path: root/tools/objtool
diff options
authorJosh Poimboeuf <jpoimboe@redhat.com>2017-03-02 16:57:23 -0600
committerIngo Molnar <mingo@kernel.org>2017-03-07 08:42:55 +0100
commit5c51f4ae84df0f9df33ac08aa5be50061a8b4242 (patch)
tree9e301e1fb51b970b742c6bf37e4f4ec622d1322c /tools/objtool
parentbb35e4515411396219431fa235bf21bf9c2794e9 (diff)
objtool: Fix another GCC jump table detection issue
Arnd Bergmann reported a (false positive) objtool warning: drivers/infiniband/sw/rxe/rxe_resp.o: warning: objtool: rxe_responder()+0xfe: sibling call from callable instruction with changed frame pointer The issue is in find_switch_table(). It tries to find a switch statement's jump table by walking backwards from an indirect jump instruction, looking for a relocation to the .rodata section. In this case it stopped walking prematurely: the first .rodata relocation it encountered was for a variable (resp_state_name) instead of a jump table, so it just assumed there wasn't a jump table. The fix is to ignore any .rodata relocation which refers to an ELF object symbol. This works because the jump tables are anonymous and have no symbols associated with them. Reported-by: Arnd Bergmann <arnd@arndb.de> Tested-by: Arnd Bergmann <arnd@arndb.de> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Fixes: 3732710ff6f2 ("objtool: Improve rare switch jump table pattern detection") Link: http://lkml.kernel.org/r/20170302225723.3ndbsnl4hkqbne7a@treble Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'tools/objtool')
3 files changed, 25 insertions, 3 deletions
diff --git a/tools/objtool/builtin-check.c b/tools/objtool/builtin-check.c
index 4cfdbb5b6967..066086dd59a8 100644
--- a/tools/objtool/builtin-check.c
+++ b/tools/objtool/builtin-check.c
@@ -805,11 +805,20 @@ static struct rela *find_switch_table(struct objtool_file *file,
insn->jump_dest->offset > orig_insn->offset))
+ /* look for a relocation which references .rodata */
text_rela = find_rela_by_dest_range(insn->sec, insn->offset,
- if (text_rela && text_rela->sym == file->rodata->sym)
- return find_rela_by_dest(file->rodata,
- text_rela->addend);
+ if (!text_rela || text_rela->sym != file->rodata->sym)
+ continue;
+ /*
+ * Make sure the .rodata address isn't associated with a
+ * symbol. gcc jump tables are anonymous data.
+ */
+ if (find_symbol_containing(file->rodata, text_rela->addend))
+ continue;
+ return find_rela_by_dest(file->rodata, text_rela->addend);
return NULL;
diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 0d7983ac63ef..d897702ce742 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -85,6 +85,18 @@ struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset)
return NULL;
+struct symbol *find_symbol_containing(struct section *sec, unsigned long offset)
+ struct symbol *sym;
+ list_for_each_entry(sym, &sec->symbol_list, list)
+ if (sym->type != STT_SECTION &&
+ offset >= sym->offset && offset < sym->offset + sym->len)
+ return sym;
+ return NULL;
struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
unsigned int len)
diff --git a/tools/objtool/elf.h b/tools/objtool/elf.h
index aa1ff6596684..731973e1a3f5 100644
--- a/tools/objtool/elf.h
+++ b/tools/objtool/elf.h
@@ -79,6 +79,7 @@ struct elf {
struct elf *elf_open(const char *name);
struct section *find_section_by_name(struct elf *elf, const char *name);
struct symbol *find_symbol_by_offset(struct section *sec, unsigned long offset);
+struct symbol *find_symbol_containing(struct section *sec, unsigned long offset);
struct rela *find_rela_by_dest(struct section *sec, unsigned long offset);
struct rela *find_rela_by_dest_range(struct section *sec, unsigned long offset,
unsigned int len);