UML kernel panic on initialization

[subashab at codeaurora.org]

On 2021-07-11 14:27, YiFei Zhu wrote:
> On Sat, Jul 10, 2021 at 4:00 PM <subashab at codeaurora.org> wrote:
>> Run /sbin/init as init process
>> init[1]: segfault at 0 ip 0000000040000af0 sp 0000007fbfb0be40 error 0
>> in ld-2.13.so[40000000+20000]
> 
> I haven't tried to reproduce this, but it looks like it failed in the
> dynamic loader. Do you know what instruction it is failing at? It
> should be at offset 1af0 in objdump -d `ld-2.13.so` assuming the first
> instruction in objdump is 1000.
> 
> Could you also check if this instruction that is segfaulting is the
> entry point address? If so, it could be that there's some sort of
> failure in mapping the VMA, so if you could check the /proc/[pid]/maps
> of the userspace traced process that would be great. You can identify
> the traced process in that it has a different VSZ than the other UML
> threads.
> 

The start of instructions is at af0 for me -

Disassembly of section .text:

0000000000000af0 <_dl_rtld_di_serinfo-0x7b10>:
      af0:       48 89 e7                mov    %rsp,%rdi

The offset at af0 from start is -

     15e0:       48 8d 35 79 97 01 00    lea    0x19779(%rip),%rsi        
# 1ad60 <calloc+0x56e0>

Here is the output of the /proc/[pid]/maps -

60000000-60719000 rwxp 00000000 103:00 12718929                          
<full_path_to_linux_binary>
60719000-6077b000 rwxp 00000000 00:00 0                                  
[heap]
6077b000-80000000 rwxs 0077b000 00:18 8                                  
/dev/shm/#8 (deleted)
80800000-80801000 rwxs 011f5000 00:18 8                                  
/dev/shm/#8 (deleted)
7ffff71d3000-7ffff71de000 r-xp 00000000 fd:00 131326                     
/lib/x86_64-linux-gnu/libnss_files-2.23.so
7ffff71de000-7ffff73dd000 ---p 0000b000 fd:00 131326                     
/lib/x86_64-linux-gnu/libnss_files-2.23.so
7ffff73dd000-7ffff73de000 r-xp 0000a000 fd:00 131326                     
/lib/x86_64-linux-gnu/libnss_files-2.23.so
7ffff73de000-7ffff73df000 rwxp 0000b000 fd:00 131326                     
/lib/x86_64-linux-gnu/libnss_files-2.23.so
7ffff73df000-7ffff73e5000 rwxp 00000000 00:00 0
7ffff73e5000-7ffff75a5000 r-xp 00000000 fd:00 131648                     
/lib/x86_64-linux-gnu/libc-2.23.so
7ffff75a5000-7ffff77a5000 ---p 001c0000 fd:00 131648                     
/lib/x86_64-linux-gnu/libc-2.23.so
7ffff77a5000-7ffff77a9000 r-xp 001c0000 fd:00 131648                     
/lib/x86_64-linux-gnu/libc-2.23.so
7ffff77a9000-7ffff77ab000 rwxp 001c4000 fd:00 131648                     
/lib/x86_64-linux-gnu/libc-2.23.so
7ffff77ab000-7ffff77af000 rwxp 00000000 00:00 0
7ffff77af000-7ffff77c7000 r-xp 00000000 fd:00 131033                     
/lib/x86_64-linux-gnu/libpthread-2.23.so
7ffff77c7000-7ffff79c6000 ---p 00018000 fd:00 131033                     
/lib/x86_64-linux-gnu/libpthread-2.23.so
7ffff79c6000-7ffff79c7000 r-xp 00017000 fd:00 131033                     
/lib/x86_64-linux-gnu/libpthread-2.23.so
7ffff79c7000-7ffff79c8000 rwxp 00018000 fd:00 131033                     
/lib/x86_64-linux-gnu/libpthread-2.23.so
7ffff79c8000-7ffff79cc000 rwxp 00000000 00:00 0
7ffff79cc000-7ffff79d3000 r-xp 00000000 fd:00 130891                     
/lib/x86_64-linux-gnu/librt-2.23.so
7ffff79d3000-7ffff7bd2000 ---p 00007000 fd:00 130891                     
/lib/x86_64-linux-gnu/librt-2.23.so
7ffff7bd2000-7ffff7bd3000 r-xp 00006000 fd:00 130891                     
/lib/x86_64-linux-gnu/librt-2.23.so
7ffff7bd3000-7ffff7bd4000 rwxp 00007000 fd:00 130891                     
/lib/x86_64-linux-gnu/librt-2.23.so
7ffff7bd4000-7ffff7bd6000 r-xp 00000000 fd:00 131650                     
/lib/x86_64-linux-gnu/libutil-2.23.so
7ffff7bd6000-7ffff7dd5000 ---p 00002000 fd:00 131650                     
/lib/x86_64-linux-gnu/libutil-2.23.so
7ffff7dd5000-7ffff7dd6000 r-xp 00001000 fd:00 131650                     
/lib/x86_64-linux-gnu/libutil-2.23.so
7ffff7dd6000-7ffff7dd7000 rwxp 00002000 fd:00 131650                     
/lib/x86_64-linux-gnu/libutil-2.23.so
7ffff7dd7000-7ffff7dfd000 r-xp 00000000 fd:00 131032                     
/lib/x86_64-linux-gnu/ld-2.23.so
7ffff7fd6000-7ffff7fdb000 rwxp 00000000 00:00 0
7ffff7ff7000-7ffff7ffa000 r--p 00000000 00:00 0                          
[vvar]
7ffff7ffa000-7ffff7ffc000 r-xp 00000000 00:00 0                          
[vdso]
7ffff7ffc000-7ffff7ffd000 r-xp 00025000 fd:00 131032                     
/lib/x86_64-linux-gnu/ld-2.23.so
7ffff7ffd000-7ffff7ffe000 rwxp 00026000 fd:00 131032                     
/lib/x86_64-linux-gnu/ld-2.23.so
7ffff7ffe000-7ffff7fff000 rwxp 00000000 00:00 0
7ffffffde000-7ffffffff000 rwxp 00000000 00:00 0                          
[stack]
ffffffffff600000-ffffffffff601000 r-xp 00000000 00:00 0                  
[vsyscall]

I don't know how to get VSZ from the maps output, so I used ps instead. 
The value is 536932.