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.
/ # gdbSegmentation fault/ # /tmp/ld-musl-armhf.so.1 /usr/bin/gdb --args ls -l /tmpGNU gdb (GDB) 12.1Copyright (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 /tmpGNU gdb (GDB) 12.1Copyright (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 /tmpGNU gdb (GDB) 12.1Copyright (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) btNo stack.(gdb) disas $pc-40,+80No registers.(gdb) info regThe program has no registers now.
* 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.