void *uc)
> -{
> - segv_triggered = true;
> -
> - /*
> - * To work with old glibc, this can't rely on siglongjmp working with
> - * shadow stack enabled, so disable shadow stack before siglongjmp().
> - */
> - ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
> - siglongjmp(jmp_buffer, -1);
> -}
> -
> -/*
> - * Transition to 32 bit mode and check that a #GP triggers a segfault.
> - */
> -int test_32bit(void)
> -{
> - struct sigaction sa = {};
> - struct sigaction *sa32;
> -
> - /* Create sigaction in 32 bit address range */
> - sa32 = mmap(0, 4096, PROT_READ | PROT_WRITE,
> - MAP_32BIT | MAP_PRIVATE | MAP_ANONYMOUS, 0, 0);
> - sa32->sa_flags = SA_SIGINFO;
> -
> - sa.sa_sigaction = segv_gp_handler;
> - sa.sa_flags = SA_SIGINFO;
> - if (sigaction(SIGSEGV, &sa, NULL))
> - return 1;
> -
> -
> - segv_triggered = false;
> -
> - /* Make sure segv_triggered is set before triggering the #GP */
> - asm volatile("" : : : "memory");
> -
> - /*
> - * Set handler to somewhere in 32 bit address space
> - */
> - sa32->sa_handler = (void *)sa32;
> - if (sigaction32(SIGUSR1, sa32, NULL))
> - return 1;
> -
> - if (!sigsetjmp(jmp_buffer, 1))
> - raise(SIGUSR1);
> -
> - if (segv_triggered)
> - printf("[OK]\t32 bit test\n");
> -
> - return !segv_triggered;
> -}
> -
> -static int parse_uint_from_file(const char *file, const char *fmt)
> -{
> - int err, ret;
> - FILE *f;
> -
> - f = fopen(file, "re");
> - if (!f) {
> - err = -errno;
> - printf("failed to open '%s': %d\n", file, err);
> - return err;
> - }
> - err = fscanf(f, fmt, &ret);
> - if (err != 1) {
> - err = err == EOF ? -EIO : -errno;
> - printf("failed to parse '%s': %d\n", file, err);
> - fclose(f);
> - return err;
> - }
> - fclose(f);
> - return ret;
> -}
> -
> -static int determine_uprobe_perf_type(void)
> -{
> - const char *file = "/sys/bus/event_source/devices/uprobe/type";
> -
> - return parse_uint_from_file(file, "%d\n");
> -}
> -
> -static int determine_uprobe_retprobe_bit(void)
> -{
> - const char *file = "/sys/bus/event_source/devices/uprobe/format/retprobe";
> -
> - return parse_uint_from_file(file, "config:%d\n");
> -}
> -
> -static ssize_t get_uprobe_offset(const void *addr)
> -{
> - size_t start, end, base;
> - char buf[256];
> - bool found = false;
> - FILE *f;
> -
> - f = fopen("/proc/self/maps", "r");
> - if (!f)
> - return -errno;
> -
> - while (fscanf(f, "%zx-%zx %s %zx %*[^\n]\n", &start, &end, buf, &base) == 4) {
> - if (buf[2] == 'x' && (uintptr_t)addr >= start && (uintptr_t)addr < end) {
> - found = true;
> - break;
> - }
> - }
> -
> - fclose(f);
> -
> - if (!found)
> - return -ESRCH;
> -
> - return (uintptr_t)addr - start + base;
> -}
> -
> -static __attribute__((noinline)) void uretprobe_trigger(void)
> -{
> - asm volatile ("");
> -}
> -
> -/*
> - * This test setups return uprobe, which is sensitive to shadow stack
> - * (crashes without extra fix). After executing the uretprobe we fail
> - * the test if we receive SIGSEGV, no crash means we're good.
> - *
> - * Helper functions above borrowed from bpf selftests.
> - */
> -static int test_uretprobe(void)
> -{
> - const size_t attr_sz = sizeof(struct perf_event_attr);
> - const char *file = "/proc/self/exe";
> - int bit, fd = 0, type, err = 1;
> - struct perf_event_attr attr;
> - struct sigaction sa = {};
> - ssize_t offset;
> -
> - type = determine_uprobe_perf_type();
> - if (type < 0) {
> - if (type == -ENOENT)
> - printf("[SKIP]\tUretprobe test, uprobes are not available\n");
> - return 0;
> - }
> -
> - offset = get_uprobe_offset(uretprobe_trigger);
> - if (offset < 0)
> - return 1;
> -
> - bit = determine_uprobe_retprobe_bit();
> - if (bit < 0)
> - return 1;
> -
> - sa.sa_sigaction = segv_gp_handler;
> - sa.sa_flags = SA_SIGINFO;
> - if (sigaction(SIGSEGV, &sa, NULL))
> - return 1;
> -
> - /* Setup return uprobe through perf event interface. */
> - memset(&attr, 0, attr_sz);
> - attr.size = attr_sz;
> - attr.type = type;
> - attr.config = 1 << bit;
> - attr.config1 = (__u64) (unsigned long) file;
> - attr.config2 = offset;
> -
> - fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,
> - -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
> - if (fd < 0)
> - goto out;
> -
> - if (sigsetjmp(jmp_buffer, 1))
> - goto out;
> -
> - ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK);
> -
> - /*
> - * This either segfaults and goes through sigsetjmp above
> - * or succeeds and we're good.
> - */
> - uretprobe_trigger();
> -
> - printf("[OK]\tUretprobe test\n");
> - err = 0;
> -
> -out:
> - ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
> - signal(SIGSEGV, SIG_DFL);
> - if (fd)
> - close(fd);
> - return err;
> -}
> -
> -/* Keep the CALL first so the function address is exactly the probed CALL. */
> -extern void uprobe_call_trigger(void);
> -asm (".pushsection .text\n"
> - ".global uprobe_call_target\n"
> - ".type uprobe_call_target, @function\n"
> - "uprobe_call_target:\n"
> - " ret\n"
> - ".size uprobe_call_target, .-uprobe_call_target\n"
> -
> - ".global uprobe_call_trigger\n"
> - ".type uprobe_call_trigger, @function\n"
> - "uprobe_call_trigger:\n"
> - " call uprobe_call_target\n"
> - " ret\n"
> - ".size uprobe_call_trigger, .-uprobe_call_trigger\n"
> - ".popsection\n"
> -);
> -
> -/* If CALL emulation misses the shadow stack update, this exits via SIGSEGV. */
> -static int test_uprobe_call(void)
> -{
> - const size_t attr_sz = sizeof(struct perf_event_attr);
> - const char *file = "/proc/self/exe";
> - int fd = -1, type, err = 1;
> - struct perf_event_attr attr;
> - struct sigaction sa = {};
> - ssize_t offset;
> -
> - type = determine_uprobe_perf_type();
> - if (type < 0) {
> - if (type == -ENOENT)
> - printf("[SKIP]\tUprobe on CALL test, uprobes are not available\n");
> - return 0;
> - }
> -
> - offset = get_uprobe_offset(uprobe_call_trigger);
> - if (offset < 0)
> - return 1;
> -
> - sa.sa_sigaction = segv_gp_handler;
> - sa.sa_flags = SA_SIGINFO;
> - if (sigaction(SIGSEGV, &sa, NULL))
> - return 1;
> -
> - /* Setup entry uprobe through perf event interface. */
> - memset(&attr, 0, attr_sz);
> - attr.size = attr_sz;
> - attr.type = type;
> - attr.config = 0;
> - attr.config1 = (__u64)(unsigned long)file;
> - attr.config2 = offset;
> -
> - fd = syscall(__NR_perf_event_open, &attr, 0 /* pid */, -1 /* cpu */,
> - -1 /* group_fd */, PERF_FLAG_FD_CLOEXEC);
> - if (fd < 0)
> - goto out;
> -
> - if (sigsetjmp(jmp_buffer, 1))
> - goto out;
> -
> - if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK))
> - goto out;
> -
> - /*
> - * This either segfaults and goes through sigsetjmp above
> - * or succeeds and we're good.
> - */
> - uprobe_call_trigger();
> -
> - printf("[OK]\tUprobe on CALL test\n");
> - err = 0;
> -
> -out:
> - ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK);
> - signal(SIGSEGV, SIG_DFL);
> - if (fd >= 0)
> - close(fd);
> - return err;
> -}
> -
> -void segv_handler_ptrace(int signum, siginfo_t *si, void *uc)
> -{
> - /* The SSP adjustment caused a segfault. */
> - exit(0);
> -}
> -
> -int test_ptrace(void)
> -{
> - unsigned long saved_ssp, ssp = 0;
> - struct sigaction sa= {};
> - struct iovec iov;
> - int status;
> - int pid;
> -
> - iov.iov_base = &ssp;
> - iov.iov_len = sizeof(ssp);
> -
> - pid = fork();
> - if (!pid) {
> - ssp = get_ssp();
> -
> - sa.sa_sigaction = segv_handler_ptrace;
> - sa.sa_flags = SA_SIGINFO;
> - if (sigaction(SIGSEGV, &sa, NULL))
> - return 1;
> -
> - ptrace(PTRACE_TRACEME, NULL, NULL, NULL);
> - /*
> - * The parent will tweak the SSP and return from this function
> - * will #CP.
> - */
> - raise(SIGTRAP);
> -
> - exit(1);
> - }
> -
> - while (waitpid(pid, &status, 0) != -1 && WSTOPSIG(status) != SIGTRAP);
> -
> - if (ptrace(PTRACE_GETREGSET, pid, NT_X86_SHSTK, &iov)) {
> - printf("[INFO]\tFailed to PTRACE_GETREGS\n");
> - goto out_kill;
> - }
> -
> - if (!ssp) {
> - printf("[INFO]\tPtrace child SSP was 0\n");
> - goto out_kill;
> - }
> -
> - saved_ssp = ssp;
> -
> - iov.iov_len = 0;
> - if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> - printf("[INFO]\tToo small size accepted via PTRACE_SETREGS\n");
> - goto out_kill;
> - }
> -
> - iov.iov_len = sizeof(ssp) + 1;
> - if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> - printf("[INFO]\tToo large size accepted via PTRACE_SETREGS\n");
> - goto out_kill;
> - }
> -
> - ssp += 1;
> - if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> - printf("[INFO]\tUnaligned SSP written via PTRACE_SETREGS\n");
> - goto out_kill;
> - }
> -
> - ssp = 0xFFFFFFFFFFFF0000;
> - if (!ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> - printf("[INFO]\tKernel range SSP written via PTRACE_SETREGS\n");
> - goto out_kill;
> - }
> -
> - /*
> - * Tweak the SSP so the child with #CP when it resumes and returns
> - * from raise()
> - */
> - ssp = saved_ssp + 8;
> - iov.iov_len = sizeof(ssp);
> - if (ptrace(PTRACE_SETREGSET, pid, NT_X86_SHSTK, &iov)) {
> - printf("[INFO]\tFailed to PTRACE_SETREGS\n");
> - goto out_kill;
> - }
> -
> - if (ptrace(PTRACE_DETACH, pid, NULL, NULL)) {
> - printf("[INFO]\tFailed to PTRACE_DETACH\n");
> - goto out_kill;
> - }
> -
> - waitpid(pid, &status, 0);
> - if (WEXITSTATUS(status))
> - return 1;
> -
> - printf("[OK]\tPtrace test\n");
> - return 0;
> -
> -out_kill:
> - kill(pid, SIGKILL);
> - return 1;
> -}
> +#include "shadow_stack.h"
>
> int main(int argc, char *argv[])
> {
> - int ret = 0;
> -
> - if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK)) {
> - printf("[SKIP]\tCould not enable Shadow stack\n");
> - return 1;
> - }
> -
> - if (ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK)) {
> - ret = 1;
> - printf("[FAIL]\tDisabling shadow stack failed\n");
> - }
> -
> - if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_SHSTK)) {
> - printf("[SKIP]\tCould not re-enable Shadow stack\n");
> - return 1;
> - }
> -
> - if (ARCH_PRCTL(ARCH_SHSTK_ENABLE, ARCH_SHSTK_WRSS)) {
> - printf("[SKIP]\tCould not enable WRSS\n");
> - ret = 1;
> - goto out;
> - }
> -
> - /* Should have succeeded if here, but this is a test, so double check. */
> - if (!get_ssp()) {
> - printf("[FAIL]\tShadow stack disabled\n");
> - return 1;
> - }
> -
> - if (test_shstk_pivot()) {
> - ret = 1;
> - printf("[FAIL]\tShadow stack pivot\n");
> - goto out;
> - }
> -
> - if (test_shstk_faults()) {
> - ret = 1;
> - printf("[FAIL]\tShadow stack fault test\n");
> - goto out;
> - }
> -
> - if (test_shstk_violation()) {
> - ret = 1;
> - printf("[FAIL]\tShadow stack violation test\n");
> - goto out;
> - }
> -
> - if (test_gup()) {
> - ret = 1;
> - printf("[FAIL]\tShadow shadow stack gup\n");
> - goto out;
> - }
> -
> - if (test_mprotect()) {
> - ret = 1;
> - printf("[FAIL]\tShadow shadow mprotect test\n");
> - goto out;
> - }
> -
> - if (test_userfaultfd()) {
> - ret = 1;
> - printf("[FAIL]\tUserfaultfd test\n");
> - goto out;
> - }
> -
> - if (test_guard_gap_other_gaps()) {
> - ret = 1;
> - printf("[FAIL]\tGuard gap test, other mappings' gaps\n");
> - goto out;
> - }
> -
> - if (test_guard_gap_new_mappings_gaps()) {
> - ret = 1;
> - printf("[FAIL]\tGuard gap test, placement mapping's gaps\n");
> - goto out;
> - }
> -
> - if (test_ptrace()) {
> - ret = 1;
> - printf("[FAIL]\tptrace test\n");
> - }
> -
> - if (test_32bit()) {
> - ret = 1;
> - printf("[FAIL]\t32 bit test\n");
> - goto out;
> - }
> -
> - if (test_uretprobe()) {
> - ret = 1;
> - printf("[FAIL]\turetprobe test\n");
> - goto out;
> - }
> -
> - if (test_uprobe_call()) {
> - ret = 1;
> - printf("[FAIL]\tuprobe on CALL test\n");
> - goto out;
> - }
> -
> - return ret;
> -
> -out:
> - /*
> - * Disable shadow stack before the function returns, or there will be a
> - * shadow stack violation.
> - */
> - if (ARCH_PRCTL(ARCH_SHSTK_DISABLE, ARCH_SHSTK_SHSTK)) {
> - ret = 1;
> - printf("[FAIL]\tDisabling shadow stack failed\n");
> - }
> -
> - return ret;
> + return shadow_stack_run_tests(SHADOW_STACK_TEST_ARCH_PRCTL);
> }
> -#endif
> diff --git a/tools/testing/selftests/x86/test_shadow_stack_prctl.c b/tools/testing/selftests/x86/test_shadow_stack_prctl.c
> new file mode 100644
> index 000000000000..4641a3b1ca03
> --- /dev/null
> +++ b/tools/testing/selftests/x86/test_shadow_stack_prctl.c
> @@ -0,0 +1,12 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +/*
> + * Same as test_shadow_stack.c but uses the PRCTL interface
> + * instead of ARCH_PRCTL.
> + */
> +#include "shadow_stack.h"
> +
> +int main(int argc, char *argv[])
> +{
> + return shadow_stack_run_tests(SHADOW_STACK_TEST_PRCTL);
> +}
>
>
> Nack'ing my own patch, Sashiko found a few useful things to fix.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] selftests/x86: add generic prctl shadow stack test
2026-08-12 18:03 ` Bill Roberts
@ 2026-08-12 18:30 ` Edgecombe, Rick P
2026-08-12 19:29 ` Bill Roberts
0 siblings, 1 reply; 6+ messages in thread
From: Edgecombe, Rick P @ 2026-08-12 18:30 UTC (permalink / raw)
To: x86@kernel.org, bp@alien8.de, dave.hansen@linux.intel.com,
pjw@kernel.org, hpa@zytor.com, aou@eecs.berkeley.edu,
mingo@redhat.com, alex@ghiti.fr, palmer@dabbelt.com,
bill.roberts@arm.com, shuah@kernel.org, tglx@kernel.org
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, bpf@vger.kernel.org
On Wed, 2026-08-12 at 13:03 -0500, Bill Roberts wrote:
> > +}
> >
> >
> > Nack'ing my own patch, Sashiko found a few useful things to fix.
Please trim the mails. That was a lot of quote to search through.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] selftests/x86: add generic prctl shadow stack test
2026-08-12 18:30 ` Edgecombe, Rick P
@ 2026-08-12 19:29 ` Bill Roberts
2026-08-12 19:34 ` Edgecombe, Rick P
0 siblings, 1 reply; 6+ messages in thread
From: Bill Roberts @ 2026-08-12 19:29 UTC (permalink / raw)
To: Edgecombe, Rick P, x86@kernel.org, bp@alien8.de,
dave.hansen@linux.intel.com, pjw@kernel.org, hpa@zytor.com,
aou@eecs.berkeley.edu, mingo@redhat.com, alex@ghiti.fr,
palmer@dabbelt.com, shuah@kernel.org, tglx@kernel.org
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, bpf@vger.kernel.org
> On Wed, 2026-08-12 at 13:03 -0500, Bill Roberts wrote:
>>> +}
>>>
>>>
>>> Nack'ing my own patch, Sashiko found a few useful things to fix.
> Please trim the mails. That was a lot of quote to search through.
>
Sorry each of the many communities across my world want it differently...
But, I would take a review while I re-spin patch v3. I am going to add
get status and lock tests
to cover those cases as well as fix the spelling mistake in patch 2's
commit message, "consisteny".
As well as fix the fork bug where -1 can be used in kill and send the
signal to everything.
Shashiko FTW
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v2 2/2] selftests/x86: add generic prctl shadow stack test
2026-08-12 19:29 ` Bill Roberts
@ 2026-08-12 19:34 ` Edgecombe, Rick P
0 siblings, 0 replies; 6+ messages in thread
From: Edgecombe, Rick P @ 2026-08-12 19:34 UTC (permalink / raw)
To: shuah@kernel.org, dave.hansen@linux.intel.com, bp@alien8.de,
pjw@kernel.org, hpa@zytor.com, mingo@redhat.com,
aou@eecs.berkeley.edu, x86@kernel.org, palmer@dabbelt.com,
bill.roberts@arm.com, alex@ghiti.fr, tglx@kernel.org
Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org,
linux-kselftest@vger.kernel.org, bpf@vger.kernel.org
On Wed, 2026-08-12 at 14:29 -0500, Bill Roberts wrote:
> > On Wed, 2026-08-12 at 13:03 -0500, Bill Roberts wrote:
> > > > +}
> > > >
> > > >
> > > > Nack'ing my own patch, Sashiko found a few useful things to fix.
> > Please trim the mails. That was a lot of quote to search through.
> >
> Sorry each of the many communities across my world want it differently...
>
> But, I would take a review while I re-spin patch v3. I am going to add
> get status and lock tests
> to cover those cases as well as fix the spelling mistake in patch 2's
> commit message, "consisteny".
> As well as fix the fork bug where -1 can be used in kill and send the
> signal to everything.
Oh! There is an existing issue. Thanks in advance.
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2026-08-12 19:34 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-08-12 17:19 [PATCH v2 1/2] x86/shstk: support via prctl Bill Roberts
2026-08-12 17:19 ` [PATCH v2 2/2] selftests/x86: add generic prctl shadow stack test Bill Roberts
2026-08-12 18:03 ` Bill Roberts
2026-08-12 18:30 ` Edgecombe, Rick P
2026-08-12 19:29 ` Bill Roberts
2026-08-12 19:34 ` Edgecombe, Rick P
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