On Wed, Sep 21, 2016 at 11:58 AM, Kyle Huey <me@xxxxxxxxxxxx> 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 > > + if (!test_and_set_thread_flag(TIF_NOCPUID)) > + /* > + * Must flip the CPU state synchronously with > + * TIF_NOCPUID in the current running context. > + */ > + switch_cpuid_faulting(true); If statements with multiple indented lines should have braces in my book. See, for example, "goto fail". static? > +int set_cpuid_mode(struct task_struct *task, unsigned long val) static? > + * Called immediately after a successful exec. > + */ > +void arch_post_exec(void) > +{ > + /* If cpuid was previously disabled for this task, re-enable it. */ > + if (test_thread_flag(TIF_NOCPUID)) > + enable_cpuid(); > +} > diff --git a/fs/exec.c b/fs/exec.c > index 6fcfb3f..0272b7e 100644 > --- a/fs/exec.c > +++ b/fs/exec.c > @@ -1287,6 +1287,7 @@ void setup_new_exec(struct linux_binprm * bprm) > else > set_dumpable(current->mm, suid_dumpable); > > + arch_post_exec(); Let's call this arch_setup_new_exec(). > perf_event_exec(); > __set_task_comm(current, kbasename(bprm->filename), true); > > diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h > index 2b5b10e..22a3f61 100644 > --- a/include/linux/thread_info.h > +++ b/include/linux/thread_info.h > @@ -130,6 +130,10 @@ static inline void check_object_size(const void *ptr, unsigned long n, > { } > #endif /* CONFIG_HARDENED_USERCOPY */ > > +#ifndef arch_post_exec > +static inline void arch_post_exec(void) {} > +#endif > + thread_info.h is a weird place for this IMO. Admittedly, elf.h isn't a whole lot better. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
