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objtool: Fix weak symbol detection

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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: 4adb236867 ("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>
This commit is contained in:
Josh Poimboeuf
2025-09-17 09:03:27 -07:00
parent c2a3e7af31
commit 72567c630d
1 changed files with 4 additions and 4 deletions
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8
tools/objtool/elf.c
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@@ -109,7 +109,7 @@ struct symbol_hole {
};
/*
* Find !section symbol where @offset is after it.
* Find the last symbol before @offset.
*/
static int symbol_hole_by_offset(const void *key, const struct rb_node *node)
{
@@ -120,8 +120,7 @@ static int symbol_hole_by_offset(const void *key, const struct rb_node *node)
return -1;
if (sh->key >= s->offset + s->len) {
if (s->type != STT_SECTION)
sh->sym = s;
sh->sym = s;
return 1;
}
@@ -428,7 +427,8 @@ static void elf_add_symbol(struct elf *elf, struct symbol *sym)
sym->len = sym->sym.st_size;
__sym_for_each(iter, &sym->sec->symbol_tree, sym->offset, sym->offset) {
if (iter->offset == sym->offset && iter->type == sym->type)
if (iter->offset == sym->offset && iter->type == sym->type &&
iter->len == sym->len)
iter->alias = sym;
}