This is a note to let you know that I've just added the patch titled
objtool: Remove annotate_{,un}reachable()
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
objtool-remove-annotate_-un-reachable.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 50b86ed96bd4f0841461dd8516a20b5259c5445a
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Thu Nov 28 10:39:04 2024 +0100
objtool: Remove annotate_{,un}reachable()
[ Upstream commit 06e24745985c8dd0da18337503afcf2f2fdbdff1 ]
There are no users of annotate_reachable() left.
And the annotate_unreachable() usage in unreachable() is plain wrong;
it will hide dangerous fall-through code-gen.
Remove both.
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Acked-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241128094312.235637588@xxxxxxxxxxxxx
Stable-dep-of: 73cfc53cc3b6 ("objtool: Fix C jump table annotations for Clang")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index 0d10d75218f51..75a83394824c4 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -109,35 +109,9 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
/* Unreachable code */
#ifdef CONFIG_OBJTOOL
-/*
- * These macros help objtool understand GCC code flow for unreachable code.
- * The __COUNTER__ based labels are a hack to make each instance of the macros
- * unique, to convince GCC not to merge duplicate inline asm statements.
- */
-#define __stringify_label(n) #n
-
-#define __annotate_reachable(c) ({ \
- asm volatile(__stringify_label(c) ":\n\t" \
- ".pushsection .discard.reachable\n\t" \
- ".long " __stringify_label(c) "b - .\n\t" \
- ".popsection\n\t"); \
-})
-#define annotate_reachable() __annotate_reachable(__COUNTER__)
-
-#define __annotate_unreachable(c) ({ \
- asm volatile(__stringify_label(c) ":\n\t" \
- ".pushsection .discard.unreachable\n\t" \
- ".long " __stringify_label(c) "b - .\n\t" \
- ".popsection\n\t" : : "i" (c)); \
-})
-#define annotate_unreachable() __annotate_unreachable(__COUNTER__)
-
/* Annotate a C jump table to allow objtool to follow the code flow */
#define __annotate_jump_table __section(".rodata..c_jump_table,\"a\",@progbits #")
-
#else /* !CONFIG_OBJTOOL */
-#define annotate_reachable()
-#define annotate_unreachable()
#define __annotate_jump_table
#endif /* CONFIG_OBJTOOL */
@@ -147,7 +121,6 @@ void ftrace_likely_update(struct ftrace_likely_data *f, int val,
* control elsewhere.
*/
#define unreachable() do { \
- annotate_unreachable(); \
barrier_before_unreachable(); \
__builtin_unreachable(); \
} while (0)
diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8e02db7e83323..3e72c9f9b7f37 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -639,47 +639,8 @@ static int add_dead_ends(struct objtool_file *file)
uint64_t offset;
/*
- * Check for manually annotated dead ends.
- */
- rsec = find_section_by_name(file->elf, ".rela.discard.unreachable");
- if (!rsec)
- goto reachable;
-
- for_each_reloc(rsec, reloc) {
- if (reloc->sym->type == STT_SECTION) {
- offset = reloc_addend(reloc);
- } else if (reloc->sym->local_label) {
- offset = reloc->sym->offset;
- } else {
- WARN("unexpected relocation symbol type in %s", rsec->name);
- return -1;
- }
-
- insn = find_insn(file, reloc->sym->sec, offset);
- if (insn)
- insn = prev_insn_same_sec(file, insn);
- else if (offset == reloc->sym->sec->sh.sh_size) {
- insn = find_last_insn(file, reloc->sym->sec);
- if (!insn) {
- WARN("can't find unreachable insn at %s+0x%" PRIx64,
- reloc->sym->sec->name, offset);
- return -1;
- }
- } else {
- WARN("can't find unreachable insn at %s+0x%" PRIx64,
- reloc->sym->sec->name, offset);
- return -1;
- }
-
- insn->dead_end = true;
- }
-
-reachable:
- /*
- * These manually annotated reachable checks are needed for GCC 4.4,
- * where the Linux unreachable() macro isn't supported. In that case
- * GCC doesn't know the "ud2" is fatal, so it generates code as if it's
- * not a dead end.
+ * UD2 defaults to being a dead-end, allow them to be annotated for
+ * non-fatal, eg WARN.
*/
rsec = find_section_by_name(file->elf, ".rela.discard.reachable");
if (!rsec)
