linux-kernel - [PATCH v1 1/6] objtool: Check various symbol types for jump table

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Message-ID: <20241015113915.12623-2-yangtiezhu@loongson.cn>
Date: Tue, 15 Oct 2024 19:39:10 +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,
	bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v1 1/6] objtool: Check various symbol types for jump table

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().

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 | 20 ++++++++++++++++----
 1 file changed, 16 insertions(+), 4 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 6604f5d038aa..cda7306d07c2 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2079,6 +2079,7 @@ 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 offset;
 
 	/*
 	 * Each @reloc is a switch table relocation which points to the target
@@ -2094,12 +2095,16 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 		if (prev_offset && reloc_offset(reloc) != prev_offset + 8)
 			break;
 
+		if (reloc->sym->type == STT_SECTION)
+			offset = reloc_addend(reloc);
+		else
+			offset = reloc->sym->offset;
+
 		/* Detect function pointers from contiguous objects: */
-		if (reloc->sym->sec == pfunc->sec &&
-		    reloc_addend(reloc) == pfunc->offset)
+		if (reloc->sym->sec == pfunc->sec && offset == pfunc->offset)
 			break;
 
-		dest_insn = find_insn(file, reloc->sym->sec, reloc_addend(reloc));
+		dest_insn = find_insn(file, reloc->sym->sec, offset);
 		if (!dest_insn)
 			break;
 
@@ -2137,6 +2142,7 @@ static struct reloc *find_jump_table(struct objtool_file *file,
 {
 	struct reloc *table_reloc;
 	struct instruction *dest_insn, *orig_insn = insn;
+	unsigned long offset;
 
 	/*
 	 * Backward search using the @first_jump_src links, these help avoid
@@ -2160,7 +2166,13 @@ static struct reloc *find_jump_table(struct objtool_file *file,
 		table_reloc = arch_find_switch_table(file, insn);
 		if (!table_reloc)
 			continue;
-		dest_insn = find_insn(file, table_reloc->sym->sec, reloc_addend(table_reloc));
+
+		if (table_reloc->sym->type == STT_SECTION)
+			offset = reloc_addend(table_reloc);
+		else
+			offset = table_reloc->sym->offset;
+
+		dest_insn = find_insn(file, table_reloc->sym->sec, offset);
 		if (!dest_insn || !insn_func(dest_insn) || insn_func(dest_insn)->pfunc != func)
 			continue;
 
-- 
2.42.0