Re: [PATCH] x86/unwind/orc: Fix unwind for newly forked tasks

[Zheng Yejian]

On 2024/10/11 23:39, Josh Poimboeuf wrote:
> On Fri, Oct 11, 2024 at 02:50:32PM +0800, Zheng Yejian wrote:
> > On 2024/9/14 07:11, Josh Poimboeuf wrote:
> > > On Fri, Sep 13, 2024 at 10:45:01AM +0800, Zheng Yejian wrote:
> > > > When arch_stack_walk_reliable() is called to unwind for newly forked
> > > > tasks, the return value is negative which means the call stack is
> > > > unreliable. This obviously does not meet expectations.
> > > >
> > > > The root cause is that after commit 3aec4ecb3d1f ("x86: Rewrite
> > > >    ret_from_fork() in C"), the 'ret_addr' of newly forked task is changed
> > > > to 'ret_from_fork_asm' (see copy_thread()), then at the start of the
> > > > unwind, it is incorrectly interprets not as a "signal" one because
> > > > 'ret_from_fork' is still used to determine the initial "signal" (see
> > > > __unwind_start()). Then the address gets incorrectly decremented in the
> > > > call to orc_find() (see unwind_next_frame()) and resulting in the
> > > > incorrect ORC data.
> > > >
> > > > To fix it, check 'ret_from_fork_asm' rather than 'ret_from_fork' in
> > > > __unwind_start().
> > > >
> > > > Fixes: 3aec4ecb3d1f ("x86: Rewrite ret_from_fork() in C")
> > > > Signed-off-by: Zheng Yejian <zhengyejian@xxxxxxxxxxxxxxx>
> > >
> > > Thanks!
> > >
> > > Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> >
> > Hi, Josh, thanks for your ack!
> > Will this patch go into mainline soon?
>
> Sorry about that, I'll go ahead and queue this up.

Thanks!

Zheng Yejian