linux-kernel - [PATCH v6 1/9] objtool: Handle various symbol types of rodata

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Message-ID: <20241217010905.13054-2-yangtiezhu@loongson.cn>
Date: Tue, 17 Dec 2024 09:08:57 +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,
	amd-gfx@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v6 1/9] objtool: Handle various symbol types of rodata

In the relocation section ".rela.rodata" of each .o file compiled with
LoongArch toolchain, there are various symbol types such as STT_NOTYPE,
STT_OBJECT, STT_FUNC in addition to the usual STT_SECTION, it needs to
use reloc symbol offset instead of reloc addend to find the destination
instruction in find_jump_table() and add_jump_table().

For the most part, an absolute relocation type is used for rodata. In the
case of STT_SECTION, reloc->sym->offset is always zero, and for the other
symbol types, reloc_addend(reloc) is always zero, thus it can use a simple
statement "reloc->sym->offset + reloc_addend(reloc)" to obtain the symbol
offset for various symbol types.

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 tools/objtool/check.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index e92c5564d9ca..f64435ad3514 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1953,6 +1953,7 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 	unsigned int prev_offset = 0;
 	struct reloc *reloc = table;
 	struct alternative *alt;
+	unsigned long sym_offset;
 
 	/*
 	 * Each @reloc is a switch table relocation which points to the target
@@ -1970,12 +1971,13 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 		if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
 			break;
 
+		sym_offset = reloc->sym->offset + reloc_addend(reloc);
+
 		/* Detect function pointers from contiguous objects: */
-		if (reloc->sym->sec == pfunc->sec &&
-		    reloc_addend(reloc) == pfunc->offset)
+		if (reloc->sym->sec == pfunc->sec && sym_offset == pfunc->offset)
 			break;
 
-		dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
+		dest_insn = find_insn(file, reloc->sym->sec, sym_offset);
 		if (!dest_insn)
 			break;
 
@@ -2013,6 +2015,7 @@ static void find_jump_table(struct objtool_file *file, struct symbol *func,
 	struct reloc *table_reloc;
 	struct instruction *dest_insn, *orig_insn = insn;
 	unsigned long table_size;
+	unsigned long sym_offset;
 
 	/*
 	 * Backward search using the @first_jump_src links, these help avoid
@@ -2036,7 +2039,10 @@ static void find_jump_table(struct objtool_file *file, struct symbol *func,
 		table_reloc = arch_find_switch_table(file, insn, &table_size);
 		if (!table_reloc)
 			continue;
-		dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
+
+		sym_offset = table_reloc->sym->offset + reloc_addend(table_reloc);
+
+		dest_insn = find_insn(file, table_reloc->sym->sec, sym_offset);
 		if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
 			continue;
 
-- 
2.42.0