Re: [PATCH v16 09/10] x86/arch_prctl: Selftest for ARCH_[GET|SET]_CPUID

[Wanpeng Li <kernellwp@gmail.com>]

Hi Kyle,
2017-03-20 16:16 GMT+08:00 Kyle Huey <me@kylehuey.com>:
> 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 ++++++++++++++++++++++++++++++

I'm not sure why this commit is not merged to upstream. I test
4.14-rc3 w/ this testcase on a haswell client, however I encounter the
below splat, any idea?

# ./cpuid_fault_64
cpuid() == {d, 756e6547, 6c65746e, 49656e69}
arch_prctl(ARCH_GET_CPUID); ARCH_GET_CPUID is unsupported on this kernel.

Regards,
Wanpeng Li

>  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
>