linux.git/tools/objtool/elf.c, branch v6.6.132 Clone of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git objtool: Fix weak symbol detection 2026-01-11T14:21:13+00:00 Josh Poimboeuf jpoimboe@kernel.org 2025-09-17T16:03:27+00:00 a8fdcac66666cabe80266d5b5f1e33e9c462ec10 [ Upstream commit 72567c630d32bc31f671977f78228c80937ed80e ] find_symbol_hole_containing() fails to find a symbol hole (aka stripped weak symbol) if its section has no symbols before the hole. This breaks weak symbol detection if -ffunction-sections is enabled. Fix that by allowing the interval tree to contain section symbols, which are always at offset zero for a given section. Fixes a bunch of (-ffunction-sections) warnings like: vmlinux.o: warning: objtool: .text.__x64_sys_io_setup+0x10: unreachable instruction Fixes: 4adb23686795 ("objtool: Ignore extra-symbol code") Acked-by: Petr Mladek <pmladek@suse.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org> 
[ Upstream commit 72567c630d32bc31f671977f78228c80937ed80e ]

find_symbol_hole_containing() fails to find a symbol hole (aka stripped
weak symbol) if its section has no symbols before the hole.  This breaks
weak symbol detection if -ffunction-sections is enabled.

Fix that by allowing the interval tree to contain section symbols, which
are always at offset zero for a given section.

Fixes a bunch of (-ffunction-sections) warnings like:

  vmlinux.o: warning: objtool: .text.__x64_sys_io_setup+0x10: unreachable instruction

Fixes: 4adb23686795 ("objtool: Ignore extra-symbol code")
Acked-by: Petr Mladek <pmladek@suse.com>
Tested-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
objtool: initialize all of struct elf 2023-07-10T07:52:28+00:00 Michal Kubecek mkubecek@suse.cz 2023-06-29T10:05:05+00:00 9f71fbcde2820f2af4658313e808cf1e579190a4 Function elf_open_read() only zero initializes the initial part of allocated struct elf; num_relocs member was recently added outside the zeroed part so that it was left uninitialized, resulting in build failures on some systems. The partial initialization is a relic of times when struct elf had large hash tables embedded. This is no longer the case so remove the trap and initialize the whole structure instead. Fixes: eb0481bbc4ce ("objtool: Fix reloc_hash size") Signed-off-by: Michal Kubecek <mkubecek@suse.cz> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Link: https://lore.kernel.org/r/20230629102051.42E8360467@lion.mk-sys.cz 
Function elf_open_read() only zero initializes the initial part of
allocated struct elf; num_relocs member was recently added outside the
zeroed part so that it was left uninitialized, resulting in build failures
on some systems.

The partial initialization is a relic of times when struct elf had large
hash tables embedded. This is no longer the case so remove the trap and
initialize the whole structure instead.

Fixes: eb0481bbc4ce ("objtool: Fix reloc_hash size")
Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20230629102051.42E8360467@lion.mk-sys.cz
objtool: Skip reading DWARF section data 2023-06-07T17:03:27+00:00 Josh Poimboeuf jpoimboe@kernel.org 2023-05-30T17:21:14+00:00 b4c96ef0add5b701eb37be9830a98610e1d9b4a3 Objtool doesn't use DWARF at all, and the DWARF sections' data take up a lot of memory. Skip reading them. Note this only skips the DWARF base sections, not the rela sections. The relas are needed because their symbol references may need to be reindexed if any local symbols get added by elf_create_symbol(). Also note the DWARF data will eventually be read by libelf anyway, when writing the object file. But that's fine, the goal here is to reduce *peak* memory usage, and the previous patch (which freed insn memory) gave some breathing room. So the allocation gets shifted to a later time, resulting in lower peak memory usage. With allyesconfig + CONFIG_DEBUG_INFO: - Before: peak heap memory consumption: 29.93G - After: peak heap memory consumption: 25.47G Link: https://lore.kernel.org/r/52a9698835861dd35f2ec35c49f96d0bb39fb177.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> 
Objtool doesn't use DWARF at all, and the DWARF sections' data take up a
lot of memory.  Skip reading them.

Note this only skips the DWARF base sections, not the rela sections.
The relas are needed because their symbol references may need to be
reindexed if any local symbols get added by elf_create_symbol().

Also note the DWARF data will eventually be read by libelf anyway, when
writing the object file.  But that's fine, the goal here is to reduce
*peak* memory usage, and the previous patch (which freed insn memory)
gave some breathing room.  So the allocation gets shifted to a later
time, resulting in lower peak memory usage.

With allyesconfig + CONFIG_DEBUG_INFO:

- Before: peak heap memory consumption: 29.93G
- After:  peak heap memory consumption: 25.47G

Link: https://lore.kernel.org/r/52a9698835861dd35f2ec35c49f96d0bb39fb177.1685464332.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
objtool: Get rid of reloc->rel[a] 2023-06-07T17:03:26+00:00 Josh Poimboeuf jpoimboe@kernel.org 2023-05-30T17:21:12+00:00 ec24b927c1fbfc91cf7a48276d9fd92072b17d3b Get the relocation entry info from the underlying rsec->data. With allyesconfig + CONFIG_DEBUG_INFO: - Before: peak heap memory consumption: 35.12G - After: peak heap memory consumption: 29.93G Link: https://lore.kernel.org/r/2be32323de6d8cc73179ee0ff14b71f4e7cefaa0.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> 
Get the relocation entry info from the underlying rsec->data.

With allyesconfig + CONFIG_DEBUG_INFO:

- Before: peak heap memory consumption: 35.12G
- After:  peak heap memory consumption: 29.93G

Link: https://lore.kernel.org/r/2be32323de6d8cc73179ee0ff14b71f4e7cefaa0.1685464332.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
objtool: Shrink elf hash nodes 2023-06-07T17:03:25+00:00 Josh Poimboeuf jpoimboe@kernel.org 2023-05-30T17:21:11+00:00 02b54001066364aee72bc4c802b42a96c6e0dc1f Instead of using hlist for the 'struct elf' hashes, use a custom single-linked list scheme. With allyesconfig + CONFIG_DEBUG_INFO: - Before: peak heap memory consumption: 36.89G - After: peak heap memory consumption: 35.12G Link: https://lore.kernel.org/r/6e8cd305ed22e743c30d6e72cfdc1be20fb94cd4.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> 
Instead of using hlist for the 'struct elf' hashes, use a custom
single-linked list scheme.

With allyesconfig + CONFIG_DEBUG_INFO:

- Before: peak heap memory consumption: 36.89G
- After:  peak heap memory consumption: 35.12G

Link: https://lore.kernel.org/r/6e8cd305ed22e743c30d6e72cfdc1be20fb94cd4.1685464332.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
objtool: Shrink reloc->sym_reloc_entry 2023-06-07T17:03:25+00:00 Josh Poimboeuf jpoimboe@kernel.org 2023-05-30T17:21:10+00:00 890f10a433f51f95eccaec13d46dde769ccc113b Convert it to a singly-linked list. With allyesconfig + CONFIG_DEBUG_INFO: - Before: peak heap memory consumption: 38.64G - After: peak heap memory consumption: 36.89G Link: https://lore.kernel.org/r/a51f0a6f9bbf2494d5a3a449807307e78a940988.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> 
Convert it to a singly-linked list.

With allyesconfig + CONFIG_DEBUG_INFO:

- Before: peak heap memory consumption: 38.64G
- After:  peak heap memory consumption: 36.89G

Link: https://lore.kernel.org/r/a51f0a6f9bbf2494d5a3a449807307e78a940988.1685464332.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
objtool: Get rid of reloc->addend 2023-06-07T17:03:23+00:00 Josh Poimboeuf jpoimboe@kernel.org 2023-05-30T17:21:08+00:00 0696b6e314dbe4bd2f24d5e749469f57ea095a9f Get the addend from the embedded GElf_Rel[a] struct. With allyesconfig + CONFIG_DEBUG_INFO: - Before: peak heap memory consumption: 42.10G - After: peak heap memory consumption: 40.37G Link: https://lore.kernel.org/r/ad2354f95d9ddd86094e3f7687acfa0750657784.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> 
Get the addend from the embedded GElf_Rel[a] struct.

With allyesconfig + CONFIG_DEBUG_INFO:

- Before: peak heap memory consumption: 42.10G
- After:  peak heap memory consumption: 40.37G

Link: https://lore.kernel.org/r/ad2354f95d9ddd86094e3f7687acfa0750657784.1685464332.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
objtool: Get rid of reloc->type 2023-06-07T17:03:22+00:00 Josh Poimboeuf jpoimboe@kernel.org 2023-05-30T17:21:07+00:00 fcee899d2794319c9dbeb7b877b0c4ac92f5dd16 Get the type from the embedded GElf_Rel[a] struct. Link: https://lore.kernel.org/r/d1c1f8da31e4f052a2478aea585fcf355cacc53a.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> 
Get the type from the embedded GElf_Rel[a] struct.

Link: https://lore.kernel.org/r/d1c1f8da31e4f052a2478aea585fcf355cacc53a.1685464332.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
objtool: Get rid of reloc->offset 2023-06-07T17:03:21+00:00 Josh Poimboeuf jpoimboe@kernel.org 2023-05-30T17:21:06+00:00 e4cbb9b81f1f7519c7ae3abda09cb15794022952 Get the offset from the embedded GElf_Rel[a] struct. With allyesconfig + CONFIG_DEBUG_INFO: - Before: peak heap memory consumption: 43.83G - After: peak heap memory consumption: 42.10G Link: https://lore.kernel.org/r/2b9ec01178baa346a99522710bf2e82159412e3a.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> 
Get the offset from the embedded GElf_Rel[a] struct.

With allyesconfig + CONFIG_DEBUG_INFO:

- Before: peak heap memory consumption: 43.83G
- After:  peak heap memory consumption: 42.10G

Link: https://lore.kernel.org/r/2b9ec01178baa346a99522710bf2e82159412e3a.1685464332.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
objtool: Get rid of reloc->idx 2023-06-07T17:03:21+00:00 Josh Poimboeuf jpoimboe@kernel.org 2023-05-30T17:21:05+00:00 be9a4c116824c39720001db5bc45fe7528b26cff Use the array offset to calculate the reloc index. With allyesconfig + CONFIG_DEBUG_INFO: - Before: peak heap memory consumption: 45.56G - After: peak heap memory consumption: 43.83G Link: https://lore.kernel.org/r/7351d2ebad0519027db14a32f6204af84952574a.1685464332.git.jpoimboe@kernel.org Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org> 
Use the array offset to calculate the reloc index.

With allyesconfig + CONFIG_DEBUG_INFO:

- Before: peak heap memory consumption: 45.56G
- After:  peak heap memory consumption: 43.83G

Link: https://lore.kernel.org/r/7351d2ebad0519027db14a32f6204af84952574a.1685464332.git.jpoimboe@kernel.org
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>