On Sep 12, 2016 10:57 AM, "Jann Horn" <jann@xxxxxxxxx> wrote: > > On Mon, Sep 12, 2016 at 09:56:11AM -0700, Andy Lutomirski wrote: > > On Sep 11, 2016 5:29 PM, "Kyle Huey" <me@xxxxxxxxxxxx> wrote: > > > > > > rr (http://rr-project.org/), a userspace record-and-replay reverse- > > > execution debugger, would like to trap and emulate the CPUID instruction. > > > This would allow us to a) mask away certain hardware features that rr does > > > not support (e.g. RDRAND) and b) enable trace portability across machines > > > by providing constant results. > > > > > > Intel supports faulting on the CPUID instruction in newer processors. Bit > > > 31 of MSR_PLATFORM_INFO advertises support for this feature. 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 this bit is preserved on fork(), then no_new_privs must be checked > > (or it must be cleared on "unsafe" exec, but that's nasty). > > I think you mean "preserved on execve()"? Indeed. So it should have defined and tested behavior on fork() and execve(). Maybe fork() should preserve the flag after all. --Andy -- 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
