On Fri, Mar 19, 2021 at 04:56:30PM +0100, Peter Zijlstra wrote:
> On Fri, Mar 19, 2021 at 10:30:26AM -0500, Josh Poimboeuf wrote:
> > On Fri, Mar 19, 2021 at 09:06:44AM +0100, Peter Zijlstra wrote:
> > > > Also doesn't the alternative code already insert nops?
> > >
> > > Problem is that the {call
On Fri, Mar 19, 2021 at 10:30:26AM -0500, Josh Poimboeuf wrote:
> On Fri, Mar 19, 2021 at 09:06:44AM +0100, Peter Zijlstra wrote:
> > > Also doesn't the alternative code already insert nops?
> >
> > Problem is that the {call,jmp} *%\reg thing is not fixed length. They're
> > 2 or 3 bytes depending
On Fri, Mar 19, 2021 at 09:06:44AM +0100, Peter Zijlstra wrote:
> > Also doesn't the alternative code already insert nops?
>
> Problem is that the {call,jmp} *%\reg thing is not fixed length. They're
> 2 or 3 bytes depending on which register is picked.
Why do they need to be fixed length? Objto
On Thu, Mar 18, 2021 at 10:29:55PM -0500, Josh Poimboeuf wrote:
> On Thu, Mar 18, 2021 at 06:11:17PM +0100, Peter Zijlstra wrote:
> > When the compiler emits: "CALL __x86_indirect_thunk_\reg" for an
> > indirect call, have objtool rewrite it to:
> >
> > ALTERNATIVE "call __x86_indirect_thunk_\
On Thu, Mar 18, 2021 at 06:11:17PM +0100, Peter Zijlstra wrote:
> When the compiler emits: "CALL __x86_indirect_thunk_\reg" for an
> indirect call, have objtool rewrite it to:
>
> ALTERNATIVE "call __x86_indirect_thunk_\reg",
> "call *%reg", ALT_NOT(X86_FEATURE_RETPOLINE)
>
When the compiler emits: "CALL __x86_indirect_thunk_\reg" for an
indirect call, have objtool rewrite it to:
ALTERNATIVE "call __x86_indirect_thunk_\reg",
"call *%reg", ALT_NOT(X86_FEATURE_RETPOLINE)
Additionally, in order to not emit endless identical
.altinst_replacem
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