Re: [PATCH, GCC, AARCH64, 5/6] Enable BTI : Add new pass for BTI.

[Andrew Pinski <pinskia@gmail.com>]

On Fri, Nov 2, 2018 at 11:39 AM Sudakshina Das <Sudi.Das@arm.com> wrote:
>
> Hi
>
> This patch is part of a series that enables ARMv8.5-A in GCC and
> adds Branch Target Identification Mechanism.
> (https://developer.arm.com/products/architecture/cpu-architecture/a-profile/exploration-tools)
>
> This patch adds a new pass called "bti" which is triggered by the
> command line argument -mbranch-protection whenever "bti" is turned on.
>
> The pass iterates through the instructions and adds appropriated BTI
> instructions based on the following:
>     * Add a new "BTI C" at the beginning of a function, unless its already
>       protected by a "PACIASP/PACIBSP". We exempt the functions that are
>       only called directly.

Coming back to this because the check only_called_directly_p does not
work if the linker will insert a veneer as the compiler does not know
about that.
This is recorded as https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106671 .

Thanks,
Andrew Pinski


>     * Add a new "BTI J" for every target of an indirect jump, jump table
>       targets, non-local goto targets or labels that might be referenced
>       by variables, constant pools, etc (NOTE_INSN_DELETED_LABEL)
>
> Since we have already changed the use of indirect tail calls to only x16
> and x17, we do not have to use "BTI JC".
> (check patch 3/6).
>
> Bootstrapped and regression tested with aarch64-none-linux-gnu. Added
> new tests.
> Is this ok for trunk?
>
> Thanks
> Sudi
>
> *** gcc/ChangeLog ***
>
> 2018-xx-xx  Sudakshina Das  <sudi.das@arm.com>
>             Ramana Radhakrishnan  <ramana.radhakrishnan@arm.com>
>
>         * config.gcc (aarch64*-*-*): Add aarch64-bti-insert.o.
>         * gcc/config/aarch64/aarch64.h: Update comment for
>         TRAMPOLINE_SIZE.
>         * config/aarch64/aarch64.c (aarch64_asm_trampoline_template):
>         Update if bti is enabled.
>         * config/aarch64/aarch64-bti-insert.c: New file.
>         * config/aarch64/aarch64-passes.def (INSERT_PASS_BEFORE): Insert
>         bti pass.
>         * config/aarch64/aarch64-protos.h (make_pass_insert_bti):
>         Declare the new bti pass.
>         * config/aarch64/aarch64.md (bti_nop): Define.
>         * config/aarch64/t-aarch64: Add rule for aarch64-bti-insert.o.
>
> *** gcc/testsuite/ChangeLog ***
>
> 2018-xx-xx  Sudakshina Das  <sudi.das@arm.com>
>
>         * gcc.target/aarch64/bti-1.c: New test.
>         * gcc.target/aarch64/bti-2.c: New test.
>         * lib/target-supports.exp
>         (check_effective_target_aarch64_bti_hw): Add new check for
>         BTI hw.
>