Re: [patch 00/38] x86/retbleed: Call depth tracking mitigation

Linus Torvalds
2022-07-19T17:35:15Z

On Tue, Jul 19, 2022 at 10:23 AM Sami Tolvanen <samitolvanen@google.com> wrote:
>
> The preamble hash is encoded into an instruction just to avoid special
> casing objtool, which would otherwise get confused about the random
> bytes. On arm64, we just emit a bare constant before the function.

Ahh.

I think objtool would want to understand about kCFI anyway, so I think
in the long run that hack isn't a goog idea.

But I get why you'd do it as a "do this as just a compiler thing and
hide it from objtool" as a development strategy.

Linus