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Re: [PATCH v3 5/7] x86: guard against straight-line speculation past RET
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Date: Thu, 12 Nov 2020 11:35:08 +0100
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On Fri, Oct 23, 2020 at 10:38:04AM +0200, Jan Beulich wrote:
> Under certain conditions CPUs can speculate into the instruction stream
> past a RET instruction. Guard against this just like 3b7dab93f240
> ("x86/spec-ctrl: Protect against CALL/JMP straight-line speculation")
> did - by inserting an "INT $3" insn. It's merely the mechanics of how to
> achieve this that differ: A set of macros gets introduced to post-
> process RET insns issued by the compiler (or living in assembly files).
>
> Unfortunately for clang this requires further features their built-in
> assembler doesn't support: We need to be able to override insn mnemonics
> produced by the compiler (which may be impossible, if internally
> assembly mnemonics never get generated)
FTR I've reported this to LLVM upstream:
https://bugs.llvm.org/show_bug.cgi?id=48159
Roger.
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