linux-kernel - [PATCH] kallsyms: ignore local block labels generated by compiler

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Date:   Fri, 28 Jan 2022 18:57:46 +0800
From:   Changbin Du <changbin.du@...il.com>
To:     Nathan Chancellor <nathan@...nel.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        linux-riscv@...ts.infradead.org,
        Changbin Du <changbin.du@...il.com>
Subject: [PATCH] kallsyms: ignore local block labels generated by compiler

The llvm compiler can generate lots of local block labels and they might
overlap with C defined symbols. So let's ignore such local labels.

Before this change, dumpstack shows a local symbol for epc:
[    0.040341][    T0] Hardware name: riscv-virtio,qemu (DT)
[    0.040376][    T0] epc : .LBB6_14+0x22/0x6a
[    0.040452][    T0]  ra : restore_all+0x12/0x6e

After this change, the C defined symbol is shown which is expected:
[    0.035795][    T0] Hardware name: riscv-virtio,qemu (DT)
[    0.036332][    T0] epc : trace_hardirqs_on+0x54/0x13c
[    0.036567][    T0]  ra : restore_all+0x12/0x6e

Signed-off-by: Changbin Du <changbin.du@...il.com>
---
 scripts/kallsyms.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/scripts/kallsyms.c b/scripts/kallsyms.c
index 54ad86d13784..5f4be9d72a32 100644
--- a/scripts/kallsyms.c
+++ b/scripts/kallsyms.c
@@ -108,6 +108,7 @@ static bool is_ignored_symbol(const char *name, char type)
 	/* Symbol names that begin with the following are ignored.*/
 	static const char * const ignored_prefixes[] = {
 		"$",			/* local symbols for ARM, MIPS, etc. */
+		".LBB",			/* local block labels generated by compiler */
 		".LASANPC",		/* s390 kasan local symbols */
 		"__crc_",		/* modversions */
 		"__efistub_",		/* arm64 EFI stub namespace */
-- 
2.32.0