From: Josh Poimboeuf <jpoimboe@redhat.com>
To: "Wangshaobo (bobo)" <bobo.shaobowang@huawei.com>
Cc: huawei.libin@huawei.com, xiexiuqi@huawei.com,
cj.chengjian@huawei.com, mingo@redhat.com, x86@kernel.org,
linux-kernel@vger.kernel.org, live-patching@vger.kernel.org,
mbenes@suse.cz, devel@etsukata.com, viro@zeniv.linux.org.uk,
esyr@redhat.com
Subject: Re: Question: livepatch failed for new fork() task stack unreliable
Date: Wed, 3 Jun 2020 21:40:51 -0500 [thread overview]
Message-ID: <20200604024051.6ovbr6tbrowwg6jr@treble> (raw)
In-Reply-To: <2225bc83-95f2-bf3d-7651-fdd10a3ddd00@huawei.com>
On Thu, Jun 04, 2020 at 09:24:55AM +0800, Wangshaobo (bobo) wrote:
>
> 在 2020/6/3 23:33, Josh Poimboeuf 写道:
> > On Wed, Jun 03, 2020 at 10:06:07PM +0800, Wangshaobo (bobo) wrote:
> > To be honest, I don't remember what I meant by sibling calls. They
> > don't even leave anything on the stack.
> >
> > For noreturns, the code might be laid out like this:
> >
> > func1:
> > ...
> > call noreturn_foo
> > func2:
> >
> > func2 is immediately after the call to noreturn_foo. So the return
> > address on the stack will actually be 'func2'. We want to retrieve the
> > ORC data for the call instruction (inside func1), instead of the
> > instruction at the beginning of func2.
> >
> > I should probably update that comment.
>
> 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.
--
Josh
next prev parent reply other threads:[~2020-06-04 2:41 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-29 10:10 Question: livepatch failed for new fork() task stack unreliable Wang ShaoBo
2020-05-29 17:44 ` Josh Poimboeuf
[not found] ` <a9ed9157-f3cf-7d2c-7a8e-56150a2a114e@huawei.com>
2020-06-01 18:05 ` Josh Poimboeuf
2020-06-02 1:22 ` Wangshaobo (bobo)
2020-06-02 13:14 ` Josh Poimboeuf
2020-06-03 14:06 ` Wangshaobo (bobo)
2020-06-03 15:33 ` Josh Poimboeuf
2020-06-04 1:24 ` Wangshaobo (bobo)
2020-06-04 2:40 ` Josh Poimboeuf [this message]
2020-06-05 1:26 ` Wangshaobo (bobo)
2020-06-05 1:51 ` Josh Poimboeuf
2020-06-30 13:04 ` Wangshaobo (bobo)
2020-06-30 21:36 ` Josh Poimboeuf
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