Peter Zijlstra c38255d8bf objtool: Fix symbol creation ... commit ead165fa10 upstream. Nathan reported objtool failing with the following messages: warning: objtool: no non-local symbols !? warning: objtool: gelf_update_symshndx: invalid section index The problem is due to commit 4abff6d48d ("objtool: Fix code relocs vs weak symbols") failing to consider the case where an object would have no non-local symbols. The problem that commit tries to address is adding a STB_LOCAL symbol to the symbol table in light of the ELF spec's requirement that: In each symbol table, all symbols with STB_LOCAL binding preced the weak and global symbols. As ``Sections'' above describes, a symbol table section's sh_info section header member holds the symbol table index for the first non-local symbol. The approach taken is to find this first non-local symbol, move that to the end and then re-use the freed spot to insert a new local symbol and increment sh_info. Except it never considered the case of object files without global symbols and got a whole bunch of details wrong -- so many in fact that it is a wonder it ever worked :/ Specifically: - It failed to re-hash the symbol on the new index, so a subsequent find_symbol_by_index() would not find it at the new location and a query for the old location would now return a non-deterministic choice between the old and new symbol. - It failed to appreciate that the GElf wrappers are not a valid disk format (it works because GElf is basically Elf64 and we only support x86_64 atm.) - It failed to fully appreciate how horrible the libelf API really is and got the gelf_update_symshndx() call pretty much completely wrong; with the direct consequence that if inserting a second STB_LOCAL symbol would require moving the same STB_GLOBAL symbol again it would completely come unstuck. Write a new elf_update_symbol() function that wraps all the magic required to update or create a new symbol at a given index. Specifically, gelf_update_sym*() require an @ndx argument that is relative to the @data argument; this means you have to manually iterate the section data descriptor list and update @ndx. Fixes: 4abff6d48d ("objtool: Fix code relocs vs weak symbols") Reported-by: Nathan Chancellor <nathan@kernel.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Borislav Petkov <bp@suse.de> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Tested-by: Nathan Chancellor <nathan@kernel.org> Cc: <stable@vger.kernel.org> Link: https://lkml.kernel.org/r/YoPCTEYjoPqE4ZxB@hirez.programming.kicks-ass.net Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>		2022-06-09 10:26:16 +02:00
..
arch/x86	objtool: Add straight-line-speculation validation	2021-12-08 19:26:50 +01:00
Documentation	objtool: Support stack layout changes in alternatives	2021-01-14 09:53:54 -06:00
include/objtool	objtool: Fix objtool regression on x32 systems	2022-06-09 10:26:16 +02:00
.gitignore	objtool: Rework header include paths	2021-01-13 18:13:14 -06:00
Build	objtool: Enable compilation of objtool for all architectures	2020-05-20 09:17:28 -05:00
builtin-check.c	objtool: Add straight-line-speculation validation	2021-12-08 19:26:50 +01:00
builtin-orc.c	objtool: Collate parse_options() users	2021-03-06 12:44:23 +01:00
check.c	objtool: Fix objtool regression on x32 systems	2022-06-09 10:26:16 +02:00
elf.c	objtool: Fix symbol creation	2022-06-09 10:26:16 +02:00
Makefile	objtool: Refactor ORC section generation	2021-01-14 09:53:42 -06:00
objtool.c	objtool: Fix pv_ops noinstr validation	2021-12-03 09:11:42 +01:00
orc_dump.c	x86/unwind/orc: Change REG_SP_INDIRECT	2021-02-10 20:53:51 +01:00
orc_gen.c	Merge branch 'objtool/urgent'	2021-10-07 00:40:17 +02:00
special.c	objtool,x86: Replace alternatives with .retpoline_sites	2021-10-28 23:25:25 +02:00
sync-check.sh	Merge branch 'x86/cpu' into WIP.x86/core, to merge the NOP changes & resolve a semantic conflict	2021-04-02 12:36:30 +02:00
weak.c	objtool: Refactor ORC section generation	2021-01-14 09:53:42 -06:00