linux-kernel - [PATCH v1 2/3] objtool/LoongArch: Fix unreachable instruction warnings about EFISTUB

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Message-ID: <20250901072156.31361-3-yangtiezhu@loongson.cn>
Date: Mon,  1 Sep 2025 15:21:55 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Nathan Chancellor <nathan@...nel.org>
Cc: loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 2/3] objtool/LoongArch: Fix unreachable instruction warnings about EFISTUB

When compiling with LLVM and CONFIG_LTO_CLANG is set, there exist the
following objtool warnings:

  vmlinux.o: warning: objtool: .head.text+0x0: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x18: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x38: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x3c: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x40: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x44: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x54: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x58: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x6c: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x84: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x94: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x9c: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0xc4: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0xf8: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0xfc: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x104: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x10c: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x11c: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x120: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x124: unreachable instruction
  vmlinux.o: warning: objtool: .head.text+0x144: unreachable instruction

The instructions in the .head.text section are related with EFISTUB,
they are image header and can be ignored by objtool, so just check the
section name in ignore_unreachable_insn() to ignore it.

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 tools/objtool/check.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 2dcebf75d95e..b7397b0f9f79 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -4039,6 +4039,10 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	    !strcmp(insn->sec->name, ".altinstr_aux"))
 		return true;
 
+	/* Ignore EFISTUB instructions usually in the .head.text section. */
+	if (!strcmp(insn->sec->name, ".head.text"))
+		return true;
+
 	/*
 	 * Whole archive runs might encounter dead code from weak symbols.
 	 * This is where the linker will have dropped the weak symbol in
-- 
2.42.0