Re: [PATCH v16 27/27] kselftest/riscv: kselftest for user mode cfi

Charlie Jenkins
2025-05-23T08:22:14Z

On Thu, May 22, 2025 at 10:31:30PM -0700, Deepak Gupta wrote:
> Adds kselftest for RISC-V control flow integrity implementation for user
> mode. There is not a lot going on in kernel for enabling landing pad for
> user mode. cfi selftest are intended to be compiled with zicfilp and
> zicfiss enabled compiler. Thus kselftest simply checks if landing pad /
> shadow stack for the process are enabled or not and executes ptrace
> selftests on cfi. selftest then register a signal handler for SIGSEGV.
> Any control flow violation are reported as SIGSEGV with si_code =
> SEGV_CPERR. Test will fail on receiving any SEGV_CPERR. Shadow stack part
> has more changes in kernel and thus there are separate tests for that
>
> - Exercise `map_shadow_stack` syscall
> - `fork` test to make sure COW works for shadow stack pages
> - gup tests
> Kernel uses FOLL_FORCE when access happens to memory via
> /proc/<pid>/mem. Not breaking that for shadow stack.
> - signal test. Make sure signal delivery results in token creation on
> shadow stack and consumes (and verifies) token on sigreturn
> - shadow stack protection test. attempts to write using regular store
> instruction on shadow stack memory must result in access faults
> - ptrace test: adds landing pad violation, clears ELP and continues
>
> In case toolchain doesn't support cfi extension, cfi kselftest wont
> get built.
>
> Test outut
> ==========
>
> """
> TAP version 13
> 1..5
> This is to ensure shadow stack is indeed enabled and working
> This is to ensure shadow stack is indeed enabled and working
> ok 1 shstk fork test
> ok 2 map shadow stack syscall
> ok 3 shadow stack gup tests
> ok 4 shadow stack signal tests
> ok 5 memory protections of shadow stack memory
> """
>
> Signed-off-by: Deepak Gupta <debug@rivosinc.com>
> Suggested-by: Charlie Jenkins <charlie@rivosinc.com>
> ---
> tools/testing/selftests/riscv/Makefile | 2 +-
> tools/testing/selftests/riscv/cfi/.gitignore | 3 +
> tools/testing/selftests/riscv/cfi/Makefile | 16 +
> tools/testing/selftests/riscv/cfi/cfi_rv_test.h | 82 +++++
> tools/testing/selftests/riscv/cfi/riscv_cfi_test.c | 173 +++++++++
> tools/testing/selftests/riscv/cfi/shadowstack.c | 385 +++++++++++++++++++++
> tools/testing/selftests/riscv/cfi/shadowstack.h | 27 ++
> 7 files changed, 687 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/riscv/Makefile b/tools/testing/selftests/riscv/Makefile
> index 099b8c1f46f8..5671b4405a12 100644
> --- a/tools/testing/selftests/riscv/Makefile
> +++ b/tools/testing/selftests/riscv/Makefile
> @@ -5,7 +5,7 @@
> ARCH ?= $(shell uname -m 2>/dev/null || echo not)
>
> ifneq (,$(filter $(ARCH),riscv))
> -RISCV_SUBTARGETS ?= abi hwprobe mm sigreturn vector
> +RISCV_SUBTARGETS ?= abi hwprobe mm sigreturn vector cfi
> else
> RISCV_SUBTARGETS :=
> endif
> diff --git a/tools/testing/selftests/riscv/cfi/.gitignore b/tools/testing/selftests/riscv/cfi/.gitignore
> new file mode 100644
> index 000000000000..82545863bac6
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/cfi/.gitignore
> @@ -0,0 +1,3 @@
> +cfitests
> +riscv_cfi_test
> +shadowstack
> diff --git a/tools/testing/selftests/riscv/cfi/Makefile b/tools/testing/selftests/riscv/cfi/Makefile
> new file mode 100644
> index 000000000000..55165a93845f
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/cfi/Makefile
> @@ -0,0 +1,16 @@
> +CFLAGS += -I$(top_srcdir)/tools/include
> +
> +CFLAGS += -march=rv64gc_zicfilp_zicfiss -fcf-protection=full
> +
> +ifeq ($(shell $(CC) $(CFLAGS) -nostdlib -xc /dev/null -o /dev/null > /dev/null 2>&1; echo $$?),0)
> +TEST_GEN_PROGS := cfitests
> +
> +include ../../lib.mk

I'm sorry, I just realized I messed up this patch :/. This line is
supposed to be above the ifeq line to get the proper definition of
$(CC).

> +
> +$(OUTPUT)/cfitests: riscv_cfi_test.c shadowstack.c
> + $(CC) -o$@ $(CFLAGS) $(LDFLAGS) $^
> +else
> +include ../../lib.mk

This include can be removed as well.

- Charlie

> +
> +$(shell echo "Toolchain doesn't support CFI, skipping CFI kselftest." >&2)
> +endif
> diff --git a/tools/testing/selftests/riscv/cfi/cfi_rv_test.h b/tools/testing/selftests/riscv/cfi/cfi_rv_test.h
> new file mode 100644
> index 000000000000..1c8043f2b778
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/cfi/cfi_rv_test.h
> @@ -0,0 +1,82 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef SELFTEST_RISCV_CFI_H
> +#define SELFTEST_RISCV_CFI_H
> +#include <stddef.h>
> +#include <sys/types.h>
> +#include "shadowstack.h"
> +
> +#define CHILD_EXIT_CODE_SSWRITE 10
> +#define CHILD_EXIT_CODE_SIG_TEST 11
> +
> +#define my_syscall5(num, arg1, arg2, arg3, arg4, arg5) \
> +({ \
> + register long _num __asm__ ("a7") = (num); \
> + register long _arg1 __asm__ ("a0") = (long)(arg1); \
> + register long _arg2 __asm__ ("a1") = (long)(arg2); \
> + register long _arg3 __asm__ ("a2") = (long)(arg3); \
> + register long _arg4 __asm__ ("a3") = (long)(arg4); \
> + register long _arg5 __asm__ ("a4") = (long)(arg5); \
> + \
> + __asm__ volatile( \
> + "ecall\n" \
> + : "+r" \
> + (_arg1) \
> + : "r"(_arg2), "r"(_arg3), "r"(_arg4), "r"(_arg5), \
> + "r"(_num) \
> + : "memory", "cc" \
> + ); \
> + _arg1; \
> +})
> +
> +#define my_syscall3(num, arg1, arg2, arg3) \
> +({ \
> + register long _num __asm__ ("a7") = (num); \
> + register long _arg1 __asm__ ("a0") = (long)(arg1); \
> + register long _arg2 __asm__ ("a1") = (long)(arg2); \
> + register long _arg3 __asm__ ("a2") = (long)(arg3); \
> + \
> + __asm__ volatile( \
> + "ecall\n" \
> + : "+r" (_arg1) \
> + : "r"(_arg2), "r"(_arg3), \
> + "r"(_num) \
> + : "memory", "cc" \
> + ); \
> + _arg1; \
> +})
> +
> +#ifndef __NR_prctl
> +#define __NR_prctl 167
> +#endif
> +
> +#ifndef __NR_map_shadow_stack
> +#define __NR_map_shadow_stack 453
> +#endif
> +
> +#define CSR_SSP 0x011
> +
> +#ifdef __ASSEMBLY__
> +#define __ASM_STR(x) x
> +#else
> +#define __ASM_STR(x) #x
> +#endif
> +
> +#define csr_read(csr) \
> +({ \
> + register unsigned long __v; \
> + __asm__ __volatile__ ("csrr %0, " __ASM_STR(csr) \
> + : "=r" (__v) : \
> + : "memory"); \
> + __v; \
> +})
> +
> +#define csr_write(csr, val) \
> +({ \
> + unsigned long __v = (unsigned long)(val); \
> + __asm__ __volatile__ ("csrw " __ASM_STR(csr) ", %0" \
> + : : "rK" (__v) \
> + : "memory"); \
> +})
> +
> +#endif
> diff --git a/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c b/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c
> new file mode 100644
> index 000000000000..486a2e779053
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/cfi/riscv_cfi_test.c
> @@ -0,0 +1,173 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include "../../kselftest.h"
> +#include <sys/signal.h>
> +#include <asm/ucontext.h>
> +#include <linux/prctl.h>
> +#include <errno.h>
> +#include <linux/ptrace.h>
> +#include <sys/wait.h>
> +#include <linux/elf.h>
> +#include <sys/uio.h>
> +#include <asm-generic/unistd.h>
> +
> +#include "cfi_rv_test.h"
> +
> +/* do not optimize cfi related test functions */
> +#pragma GCC push_options
> +#pragma GCC optimize("O0")
> +
> +void sigsegv_handler(int signum, siginfo_t *si, void *uc)
> +{
> + struct ucontext *ctx = (struct ucontext *)uc;
> +
> + if (si->si_code == SEGV_CPERR) {
> + ksft_print_msg("Control flow violation happened somewhere\n");
> + ksft_print_msg("PC where violation happened %lx\n", ctx->uc_mcontext.gregs[0]);
> + exit(-1);
> + }
> +
> + /* all other cases are expected to be of shadow stack write case */
> + exit(CHILD_EXIT_CODE_SSWRITE);
> +}
> +
> +bool register_signal_handler(void)
> +{
> + struct sigaction sa = {};
> +
> + sa.sa_sigaction = sigsegv_handler;
> + sa.sa_flags = SA_SIGINFO;
> + if (sigaction(SIGSEGV, &sa, NULL)) {
> + ksft_print_msg("Registering signal handler for landing pad violation failed\n");
> + return false;
> + }
> +
> + return true;
> +}
> +
> +long ptrace(int request, pid_t pid, void *addr, void *data);
> +
> +bool cfi_ptrace_test(void)
> +{
> + pid_t pid;
> + int status, ret = 0;
> + unsigned long ptrace_test_num = 0, total_ptrace_tests = 2;
> +
> + struct user_cfi_state cfi_reg;
> + struct iovec iov;
> +
> + pid = fork();
> +
> + if (pid == -1) {
> + ksft_exit_fail_msg("%s: fork failed\n", __func__);
> + exit(1);
> + }
> +
> + if (pid == 0) {
> + /* allow to be traced */
> + ptrace(PTRACE_TRACEME, 0, NULL, NULL);
> + raise(SIGSTOP);
> + asm volatile (
> + "la a5, 1f\n"
> + "jalr a5 \n"
> + "nop \n"
> + "nop \n"
> + "1: nop\n"
> + : : : "a5");
> + exit(11);
> + /* child shouldn't go beyond here */
> + }
> +
> + /* parent's code goes here */
> + iov.iov_base = &cfi_reg;
> + iov.iov_len = sizeof(cfi_reg);
> +
> + while (ptrace_test_num < total_ptrace_tests) {
> + memset(&cfi_reg, 0, sizeof(cfi_reg));
> + waitpid(pid, &status, 0);
> + if (WIFSTOPPED(status)) {
> + errno = 0;
> + ret = ptrace(PTRACE_GETREGSET, pid, (void *)NT_RISCV_USER_CFI, &iov);
> + if (ret == -1 && errno)
> + ksft_exit_fail_msg("%s: PTRACE_GETREGSET failed\n", __func__);
> + } else
> + ksft_exit_fail_msg("%s: child didn't stop, failed\n", __func__);
> +
> + switch (ptrace_test_num) {
> +#define CFI_ENABLE_MASK (PTRACE_CFI_LP_EN_STATE | \
> + PTRACE_CFI_SS_EN_STATE | \
> + PTRACE_CFI_SS_PTR_STATE)
> + case 0:
> + if ((cfi_reg.cfi_status.cfi_state & CFI_ENABLE_MASK) != CFI_ENABLE_MASK)
> + ksft_exit_fail_msg("%s: ptrace_getregset failed, %llu\n", __func__,
> + cfi_reg.cfi_status.cfi_state);
> + if (!cfi_reg.shstk_ptr)
> + ksft_exit_fail_msg("%s: NULL shadow stack pointer, test failed\n",
> + __func__);
> + break;
> + case 1:
> + if (!(cfi_reg.cfi_status.cfi_state & PTRACE_CFI_ELP_STATE))
> + ksft_exit_fail_msg("%s: elp must have been set\n", __func__);
> + /* clear elp state. not interested in anything else */
> + cfi_reg.cfi_status.cfi_state = 0;
> +
> + ret = ptrace(PTRACE_SETREGSET, pid, (void *)NT_RISCV_USER_CFI, &iov);
> + if (ret == -1 && errno)
> + ksft_exit_fail_msg("%s: PTRACE_GETREGSET failed\n", __func__);
> + break;
> + default:
> + ksft_exit_fail_msg("%s: unreachable switch case\n", __func__);
> + break;
> + }
> + ptrace(PTRACE_CONT, pid, NULL, NULL);
> + ptrace_test_num++;
> + }
> +
> + waitpid(pid, &status, 0);
> + if (WEXITSTATUS(status) != 11)
> + ksft_print_msg("%s, bad return code from child\n", __func__);
> +
> + ksft_print_msg("%s, ptrace test succeeded\n", __func__);
> + return true;
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + int ret = 0;
> + unsigned long lpad_status = 0, ss_status = 0;
> +
> + ksft_print_header();
> +
> + ksft_print_msg("Starting risc-v tests\n");
> +
> + /*
> + * Landing pad test. Not a lot of kernel changes to support landing
> + * pad for user mode except lighting up a bit in senvcfg via a prctl
> + * Enable landing pad through out the execution of test binary
> + */
> + ret = my_syscall5(__NR_prctl, PR_GET_INDIR_BR_LP_STATUS, &lpad_status, 0, 0, 0);
> + if (ret)
> + ksft_exit_fail_msg("Get landing pad status failed with %d\n", ret);
> +
> + if (!(lpad_status & PR_INDIR_BR_LP_ENABLE))
> + ksft_exit_fail_msg("Landing pad is not enabled, should be enabled via glibc\n");
> +
> + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0);
> + if (ret)
> + ksft_exit_fail_msg("Get shadow stack failed with %d\n", ret);
> +
> + if (!(ss_status & PR_SHADOW_STACK_ENABLE))
> + ksft_exit_fail_msg("Shadow stack is not enabled, should be enabled via glibc\n");
> +
> + if (!register_signal_handler())
> + ksft_exit_fail_msg("Registering signal handler for SIGSEGV failed\n");
> +
> + ksft_print_msg("Landing pad and shadow stack are enabled for binary\n");
> + cfi_ptrace_test();
> +
> + execute_shadow_stack_tests();
> +
> + return 0;
> +}
> +
> +#pragma GCC pop_options
> diff --git a/tools/testing/selftests/riscv/cfi/shadowstack.c b/tools/testing/selftests/riscv/cfi/shadowstack.c
> new file mode 100644
> index 000000000000..53387dbd9cf5
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/cfi/shadowstack.c
> @@ -0,0 +1,385 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +#include "../../kselftest.h"
> +#include <sys/wait.h>
> +#include <signal.h>
> +#include <fcntl.h>
> +#include <asm-generic/unistd.h>
> +#include <sys/mman.h>
> +#include "shadowstack.h"
> +#include "cfi_rv_test.h"
> +
> +static struct shadow_stack_tests shstk_tests[] = {
> + { "shstk fork test\n", shadow_stack_fork_test },
> + { "map shadow stack syscall\n", shadow_stack_map_test },
> + { "shadow stack gup tests\n", shadow_stack_gup_tests },
> + { "shadow stack signal tests\n", shadow_stack_signal_test},
> + { "memory protections of shadow stack memory\n", shadow_stack_protection_test }
> +};
> +
> +#define RISCV_SHADOW_STACK_TESTS ARRAY_SIZE(shstk_tests)
> +
> +/* do not optimize shadow stack related test functions */
> +#pragma GCC push_options
> +#pragma GCC optimize("O0")
> +
> +void zar(void)
> +{
> + unsigned long ssp = 0;
> +
> + ssp = csr_read(CSR_SSP);
> + ksft_print_msg("Spewing out shadow stack ptr: %lx\n"
> + " This is to ensure shadow stack is indeed enabled and working\n",
> + ssp);
> +}
> +
> +void bar(void)
> +{
> + zar();
> +}
> +
> +void foo(void)
> +{
> + bar();
> +}
> +
> +void zar_child(void)
> +{
> + unsigned long ssp = 0;
> +
> + ssp = csr_read(CSR_SSP);
> + ksft_print_msg("Spewing out shadow stack ptr: %lx\n"
> + " This is to ensure shadow stack is indeed enabled and working\n",
> + ssp);
> +}
> +
> +void bar_child(void)
> +{
> + zar_child();
> +}
> +
> +void foo_child(void)
> +{
> + bar_child();
> +}
> +
> +typedef void (call_func_ptr)(void);
> +/*
> + * call couple of functions to test push pop.
> + */
> +int shadow_stack_call_tests(call_func_ptr fn_ptr, bool parent)
> +{
> + ksft_print_msg("dummy calls for sspush and sspopchk in context of %s\n",
> + parent ? "parent" : "child");
> +
> + (fn_ptr)();
> +
> + return 0;
> +}
> +
> +/* forks a thread, and ensure shadow stacks fork out */
> +bool shadow_stack_fork_test(unsigned long test_num, void *ctx)
> +{
> + int pid = 0, child_status = 0, parent_pid = 0, ret = 0;
> + unsigned long ss_status = 0;
> +
> + ksft_print_msg("Exercising shadow stack fork test\n");
> +
> + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0);
> + if (ret) {
> + ksft_exit_skip("Shadow stack get status prctl failed with errorcode %d\n", ret);
> + return false;
> + }
> +
> + if (!(ss_status & PR_SHADOW_STACK_ENABLE))
> + ksft_exit_skip("Shadow stack is not enabled, should be enabled via glibc\n");
> +
> + parent_pid = getpid();
> + pid = fork();
> +
> + if (pid) {
> + ksft_print_msg("Parent pid %d and child pid %d\n", parent_pid, pid);
> + shadow_stack_call_tests(&foo, true);
> + } else {
> + shadow_stack_call_tests(&foo_child, false);
> + }
> +
> + if (pid) {
> + ksft_print_msg("Waiting on child to finish\n");
> + wait(&child_status);
> + } else {
> + /* exit child gracefully */
> + exit(0);
> + }
> +
> + if (pid && WIFSIGNALED(child_status)) {
> + ksft_print_msg("Child faulted, fork test failed\n");
> + return false;
> + }
> +
> + return true;
> +}
> +
> +/* exercise `map_shadow_stack`, pivot to it and call some functions to ensure it works */
> +#define SHADOW_STACK_ALLOC_SIZE 4096
> +bool shadow_stack_map_test(unsigned long test_num, void *ctx)
> +{
> + unsigned long shdw_addr;
> + int ret = 0;
> +
> + ksft_print_msg("Exercising shadow stack map test\n");
> +
> + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0);
> +
> + if (((long)shdw_addr) <= 0) {
> + ksft_print_msg("map_shadow_stack failed with error code %d\n",
> + (int)shdw_addr);
> + return false;
> + }
> +
> + ret = munmap((void *)shdw_addr, SHADOW_STACK_ALLOC_SIZE);
> +
> + if (ret) {
> + ksft_print_msg("munmap failed with error code %d\n", ret);
> + return false;
> + }
> +
> + return true;
> +}
> +
> +/*
> + * shadow stack protection tests. map a shadow stack and
> + * validate all memory protections work on it
> + */
> +bool shadow_stack_protection_test(unsigned long test_num, void *ctx)
> +{
> + unsigned long shdw_addr;
> + unsigned long *write_addr = NULL;
> + int ret = 0, pid = 0, child_status = 0;
> +
> + ksft_print_msg("Exercising shadow stack protection test (WPT)\n");
> +
> + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0);
> +
> + if (((long)shdw_addr) <= 0) {
> + ksft_print_msg("map_shadow_stack failed with error code %d\n",
> + (int)shdw_addr);
> + return false;
> + }
> +
> + write_addr = (unsigned long *)shdw_addr;
> + pid = fork();
> +
> + /* no child was created, return false */
> + if (pid == -1)
> + return false;
> +
> + /*
> + * try to perform a store from child on shadow stack memory
> + * it should result in SIGSEGV
> + */
> + if (!pid) {
> + /* below write must lead to SIGSEGV */
> + *write_addr = 0xdeadbeef;
> + } else {
> + wait(&child_status);
> + }
> +
> + /* test fail, if 0xdeadbeef present on shadow stack address */
> + if (*write_addr == 0xdeadbeef) {
> + ksft_print_msg("Shadow stack WPT failed\n");
> + return false;
> + }
> +
> + /* if child reached here, then fail */
> + if (!pid) {
> + ksft_print_msg("Shadow stack WPT failed: child reached unreachable state\n");
> + return false;
> + }
> +
> + /* if child exited via signal handler but not for write on ss */
> + if (WIFEXITED(child_status) &&
> + WEXITSTATUS(child_status) != CHILD_EXIT_CODE_SSWRITE) {
> + ksft_print_msg("Shadow stack WPT failed: child wasn't signaled for write\n");
> + return false;
> + }
> +
> + ret = munmap(write_addr, SHADOW_STACK_ALLOC_SIZE);
> + if (ret) {
> + ksft_print_msg("Shadow stack WPT failed: munmap failed, error code %d\n",
> + ret);
> + return false;
> + }
> +
> + return true;
> +}
> +
> +#define SS_MAGIC_WRITE_VAL 0xbeefdead
> +
> +int gup_tests(int mem_fd, unsigned long *shdw_addr)
> +{
> + unsigned long val = 0;
> +
> + lseek(mem_fd, (unsigned long)shdw_addr, SEEK_SET);
> + if (read(mem_fd, &val, sizeof(val)) < 0) {
> + ksft_print_msg("Reading shadow stack mem via gup failed\n");
> + return 1;
> + }
> +
> + val = SS_MAGIC_WRITE_VAL;
> + lseek(mem_fd, (unsigned long)shdw_addr, SEEK_SET);
> + if (write(mem_fd, &val, sizeof(val)) < 0) {
> + ksft_print_msg("Writing shadow stack mem via gup failed\n");
> + return 1;
> + }
> +
> + if (*shdw_addr != SS_MAGIC_WRITE_VAL) {
> + ksft_print_msg("GUP write to shadow stack memory failed\n");
> + return 1;
> + }
> +
> + return 0;
> +}
> +
> +bool shadow_stack_gup_tests(unsigned long test_num, void *ctx)
> +{
> + unsigned long shdw_addr = 0;
> + unsigned long *write_addr = NULL;
> + int fd = 0;
> + bool ret = false;
> +
> + ksft_print_msg("Exercising shadow stack gup tests\n");
> + shdw_addr = my_syscall3(__NR_map_shadow_stack, NULL, SHADOW_STACK_ALLOC_SIZE, 0);
> +
> + if (((long)shdw_addr) <= 0) {
> + ksft_print_msg("map_shadow_stack failed with error code %d\n", (int)shdw_addr);
> + return false;
> + }
> +
> + write_addr = (unsigned long *)shdw_addr;
> +
> + fd = open("/proc/self/mem", O_RDWR);
> + if (fd == -1)
> + return false;
> +
> + if (gup_tests(fd, write_addr)) {
> + ksft_print_msg("gup tests failed\n");
> + goto out;
> + }
> +
> + ret = true;
> +out:
> + if (shdw_addr && munmap(write_addr, SHADOW_STACK_ALLOC_SIZE)) {
> + ksft_print_msg("munmap failed with error code %d\n", ret);
> + ret = false;
> + }
> +
> + return ret;
> +}
> +
> +volatile bool break_loop;
> +
> +void sigusr1_handler(int signo)
> +{
> + break_loop = true;
> +}
> +
> +bool sigusr1_signal_test(void)
> +{
> + struct sigaction sa = {};
> +
> + sa.sa_handler = sigusr1_handler;
> + sa.sa_flags = 0;
> + sigemptyset(&sa.sa_mask);
> + if (sigaction(SIGUSR1, &sa, NULL)) {
> + ksft_print_msg("Registering signal handler for SIGUSR1 failed\n");
> + return false;
> + }
> +
> + return true;
> +}
> +
> +/*
> + * shadow stack signal test. shadow stack must be enabled.
> + * register a signal, fork another thread which is waiting
> + * on signal. Send a signal from parent to child, verify
> + * that signal was received by child. If not test fails
> + */
> +bool shadow_stack_signal_test(unsigned long test_num, void *ctx)
> +{
> + int pid = 0, child_status = 0, ret = 0;
> + unsigned long ss_status = 0;
> +
> + ksft_print_msg("Exercising shadow stack signal test\n");
> +
> + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &ss_status, 0, 0, 0);
> + if (ret) {
> + ksft_print_msg("Shadow stack get status prctl failed with errorcode %d\n", ret);
> + return false;
> + }
> +
> + if (!(ss_status & PR_SHADOW_STACK_ENABLE))
> + ksft_print_msg("Shadow stack is not enabled, should be enabled via glibc\n");
> +
> + /* this should be caught by signal handler and do an exit */
> + if (!sigusr1_signal_test()) {
> + ksft_print_msg("Registering sigusr1 handler failed\n");
> + exit(-1);
> + }
> +
> + pid = fork();
> +
> + if (pid == -1) {
> + ksft_print_msg("Signal test: fork failed\n");
> + goto out;
> + }
> +
> + if (pid == 0) {
> + while (!break_loop)
> + sleep(1);
> +
> + exit(11);
> + /* child shouldn't go beyond here */
> + }
> +
> + /* send SIGUSR1 to child */
> + kill(pid, SIGUSR1);
> + wait(&child_status);
> +
> +out:
> +
> + return (WIFEXITED(child_status) &&
> + WEXITSTATUS(child_status) == 11);
> +}
> +
> +int execute_shadow_stack_tests(void)
> +{
> + int ret = 0;
> + unsigned long test_count = 0;
> + unsigned long shstk_status = 0;
> + bool test_pass = false;
> +
> + ksft_print_msg("Executing RISC-V shadow stack self tests\n");
> + ksft_set_plan(RISCV_SHADOW_STACK_TESTS);
> +
> + ret = my_syscall5(__NR_prctl, PR_GET_SHADOW_STACK_STATUS, &shstk_status, 0, 0, 0);
> +
> + if (ret != 0)
> + ksft_exit_fail_msg("Get shadow stack status failed with %d\n", ret);
> +
> + /*
> + * If we are here that means get shadow stack status succeeded and
> + * thus shadow stack support is baked in the kernel.
> + */
> + while (test_count < RISCV_SHADOW_STACK_TESTS) {
> + test_pass = (*shstk_tests[test_count].t_func)(test_count, NULL);
> + ksft_test_result(test_pass, shstk_tests[test_count].name);
> + test_count++;
> + }
> +
> + ksft_finished();
> +
> + return 0;
> +}
> +
> +#pragma GCC pop_options
> diff --git a/tools/testing/selftests/riscv/cfi/shadowstack.h b/tools/testing/selftests/riscv/cfi/shadowstack.h
> new file mode 100644
> index 000000000000..0be510167de3
> --- /dev/null
> +++ b/tools/testing/selftests/riscv/cfi/shadowstack.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef SELFTEST_SHADOWSTACK_TEST_H
> +#define SELFTEST_SHADOWSTACK_TEST_H
> +#include <stddef.h>
> +#include <linux/prctl.h>
> +
> +/*
> + * a cfi test returns true for success or false for fail
> + * takes a number for test number to index into array and void pointer.
> + */
> +typedef bool (*shstk_test_func)(unsigned long test_num, void *);
> +
> +struct shadow_stack_tests {
> + char *name;
> + shstk_test_func t_func;
> +};
> +
> +bool shadow_stack_fork_test(unsigned long test_num, void *ctx);
> +bool shadow_stack_map_test(unsigned long test_num, void *ctx);
> +bool shadow_stack_protection_test(unsigned long test_num, void *ctx);
> +bool shadow_stack_gup_tests(unsigned long test_num, void *ctx);
> +bool shadow_stack_signal_test(unsigned long test_num, void *ctx);
> +
> +int execute_shadow_stack_tests(void);
> +
> +#endif
>
> --
> 2.43.0
>