linux-kernel - [PATCH v6 33/33] objtool: revert c_file fallthrough detection for arm64

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Date:   Thu, 23 Jun 2022 09:49:17 +0800
From:   Chen Zhongjin <chenzhongjin@...wei.com>
To:     <linux-kernel@...r.kernel.org>, <linux-arch@...r.kernel.org>,
        <linuxppc-dev@...ts.ozlabs.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kbuild@...r.kernel.org>, <live-patching@...r.kernel.org>
CC:     <jpoimboe@...nel.org>, <peterz@...radead.org>,
        <catalin.marinas@....com>, <will@...nel.org>,
        <masahiroy@...nel.org>, <michal.lkml@...kovi.net>,
        <ndesaulniers@...gle.com>, <mark.rutland@....com>,
        <pasha.tatashin@...een.com>, <broonie@...nel.org>,
        <chenzhongjin@...wei.com>, <rmk+kernel@...linux.org.uk>,
        <madvenka@...ux.microsoft.com>, <christophe.leroy@...roup.eu>,
        <daniel.thompson@...aro.org>
Subject: [PATCH v6 33/33] objtool: revert c_file fallthrough detection for arm64

'commit 08feafe8d195 ("objtool: Fix function fallthrough detection for vmlinux")'
This commit canceled c_file which used to make fallthrough detection
only works on C objects.

However in arm64/crypto/aes-mods.S, there are cases that JUMP at the
end of function which make objtool wrongly detected them as fall through.

Revert c_file before this is fixed.

Signed-off-by: Chen Zhongjin <chenzhongjin@...wei.com>
---
 tools/objtool/check.c                   | 3 +--
 tools/objtool/include/objtool/objtool.h | 2 +-
 tools/objtool/objtool.c                 | 1 +
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 8ff7c30df513..95cb88da4ed5 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -541,7 +541,6 @@ static struct instruction *find_last_insn(struct objtool_file *file,
 	struct instruction *insn = NULL;
 	unsigned int offset;
 	unsigned int end = (sec->sh.sh_size > 10) ? sec->sh.sh_size - 10 : 0;
-
 	for (offset = sec->sh.sh_size - 1; offset >= end && !insn; offset--)
 		insn = find_insn(file, sec, offset);
 
@@ -3220,7 +3219,7 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 	while (1) {
 		next_insn = next_insn_to_validate(file, insn);
 
-		if (func && insn->func && func != insn->func->pfunc) {
+		if (file->c_file && func && insn->func && func != insn->func->pfunc) {
 			WARN("%s() falls through to next function %s()",
 			     func->name, insn->func->name);
 			return 1;
diff --git a/tools/objtool/include/objtool/objtool.h b/tools/objtool/include/objtool/objtool.h
index a6e72d916807..7a5c13a78f87 100644
--- a/tools/objtool/include/objtool/objtool.h
+++ b/tools/objtool/include/objtool/objtool.h
@@ -27,7 +27,7 @@ struct objtool_file {
 	struct list_head static_call_list;
 	struct list_head mcount_loc_list;
 	struct list_head endbr_list;
-	bool ignore_unreachables, hints, rodata;
+	bool ignore_unreachables, c_file, hints, rodata;
 
 	unsigned int nr_endbr;
 	unsigned int nr_endbr_int;
diff --git a/tools/objtool/objtool.c b/tools/objtool/objtool.c
index 512669ce064c..d33620b1392d 100644
--- a/tools/objtool/objtool.c
+++ b/tools/objtool/objtool.c
@@ -105,6 +105,7 @@ struct objtool_file *objtool_open_read(const char *_objname)
 	INIT_LIST_HEAD(&file.static_call_list);
 	INIT_LIST_HEAD(&file.mcount_loc_list);
 	INIT_LIST_HEAD(&file.endbr_list);
+	file.c_file = !opts.link && find_section_by_name(file.elf, ".comment");
 	file.ignore_unreachables = opts.no_unreachable;
 	file.hints = false;
 
-- 
2.17.1