New x86-64 micro-architecture levels
Wed Jul 15 14:56:00 GMT 2020
* Mark Wielaard:
> One thing that wasn't clear to me from this proposal is how the glibc
> dynamic loader checks for the CPU feature flags. This is important for
> valgrind since it can communicate those through different means. cpuid
> interception, auxv AT_HWCAP/AT_HWCAP2 interception (but not AT_PLATFORM
> at the moment) and of course we can generate SIGILL for unsupported
> instructions. We currently don't intercept /proc/cpuinfo (but could).
glibc uses CPUID in combination with XGETBV. There is also a masking
feature which I have not reviewed, but given that it only takes features
away, I don't think it matters to valgrind.
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