Hi James

On 29/11/18 16:47, Sudakshina Das wrote:
> Hi
> 
> On 13/11/18 14:47, Sudakshina Das wrote:
>> Hi
>>
>> On 02/11/18 18:38, Sudakshina Das 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.
>>>        * 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).
>>>
>>
>> I missed out on the explanation for the changes to the trampoline code.
>> The patch also updates the trampoline code in case BTI is enabled. Since
>> the trampoline code is a target of an indirect branch, we need to add an
>> appropriate BTI instruction at the beginning of it to avoid a branch
>> target exception.
>>
>>> 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.
>>>
>>
>> Updated patch attached with more comments and a bit of simplification
>> in aarch64-bti-insert.c. ChangeLog still applies.
>>
>> Thanks
>> Sudi
>>
> 
> I found a missed case in the bti pass and edited the patch to include
> it. This made me realize that the only 2 regressions I saw with the
> BTI enabled model can now be avoided. (as quoted below from my 6/6
> patch)
> "Bootstrapped and regression tested with aarch64-none-linux-gnu with
> and without the configure option turned on.
> Also tested on aarch64-none-elf with and without configure option with a
> BTI enabled aem. Only 2 regressions and these were because newlib
> requires patches to protect hand coded libraries with BTI."
> 
> The ChangeLog still applies.
> 
> Sudi
> 
I have updated the patch according to our discussions offline.
The md pattern is now split into 4 patterns and i have added a new
test for the setjmp case along with some comments where missing.

*** 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 (unspecv): Add UNSPECV_BTI_NOARG,
	UNSPECV_BTI_C, UNSPECV_BTI_J and UNSPECV_BTI_JC.
	(bti_noarg, bti_j, bti_c, bti_jc): New define_insns.
	* 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.
	* gcc.target/aarch64/bti-3.c: New test.
	* lib/target-supports.exp
	(check_effective_target_aarch64_bti_hw): Add new check for
	BTI hw.

Thanks
Sudi