linux-kernel - [PATCH 2/2] kallsyms: expand symbol name into comment for debugging

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Message-Id: <20230306101451.375844-2-arnd@kernel.org>
Date:   Mon,  6 Mar 2023 11:14:51 +0100
From:   Arnd Bergmann <arnd@...nel.org>
To:     linux-kbuild@...r.kernel.org
Cc:     Masahiro Yamada <masahiroy@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Nicolas Schier <nicolas@...sle.eu>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kees Cook <keescook@...omium.org>,
        Miguel Ojeda <ojeda@...nel.org>,
        Zhen Lei <thunder.leizhen@...wei.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        linux-kernel@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: [PATCH 2/2] kallsyms: expand symbol name into comment for debugging

From: Arnd Bergmann <arnd@...db.de>

The assembler output of kallsyms.c is not meant for people to understand,
and is generally not helpful when debugging "Inconsistent kallsyms data"
warnings. I have previously struggled with these, but found it helpful
to list which symbols changed between the first and second pass in the
.tmp_vmlinux.kallsyms*.S files.

As this file is preprocessed, it's possible to add a C-style multiline
comment with the full type/name tuple.

Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
No idea if there is already a better way to debug this kind of problem,
or if this causes a notable slowdown.
---
 scripts/kallsyms.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index a239a87e7bec..ea1e3d3aaa6b 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -525,7 +525,8 @@ static void write_src(void)
 					table[i]->addr);
 				exit(EXIT_FAILURE);
 			}
-			printf("\t.long\t%#x\n", (int)offset);
+			expand_symbol(table[i]->sym, table[i]->len, buf);
+			printf("\t.long\t%#x	/* %s */\n", (int)offset, buf);
 		} else if (!symbol_absolute(table[i])) {
 			output_address(table[i]->addr);
 		} else {
-- 
2.39.2