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| author |   Peter Zijlstra <peterz@infradead.org> | 2021-06-11 08:33:36 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2021-06-14 14:05:36 +0200 |
| commit | d33b9035e14a35f6f2a5f067f0b156a93581811d (patch) | |
| tree | c1ea88952eeffb4a3b2967108fe769e7369f7f36 /tools/objtool | |
| parent | instrumentation.h: Avoid using inline asm operand modifiers (diff) | |
| download | linux-dev-d33b9035e14a35f6f2a5f067f0b156a93581811d.tar.xz linux-dev-d33b9035e14a35f6f2a5f067f0b156a93581811d.zip | |
objtool: Improve reloc hash size guestimate
Nathan reported that LLVM ThinLTO builds have a performance regression
with commit 25cf0d8aa2a3 ("objtool: Rewrite hashtable sizing"). Sami
was quick to note that this is due to their use of -ffunction-sections.
As a result the .text section is small and basing the number of relocs
off of that no longer works. Instead have read_sections() compute the
sum of all SHF_EXECINSTR sections and use that.
Fixes: 25cf0d8aa2a3 ("objtool: Rewrite hashtable sizing")
Reported-by: Nathan Chancellor <nathan@kernel.org>
Debugged-by: Sami Tolvanen <samitolvanen@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lkml.kernel.org/r/YMJpGLuGNsGtA5JJ@hirez.programming.kicks-ass.net
Diffstat (limited to 'tools/objtool')
| -rw-r--r-- | tools/objtool/elf.c | 11 | ||||
| -rw-r--r-- | tools/objtool/include/objtool/elf.h | 1 |
2 files changed, 5 insertions, 7 deletions
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index a8a0ee21f71a..2371ccc412eb 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -288,6 +288,9 @@ static int read_sections(struct elf *elf) } sec->len = sec->sh.sh_size; + if (sec->sh.sh_flags & SHF_EXECINSTR) + elf->text_size += sec->len; + list_add_tail(&sec->list, &elf->sections); elf_hash_add(section, &sec->hash, sec->idx); elf_hash_add(section_name, &sec->name_hash, str_hash(sec->name)); @@ -581,13 +584,7 @@ static int read_relocs(struct elf *elf) unsigned int symndx; unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0; - sec = find_section_by_name(elf, ".text"); - if (!sec) { - WARN("no .text"); - return -1; - } - - if (!elf_alloc_hash(reloc, sec->len / 16)) + if (!elf_alloc_hash(reloc, elf->text_size / 16)) return -1; list_for_each_entry(sec, &elf->sections, list) { diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h index 90082751f851..e34395047530 100644 --- a/tools/objtool/include/objtool/elf.h +++ b/tools/objtool/include/objtool/elf.h @@ -83,6 +83,7 @@ struct elf { int fd; bool changed; char *name; + unsigned int text_size; struct list_head sections; int symbol_bits; |