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Date: Tue, 10 Oct 2017 20:56:52 -0700
From: Kyle Huey <me@...ehuey.com>
To: Wanpeng Li <kernellwp@...il.com>
Cc: "Robert O'Callahan" <robert@...llahan.org>,
Thomas Gleixner <tglx@...utronix.de>,
Andy Lutomirski <luto@...nel.org>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
"the arch/x86 maintainers" <x86@...nel.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Jeff Dike <jdike@...toit.com>,
Richard Weinberger <richard@....at>,
Alexander Viro <viro@...iv.linux.org.uk>,
Shuah Khan <shuah@...nel.org>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Borislav Petkov <bp@...e.de>,
Peter Zijlstra <peterz@...radead.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
Len Brown <len.brown@...el.com>,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Dmitry Safonov <dsafonov@...tuozzo.com>,
David Matlack <dmatlack@...gle.com>,
Nadav Amit <nadav.amit@...il.com>,
Andi Kleen <andi@...stfloor.org>,
Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"open list:USER-MODE LINUX (UML)"
<user-mode-linux-devel@...ts.sourceforge.net>,
"open list:USER-MODE LINUX (UML)"
<user-mode-linux-user@...ts.sourceforge.net>,
"open list:FILESYSTEMS (VFS and infrastructure)"
<linux-fsdevel@...r.kernel.org>,
"open list:KERNEL SELFTEST FRAMEWORK"
<linux-kselftest@...r.kernel.org>, kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH v16 09/10] x86/arch_prctl: Selftest for ARCH_[GET|SET]_CPUID
On Tue, Oct 10, 2017 at 8:35 PM, Wanpeng Li <kernellwp@...il.com> wrote:
> Hi Kyle,
> 2017-03-20 16:16 GMT+08:00 Kyle Huey <me@...ehuey.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@...ehuey.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?
Thanks for pointing out that this never got merged. That's quite
disappointing, especially after reviewers insisted I write this test.
The failure you're seeing is because the values of ARCH_GET_CPUID and
ARCH_SET_CPUID changed and the values hardcoded in the test are no
longer accurate. If you set them to the correct values (0x1011 and
0x1012 respectively) the test should pass.
- Kyle
> # ./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
>>
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