[Lldb-commits] [PATCH] D117928: [lldb] Disable tests for x86 that uses write command on XMM registers

Sun Jan 23 18:06:08 PST 2022

ljmf00 added a comment.

In D117928#3263992 <https://reviews.llvm.org/D117928#3263992>, @mgorny wrote:

> Thank you. Yes, please test on an older kernel, in case it's specifically a kernel regression.

I can confirm regression on Linux LTS 5.10.93. Probably later and introduced by the patch I mentioned. I reported to the kernel bug tracker. See https://bugzilla.kernel.org/show_bug.cgi?id=215524 .

In D117928#3264795 <https://reviews.llvm.org/D117928#3264795>, @labath wrote:

> If this is a problem with PTRACE_SETREGSET(NT_FPREGSET), then we might be able to work around it by using PTRACE_POKEUSER instead. But it'd definitely be good to confirm this, so that we can report the bug to kernel devs.

According to `ptrace` documentation `PTRACE_SETFPREGS` seems a better fit, although either this and `PTRACE_POKEUSER` disallow writing in some specific general-purpose registers, so we should only use this for FP/XMM registers? AFAIK BSD-based kernels implements `PT_SETXMMREGS` although I don't see any documentation on the Linux kernel side about this.

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https://reviews.llvm.org/D117928