[PATCH 1/2, AARCH64]: Machine descriptions: Re: [RFC] [PATCH, AARCH64] : Using standard patterns for stack protection.

[Venkataramanan Kumar]

Hi Marcus,

On 14 March 2014 19:42, Marcus Shawcroft <marcus.shawcroft@gmail.com> wrote:
> Hi Venkat
>
> On 5 February 2014 10:29, Venkataramanan Kumar
> <venkataramanan.kumar@linaro.org> wrote:
>> Hi Marcus,
>>
>>> +  "ldr\\t%x2, %1\;str\\t%x2, %0\;mov\t%x2,0"
>>> +  [(set_attr "length" "12")])
>>>
>>> This pattern emits an opaque sequence of instructions that cannot be
>>> scheduled, is that necessary? Can we not expand individual
>>> instructions or at least split ?
>>
>> Almost all the ports emits a template of assembly instructions.
>> I m not sure why they have to be generated this way.
>> But usage of these pattern is to clear the register that holds canary
>> value immediately after its usage.
>
> I've just read the thread Andrew pointed out, thanks, I'm happy that
> there is a good reason to do it this way.  Andrew, thanks for
> providing the background.
>
> +  [(set_attr "length" "12")])
> +
>
> These patterns should also set the "type" attribute,  a reasonable
> value would be "multiple".
>

I have incorporated your review comments and split the patch into two.

The first patch attached here contains Aarch64 machine descriptions
for the stack protect patterns.

ChangeLog.

2014-03-19 Venkataramanan Kumar  <venkataramanan.kumar@linaro.org>
        * config/aarch64/aarch64.md (stack_protect_set, stack_protect_test)
        (stack_protect_set_<mode>, stack_protect_test_<mode>): Add
        machine descriptions for Stack Smashing Protector.

Tested  for aarch64-none-linux-gnu target under QEMU .

regards,
Venkat.
-------------- next part --------------
Index: gcc/config/aarch64/aarch64.md
===================================================================
--- gcc/config/aarch64/aarch64.md	(revision 208609)
+++ gcc/config/aarch64/aarch64.md	(working copy)
@@ -102,6 +102,8 @@
     UNSPEC_TLSDESC
     UNSPEC_USHL_2S
     UNSPEC_VSTRUCTDUMMY
+    UNSPEC_SP_SET
+    UNSPEC_SP_TEST
 ])
 
 (define_c_enum "unspecv" [
@@ -3634,6 +3636,67 @@
   DONE;
 })
 
+;; Named patterns for stack smashing protection.
+(define_expand "stack_protect_set"
+  [(match_operand 0 "memory_operand")
+   (match_operand 1 "memory_operand")]
+  ""
+{
+  enum machine_mode mode = GET_MODE (operands[0]);
+
+  emit_insn ((mode == DImode
+	      ? gen_stack_protect_set_di
+	      : gen_stack_protect_set_si) (operands[0], operands[1]));
+  DONE;
+})
+
+(define_insn "stack_protect_set_<mode>"
+  [(set (match_operand:PTR 0 "memory_operand" "=m")
+	(unspec:PTR [(match_operand:PTR 1 "memory_operand" "m")]
+	 UNSPEC_SP_SET))
+   (set (match_scratch:PTR 2 "=&r") (const_int 0))]
+  ""
+  "ldr\\t%x2, %1\;str\\t%x2, %0\;mov\t%x2,0"
+  [(set_attr "length" "12")
+   (set_attr "type" "multiple")])
+
+(define_expand "stack_protect_test"
+  [(match_operand 0 "memory_operand")
+   (match_operand 1 "memory_operand")
+   (match_operand 2)]
+  ""
+{
+
+  rtx result = gen_reg_rtx (Pmode);
+
+  enum machine_mode mode = GET_MODE (operands[0]);
+
+  emit_insn ((mode == DImode
+	      ? gen_stack_protect_test_di
+	      : gen_stack_protect_test_si) (result,
+					    operands[0],
+					    operands[1]));
+
+  if (mode == DImode)
+    emit_jump_insn (gen_cbranchdi4 (gen_rtx_EQ (VOIDmode, result, const0_rtx),
+				    result, const0_rtx, operands[2]));
+  else
+    emit_jump_insn (gen_cbranchsi4 (gen_rtx_EQ (VOIDmode, result, const0_rtx),
+				    result, const0_rtx, operands[2]));
+  DONE;
+})
+
+(define_insn "stack_protect_test_<mode>"
+  [(set (match_operand:PTR 0 "register_operand")
+	(unspec:PTR [(match_operand:PTR 1 "memory_operand" "m")
+		     (match_operand:PTR 2 "memory_operand" "m")]
+	 UNSPEC_SP_TEST))
+   (clobber (match_scratch:PTR 3 "=&r"))]
+  ""
+  "ldr\t%x3, %x1\;ldr\t%x0, %x2\;eor\t%x0, %x3, %x0"
+  [(set_attr "length" "12")
+   (set_attr "type" "multiple")])
+
 ;; AdvSIMD Stuff
 (include "aarch64-simd.md")