Re: [PATCH] prctl,x86 Add PR_[GET|SET]_CPUID for controlling the CPUID instruction.
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From: Jann Horn <hidden>
Date: 2016-09-12 17:57:10
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On Mon, Sep 12, 2016 at 09:56:11AM -0700, Andy Lutomirski wrote:
On Sep 11, 2016 5:29 PM, "Kyle Huey" [off-list ref] wrote:quoted
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.
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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()"?