From 6ac83d350604c3e934d5e8a455ba7ec1c1c0240b Mon Sep 17 00:00:00 2001
From: Szabolcs Nagy <szabolcs.nagy@arm.com>
Date: Fri, 24 Apr 2020 17:36:02 +0100
Subject: [PATCH] aarch64: don't emit bti j after NOTE_INSN_DELETED_LABEL
[PR94748]
It was previously discussed that indirect branches cannot go to
NOTE_INSN_DELETED_LABEL so inserting a landing pad is unnecessary.
See https://gcc.gnu.org/pipermail/gcc-patches/2019-May/522625.html
Before the patch a bti j was inserted after the label in
__attribute__((target("branch-protection=bti")))
int foo (void)
{
label:
return 0;
}
This is not necessary and weakens the security protection.
gcc/ChangeLog:
PR target/94748
* config/aarch64/aarch64-bti-insert.c (rest_of_insert_bti): Remove
the check for NOTE_INSN_DELETED_LABEL.
gcc/testsuite/ChangeLog:
PR target/94748
* gcc.target/aarch64/pr94748.c: New test.
---
gcc/ChangeLog | 6 ++++++
gcc/config/aarch64/aarch64-bti-insert.c | 8 ++------
gcc/testsuite/ChangeLog | 5 +++++
gcc/testsuite/gcc.target/aarch64/pr94748.c | 10 ++++++++++
4 files changed, 23 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/gcc.target/aarch64/pr94748.c
diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 5b69334a26b8..c81801f289e9 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2020-04-30 Szabolcs Nagy <szabolcs.nagy@arm.com>
+
+ PR target/94748
+ * config/aarch64/aarch64-bti-insert.c (rest_of_insert_bti): Remove
+ the check for NOTE_INSN_DELETED_LABEL.
+
2020-04-30 Jakub Jelinek <jakub@redhat.com>
* configure.ac (--with-documentation-root-url,
diff --git a/gcc/config/aarch64/aarch64-bti-insert.c b/gcc/config/aarch64/aarch64-bti-insert.c
index aa091c308f61..57663ee23b49 100644
--- a/gcc/config/aarch64/aarch64-bti-insert.c
+++ b/gcc/config/aarch64/aarch64-bti-insert.c
@@ -139,14 +139,10 @@ rest_of_insert_bti (void)
insn = NEXT_INSN (insn))
{
/* If a label is marked to be preserved or can be a non-local goto
- target, it must be protected with a BTI J. The same applies to
- NOTE_INSN_DELETED_LABEL since they are basically labels that might
- be referenced via variables or constant pool. */
- if ((LABEL_P (insn)
+ target, it must be protected with a BTI J. */
+ if (LABEL_P (insn)
&& (LABEL_PRESERVE_P (insn)
|| bb->flags & BB_NON_LOCAL_GOTO_TARGET))
- || (NOTE_P (insn)
- && NOTE_KIND (insn) == NOTE_INSN_DELETED_LABEL))
{
bti_insn = gen_bti_j ();
emit_insn_after (bti_insn, insn);
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 9d5944b68866..66ac6705a05d 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-04-30 Szabolcs Nagy <szabolcs.nagy@arm.com>
+
+ PR target/94748
+ * gcc.target/aarch64/pr94748.c: New test.
+
2020-04-30 Andreas Krebbel <krebbel@linux.ibm.com>
* gcc.target/s390/zvector/vec_load_len_r.c: New test.
diff --git a/gcc/testsuite/gcc.target/aarch64/pr94748.c b/gcc/testsuite/gcc.target/aarch64/pr94748.c
new file mode 100644
index 000000000000..2a2850d2fac0
--- /dev/null
+++ b/gcc/testsuite/gcc.target/aarch64/pr94748.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+
+__attribute__ ((target("branch-protection=bti")))
+int foo ()
+{
+label:
+ return 0;
+}
+
+/* { dg-final { scan-assembler-not {hint (36|38) // bti (j|jc)} } } */
--
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