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

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Message-ID: <ef3f7784-7129-436a-a5f7-1630b278b101@orange.com>
Date: Fri, 17 Jan 2025 16:28:32 +0100
From: Alexandre Ferrieux <alexandre.ferrieux@...il.com>
To: Alexandre Ferrieux <alexandre.ferrieux@...il.com>,
 Lorenzo Stoakes <lorenzo.stoakes@...cle.com>,
 Steven Rostedt <rostedt@...dmis.org>
Cc: 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 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)