> -----Original Message-----
> From: Szabolcs Nagy <szabolcs.n...@arm.com>
> Sent: 28 April 2020 16:51
> To: gcc-patches@gcc.gnu.org
> Cc: Richard Earnshaw <richard.earns...@arm.com>; Kyrylo Tkachov
> <kyrylo.tkac...@arm.com>; Sudakshina Das <sudi....@arm.com>
> 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.
Ok if testing is successful.
Thanks,
Kyrill
>
> gcc/ChangeLog:
>
> 2020-04-28 Szabolcs Nagy <szabolcs.n...@arm.com>
>
> PR target/94748
> * config/aarch64/aarch64-bti-insert.c (rest_of_insert_bti): Remove
> the check for NOTE_INSN_DELETED_LABEL.
>
> gcc/testsuite/ChangeLog:
>
> 2020-04-28 Szabolcs Nagy <szabolcs.n...@arm.com>
>
> PR target/94748
> * gcc.target/aarch64/pr94748.c: New test.
> ---
> gcc/config/aarch64/aarch64-bti-insert.c | 8 ++------
> gcc/testsuite/gcc.target/aarch64/pr94748.c | 10 ++++++++++
> 2 files changed, 12 insertions(+), 6 deletions(-)
> create mode 100644 gcc/testsuite/gcc.target/aarch64/pr94748.c
>
> diff --git a/gcc/config/aarch64/aarch64-bti-insert.c
> b/gcc/config/aarch64/aarch64-bti-insert.c
> index aa091c308f6..57663ee23b4 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/gcc.target/aarch64/pr94748.c
> b/gcc/testsuite/gcc.target/aarch64/pr94748.c
> new file mode 100644
> index 00000000000..2a2850d2fac
> --- /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)} } } */
> --
> 2.17.1
