linux-kernel - [PATCH v3 04/10] objtool: Handle PC relative relocation type

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Message-ID: <20241119065655.21123-5-yangtiezhu@loongson.cn>
Date: Tue, 19 Nov 2024 14:56:49 +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 04/10] objtool: Handle PC relative relocation type

When compling with Clang on LoongArch, there exists 32 bit PC relative
relocation type, it needs to get the offset with "S + A - PC" according
to the spec of "ELF for the LoongArch Architecture".

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

Link: https://github.com/loongson/la-abi-specs/blob/release/laelf.adoc
Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 tools/objtool/check.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index af824bfd0973..eb4c89501493 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2118,6 +2118,11 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 		if (reloc->sym->type == STT_SECTION) {
 			/* Addend field in the relocation entry associated with the symbol */
 			offset = reloc_addend(reloc);
+			/* Handle the special cases compiled with Clang on LoongArch */
+			if (file->elf->ehdr.e_machine == EM_LOONGARCH &&
+			    reloc_type(reloc) == R_LARCH_32_PCREL)
+				offset = reloc->sym->offset + reloc_addend(reloc) -
+					 (reloc_offset(reloc) - reloc_offset(table));
 		} else {
 			/* The address of the symbol in the relocation entry */
 			offset = reloc->sym->offset;
-- 
2.42.0