linux-kernel - Re: [BUG] general protection fault when reading /proc/kcore

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Message-ID: <d05f4d38-fdb8-29a6-202e-19d65cd0b1f1@redhat.com>
Date:   Mon, 16 Aug 2021 19:54:24 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Jiri Olsa <jolsa@...hat.com>, Mike Rapoport <rppt@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [BUG] general protection fault when reading /proc/kcore

On 16.08.21 19:49, David Hildenbrand wrote:
> On 16.08.21 19:34, Jiri Olsa wrote:
>> hi,
>> I'm getting fault below when running:
>>
>> 	# cat /proc/kallsyms | grep ksys_read
>> 	ffffffff8136d580 T ksys_read
>> 	# objdump -d --start-address=0xffffffff8136d580 --stop-address=0xffffffff8136d590 /proc/kcore
>>
>> 	/proc/kcore:     file format elf64-x86-64
>>
>> 	Segmentation fault
>>
>> any idea? config is attached
> 
> Just tried with a different config on 5.14.0-rc6+
> 
> [root@...alhost ~]# cat /proc/kallsyms | grep ksys_read
> ffffffff8927a800 T ksys_readahead
> ffffffff89333660 T ksys_read
> 
> [root@...alhost ~]# objdump -d --start-address=0xffffffff89333660
> --stop-address=0xffffffff89333670
> 
> a.out:     file format elf64-x86-64


Sorry, missed the /proc/kcore part:

[root@...alhost ~]# cat /proc/kallsyms | grep ksys_read
ffffffffba27a800 T ksys_readahead
ffffffffba333660 T ksys_read
[root@...alhost ~]# objdump -d --start-address=0xffffffffba333660 
--stop-address=0xffffffffba333670 /proc/kcore

/proc/kcore:     file format elf64-x86-64


Disassembly of section load1:

ffffffffba333660 <load1+0x333660>:
ffffffffba333660:       0f 1f 44 00 00          nopl   0x0(%rax,%rax,1)
ffffffffba333665:       41 55                   push   %r13
ffffffffba333667:       49 89 d5                mov    %rdx,%r13
ffffffffba33366a:       41 54                   push   %r12
ffffffffba33366c:       49 89 f4                mov    %rsi,%r12
ffffffffba33366f:       55                      push   %rbp


-- 
Thanks,

David / dhildenb