linux-kernel - [PATCH v5 04/15] objtool: Fix JUMP_ENTRY

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Message-ID: <908df81a11d6d48353a096256f2acdc1833f1cec.1736955567.git.christophe.leroy@csgroup.eu>
Date: Wed, 15 Jan 2025 23:42:44 +0100
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Julien Thierry <jthierry@...hat.com>,
	Miroslav Benes <mbenes@...e.cz>,
	Raphael Gault <raphael.gault@....com>,
	Michael Ellerman <mpe@...erman.id.au>,
	Nicholas Piggin <npiggin@...il.com>,
	Naveen N Rao <naveen@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org,
	linuxppc-dev@...ts.ozlabs.org,
	llvm@...ts.linux.dev
Subject: [PATCH v5 04/15] objtool: Fix JUMP_ENTRY_SIZE for bi-arch like powerpc

	struct jump_entry {
		s32 code;
		s32 target;
		long key;
	};

It means that the size of the third argument depends on
whether we are building a 32 bits or 64 bits kernel.

Therefore JUMP_ENTRY_SIZE must depend on elf_class_addrsize(elf).

To allow that, entries[] table must be initialised at runtime. This is
easily done by moving it into its only user which is special_get_alts().

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
---
 .../arch/powerpc/include/arch/special.h       |  2 +-
 tools/objtool/special.c                       | 55 +++++++++----------
 2 files changed, 28 insertions(+), 29 deletions(-)

diff --git a/tools/objtool/arch/powerpc/include/arch/special.h b/tools/objtool/arch/powerpc/include/arch/special.h
index ffef9ada7133..b17802dcf436 100644
--- a/tools/objtool/arch/powerpc/include/arch/special.h
+++ b/tools/objtool/arch/powerpc/include/arch/special.h
@@ -6,7 +6,7 @@
 #define EX_ORIG_OFFSET 0
 #define EX_NEW_OFFSET 4
 
-#define JUMP_ENTRY_SIZE 16
+#define JUMP_ENTRY_SIZE (8 + elf_addr_size(elf)) /* 12 on PPC32, 16 on PPC64 */
 #define JUMP_ORIG_OFFSET 0
 #define JUMP_NEW_OFFSET 4
 #define JUMP_KEY_OFFSET 8
diff --git a/tools/objtool/special.c b/tools/objtool/special.c
index 097a69db82a0..7780ed8a084a 100644
--- a/tools/objtool/special.c
+++ b/tools/objtool/special.c
@@ -26,34 +26,6 @@ struct special_entry {
 	unsigned char key; /* jump_label key */
 };
 
-static const struct special_entry entries[] = {
-	{
-		.sec = ".altinstructions",
-		.group = true,
-		.size = ALT_ENTRY_SIZE,
-		.orig = ALT_ORIG_OFFSET,
-		.orig_len = ALT_ORIG_LEN_OFFSET,
-		.new = ALT_NEW_OFFSET,
-		.new_len = ALT_NEW_LEN_OFFSET,
-		.feature = ALT_FEATURE_OFFSET,
-	},
-	{
-		.sec = "__jump_table",
-		.jump_or_nop = true,
-		.size = JUMP_ENTRY_SIZE,
-		.orig = JUMP_ORIG_OFFSET,
-		.new = JUMP_NEW_OFFSET,
-		.key = JUMP_KEY_OFFSET,
-	},
-	{
-		.sec = "__ex_table",
-		.size = EX_ENTRY_SIZE,
-		.orig = EX_ORIG_OFFSET,
-		.new = EX_NEW_OFFSET,
-	},
-	{},
-};
-
 void __weak arch_handle_alternative(unsigned short feature, struct special_alt *alt)
 {
 }
@@ -144,6 +116,33 @@ int special_get_alts(struct elf *elf, struct list_head *alts)
 	unsigned int nr_entries;
 	struct special_alt *alt;
 	int idx, ret;
+	const struct special_entry entries[] = {
+		{
+			.sec = ".altinstructions",
+			.group = true,
+			.size = ALT_ENTRY_SIZE,
+			.orig = ALT_ORIG_OFFSET,
+			.orig_len = ALT_ORIG_LEN_OFFSET,
+			.new = ALT_NEW_OFFSET,
+			.new_len = ALT_NEW_LEN_OFFSET,
+			.feature = ALT_FEATURE_OFFSET,
+		},
+		{
+			.sec = "__jump_table",
+			.jump_or_nop = true,
+			.size = JUMP_ENTRY_SIZE,
+			.orig = JUMP_ORIG_OFFSET,
+			.new = JUMP_NEW_OFFSET,
+			.key = JUMP_KEY_OFFSET,
+		},
+		{
+			.sec = "__ex_table",
+			.size = EX_ENTRY_SIZE,
+			.orig = EX_ORIG_OFFSET,
+			.new = EX_NEW_OFFSET,
+		},
+		{},
+	};
 
 	INIT_LIST_HEAD(alts);
 
-- 
2.47.0