linux-kernel - [PATCH v4 23/28] objtool: Provide access to feature and flags of group alternatives

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Message-ID: <20251113164917.2563486-24-alexandre.chartre@oracle.com>
Date: Thu, 13 Nov 2025 17:49:12 +0100
From: Alexandre Chartre <alexandre.chartre@...cle.com>
To: linux-kernel@...r.kernel.org, mingo@...nel.org, jpoimboe@...nel.org,
        peterz@...radead.org
Cc: alexandre.chartre@...cle.com
Subject: [PATCH v4 23/28] objtool: Provide access to feature and flags of group alternatives

Each alternative of a group alternative depends on a specific
feature and flags. Provide access to the feature/flags for each
alternative as an attribute (feature) in struct alt_group.

Signed-off-by: Alexandre Chartre <alexandre.chartre@...cle.com>
---
 tools/objtool/check.c                   | 2 ++
 tools/objtool/include/objtool/check.h   | 1 +
 tools/objtool/include/objtool/special.h | 2 +-
 tools/objtool/special.c                 | 2 ++
 4 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 25c1c7185d4f6..817ac70fed9fa 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1738,6 +1738,7 @@ static int handle_group_alt(struct objtool_file *file,
 		orig_alt_group->last_insn = last_orig_insn;
 		orig_alt_group->nop = NULL;
 		orig_alt_group->ignore = orig_insn->ignore_alts;
+		orig_alt_group->feature = 0;
 	} else {
 		if (orig_alt_group->last_insn->offset + orig_alt_group->last_insn->len -
 		    orig_alt_group->first_insn->offset != special_alt->orig_len) {
@@ -1841,6 +1842,7 @@ static int handle_group_alt(struct objtool_file *file,
 	new_alt_group->nop = nop;
 	new_alt_group->ignore = (*new_insn)->ignore_alts;
 	new_alt_group->cfi = orig_alt_group->cfi;
+	new_alt_group->feature = special_alt->feature;
 	return 0;
 }
 
diff --git a/tools/objtool/include/objtool/check.h b/tools/objtool/include/objtool/check.h
index 73310c56e91b6..c54dd0aae1f60 100644
--- a/tools/objtool/include/objtool/check.h
+++ b/tools/objtool/include/objtool/check.h
@@ -36,6 +36,7 @@ struct alt_group {
 	struct cfi_state **cfi;
 
 	bool ignore;
+	unsigned int feature;
 };
 
 enum alternative_type {
diff --git a/tools/objtool/include/objtool/special.h b/tools/objtool/include/objtool/special.h
index 72d09c0adf1a1..b22410745e4a1 100644
--- a/tools/objtool/include/objtool/special.h
+++ b/tools/objtool/include/objtool/special.h
@@ -25,7 +25,7 @@ struct special_alt {
 	struct section *new_sec;
 	unsigned long new_off;
 
-	unsigned int orig_len, new_len; /* group only */
+	unsigned int orig_len, new_len, feature; /* group only */
 };
 
 int special_get_alts(struct elf *elf, struct list_head *alts);
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index c80fed8a840ee..93fb371b05207 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -82,6 +82,8 @@ static int get_alt_entry(struct elf *elf, const struct special_entry *entry,
 						   entry->orig_len);
 		alt->new_len = *(unsigned char *)(sec->data->d_buf + offset +
 						  entry->new_len);
+		alt->feature = *(unsigned int *)(sec->data->d_buf + offset +
+						 entry->feature);
 	}
 
 	orig_reloc = find_reloc_by_dest(elf, sec, offset + entry->orig);
-- 
2.43.5