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objtool: Generic annotation infrastructure

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Avoid endless .discard.foo sections for each annotation, create a
single .discard.annotate_insn section that takes an annotation type along
with the instruction.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://lore.kernel.org/r/20241128094310.932794537@infradead.org
This commit is contained in:
Peter Zijlstra 2024-11-28 10:38:52 +01:00
parent 40384c840e
commit 2116b349e2
2 changed files with 63 additions and 0 deletions
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18
include/linux/objtool.h
View File

@ -57,6 +57,13 @@
".long 998b\n\t" \
".popsection\n\t"
#define ASM_ANNOTATE(type) \
"911:\n\t" \
".pushsection .discard.annotate_insn,\"M\",@progbits,8\n\t" \
".long 911b - .\n\t" \
".long " __stringify(type) "\n\t" \
".popsection\n\t"
#else /* __ASSEMBLY__ */
/*
@ -146,6 +153,14 @@
.popsection
.endm
.macro ANNOTATE type:req
.Lhere_\@:
.pushsection .discard.annotate_insn,"M",@progbits,8
.long .Lhere_\@ - .
.long \type
.popsection
.endm
#endif /* __ASSEMBLY__ */
#else /* !CONFIG_OBJTOOL */
@ -155,6 +170,7 @@
#define UNWIND_HINT(type, sp_reg, sp_offset, signal) "\n\t"
#define STACK_FRAME_NON_STANDARD(func)
#define STACK_FRAME_NON_STANDARD_FP(func)
#define ASM_ANNOTATE(type)
#define ANNOTATE_NOENDBR
#define ASM_REACHABLE
#else
@ -167,6 +183,8 @@
.endm
.macro REACHABLE
.endm
.macro ANNOTATE type:req
.endm
#endif
#endif /* CONFIG_OBJTOOL */

45
tools/objtool/check.c
View File

@ -2373,6 +2373,49 @@ static int read_unwind_hints(struct objtool_file *file)
return 0;
}
static int read_annotate(struct objtool_file *file, void (*func)(int type, struct instruction *insn))
{
struct section *sec;
struct instruction *insn;
struct reloc *reloc;
int type;
sec = find_section_by_name(file->elf, ".discard.annotate_insn");
if (!sec)
return 0;
if (!sec->rsec)
return 0;
if (sec->sh.sh_entsize != 8) {
static bool warned = false;
if (!warned) {
WARN("%s: dodgy linker, sh_entsize != 8", sec->name);
warned = true;
}
sec->sh.sh_entsize = 8;
}
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));
if (!insn) {
WARN("bad .discard.annotate_insn entry: %d of type %d", reloc_idx(reloc), type);
return -1;
}
func(type, insn);
}
return 0;
}
static void __annotate_nop(int type, struct instruction *insn)
{
}
static int read_noendbr_hints(struct objtool_file *file)
{
struct instruction *insn;
@ -2670,6 +2713,8 @@ static int decode_sections(struct objtool_file *file)
if (ret)
return ret;
read_annotate(file, __annotate_nop);
/*
* Must be before read_unwind_hints() since that needs insn->noendbr.
*/