[PATCH 06/11] objtool: Convert ANNOTATE_IGNORE_ALTERNATIVE to ANNOTATE

Peter Zijlstra
2023-12-04T09:39:59Z

arch/x86/include/asm/alternative.h | 14 ++---------
include/linux/objtool_types.h | 1
tools/include/linux/objtool_types.h | 1
tools/objtool/check.c | 45 ++++++++----------------------------
4 files changed, 15 insertions(+), 46 deletions(-)

--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -4,6 +4,7 @@

#include <linux/types.h>
#include <linux/stringify.h>
+#include <linux/objtool.h>
#include <asm/asm.h>

#define ALT_FLAGS_SHIFT 16
@@ -55,11 +56,7 @@
* objtool annotation to ignore the alternatives and only consider the original
* instruction(s).
*/
-#define ANNOTATE_IGNORE_ALTERNATIVE \
- "999:\n\t" \
- ".pushsection .discard.ignore_alts\n\t" \
- ".long 999b\n\t" \
- ".popsection\n\t"
+#define ANNOTATE_IGNORE_ALTERNATIVE ASM_ANNOTATE(ANNOTYPE_IGNORE_ALTS)

/*
* The patching flags are part of the upper bits of the @ft_flags parameter when
@@ -349,12 +346,7 @@ static inline int alternatives_text_rese
* objtool annotation to ignore the alternatives and only consider the original
* instruction(s).
*/
-.macro ANNOTATE_IGNORE_ALTERNATIVE
- .Lannotate_\@:
- .pushsection .discard.ignore_alts
- .long .Lannotate_\@
- .popsection
-.endm
+#define ANNOTATE_IGNORE_ALTERNATIVE ANNOTATE type=ANNOTYPE_IGNORE_ALTS

/*
* Issue one struct alt_instr descriptor entry (need to put it into
--- a/include/linux/objtool_types.h
+++ b/include/linux/objtool_types.h
@@ -62,5 +62,6 @@ struct unwind_hint {
#define ANNOTYPE_INSTR_BEGIN 3
#define ANNOTYPE_INSTR_END 4
#define ANNOTYPE_UNRET_BEGIN 5
+#define ANNOTYPE_IGNORE_ALTS 6

#endif /* _LINUX_OBJTOOL_TYPES_H */
--- a/tools/include/linux/objtool_types.h
+++ b/tools/include/linux/objtool_types.h
@@ -62,5 +62,6 @@ struct unwind_hint {
#define ANNOTYPE_INSTR_BEGIN 3
#define ANNOTYPE_INSTR_END 4
#define ANNOTYPE_UNRET_BEGIN 5
+#define ANNOTYPE_IGNORE_ALTS 6

#endif /* _LINUX_OBJTOOL_TYPES_H */
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1255,40 +1255,6 @@ static void add_uaccess_safe(struct objt
}

/*
- * FIXME: For now, just ignore any alternatives which add retpolines. This is
- * a temporary hack, as it doesn't allow ORC to unwind from inside a retpoline.
- * But it at least allows objtool to understand the control flow *around* the
- * retpoline.
- */
-static int add_ignore_alternatives(struct objtool_file *file)
-{
- struct section *rsec;
- struct reloc *reloc;
- struct instruction *insn;
-
- rsec = find_section_by_name(file->elf, ".rela.discard.ignore_alts");
- if (!rsec)
- return 0;
-
- for_each_reloc(rsec, reloc) {
- if (reloc->sym->type != STT_SECTION) {
- WARN("unexpected relocation symbol type in %s", rsec->name);
- return -1;
- }
-
- insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
- if (!insn) {
- WARN("bad .discard.ignore_alts entry");
- return -1;
- }
-
- insn->ignore_alts = true;
- }
-
- return 0;
-}
-
-/*
* Symbols that replace INSN_CALL_DYNAMIC, every (tail) call to such a symbol
* will be added to the .retpoline_sites section.
*/
@@ -2341,6 +2307,15 @@ static int read_annotate(struct objtool_
return 0;
}

+static int __annotate_ignore_alts(int type, struct instruction *insn)
+{
+ if (type != ANNOTYPE_IGNORE_ALTS)
+ return 0;
+
+ insn->ignore_alts = true;
+ return 0;
+}
+
static int __annotate_noendbr(int type, struct instruction *insn)
{
if (type != ANNOTYPE_NOENDBR)
@@ -2550,7 +2525,7 @@ static int decode_sections(struct objtoo
add_ignores(file);
add_uaccess_safe(file);

- ret = add_ignore_alternatives(file);
+ ret = read_annotate(file, __annotate_ignore_alts);
if (ret)
return ret;