Feng Xue OS via Gcc-patches <gcc-patches@gcc.gnu.org> writes: > This patch extends option -mbranch-protection=bti with an optional argument > as bti[+all] to force compiler to unconditionally insert bti for all > functions. Because a direct function call at the stage of compiling might be > rewritten to an indirect call with some kind of linker-generated thunk stub > as invocation relay for some reasons. One instance is if a direct callee is > placed far from its caller, direct BL {imm} instruction could not represent > the distance, so indirect BLR {reg} should be used. For this case, a bti is > required at the beginning of the callee. > > caller() { > bl callee > } > > => > > caller() { > adrp reg, <callee> > add reg, reg, #constant > blr reg > } > > Although the issue could be fixed with a pretty new version of ld, here we > provide another means for user who has to rely on the old ld or other non-ld > linker. I also checked LLVM, by default, it implements bti just as the > proposed > -mbranch-protection=bti+all. > > Feng > > --- > gcc/config/aarch64/aarch64.cc | 12 +++++++----- > gcc/config/aarch64/aarch64.opt | 2 +- > gcc/config/arm/aarch-bti-insert.cc | 3 ++- > gcc/config/arm/aarch-common.cc | 22 ++++++++++++++++++---- > gcc/config/arm/aarch-common.h | 18 ++++++++++++++++++ > gcc/config/arm/arm.cc | 4 ++-- > gcc/config/arm/arm.opt | 2 +- > gcc/doc/invoke.texi | 16 ++++++++++------ > gcc/testsuite/gcc.target/aarch64/bti-5.c | 17 +++++++++++++++++ > 9 files changed, 76 insertions(+), 20 deletions(-) > create mode 100644 gcc/testsuite/gcc.target/aarch64/bti-5.c
[...] Hi Feng, I think this patch is missing its ChangeLog entry. Also you should specify the state of the testing and regression for this patch, please see [1]. > diff --git a/gcc/testsuite/gcc.target/aarch64/bti-5.c > b/gcc/testsuite/gcc.target/aarch64/bti-5.c > new file mode 100644 > index 00000000000..654cd0cce7e > --- /dev/null > +++ b/gcc/testsuite/gcc.target/aarch64/bti-5.c > @@ -0,0 +1,17 @@ > +/* { dg-do run } */ > +/* { dg-options "-O1 -save-temps" } */ > +/* { dg-require-effective-target lp64 } */ > +/* { dg-additional-options "-mbranch-protection=bti+all" { target { ! > default_branch_protection } } } */ I see the other bti execution tests we have require "aarch64_bti_hw" as effective target, do you think here is not necessary? If yes why? Thanks Andrea [1] <https://gcc.gnu.org/contribute.html#patches>