linux-kernel - Re: Question: livepatch failed for new fork() task stack unreliable

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Date:   Thu, 4 Jun 2020 20:51:42 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     "Wangshaobo (bobo)" <bobo.shaobowang@...wei.com>
Cc:     huawei.libin@...wei.com, xiexiuqi@...wei.com,
        cj.chengjian@...wei.com, mingo@...hat.com, x86@...nel.org,
        linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
        mbenes@...e.cz, devel@...ukata.com, viro@...iv.linux.org.uk,
        esyr@...hat.com
Subject: Re: Question: livepatch failed for new fork() task stack unreliable

On Fri, Jun 05, 2020 at 09:26:42AM +0800, Wangshaobo (bobo) wrote:
> > > So, I want to ask is there any side effects if i modify like this ? this
> > > modification is based on
> > > 
> > > your fix. It looks like ok with proper test.
> > > 
> > > diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
> > > index e9cc182aa97e..ecce5051e8fd 100644
> > > --- a/arch/x86/kernel/unwind_orc.c
> > > +++ b/arch/x86/kernel/unwind_orc.c
> > > @@ -620,6 +620,7 @@ void __unwind_start(struct unwind_state *state, struct
> > > task_struct *task,
> > >                  state->sp = task->thread.sp;
> > >                  state->bp = READ_ONCE_NOCHECK(frame->bp);
> > >                  state->ip = READ_ONCE_NOCHECK(frame->ret_addr);
> > > +              state->signal = ((void *)state->ip == ret_from_fork);
> > >          }
> > > 
> > > diff --git a/arch/x86/kernel/unwind_orc.c b/arch/x86/kernel/unwind_orc.c
> > > index 7f969b2d240f..d7396431261a 100644
> > > --- a/arch/x86/kernel/unwind_orc.c
> > > +++ b/arch/x86/kernel/unwind_orc.c
> > > @@ -540,7 +540,7 @@ bool unwind_next_frame(struct unwind_state *state)
> > >           state->sp = sp;
> > >           state->regs = NULL;
> > >           state->prev_regs = NULL;
> > > -        state->signal = ((void *)state->ip == ret_from_fork);
> > > +        state->signal = false;
> > >           break;
> > Yes that's correct.
> 
> Hi, josh
> 
> Could i ask when are you free to send the patch, all the tests are passed
> by.

I want to run some regression tests, so it will probably be next week.

-- 
Josh