objtool/klp: Fix extraction of text annotations for alternatives

Objtool is failing to extract text annotations which reference
.altinstr_replacement instructions:

  1) Alternative replacement fake symbols are NOTYPE rather than FUNC,
     and they don't have sym->included set, thus they aren't recognized
     by should_keep_special_sym().

  2) .discard.annotate_insn gets processed before .altinstr_replacement,
     so the referenced (fake) symbols don't have clones yet.

Fix the first issue by checking for a valid clone instead of
sym->included and by accepting NOTYPE symbols when processing
.discard.annotate_insn.

Fix the second issue by deferring text annotation processing until after
the other special sections have been cloned.

Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Acked-by: Song Liu <song@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>

1 files changed, 28 insertions, 5 deletions

diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index 17a6146b9406..42970b38728f 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -1437,6 +1437,7 @@ entsize:
 /* Keep a special section entry if it references an included function */
 static bool should_keep_special_sym(struct elf *elf, struct symbol *sym)
 {
+	bool annotate_insn = !strcmp(sym->sec->name, ".discard.annotate_insn");
 	struct reloc *reloc;
 
 	if (is_sec_sym(sym) || !sym->sec->rsec)
@@ -1446,7 +1447,16 @@ static bool should_keep_special_sym(struct elf *elf, struct symbol *sym)
 		if (convert_reloc_sym(elf, reloc))
 			continue;
 
-		if (is_func_sym(reloc->sym) && reloc->sym->included)
+		if (!reloc->sym->clone || is_undef_sym(reloc->sym->clone))
+			continue;
+
+		/*
+		 * Keep special section references to cloned functions.
+		 * In some cases annotate_insn can also reference cloned alt
+		 * replacement fake symbols; keep those references as well.
+		 */
+		if (is_func_sym(reloc->sym) ||
+		    (annotate_insn && is_notype_sym(reloc->sym)))
 			return true;
 	}
 
@@ -1590,15 +1600,28 @@ static int clone_special_section(struct elfs *e, struct section *patched_sec)
 /* Extract only the needed bits from special sections */
 static int clone_special_sections(struct elfs *e)
 {
-	struct section *patched_sec;
+	struct section *sec, *annotate_insn = NULL;
 
-	for_each_sec(e->patched, patched_sec) {
-		if (is_special_section(patched_sec)) {
-			if (clone_special_section(e, patched_sec))
+	for_each_sec(e->patched, sec) {
+		if (is_special_section(sec)) {
+			if (!strcmp(sec->name, ".discard.annotate_insn")) {
+				annotate_insn = sec;
+				continue;
+			}
+			if (clone_special_section(e, sec))
 				return -1;
 		}
 	}
 
+	/*
+	 * Do .discard.annotate_insn last, it can reference other special
+	 * sections (alt replacements) so they need to be cloned first.
+	 */
+	if (annotate_insn) {
+		if (clone_special_section(e, annotate_insn))
+			return -1;
+	}
+
 	return 0;
 }