Re: [PATCH,i386] Add -mstack-protector-guard= for i386

[Andrew Hsieh <andrewhsieh at google dot com>]

Introduced TARGET_SSP_GLOBAL_GUARD and TARGET_SSP_TLS_GUARD as suggested.
As for handling default in ix86_option_override_internal, is it
possible to achieve the same "default to SSP_GLOBAL if bionic"
entirely in i386.opt?

===
2013-04-12  Andrew Hsieh  <andrewhsieh.google.com>

        * config/i386/i386.opt: New option mstack-protector-guard=.
        * config/i386/i386-opts.h: Add enum stack_protector_guard.
        * config/i386/i386.h: Introduce TARGET_SSP_GLOBAL_GUARD and
        TARGET_SSP_TLS_GUARD.
        * config/i386/i386.c (ix86_option_override_internal): Default
        to SSP_TLS unless it's bionic
        * config/i386/i386.md: define_expand/insn "stack_protect_set/test..."
        if TARGET_SSP_TLS_GUARD
        * doc/invoke.texi (i386 Option): Document.

Index: gcc/config/i386/i386.opt
===================================================================
--- gcc/config/i386/i386.opt (revision 197837)
+++ gcc/config/i386/i386.opt (working copy)
@@ -626,3 +626,17 @@
 mrtm
 Target Report Mask(ISA_RTM) Var(ix86_isa_flags) Save
 Support RTM built-in functions and code generation
+
+mstack-protector-guard=
+Target RejectNegative Joined Enum(stack_protector_guard)
Var(ix86_stack_protector_guard) Init(SSP_TLS)
+Use given stack-protector guard
+
+Enum
+Name(stack_protector_guard) Type(enum stack_protector_guard)
+Known stack protector guard (for use with the -mstack-protector-guard= option):
+
+EnumValue
+Enum(stack_protector_guard) String(tls) Value(SSP_TLS)
+
+EnumValue
+Enum(stack_protector_guard) String(global) Value(SSP_GLOBAL)
Index: gcc/config/i386/i386.md
===================================================================
--- gcc/config/i386/i386.md (revision 197837)
+++ gcc/config/i386/i386.md (working copy)
@@ -17058,7 +17058,7 @@
 (define_expand "stack_protect_set"
   [(match_operand 0 "memory_operand")
    (match_operand 1 "memory_operand")]
-  "!TARGET_HAS_BIONIC"
+  "TARGET_SSP_TLS_GUARD"
 {
   rtx (*insn)(rtx, rtx);

@@ -17083,7 +17083,7 @@
     UNSPEC_SP_SET))
    (set (match_scratch:PTR 2 "=&r") (const_int 0))
    (clobber (reg:CC FLAGS_REG))]
-  "!TARGET_HAS_BIONIC"
+  "TARGET_SSP_TLS_GUARD"
   "mov{<imodesuffix>}\t{%1, %2|%2, %1}\;mov{<imodesuffix>}\t{%2,
%0|%0, %2}\;xor{l}\t%k2, %k2"
   [(set_attr "type" "multi")])

@@ -17101,7 +17101,7 @@
   [(match_operand 0 "memory_operand")
    (match_operand 1 "memory_operand")
    (match_operand 2)]
-  "!TARGET_HAS_BIONIC"
+  "TARGET_SSP_TLS_GUARD"
 {
   rtx flags = gen_rtx_REG (CCZmode, FLAGS_REG);

@@ -17131,7 +17131,7 @@
      (match_operand:PTR 2 "memory_operand" "m")]
     UNSPEC_SP_TEST))
    (clobber (match_scratch:PTR 3 "=&r"))]
-  "!TARGET_HAS_BIONIC"
+  "TARGET_SSP_TLS_GUARD"
   "mov{<imodesuffix>}\t{%1, %3|%3, %1}\;xor{<imodesuffix>}\t{%2, %3|%3, %2}"
   [(set_attr "type" "multi")])

Index: gcc/config/i386/i386-opts.h
===================================================================
--- gcc/config/i386/i386-opts.h (revision 197837)
+++ gcc/config/i386/i386-opts.h (working copy)
@@ -85,4 +85,9 @@
   ix86_veclibabi_type_acml
 };

+enum stack_protector_guard {
+  SSP_TLS,      /* per-thread canary at %gs:20 */
+  SSP_GLOBAL    /* global canary */
+};
+
 #endif
Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c (revision 197837)
+++ gcc/config/i386/i386.c (working copy)
@@ -3922,6 +3922,12 @@
   if (main_args_p)
     target_option_default_node = target_option_current_node
       = build_target_option_node ();
+
+  /* Handle stack protector */
+  if (!global_options_set.x_ix86_stack_protector_guard)
+    {
+      ix86_stack_protector_guard = TARGET_HAS_BIONIC? SSP_GLOBAL : SSP_TLS;
+    }
 }

 /* Implement the TARGET_OPTION_OVERRIDE hook.  */
Index: gcc/config/i386/i386.h
===================================================================
--- gcc/config/i386/i386.h (revision 197837)
+++ gcc/config/i386/i386.h (working copy)
@@ -486,6 +486,9 @@
 #define TARGET_TLS_DIRECT_SEG_REFS_DEFAULT 0
 #endif

+#define TARGET_SSP_GLOBAL_GUARD (ix86_stack_protector_guard == SSP_GLOBAL)
+#define TARGET_SSP_TLS_GUARD    (ix86_stack_protector_guard == SSP_TLS)
+
 /* Fence to use after loop using storent.  */

 extern tree x86_mfence;
Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi (revision 197837)
+++ gcc/doc/invoke.texi (working copy)
@@ -656,7 +656,8 @@
 -mcmodel=@var{code-model} -mabi=@var{name} -maddress-mode=@var{mode} @gol
 -m32 -m64 -mx32 -mlarge-data-threshold=@var{num} @gol
 -msse2avx -mfentry -m8bit-idiv @gol
--mavx256-split-unaligned-load -mavx256-split-unaligned-store}
+-mavx256-split-unaligned-load -mavx256-split-unaligned-store @gol
+-mstack-protector-guard=@var{guard}}

 @emph{i386 and x86-64 Windows Options}
 @gccoptlist{-mconsole -mcygwin -mno-cygwin -mdll @gol
@@ -14521,6 +14522,13 @@
 @opindex avx256-split-unaligned-store
 Split 32-byte AVX unaligned load and store.

+@item -mstack-protector-guard=@var{guard}
+@opindex mstack-protector-guard=@var{guard}
+Generate stack protection code using canary at @var{guard}.  Supported
+locations are @samp{global} or @samp{tls} per thread at %gs:20 (the default).
+This option has effect only when @option{-fstack-protector}
+or @option{-fstack-protector-all} is also specified.
+
 @end table

 These @samp{-m} switches are supported in addition to the above

On Fri, Apr 12, 2013 at 2:45 PM, Uros Bizjak <ubizjak@gmail.com> wrote:
> Hello!
>
>> Bionic in Android 4.2 starts to support stack-protector canary at TLS for x86.
>>
>> Android prior to 4.2 still looks at a global variable for stack
>> canary.  To maintain backward compatibility, I propose to add a new
>> option -mstack-protector-guard={global,tls} for i386 back-end to use
>> canary at global or per-thread at %gs:20, respectively.
>>
>> "global" is the default for bionic (*1); otherwise "tls" is the default
>
>  (define_expand "stack_protect_set"
>    [(match_operand 0 "memory_operand")
>     (match_operand 1 "memory_operand")]
> -  "!TARGET_HAS_BIONIC"
> +  "ix86_stack_protector_guard == SSP_TLS"
>
> Please introduce TARGET_SSP_GLOBAL_GUARD and TARGET_SSP_TLS_GUARD
> defines to i386.h (please follow an example of TARGET_GNU_TLS).
>
>      target_option_default_node = target_option_current_node
>        = build_target_option_node ();
> +
> +  /* Handle stack protector */
> +  if (!global_options_set.x_ix86_stack_protector_guard)
> +    {
> +      ix86_stack_protector_guard = TARGET_HAS_BIONIC? SSP_GLOBAL : SSP_TLS;
> +    }
>  }
>
> You should not need this part, JoinedVar directive should handle this
> functionality by itself. Again, please see ix86_tls_dialect handling.
>
> Uros.



-- 
Thanks,
Andrew