On Tue, Jul 3, 2018 at 5:32 PM, H.J. Lu <hjl.to...@gmail.com> wrote:
> On Fri, Jun 8, 2018 at 3:27 AM, H.J. Lu <hongjiu...@intel.com> wrote:
>> On x86, swapcontext may return via indirect branch when shadow stack
>> is enabled. To support code instrumentation of control-flow transfers
>> with -fcf-protection, add indirect_return function attribute to inform
>> compiler that a function may return via indirect branch.
>>
>> Note: Unlike setjmp, swapcontext only returns once. Mark it return
>> twice will unnecessarily disable compiler optimization.
>>
>> OK for trunk?
>>
>> H.J.
>> ----
>> gcc/
>>
>> PR target/85620
>> * config/i386/i386.c (rest_of_insert_endbranch): Also generate
>> ENDBRANCH for non-tail call which may return via indirect branch.
>> * doc/extend.texi: Document indirect_return attribute.
>>
>> gcc/testsuite/
>>
>> PR target/85620
>> * gcc.target/i386/pr85620-1.c: New test.
>> * gcc.target/i386/pr85620-2.c: Likewise.
>>
>
> Here is the updated patch with a testcase to show the impact of
> returns_twice attribute.
>
> Jan, Uros, can you take a look?
LGTM for the implementation, can't say if attribute is really needed or not.
+@item indirect_return
+@cindex @code{indirect_return} function attribute, x86
+
+The @code{indirect_return} attribute on a function is used to inform
+the compiler that the function may return via indiret branch.
s/indiret/indirect/
Uros.
