linux-kernel - [RFC PATCH v1 13/23] objtool: Add next member in struct reloc

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Message-Id: <1687247415-32057-4-git-send-email-tangyouling@loongson.cn>
Date:   Tue, 20 Jun 2023 15:50:09 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Huacai Chen <chenhuacai@...nel.org>,
        madvenka@...ux.microsoft.com
Cc:     chenzhongjin@...wei.com, WANG Xuerui <kernel@...0n.name>,
        Xi Ruoyao <xry111@...111.site>, live-patching@...r.kernel.org,
        linux-kernel@...r.kernel.org, loongarch@...ts.linux.dev,
        tangyouling00@...il.com, youling.tang@...look.com,
        Jinyang He <hejinyang@...ngson.cn>
Subject: [RFC PATCH v1 13/23] objtool: Add next member in struct reloc

In LoongArch, there may be multiple relocation information in one location,
so the next member is added to handle this situation.

The following warning appears when the next member is not added,
warning: objtool: unexpected relocation symbol type in .rela.discard.unreachable

Relocation section '.rela.discard.unreachable' at offset 0x1a58 contains 4 entries:
    Offset             Info             Type               Symbol's Value  Symbol's Name + Addend
0000000000000000  0000000200000032 R_LARCH_ADD32          0000000000000000 .text + 354
0000000000000000  0000000900000037 R_LARCH_SUB32          0000000000000000 L0^A + 0

Co-developed-by: Jinyang He <hejinyang@...ngson.cn>
Signed-off-by: Jinyang He <hejinyang@...ngson.cn>
Signed-off-by: Youling Tang <tangyouling@...ngson.cn>
---
 tools/objtool/elf.c                 | 11 ++++++++++-
 tools/objtool/include/objtool/elf.h |  1 +
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c
index 6806ce01d933..d345300d269b 100644
--- a/tools/objtool/elf.c
+++ b/tools/objtool/elf.c
@@ -895,7 +895,7 @@ static int read_relocs(struct elf *elf)
 {
 	unsigned long nr_reloc, max_reloc = 0, tot_reloc = 0;
 	struct section *sec;
-	struct reloc *reloc;
+	struct reloc *reloc, *next_reloc;
 	unsigned int symndx;
 	struct symbol *sym;
 	int i;
@@ -915,6 +915,7 @@ static int read_relocs(struct elf *elf)
 			return -1;
 		}
 
+		next_reloc = NULL;
 		sec->base->reloc = sec;
 
 		nr_reloc = 0;
@@ -946,6 +947,14 @@ static int read_relocs(struct elf *elf)
 				return -1;
 			}
 
+			if (next_reloc && reloc->offset == next_reloc->offset) {
+				next_reloc->next = reloc;
+				next_reloc = reloc;
+				continue;
+			}
+
+			next_reloc = reloc;
+
 			list_add_tail(&reloc->sym_reloc_entry, &sym->reloc_list);
 			list_add_tail(&reloc->list, &sec->reloc_list);
 			elf_hash_add(reloc, &reloc->hash, reloc_hash(reloc));
diff --git a/tools/objtool/include/objtool/elf.h b/tools/objtool/include/objtool/elf.h
index ad0024da262b..7877298fe401 100644
--- a/tools/objtool/include/objtool/elf.h
+++ b/tools/objtool/include/objtool/elf.h
@@ -68,6 +68,7 @@ struct symbol {
 struct reloc {
 	struct list_head list;
 	struct hlist_node hash;
+	struct reloc *next;
 	union {
 		GElf_Rela rela;
 		GElf_Rel  rel;
-- 
2.39.2