Re: [PATCH] x86/build: Move '-mindirect-branch-cs-prefix' out of GCC-only block

[Peter Zijlstra]

On Thu, Aug 18, 2022 at 09:45:39AM +0200, Peter Zijlstra wrote:

> The thing to do is boot with (warning, *very* verbose):
> 
> 	"spectre_v2=retpoline,lfence debug-alternative"
> 
> and observe that the retpoline sites all replace:
> 
> 	"cs call __x86_indirect_thunk_r11" (6 bytes)
> 
> with:
> 
> 	"lfence; jmp *%r11" (6 bytes)

		^^ call, ofc, unless the original was jmp then jmp...

/me goes get more morning juice in an attempt to wake up.

> 
> 
> This being clang, you'll ofcourse still have a few weird:
> 
> 	"Jcc.d32 __x86_indirect_thunk_r11"
> 
> sites that will not be able to be replaced, but there's nothing I can do
> about that other than to continue to encourage y'all to stop emitting
> them ;-)