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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: Tue, 10 Nov 2020 10:31:42 +0100
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "Andrew Cooper" <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>
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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), and we want to use \(text)
> escaping / quoting in the auxiliary macro.
Could this have an option to enable/disable at build time?
FreeBSD will drop GNU as quite soon from base, and albeit it can be
installed as a package I would like to be able to build Xen using a
toolchain based on LLVM exclusively.
Thanks, Roger.
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