Re: [musl] Segmentation fault musl 1.2.4

[Cody Wetzel <codyawetzel@gmail.com>]

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So maybe I'm not understanding how gdb works or is used. I'm getting no
meaningful output even though these commands should result in a
segmentation fault.

> / # gdb
> Segmentation fault
> / # /tmp/ld-musl-armhf.so.1 /usr/bin/gdb --args ls -l /tmp
> GNU gdb (GDB) 12.1
> Copyright (C) 2022 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <
> http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.
> Type "show copying" and "show warranty" for details.
> This GDB was configured as "armv7-alpine-linux-musleabihf".
> Type "show configuration" for configuration details.
> For bug reporting instructions, please see:
> <https://www.gnu.org/software/gdb/bugs/>.
> Find the GDB manual and other documentation resources online at:
> <http://www.gnu.org/software/gdb/documentation/>.
> For help, type "help".
> Type "apropos word" to search for commands related to "word"...
> Reading symbols from ls...
> (No debugging symbols found in ls)
> (gdb)
> quit
> / # /tmp/ld-musl-armhf.so.1 /usr/bin/gdb --args cd /tmp
> GNU gdb (GDB) 12.1
> Copyright (C) 2022 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <
> http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.
> Type "show copying" and "show warranty" for details.
> This GDB was configured as "armv7-alpine-linux-musleabihf".
> Type "show configuration" for configuration details.
> For bug reporting instructions, please see:
> <https://www.gnu.org/software/gdb/bugs/>.
> Find the GDB manual and other documentation resources online at:
> <http://www.gnu.org/software/gdb/documentation/>.
> For help, type "help".
> Type "apropos word" to search for commands related to "word"...
> cd: No such file or directory.
> (gdb)
> quit
> / # /tmp/ld-musl-armhf.so.1 /usr/bin/gdb --args apk -h /tmp
> GNU gdb (GDB) 12.1
> Copyright (C) 2022 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later <
> http://gnu.org/licenses/gpl.html>
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.
> Type "show copying" and "show warranty" for details.
> This GDB was configured as "armv7-alpine-linux-musleabihf".
> Type "show configuration" for configuration details.
> For bug reporting instructions, please see:
> <https://www.gnu.org/software/gdb/bugs/>.
> Find the GDB manual and other documentation resources online at:
> <http://www.gnu.org/software/gdb/documentation/>.
> For help, type "help".
> Type "apropos word" to search for commands related to "word"...
> Reading symbols from apk...
> (No debugging symbols found in apk)
> (gdb) bt
> No stack.
> (gdb) disas $pc-40,+80
> No registers.
> (gdb) info reg
> The program has no registers now.


On Thu, Jan 4, 2024 at 8:48 AM Szabolcs Nagy <nsz@port70.net> wrote:

> * Cody Wetzel <codyawetzel@gmail.com> [2024-01-03 11:20:29 -0600]:
> > Hello musl team,
> >
> > I tried getting a core dump but I'm not sure if I'm doing something
> wrong...
> >
> > / # cat /proc/sys/kernel/core_pattern/tmp/core-%e-%s-%u-%g-%p-%t/ #
> > apk upgrade busybox
> > --repository=https://dl-cdn.alpinelinux.org/alpine/v3.18/main
> > --repository=https://dl-cdn.alpinelinux.org/alpine/v3.18/communityfetch
> >
> https://dl-cdn.alpinelinux.org/alpine/v3.18/community/armv7/APKINDEX.tar.gzfetch
> >
> https://dl-cdn.alpinelinux.org/alpine/v3.18/main/armv7/APKINDEX.tar.gzfetch
> >
> https://dl-cdn.alpinelinux.org/alpine/v3.17/main/armv7/APKINDEX.tar.gzfetch
> >
> https://dl-cdn.alpinelinux.org/alpine/v3.17/community/armv7/APKINDEX.tar.gz(1/3)
> > Upgrading busybox (1.35.0-r29 -> 1.36.1-r5)Executing
> > busybox-1.36.1-r5.post-upgrade(2/3) Upgrading busybox-binsh
> > (1.35.0-r29 -> 1.36.1-r5)(3/3) Upgrading ssl_client (1.35.0-r29 ->
> > 1.36.1-r5)Executing busybox-1.36.1-r5.triggerOK: 5 MiB in 15 packages/
> > # apk upgrade musl
> > --repository=https://dl-cdn.alpinelinux.org/alpine/v3.18/main
> > --repository=https://dl-cdn.alpinelinux.org/alpine/v3.18/community(1/1)
> > Upgrading musl (1.2.3-r5 -> 1.2.4-r2)OK: 5 MiB in 15 packages/ # apk
> > upgrade rust --repository=
> https://dl-cdn.alpinelinux.org/alpine/v3.18/main
> > --repository=
> https://dl-cdn.alpinelinux.org/alpine/v3.18/communitySegmentation
> > fault/ # apk -hSegmentation fault/ # ls /tmp/core*Segmentation fault/
> > # cd /tmp/tmp # lsSegmentation fault
>
> i'd
>
> # cp /lib/ld-musl-armhf.so.1 /tmp
> # apk add gdb musl-dbg apk-tools-static
>
> then upgrade musl using apk.static, then debug via
>
> # /tmp/ld-musl-armhf.so.1 /usr/bin/gdb --args ls -l /tmp
>
> or analyze a core dump, you can always install more debug tools
> via apk.static and run commands using the old ld-musl-armhf.so.1
>
> in gdb, you want to do
>
> bt
> disas $pc-40,+80
> info reg
> info proc map
>
> as a starting point and post the results.
>
> strace output can be useful too as well as readelf -aW of ld.so
> depending on what is going on.
>


-- 
Cody Wetzel
codyawetzel@gmail.com
(402)490-9242

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