Re: [committed][PATCH] Stack clash protection patch 04/08 - V4

[Rainer Orth <ro at CeBiTec dot Uni-Bielefeld dot DE>]

Jeff Law <law@redhat.com> writes:

> This patch introduces the x86 stack clash protected prologue support as
> well as the tests.  I believe the only change since V3 was the more
> aggressive introduction of scheduling barriers.  It also enables the
> stack-clash tests for x86 targets.
>
> The scheduling barriers prevent the memory dependency breaking bits in
> the scheduler from rewriting and rearranging the allocations and probes.
>  While I haven't seen problems from that on x86, I did see the scheduler
> muck things up on aarch64 and there's a test for that in the aarch64
> specific patches.  Better to be safe here and just emit the scheduling
> barriers.
>
> Bootstrapped and regression tested on x86.  Installing on the trunk.
>
> Jeff
>
> commit 57e17e31cb358fcd0d7cea8264b5063762ab3971
> Author: law <law@138bc75d-0d04-0410-961f-82ee72b054a4>
> Date:   Wed Sep 20 05:35:07 2017 +0000
>
>             * config/i386/i386.c (ix86_adjust_stack_and_probe_stack_clash): New.
>             (ix86_expand_prologue): Dump stack clash info as needed.
>             Call ix86_adjust_stack_and_probe_stack_clash as needed.
>     
>             * gcc.dg/stack-check-4.c: New test.
>             * gcc.dg/stack-check-5.c: New test.
>             * gcc.dg/stack-check-6.c: New test.
>             * gcc.dg/stack-check-6a.c: New test.
>             * gcc.dg/stack-check-7.c: New test.
>             * gcc.dg/stack-check-8.c: New test.
>             * gcc.dg/stack-check-9.c: New test.
>             * gcc.dg/stack-check-10.c: New test.
>             * lib/target-supports.exp
>             (check_effective_target_supports_stack_clash_protection): Enable for
>             x86 and x86_64 targets.

Some of the new tests FAIL on Solaris/x86:

+FAIL: gcc.dg/stack-check-10.c scan-rtl-dump-times pro_and_epilogue "Stack clash no frame pointer needed" 2
+FAIL: gcc.dg/stack-check-5.c scan-rtl-dump-times pro_and_epilogue "Stack clash no frame pointer needed" 4
+FAIL: gcc.dg/stack-check-6.c scan-rtl-dump-times pro_and_epilogue "Stack clash no frame pointer needed" 4
+FAIL: gcc.dg/stack-check-6a.c scan-rtl-dump-times pro_and_epilogue "Stack clash no frame pointer needed" 4
+FAIL: gcc.dg/stack-check-9.c scan-rtl-dump-times pro_and_epilogue "Stack clash no frame pointer needed" 1

for both 32 and 64-bit, all are guarded by ! frame_pointer_for_non_leaf.

frame_pointer_for_non_leaf currently only true for aarch*-*-*, but
i386/sol2.h has

#define USE_IX86_FRAME_POINTER 1
#define USE_X86_64_FRAME_POINTER 1

unlike i386/i386.c where both are 0 by default.  Fixed with the
following patch:

diff --git a/gcc/testsuite/lib/target-supports.exp b/gcc/testsuite/lib/target-supports.exp
--- a/gcc/testsuite/lib/target-supports.exp
+++ b/gcc/testsuite/lib/target-supports.exp
@@ -8663,6 +8663,12 @@ proc check_effective_target_frame_pointe
   if { [istarget aarch*-*-*] } {
 	return 1
   }
+
+  # Solaris/x86 defaults to -fno-omit-frame-pointer.
+  if { [istarget i?86-*-solaris*] || [istarget x86_64-*-solaris*] } {
+    return 1
+  }
+
   return 0
 }
 

+FAIL: gcc.target/i386/stack-check-11.c scan-assembler-times orq 3
+FAIL: gcc.target/i386/stack-check-11.c scan-assembler-times subq 4

32-bit only, generic 32-bit x86, already fixed, I believe.

The following are 64-bit only and remain even after the
frame_pointer_non_leaf fix:

+FAIL: gcc.dg/stack-check-10.c scan-rtl-dump-times pro_and_epilogue "Stack clash residual allocation in prologue" 2

+FAIL: gcc.dg/stack-check-5.c scan-rtl-dump-times pro_and_epilogue "Stack clash no residual allocation in prologue" 1
+FAIL: gcc.dg/stack-check-5.c scan-rtl-dump-times pro_and_epilogue "Stack clash residual allocation in prologue" 3

	Rainer

-- 
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Rainer Orth, Center for Biotechnology, Bielefeld University