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SubjectRe: [PATCH v2 08/14] x86/retpoline: Create a retpoline thunk array
On Wed, Oct 20, 2021 at 05:46:39PM +0100, Andrew Cooper wrote:
> On 20/10/2021 16:57, Josh Poimboeuf wrote:
> > On Wed, Oct 20, 2021 at 12:44:50PM +0200, Peter Zijlstra wrote:
> >> Stick all the retpolines in a single symbol and have the individual
> >> thunks as inner labels, this should guarantee thunk order and layout.
> > How so?
> >
> > Just wondering what the purpose of the array is. It doesn't seem to be
> > referenced anywhere.
>
> The array property is what makes:
>
> > + reg = (target - &__x86_indirect_thunk_rax) /
> > + (&__x86_indirect_thunk_rcx - &__x86_indirect_thunk_rax);
>
> safe in the next path.

Arguably I should probably write that like:

(target - &__x86_indirect_thunk_array) / __x86_indirect_thunk_size;

or something, and also generate and expose that latter symbol from .S.

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