On Tue, Nov 08, 2016 at 10:39:55AM -0800, Kyle Huey wrote: > Intel supports faulting on the CPUID instruction beginning with Ivy Bridge. > When enabled, the processor will fault on attempts to execute the CPUID > instruction with CPL>0. Exposing this feature to userspace will allow a > ptracer to trap and emulate the CPUID instruction. > > When supported, this feature is controlled by toggling bit 0 of > MSR_MISC_FEATURES_ENABLES. It is documented in detail in Section 2.3.2 of > http://www.intel.com/content/dam/www/public/us/en/documents/application-notes/virtualization-technology-flexmigration-application-note.pdf > > Implement a new pair of arch_prctls, available on both x86-32 and x86-64. > > ARCH_GET_CPUID: Returns the current CPUID faulting state, either > ARCH_CPUID_ENABLE or ARCH_CPUID_SIGSEGV. arg2 must be 0. > > ARCH_SET_CPUID: Set the CPUID faulting state to arg2, which must be either > ARCH_CPUID_ENABLE or ARCH_CPUID_SIGSEGV. Returns EINVAL if arg2 is > another value or CPUID faulting is not supported on this system. > > The state of the CPUID faulting flag is propagated across forks, but reset > upon exec. > > Signed-off-by: Kyle Huey <khuey@xxxxxxxxxxxx> > --- ... > diff --git a/tools/testing/selftests/x86/cpuid-fault.c b/tools/testing/selftests/x86/cpuid-fault.c > new file mode 100644 > index 0000000..65419de > --- /dev/null > +++ b/tools/testing/selftests/x86/cpuid-fault.c > @@ -0,0 +1,250 @@ > + > +/* > + * 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 > +#define ARCH_CPUID_ENABLE 1 > +#define ARCH_CPUID_SIGSEGV 2 > +#ifdef __x86_64__ > +#define SYS_arch_prctl 158 > +#else > +#define SYS_arch_prctl 385 > +#endif > +*/ > + > +const char *cpuid_names[] = { > + [0] = "[not set]", > + [ARCH_CPUID_ENABLE] = "ARCH_CPUID_ENABLE", > + [ARCH_CPUID_SIGSEGV] = "ARCH_CPUID_SIGSEGV", > +}; > + > +int arch_prctl(int code, unsigned long arg2) > +{ > + return syscall(SYS_arch_prctl, code, 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 != ARCH_CPUID_SIGSEGV) > + errx(1, "How did cpuid get re-enabled on fork?"); > + > + if ((child = fork()) == 0) { ERROR: do not use assignment in if condition #513: FILE: tools/testing/selftests/x86/cpuid-fault.c:64: + if ((child = fork()) == 0) { There are more in that file. -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) -- -- To unsubscribe from this list: send the line "unsubscribe linux-kselftest" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
