linux-kernel - [tip: objtool/core] objtool: Fix weak symbol detection

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Message-ID: <176060837740.709179.15954898643494638439.tip-bot2@tip-bot2>
Date: Thu, 16 Oct 2025 09:52:57 -0000
From: "tip-bot2 for Josh Poimboeuf" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Petr Mladek <pmladek@...e.com>, Joe Lawrence <joe.lawrence@...hat.com>,
 Josh Poimboeuf <jpoimboe@...nel.org>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: objtool/core] objtool: Fix weak symbol detection

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     72567c630d32bc31f671977f78228c80937ed80e
Gitweb:        https://git.kernel.org/tip/72567c630d32bc31f671977f78228c80937ed80e
Author:        Josh Poimboeuf <jpoimboe@...nel.org>
AuthorDate:    Wed, 17 Sep 2025 09:03:27 -07:00
Committer:     Josh Poimboeuf <jpoimboe@...nel.org>
CommitterDate: Tue, 14 Oct 2025 14:45:23 -07:00

objtool: Fix weak symbol detection

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@...e.com>
Tested-by: Joe Lawrence <joe.lawrence@...hat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@...nel.org>
---
 tools/objtool/elf.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index c024937..d7fb3d0 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -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;
 	}