linux-kernel - Re: Bug: broken /proc/kcore in 6.13

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Message-ID: <9f3ba47b-e0ce-4d7a-b60f-e5b8d96b0f2b@lucifer.local>
Date: Fri, 17 Jan 2025 16:31:54 +0000
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Alexandre Ferrieux <alexandre.ferrieux@...il.com>
Cc: Steven Rostedt <rostedt@...dmis.org>, linux-trace-users@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: Bug: broken /proc/kcore in 6.13

On Fri, Jan 17, 2025 at 04:28:32PM +0100, Alexandre Ferrieux wrote:
>
>
> On 17/01/2025 16:19, Alexandre Ferrieux wrote:
> > On 17/01/2025 15:44, Lorenzo Stoakes wrote:
> >>> Alexandre Ferrieux <alexandre.ferrieux@...il.com> wrote:
> >>>
> >>>> Hi,
> >>>>
> >>>> Somewhere in the 6.13 branch (not bisected yet, sorry), it stopped being
> >>>> possible to disassemble the running kernel from gdb through /proc/kcore.
> >> Thanks for the report! Much appreciated.
> >>
> >> I may try to bisect here also unless you're close to finding the commit that
> >> broke this?
> >
> > I'm currently homing in on copy_page_to_iter_nofault(), will report shortly :)
>
> Hmm, actually, that baby ain't cooperative:
>
>   [Fri Jan 17 15:23:05 2025] trace_kprobe: Could not probe notrace function
>   copy_page_to_iter_nofault
>
> ... if I cannot insert kprobes to sniff around, I'm a bit stuck :}
> So I think you'll reach the goal faster than me !
>
> PS: For your bisection: the last working kernel I know of is Debian's 6.12 final:
>
>   ii  linux-image-6.12.9-amd64         6.12.9-1                         amd64
>     Linux 6.12 for 64-bit PCs (signed)
>
>

Cheers much appreciated, have been able to repro and am bisecting now! Will
update with results when done.