[PATCH 33/35] selftests/x86: Add map_shadow_stack syscall test

Rick Edgecombe
2022-01-30T21:25:49Z

Add a simple selftest for exercising the new map_shadow_stack syscall.

Co-developed-by: Yu, Yu-cheng <yu-cheng.yu@intel.com>
Signed-off-by: Yu, Yu-cheng <yu-cheng.yu@intel.com>
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---

v1:
- New patch.

tools/testing/selftests/x86/Makefile | 9 ++-
.../selftests/x86/test_map_shadow_stack.c | 75 +++++++++++++++++++
2 files changed, 83 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/x86/test_map_shadow_stack.c

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 8a1f62ab3c8e..9114943336f9 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -9,11 +9,13 @@ UNAME_M := $(shell uname -m)
CAN_BUILD_I386 := $(shell ./check_cc.sh $(CC) trivial_32bit_program.c -m32)
CAN_BUILD_X86_64 := $(shell ./check_cc.sh $(CC) trivial_64bit_program.c)
CAN_BUILD_WITH_NOPIE := $(shell ./check_cc.sh $(CC) trivial_program.c -no-pie)
+CAN_BUILD_WITH_SHSTK := $(shell ./check_cc.sh $(CC) trivial_program.c -mshstk -fcf-protection)

TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt test_mremap_vdso \
check_initial_reg_state sigreturn iopl ioperm \
test_vsyscall mov_ss_trap \
- syscall_arg_fault fsgsbase_restore sigaltstack
+ syscall_arg_fault fsgsbase_restore sigaltstack \
+ test_map_shadow_stack
TARGETS_C_32BIT_ONLY := entry_from_vm86 test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
vdso_restorer
@@ -105,3 +107,8 @@ $(OUTPUT)/test_syscall_vdso_32: thunks_32.S
# state.
$(OUTPUT)/check_initial_reg_state_32: CFLAGS += -Wl,-ereal_start -static
$(OUTPUT)/check_initial_reg_state_64: CFLAGS += -Wl,-ereal_start -static
+
+ifeq ($(CAN_BUILD_WITH_SHSTK),1)
+$(OUTPUT)/test_map_shadow_stack_64: CFLAGS += -mshstk -fcf-protection
+$(OUTPUT)/test_map_shadow_stack_32: CFLAGS += -mshstk -fcf-protection
+endif
\ No newline at end of file
diff --git a/tools/testing/selftests/x86/test_map_shadow_stack.c b/tools/testing/selftests/x86/test_map_shadow_stack.c
new file mode 100644
index 000000000000..dfd94ef0176d
--- /dev/null
+++ b/tools/testing/selftests/x86/test_map_shadow_stack.c
@@ -0,0 +1,75 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define _GNU_SOURCE
+
+#include <sys/syscall.h>
+#include <sys/mman.h>
+#include <sys/stat.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>
+
+#define SS_SIZE 0x200000
+
+void *create_shstk(void)
+{
+ return (void *)syscall(__NR_map_shadow_stack, SS_SIZE, SHADOW_STACK_SET_TOKEN);
+}
+
+#if (__GNUC__ < 8) || (__GNUC__ == 8 && __GNUC_MINOR__ < 5)
+int main(int argc, char *argv[])
+{
+ printf("SKIP: compiler does not support CET.");
+ return 0;
+}
+#else
+void try_shstk(unsigned long new_ssp)
+{
+ unsigned long ssp0, ssp1;
+
+ printf("pid=%d\n", getpid());
+ printf("new_ssp = %lx, *new_ssp = %lx\n",
+ new_ssp, *((unsigned long *)new_ssp));
+
+ ssp0 = _get_ssp();
+ printf("changing ssp from %lx to %lx\n", ssp0, new_ssp);
+
+ /* Make sure is aligned to 8 bytes */
+ if ((ssp0 & 0xf) != 0)
+ ssp0 &= -8;
+
+ asm volatile("rstorssp (%0)\n":: "r" (new_ssp));
+ asm volatile("saveprevssp");
+ ssp1 = _get_ssp();
+ printf("ssp is now %lx\n", ssp1);
+
+ ssp0 -= 8;
+ asm volatile("rstorssp (%0)\n":: "r" (ssp0));
+ asm volatile("saveprevssp");
+}
+
+int main(int argc, char *argv[])
+{
+ void *shstk;
+
+ if (!_get_ssp()) {
+ printf("SKIP: shadow stack disabled.");
+ return 0;
+ }
+
+ shstk = create_shstk();
+ if (shstk == MAP_FAILED) {
+ printf("FAIL: Error creating shadow stack: %d\n", errno);
+ return 1;
+ }
+ try_shstk((unsigned long)shstk + SS_SIZE - 8);
+
+ printf("PASS.\n");
+ return 0;
+}
+#endif
--
2.17.1