linux-kernel - [PATCH v3 05/10] objtool: Handle unreachable entry of rodata

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Message-ID: <20241119065655.21123-6-yangtiezhu@loongson.cn>
Date: Tue, 19 Nov 2024 14:56:50 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Cc: loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 05/10] objtool: Handle unreachable entry of rodata

When compling with Clang on LoongArch, there exists unreachable entry
of rodata which points to a nop instruction after the function return
instruction, this is generated by compiler to fill the non-existent
switch case, just skip the entry when parsing the relocation section
of rodata.

This is preparation for later patch on LoongArch, there is no effect
for the other archs with this patch.

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 tools/objtool/check.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index eb4c89501493..17df3738e087 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2136,6 +2136,14 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 		if (!dest_insn)
 			break;
 
+		/* Handle the special cases compiled with Clang on LoongArch */
+		if (file->elf->ehdr.e_machine == EM_LOONGARCH &&
+		    reloc->sym->type == STT_SECTION && dest_insn->type == INSN_NOP &&
+		    (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)) {
+			prev_offset = reloc_offset(reloc);
+			continue;
+		}
+
 		/* Make sure the destination is in the same function: */
 		if (!insn_func(dest_insn) || insn_func(dest_insn)->pfunc != pfunc)
 			break;
-- 
2.42.0