Re: [PATCH v2 2/2] x86: Rewrite ret_from_fork() in C

[Peter Zijlstra]

On Wed, Jul 19, 2023 at 05:21:11PM +0200, Petr Mladek wrote:

> This patch broke livepatching. Kthreads never have a reliable stack.
> It works when I revert it.

> > +SYM_CODE_START(ret_from_fork_asm)
> > +	UNWIND_HINT_REGS

It works again when I change the above hint to UNWIND_HINT_END_OF_STACK,
so yeah. Doing this makes objtool unhappy with something else though,
so I'll go prod at things with something sharp...

Thanks!

> >  	ANNOTATE_NOENDBR // copy_thread
> >  	CALL_DEPTH_ACCOUNT
> >  
> > +	movq	%rax, %rdi		/* prev */
> > +	movq	%rsp, %rsi		/* regs */
> > +	movq	%rbx, %rdx		/* fn */
> > +	movq	%r12, %rcx		/* fn_arg */
> > +	call	ret_from_fork
> >  
> > +SYM_CODE_END(ret_from_fork_asm)