linux-kernel - [PATCH v4 10/15] objtool: When looking for switch tables also follow conditional and dynamic jumps

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Message-ID: <a3482907d27f322f5964f84839e353dae3f776c8.1689091394.git.christophe.leroy@csgroup.eu>
Date:   Tue, 11 Jul 2023 18:08:36 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Nicholas Piggin <npiggin@...il.com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sathvika Vasireddy <sv@...ux.ibm.com>,
        Naveen N Rao <naveen@...nel.org>
Cc:     Christophe Leroy <christophe.leroy@...roup.eu>,
        linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v4 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 361c832aefc8..ea0945f2195f 100644
--- a/tools/objtool/check.c
+++ b/tools/objtool/check.c
@@ -2034,6 +2034,8 @@ 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) {
@@ -2068,6 +2070,9 @@ static struct reloc *find_jump_table(struct objtool_file *file,
 		    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 &&
@@ -2130,8 +2135,7 @@ 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) {
 
-- 
2.41.0