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Subject[PATCH v16 09/10] x86/arch_prctl: Selftest for ARCH_[GET|SET]_CPUID
Date
Test disabling and reenabling the cpuid instruction via the new arch_prctl
ARCH_SET_CPUID, retrieving the current state via ARCH_GET_CPUID, and the
expected behaviors across fork() and exec().

Signed-off-by: Kyle Huey <khuey@kylehuey.com>
---
tools/testing/selftests/x86/Makefile | 2 +-
tools/testing/selftests/x86/cpuid_fault.c | 251 ++++++++++++++++++++++++++++++
2 files changed, 252 insertions(+), 1 deletion(-)
create mode 100644 tools/testing/selftests/x86/cpuid_fault.c

diff --git a/tools/testing/selftests/x86/Makefile b/tools/testing/selftests/x86/Makefile
index 38e0a9ca5d71..acda4e5fcf25 100644
--- a/tools/testing/selftests/x86/Makefile
+++ b/tools/testing/selftests/x86/Makefile
@@ -6,7 +6,7 @@ include ../lib.mk

TARGETS_C_BOTHBITS := single_step_syscall sysret_ss_attrs syscall_nt ptrace_syscall test_mremap_vdso \
check_initial_reg_state sigreturn ldt_gdt iopl mpx-mini-test ioperm \
- protection_keys test_vdso
+ protection_keys test_vdso cpuid_fault
TARGETS_C_32BIT_ONLY := entry_from_vm86 syscall_arg_fault test_syscall_vdso unwind_vdso \
test_FCMOV test_FCOMI test_FISTTP \
vdso_restorer
diff --git a/tools/testing/selftests/x86/cpuid_fault.c b/tools/testing/selftests/x86/cpuid_fault.c
new file mode 100644
index 000000000000..e3b93c28c655
--- /dev/null
+++ b/tools/testing/selftests/x86/cpuid_fault.c
@@ -0,0 +1,251 @@
+
+/*
+ * Tests for arch_prctl(ARCH_GET_CPUID, ...) / arch_prctl(ARCH_SET_CPUID, ...)
+ *
+ * Basic test to test behaviour of ARCH_GET_CPUID and ARCH_SET_CPUID
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <signal.h>
+#include <inttypes.h>
+#include <cpuid.h>
+#include <err.h>
+#include <errno.h>
+#include <sys/wait.h>
+
+#include <sys/prctl.h>
+#include <linux/prctl.h>
+
+/*
+#define ARCH_GET_CPUID 0x1005
+#define ARCH_SET_CPUID 0x1006
+#ifdef __x86_64__
+#define SYS_arch_prctl 158
+#else
+#define SYS_arch_prctl 384
+#endif
+*/
+
+const char *cpuid_names[] = {
+ [0] = "[cpuid disabled]",
+ [1] = "[cpuid enabled]",
+};
+
+int arch_prctl(int option, unsigned long arg2)
+{
+ return syscall(SYS_arch_prctl, option, arg2);
+}
+
+int cpuid(unsigned int *eax, unsigned int *ebx, unsigned int *ecx,
+ unsigned int *edx)
+{
+ return __get_cpuid(0, eax, ebx, ecx, edx);
+}
+
+int do_child_exec_test(int eax, int ebx, int ecx, int edx)
+{
+ int cpuid_val = 0, child = 0, status = 0;
+
+ printf("arch_prctl(ARCH_GET_CPUID); ");
+
+ cpuid_val = arch_prctl(ARCH_GET_CPUID, 0);
+ if (cpuid_val < 0)
+ errx(1, "ARCH_GET_CPUID fails now, but not before?");
+
+ printf("cpuid_val == %s\n", cpuid_names[cpuid_val]);
+ if (cpuid_val != 0)
+ errx(1, "How did cpuid get re-enabled on fork?");
+
+ child = fork();
+ if (child == 0) {
+ cpuid_val = arch_prctl(ARCH_GET_CPUID, 0);
+ if (cpuid_val < 0)
+ errx(1, "ARCH_GET_CPUID fails now, but not before?");
+
+ printf("cpuid_val == %s\n", cpuid_names[cpuid_val]);
+ if (cpuid_val != 0)
+ errx(1, "How did cpuid get re-enabled on fork?");
+
+ printf("exec\n");
+ execl("/proc/self/exe", "cpuid-fault", "-early-return", NULL);
+ }
+
+ if (child != waitpid(child, &status, 0))
+ errx(1, "waitpid failed!?");
+
+ if (WEXITSTATUS(status) != 0)
+ errx(1, "Execed child exited abnormally");
+
+ return 0;
+}
+
+int child_received_signal;
+
+void child_sigsegv_cb(int sig)
+{
+ int cpuid_val = 0;
+
+ child_received_signal = 1;
+ printf("[ SIG_SEGV ]\n");
+ printf("arch_prctl(ARCH_GET_CPUID); ");
+
+ cpuid_val = arch_prctl(ARCH_GET_CPUID, 0);
+ if (cpuid_val < 0)
+ errx(1, "ARCH_GET_CPUID fails now, but not before?");
+
+ printf("cpuid_val == %s\n", cpuid_names[cpuid_val]);
+ printf("arch_prctl(ARCH_SET_CPUID, 1)\n");
+ if (arch_prctl(ARCH_SET_CPUID, 1) != 0)
+ exit(errno);
+
+ printf("cpuid() == ");
+}
+
+int do_child_test(void)
+{
+ unsigned int eax = 0, ebx = 0, ecx = 0, edx = 0;
+
+ signal(SIGSEGV, child_sigsegv_cb);
+
+ /* the child starts out with cpuid disabled, the signal handler
+ * attempts to enable and retry
+ */
+ printf("cpuid() == ");
+ cpuid(&eax, &ebx, &ecx, &edx);
+ printf("{%x, %x, %x, %x}\n", eax, ebx, ecx, edx);
+ return child_received_signal ? 0 : 42;
+}
+
+int signal_count;
+
+void sigsegv_cb(int sig)
+{
+ int cpuid_val = 0;
+
+ signal_count++;
+ printf("[ SIG_SEGV ]\n");
+ printf("arch_prctl(ARCH_GET_CPUID); ");
+
+ cpuid_val = arch_prctl(ARCH_GET_CPUID, 0);
+ if (cpuid_val < 0)
+ errx(1, "ARCH_GET_CPUID fails now, but not before?");
+
+ printf("cpuid_val == %s\n", cpuid_names[cpuid_val]);
+ printf("arch_prctl(ARC_SET_CPUID, 1)\n");
+ if (arch_prctl(ARCH_SET_CPUID, 1) != 0)
+ errx(1, "ARCH_SET_CPUID failed!");
+
+ printf("cpuid() == ");
+}
+
+int main(int argc, char **argv)
+{
+ int cpuid_val = 0, child = 0, status = 0;
+ unsigned int eax = 0, ebx = 0, ecx = 0, edx = 0;
+
+ signal(SIGSEGV, sigsegv_cb);
+ setvbuf(stdout, NULL, _IONBF, 0);
+
+ cpuid(&eax, &ebx, &ecx, &edx);
+ printf("cpuid() == {%x, %x, %x, %x}\n", eax, ebx, ecx, edx);
+ printf("arch_prctl(ARCH_GET_CPUID); ");
+
+ cpuid_val = arch_prctl(ARCH_GET_CPUID, 0);
+ if (cpuid_val < 0) {
+ if (errno == EINVAL) {
+ printf("ARCH_GET_CPUID is unsupported on this kernel.\n");
+ fflush(stdout);
+ exit(0); /* no ARCH_GET_CPUID on this system */
+ } else if (errno == ENODEV) {
+ printf("ARCH_GET_CPUID is unsupported on this hardware.\n");
+ fflush(stdout);
+ exit(0); /* no ARCH_GET_CPUID on this system */
+ } else {
+ errx(errno, "ARCH_GET_CPUID failed unexpectedly!");
+ }
+ }
+
+ printf("cpuid_val == %s\n", cpuid_names[cpuid_val]);
+ cpuid(&eax, &ebx, &ecx, &edx);
+ printf("cpuid() == {%x, %x, %x, %x}\n", eax, ebx, ecx, edx);
+ printf("arch_prctl(ARCH_SET_CPUID, 1)\n");
+
+ if (arch_prctl(ARCH_SET_CPUID, 1) != 0) {
+ if (errno == EINVAL) {
+ printf("ARCH_SET_CPUID is unsupported on this kernel.");
+ exit(0); /* no ARCH_SET_CPUID on this system */
+ } else if (errno == ENODEV) {
+ printf("ARCH_SET_CPUID is unsupported on this hardware.");
+ exit(0); /* no ARCH_SET_CPUID on this system */
+ } else {
+ errx(errno, "ARCH_SET_CPUID failed unexpectedly!");
+ }
+ }
+
+
+ cpuid(&eax, &ebx, &ecx, &edx);
+ printf("cpuid() == {%x, %x, %x, %x}\n", eax, ebx, ecx, edx);
+ printf("arch_prctl(ARCH_SET_CPUID, 0)\n");
+ fflush(stdout);
+
+ if (arch_prctl(ARCH_SET_CPUID, 0) == -1)
+ errx(1, "ARCH_SET_CPUID failed!");
+
+ printf("cpuid() == ");
+ eax = ebx = ecx = edx = 0;
+ cpuid(&eax, &ebx, &ecx, &edx);
+ printf("{%x, %x, %x, %x}\n", eax, ebx, ecx, edx);
+ printf("arch_prctl(ARCH_SET_CPUID, 0)\n");
+
+ if (signal_count != 1)
+ errx(1, "cpuid didn't fault!");
+
+ if (arch_prctl(ARCH_SET_CPUID, 0) == -1)
+ errx(1, "ARCH_SET_CPUID failed!");
+
+ if (argc > 1)
+ exit(0); /* Don't run the whole test again if we were execed */
+
+ printf("do_child_test\n");
+ child = fork();
+ if (child == 0)
+ return do_child_test();
+
+ if (child != waitpid(child, &status, 0))
+ errx(1, "waitpid failed!?");
+
+ if (WEXITSTATUS(status) != 0)
+ errx(1, "Child exited abnormally!");
+
+ /* The child enabling cpuid should not have affected us */
+ printf("cpuid() == ");
+ eax = ebx = ecx = edx = 0;
+ cpuid(&eax, &ebx, &ecx, &edx);
+ printf("{%x, %x, %x, %x}\n", eax, ebx, ecx, edx);
+ printf("arch_prctl(ARCH_SET_CPUID, 0)\n");
+
+ if (signal_count != 2)
+ errx(1, "cpuid didn't fault!");
+
+ if (arch_prctl(ARCH_SET_CPUID, 0) == -1)
+ errx(1, "ARCH_SET_CPUID failed!");
+
+ /* Our ARCH_CPUID_SIGSEGV should not propagate through exec */
+ printf("do_child_exec_test\n");
+ fflush(stdout);
+
+ child = fork();
+ if (child == 0)
+ return do_child_exec_test(eax, ebx, ecx, edx);
+
+ if (child != waitpid(child, &status, 0))
+ errx(1, "waitpid failed!?");
+
+ if (WEXITSTATUS(status) != 0)
+ errx(1, "Child exited abnormally!");
+
+ printf("All tests passed!\n");
+ exit(EXIT_SUCCESS);
+}
--
2.11.0
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