Re: [PATCH 4/7] objtool: Add support for return trampoline call

[Alexandre Chartre]

On 4/2/20 5:27 PM, Peter Zijlstra wrote:
> On Thu, Apr 02, 2020 at 10:22:17AM +0200, Alexandre Chartre wrote:
> > With retpoline, the return instruction is used to branch to an address
> > stored on the stack. So, unlike a regular return instruction, when a
> > retpoline return instruction is reached the stack has been modified
> > compared to what we have when the function was entered.
> >
> > Provide the mechanism to explicitly call-out such return instruction
> > so that objtool can correctly handle them.
>
> https://lkml.kernel.org/r/20200331222703.GH2452@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
>
> And also, the split out version:
>
>    https://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git/commit/?h=core/objtool&id=ec9d9549901dfd2ff411676dfc624e50219e4d5a

Okay, so I can get rid of my retpoline_ret annotation and use UNWIND_HINT_RET_OFFSET
instead (which is more generic). Basically I can change my RETPOLINE_RET macro to:

.macro RETPOLINE_RET
	UNWIND_HINT_RET_OFFSET
	ret
.endm

Thanks,

alex.