From: Alessandro Carminati <alessandro.carminati@xxxxxxxxx> Date: Fri, 21 Jul 2023 14:40:54 +0200 > Hello, > > I apologize for being noisy today. > > In an effort to be collaborative, I would like to share my thoughts on why I > see duplicate symbols in fs/binfmt_elf.c. [...] > ~ $ nm -n built-in.a | grep set_brk -B100| egrep "set_brk|\.o:$" > fs/binfmt_elf.o: > 00000000000000d4 t set_brk > fs/compat_binfmt_elf.o: > 00000000000000d4 t set_brk > ``` > > These two symbols come from fs/binfmt_elf.o and fs/compat_binfmt_elf.o, and > they are just two symbols that happen to share the same name, as is common > in the kernel. > > at the same time, addr2line reports symbols to be generated from the same file. > > ``` > ~ $ llvm-addr2line-14 -fe vmlinux ffff8000082f1d2c ffff8000082f4454 > set_brk > /home/alessandro/src/lka64/linux-6.4/fs/binfmt_elf.c:114 > set_brk > /home/alessandro/src/lka64/linux-6.4/fs/binfmt_elf.c:114 > ~ $ > ~ $ addr2line -fe vmlinux ffff8000082f1d2c ffff8000082f4454 > set_brk > /home/alessandro/src/lka64/linux-6.4/fs/binfmt_elf.c:114 > set_brk > /home/alessandro/src/lka64/linux-6.4/fs/binfmt_elf.c:114 > ``` > looking at the source code: > https://elixir.bootlin.com/linux/v6.4/source/fs/compat_binfmt_elf.c#L144 > the cause of this behavior, which is unexpected but correct. Oh man, that's some deep investigation! Let me go back to my old tree I was sending RFC from and check that particular case there... $ grep set_brk test_ksyms ffffffff814b46c0 t fs/binfmt_elf.c:set_brk ffffffff814b7040 t fs/compat_binfmt_elf.c:set_brk Looks a bit better :D > > The rationale is that using source file + line number iproduces better kallsyms > table, but it is still do not produce unique names. > > BR > Alessandro >> As a final note, please understand that my patch was not intended to undermine >> anyone's work. I simply encountered a problem that I wanted to help solve. >> Attached to this message is my code, in case anyone wants to replicate it. >> I would appreciate being kept in the loop, as I genuinely want to assist in >> fixing this problem. Thanks, Olek
