objtool: Default ignore INT3 for unreachable

stable inclusion
from stable-v5.10.133
commit 03c5c33e043e77a1a848c52f37c512efb412f2c3
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5PTAS
CVE: CVE-2022-29900,CVE-2022-23816,CVE-2022-29901

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=03c5c33e043e77a1a848c52f37c512efb412f2c3

--------------------------------

commit 1ffbe4e9 upstream.

Ignore all INT3 instructions for unreachable code warnings, similar to NOP.
This allows using INT3 for various paddings instead of NOPs.
Signed-off-by: NPeter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: NJosh Poimboeuf <jpoimboe@redhat.com>
Link: https://lore.kernel.org/r/20220308154317.343312938@infradead.orgSigned-off-by: NThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: NBen Hutchings <ben@decadent.org.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NLin Yujun <linyujun809@huawei.com>
Reviewed-by: NZhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

tools/objtool/check.c

@@ -2775,9 +2775,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 		switch (insn->type) {
 
 		case INSN_RETURN:
-			if (next_insn && next_insn->type == INSN_TRAP) {
-				next_insn->ignore = true;
-			} else if (sls && !insn->retpoline_safe) {
+			if (sls && !insn->retpoline_safe &&
+			    next_insn && next_insn->type != INSN_TRAP) {
 				WARN_FUNC("missing int3 after ret",
 					  insn->sec, insn->offset);
 			}
@@ -2824,9 +2823,8 @@ static int validate_branch(struct objtool_file *file, struct symbol *func,
 			break;
 
 		case INSN_JUMP_DYNAMIC:
-			if (next_insn && next_insn->type == INSN_TRAP) {
-				next_insn->ignore = true;
-			} else if (sls && !insn->retpoline_safe) {
+			if (sls && !insn->retpoline_safe &&
+			    next_insn && next_insn->type != INSN_TRAP) {
 				WARN_FUNC("missing int3 after indirect jump",
 					  insn->sec, insn->offset);
 			}
@@ -2997,7 +2995,7 @@ static bool ignore_unreachable_insn(struct objtool_file *file, struct instructio
 	int i;
 	struct instruction *prev_insn;
 
-	if (insn->ignore || insn->type == INSN_NOP)
+	if (insn->ignore || insn->type == INSN_NOP || insn->type == INSN_TRAP)
 		return true;
 
 	/*