linux-kernel - [RFC PATCH 3/4] objtool/LoongArch: Add support for jump table

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Message-ID: <20240712091506.28140-4-yangtiezhu@loongson.cn>
Date: Fri, 12 Jul 2024 17:15:05 +0800
From: Tiezhu Yang <yangtiezhu@...ngson.cn>
To: Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Huacai Chen <chenhuacai@...nel.org>
Cc: Xi Ruoyao <xry111@...111.site>,
	loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [RFC PATCH 3/4] objtool/LoongArch: Add support for jump table

Signed-off-by: Tiezhu Yang <yangtiezhu@...ngson.cn>
---
 tools/objtool/arch/loongarch/special.c | 54 +++++++++++++++++++++++++-
 1 file changed, 53 insertions(+), 1 deletion(-)

diff --git a/tools/objtool/arch/loongarch/special.c b/tools/objtool/arch/loongarch/special.c
index 9bba1e9318e0..3e08ad3a507c 100644
--- a/tools/objtool/arch/loongarch/special.c
+++ b/tools/objtool/arch/loongarch/special.c
@@ -1,5 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0-or-later
+#include <string.h>
+
 #include <objtool/special.h>
+#include <objtool/warn.h>
 
 bool arch_support_alt_relocation(struct special_alt *special_alt,
 				 struct instruction *insn,
@@ -8,8 +11,57 @@ bool arch_support_alt_relocation(struct special_alt *special_alt,
 	return false;
 }
 
+static struct reloc *find_reloc_by_tablejump_annotate(struct objtool_file *file,
+						      struct instruction *insn)
+{
+	struct section *rsec;
+	struct reloc *reloc;
+	unsigned long offset;
+
+	rsec = find_section_by_name(file->elf, ".rela.discard.tablejump_annotate");
+	if (!rsec)
+		return NULL;
+
+	for_each_reloc(rsec, reloc) {
+		if (reloc->sym->sec->rodata)
+			continue;
+
+		if (strcmp(insn->sec->name, reloc->sym->sec->name))
+			continue;
+
+		offset = reloc->sym->offset;
+		if (insn->offset == offset) {
+			reloc++;
+			return reloc;
+		}
+	}
+
+	return NULL;
+}
+
 struct reloc *arch_find_switch_table(struct objtool_file *file,
 				     struct instruction *insn)
 {
-	return NULL;
+	struct reloc *annotate_reloc;
+	struct reloc *rodata_reloc;
+	struct section *table_sec;
+	unsigned long table_offset;
+
+	annotate_reloc = find_reloc_by_tablejump_annotate(file, insn);
+	if (!annotate_reloc)
+		return NULL;
+
+	table_sec = annotate_reloc->sym->sec;
+	table_offset = annotate_reloc->sym->offset;
+
+	/*
+	 * Each table entry has a rela associated with it.  The rela
+	 * should reference text in the same function as the original
+	 * instruction.
+	 */
+	rodata_reloc = find_reloc_by_dest(file->elf, table_sec, table_offset);
+	if (!rodata_reloc)
+		return NULL;
+
+	return rodata_reloc;
 }
-- 
2.42.0