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Message-ID: <20241128094312.353431347@infradead.org>
Date: Thu, 28 Nov 2024 10:39:05 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: jpoimboe@...nel.org
Cc: chenhuacai@...nel.org,
kernel@...0n.name,
x86@...nel.org,
peterz@...radead.org,
loongarch@...ts.linux.dev,
linux-kernel@...r.kernel.org,
Josh Poimboeuf <jpoimboe@...hat.com>
Subject: [PATCH v2 14/16] objtool: Convert {.UN}REACHABLE to ANNOTATE
Suggested-by: Josh Poimboeuf <jpoimboe@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
arch/loongarch/include/asm/bug.h | 2
arch/x86/entry/entry_64.S | 4 -
arch/x86/include/asm/bug.h | 2
arch/x86/include/asm/irq_stack.h | 2
include/linux/objtool.h | 18 +++----
include/linux/objtool_types.h | 1
tools/include/linux/objtool_types.h | 1
tools/objtool/check.c | 82 +++++++++---------------------------
8 files changed, 36 insertions(+), 76 deletions(-)
--- a/arch/loongarch/include/asm/bug.h
+++ b/arch/loongarch/include/asm/bug.h
@@ -45,7 +45,7 @@
#define __WARN_FLAGS(flags) \
do { \
instrumentation_begin(); \
- __BUG_FLAGS(BUGFLAG_WARNING|(flags), ASM_REACHABLE); \
+ __BUG_FLAGS(BUGFLAG_WARNING|(flags), ANNOTATE_REACHABLE);\
instrumentation_end(); \
} while (0)
--- a/arch/x86/entry/entry_64.S
+++ b/arch/x86/entry/entry_64.S
@@ -311,7 +311,7 @@ SYM_CODE_END(xen_error_entry)
call \cfunc
/* For some configurations \cfunc ends up being a noreturn. */
- REACHABLE
+ ANNOTATE_REACHABLE
jmp error_return
.endm
@@ -532,7 +532,7 @@ SYM_CODE_START(\asmsym)
call \cfunc
/* For some configurations \cfunc ends up being a noreturn. */
- REACHABLE
+ ANNOTATE_REACHABLE
jmp paranoid_exit
--- a/arch/x86/include/asm/bug.h
+++ b/arch/x86/include/asm/bug.h
@@ -92,7 +92,7 @@ do { \
do { \
__auto_type __flags = BUGFLAG_WARNING|(flags); \
instrumentation_begin(); \
- _BUG_FLAGS(ASM_UD2, __flags, ASM_REACHABLE); \
+ _BUG_FLAGS(ASM_UD2, __flags, ANNOTATE_REACHABLE); \
instrumentation_end(); \
} while (0)
--- a/arch/x86/include/asm/irq_stack.h
+++ b/arch/x86/include/asm/irq_stack.h
@@ -101,7 +101,7 @@
#define ASM_CALL_ARG0 \
"call %c[__func] \n" \
- ASM_REACHABLE
+ ANNOTATE_REACHABLE
#define ASM_CALL_ARG1 \
"movq %[arg1], %%rdi \n" \
--- a/include/linux/objtool.h
+++ b/include/linux/objtool.h
@@ -111,14 +111,6 @@
#endif
.endm
-
-.macro REACHABLE
-.Lhere_\@:
- .pushsection .discard.reachable
- .long .Lhere_\@
- .popsection
-.endm
-
.macro ANNOTATE type:req
.Lhere_\@:
.pushsection .discard.annotate_insn,"M",@progbits,8
@@ -138,14 +130,11 @@
#define STACK_FRAME_NON_STANDARD_FP(func)
#define __ASM_ANNOTATE(label, type)
#define ASM_ANNOTATE(type)
-#define ASM_REACHABLE
#else
.macro UNWIND_HINT type:req sp_reg=0 sp_offset=0 signal=0
.endm
.macro STACK_FRAME_NON_STANDARD func:req
.endm
-.macro REACHABLE
-.endm
.macro ANNOTATE type:req
.endm
#endif
@@ -187,6 +176,12 @@
* it will be ignored.
*/
#define ANNOTATE_UNRET_BEGIN ASM_ANNOTATE(ANNOTYPE_UNRET_BEGIN)
+/*
+ * This should be used directly after an instruction that is considered
+ * terminating, like a noreturn CALL or UD2 when we know they are not -- eg
+ * WARN using UD2.
+ */
+#define ANNOTATE_REACHABLE ASM_ANNOTATE(ANNOTYPE_REACHABLE)
#else
#define ANNOTATE_NOENDBR ANNOTATE type=ANNOTYPE_NOENDBR
@@ -196,6 +191,7 @@
#define ANNOTATE_IGNORE_ALTERNATIVE ANNOTATE type=ANNOTYPE_IGNORE_ALTS
#define ANNOTATE_INTRA_FUNCTION_CALL ANNOTATE type=ANNOTYPE_INTRA_FUNCTION_CALL
#define ANNOTATE_UNRET_BEGIN ANNOTATE type=ANNOTYPE_UNRET_BEGIN
+#define ANNOTATE_REACHABLE ANNOTATE type=ANNOTYPE_REACHABLE
#endif
#if defined(CONFIG_NOINSTR_VALIDATION) && \
--- a/include/linux/objtool_types.h
+++ b/include/linux/objtool_types.h
@@ -64,5 +64,6 @@ struct unwind_hint {
#define ANNOTYPE_UNRET_BEGIN 5
#define ANNOTYPE_IGNORE_ALTS 6
#define ANNOTYPE_INTRA_FUNCTION_CALL 7
+#define ANNOTYPE_REACHABLE 8
#endif /* _LINUX_OBJTOOL_TYPES_H */
--- a/tools/include/linux/objtool_types.h
+++ b/tools/include/linux/objtool_types.h
@@ -64,5 +64,6 @@ struct unwind_hint {
#define ANNOTYPE_UNRET_BEGIN 5
#define ANNOTYPE_IGNORE_ALTS 6
#define ANNOTYPE_INTRA_FUNCTION_CALL 7
+#define ANNOTYPE_REACHABLE 8
#endif /* _LINUX_OBJTOOL_TYPES_H */
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -627,56 +627,6 @@ static struct instruction *find_last_ins
return insn;
}
-/*
- * Mark "ud2" instructions and manually annotated dead ends.
- */
-static int add_dead_ends(struct objtool_file *file)
-{
- struct section *rsec;
- struct reloc *reloc;
- struct instruction *insn;
- uint64_t offset;
-
- /*
- * 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)
- return 0;
-
- 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 reachable insn at %s+0x%" PRIx64,
- reloc->sym->sec->name, offset);
- return -1;
- }
- } else {
- WARN("can't find reachable insn at %s+0x%" PRIx64,
- reloc->sym->sec->name, offset);
- return -1;
- }
-
- insn->dead_end = false;
- }
-
- return 0;
-}
-
static int create_static_call_sections(struct objtool_file *file)
{
struct static_call_site *site;
@@ -2306,6 +2256,7 @@ static int read_annotate(struct objtool_
struct section *sec;
struct instruction *insn;
struct reloc *reloc;
+ uint64_t offset;
int type, ret;
sec = find_section_by_name(file->elf, ".discard.annotate_insn");
@@ -2327,8 +2278,19 @@ static int read_annotate(struct objtool_
for_each_reloc(sec->rsec, reloc) {
type = *(u32 *)(sec->data->d_buf + (reloc_idx(reloc) * sec->sh.sh_entsize) + 4);
- insn = find_insn(file, reloc->sym->sec,
- reloc->sym->offset + reloc_addend(reloc));
+ offset = reloc->sym->offset + reloc_addend(reloc);
+ insn = find_insn(file, reloc->sym->sec, offset);
+
+ /*
+ * Reachable annotations are 'funneh' and act on the previous instruction :/
+ */
+ if (type == ANNOTYPE_REACHABLE) {
+ 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("bad .discard.annotate_insn entry: %d of type %d", reloc_idx(reloc), type);
return -1;
@@ -2420,6 +2382,10 @@ static int __annotate_late(struct objtoo
insn->unret = 1;
break;
+ case ANNOTYPE_REACHABLE:
+ insn->dead_end = false;
+ break;
+
default:
break;
}
@@ -2566,14 +2532,6 @@ static int decode_sections(struct objtoo
if (ret)
return ret;
- /*
- * Must be after add_call_destinations() such that it can override
- * dead_end_function() marks.
- */
- ret = add_dead_ends(file);
- if (ret)
- return ret;
-
ret = add_jump_table_alts(file);
if (ret)
return ret;
@@ -2582,6 +2540,10 @@ static int decode_sections(struct objtoo
if (ret)
return ret;
+ /*
+ * Must be after add_call_destinations() such that it can override
+ * dead_end_function() marks.
+ */
ret = read_annotate(file, __annotate_late);
if (ret)
return ret;
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