Patchwork [i386] Add -mstack-protector-guard= for i386

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Submitter Andrew Hsieh
Date April 12, 2013, 6:16 a.m.
Message ID <CABySjRsJ-qRHw9RA9m1v+03wp2bk03wPZ22uz2hAKcQT0T_FDQ@mail.gmail.com>
Download mbox | patch
Permalink /patch/235974/
State New
Headers show

Comments

Andrew Hsieh - April 12, 2013, 6:16 a.m.
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

Developer build for Android/x86 4.2 and later can choose to add
-mstack-protector-guard=tls

(*1) Including AOSP compiler at
prebuilts/gcc/linux-x86/x86/i686-linux-android-4.7, and the same
compiler released in NDK r8d and later.


--
Thanks,
Andrew

Patch

====
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.c (ix86_option_override_internal): Default
        to SSP_TLS unless it's bionic
        * config/i386/i386.md: define_expand/insn "stack_protect_set/test..."
        only if ix86_stack_protector_guard == SSP_TLS.

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"
+  "ix86_stack_protector_guard == SSP_TLS"
 {
   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"
+  "ix86_stack_protector_guard == SSP_TLS"
   "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"
+  "ix86_stack_protector_guard == SSP_TLS"
 {
   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"
+  "ix86_stack_protector_guard == SSP_TLS"
   "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/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 +14522,11 @@ 
 @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).
+
 @end table

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