objtool: Skip reading DWARF section data
authorJosh Poimboeuf <jpoimboe@kernel.org>
Tue, 30 May 2023 17:21:14 +0000 (10:21 -0700)
committerJosh Poimboeuf <jpoimboe@kernel.org>
Wed, 7 Jun 2023 17:03:27 +0000 (10:03 -0700)
commitb4c96ef0add5b701eb37be9830a98610e1d9b4a3
tree7ab7519c4077033a7568c3f16509fb6c5e9f2dca
parentd93b5935fd47007597aed5105a902a10204bc30e
objtool: Skip reading DWARF section data

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>
tools/objtool/elf.c