linux-kernel - [PATCH v5 10/15] objtool: When looking for switch tables also follow conditional and dynamic jumps

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Message-ID: <a191a5fb599889c3c64489adaf6adfe38746035d.1736955567.git.christophe.leroy@csgroup.eu>
Date: Wed, 15 Jan 2025 23:42:50 +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 10/15] objtool: When looking for switch tables also follow conditional and dynamic jumps

When walking backward to find the base address of a switch table,
also take into account conditionnal branches and dynamic jumps from
a previous switch table.

To avoid mis-routing, break when stumbling on a function return.

Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 tools/objtool/check.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/tools/objtool/check.c b/tools/objtool/check.c
index 0ad2bdd92232..87b81d8e01c0 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -1998,6 +1998,8 @@ static int add_jump_table(struct objtool_file *file, struct instruction *insn,
 		alt->next = insn->alts;
 		insn->alts = alt;
 		prev_offset = reloc_offset(reloc);
+		if (!dest_insn->first_jump_src)
+			dest_insn->first_jump_src = insn;
 	}
 
 	if (!prev_offset) {
@@ -2032,6 +2034,9 @@ static void find_jump_table(struct objtool_file *file, struct symbol *func,
 		    insn->gpr == orig_insn->gpr)
 			break;
 
+		if (insn->type == INSN_RETURN)
+			break;
+
 		/* allow small jumps within the range */
 		if (insn->type == INSN_JUMP_UNCONDITIONAL &&
 		    insn->jump_dest &&
@@ -2093,8 +2098,7 @@ static int mark_add_func_jump_tables(struct objtool_file *file,
 		 * that find_jump_table() can back-track using those and
 		 * avoid some potentially confusing code.
 		 */
-		if (insn->type == INSN_JUMP_UNCONDITIONAL && insn->jump_dest &&
-		    insn->offset > last->offset &&
+		if (is_static_jump(insn) && insn->jump_dest &&
 		    insn->jump_dest->offset > insn->offset &&
 		    !insn->jump_dest->first_jump_src) {
 
-- 
2.47.0