[tip: objtool/core] objtool: Identify the different types of alternatives

["tip-bot2 for Alexandre Chartre" <tip-bot2@linutronix.de>]

The following commit has been merged into the objtool/core branch of tip:

Commit-ID:     d490aa21973fe66ec35ad825c19f88ac7f7abb27
Gitweb:        https://git.kernel.org/tip/d490aa21973fe66ec35ad825c19f88ac7f7abb27
Author:        Alexandre Chartre <alexandre.chartre@oracle.com>
AuthorDate:    Fri, 21 Nov 2025 10:53:23 +01:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 21 Nov 2025 15:30:11 +01:00

objtool: Identify the different types of alternatives

Alternative code, including jump table and exception table, is represented
with the same struct alternative structure. But there is no obvious way to
identify whether the struct represents alternative instructions, a jump
table or an exception table.

So add a type to struct alternative to clearly identify the type of
alternative.

Signed-off-by: Alexandre Chartre <alexandre.chartre@oracle.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
Link: https://patch.msgid.link/20251121095340.464045-14-alexandre.chartre@oracle.com
---
 tools/objtool/check.c                 | 13 ++++++++-----
 tools/objtool/include/objtool/check.h | 12 ++++++++++++
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index a02f8db..93aaa4b 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -27,11 +27,6 @@
 #include <linux/static_call_types.h>
 #include <linux/string.h>
 
-struct alternative {
-	struct alternative *next;
-	struct instruction *insn;
-};
-
 static unsigned long nr_cfi, nr_cfi_reused, nr_cfi_cache;
 
 static struct cfi_init_state initial_func_cfi;
@@ -1924,6 +1919,7 @@ static int add_special_section_alts(struct objtool_file *file)
 	struct list_head special_alts;
 	struct instruction *orig_insn, *new_insn;
 	struct special_alt *special_alt, *tmp;
+	enum alternative_type alt_type;
 	struct alternative *alt;
 
 	if (special_get_alts(file->elf, &special_alts))
@@ -1959,9 +1955,15 @@ static int add_special_section_alts(struct objtool_file *file)
 			if (handle_group_alt(file, special_alt, orig_insn, &new_insn))
 				return -1;
 
+			alt_type = ALT_TYPE_INSTRUCTIONS;
+
 		} else if (special_alt->jump_or_nop) {
 			if (handle_jump_alt(file, special_alt, orig_insn, &new_insn))
 				return -1;
+
+			alt_type = ALT_TYPE_JUMP_TABLE;
+		} else {
+			alt_type = ALT_TYPE_EX_TABLE;
 		}
 
 		alt = calloc(1, sizeof(*alt));
@@ -1972,6 +1974,7 @@ static int add_special_section_alts(struct objtool_file *file)
 
 		alt->insn = new_insn;
 		alt->next = orig_insn->alts;
+		alt->type = alt_type;
 		orig_insn->alts = alt;
 
 		list_del(&special_alt->list);
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index fde9586..cbf4af5 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -38,6 +38,18 @@ struct alt_group {
 	bool ignore;
 };
 
+enum alternative_type {
+	ALT_TYPE_INSTRUCTIONS,
+	ALT_TYPE_JUMP_TABLE,
+	ALT_TYPE_EX_TABLE,
+};
+
+struct alternative {
+	struct alternative *next;
+	struct instruction *insn;
+	enum alternative_type type;
+};
+
 #define INSN_CHUNK_BITS		8
 #define INSN_CHUNK_SIZE		(1 << INSN_CHUNK_BITS)
 #define INSN_CHUNK_MAX		(INSN_CHUNK_SIZE - 1)