Add -mstack-protector-guard= to x86 compilers

To choose between "global" (default) and "tls" (new)
for -fstack-protector, -fstack-protector-all, and
-fstack-protector-strong (GCC 4.6+).

Note that this alone doesn't enable any -fstack-protector*

For NDK: The default "global" generates code backward
compatible with older bionic

For AOSP: build may add "-mstack-protector-guard=tls" to
build platform code with new bionic (*1)

Related CL:
  https://android-review.googlesource.com/#/c/45416 (*1)
  https://android-review.googlesource.com/#/c/45784

Change-Id: Iedf5b7ae5148572db2e35f0add93bc3d13511304

4 files changed, 30 insertions, 4 deletions

diff --git a/gcc-4.7/gcc/config/i386/i386-opts.h b/gcc-4.7/gcc/config/i386/i386-opts.h
index 3cc2253c3..8904491de 100644
--- a/gcc-4.7/gcc/config/i386/i386-opts.h
+++ b/gcc-4.7/gcc/config/i386/i386-opts.h
@@ -82,4 +82,9 @@ enum ix86_veclibabi {
   ix86_veclibabi_type_acml
 };
 
+enum stack_protector_guard {
+  SSP_TLS,      /* per-thread canary at %gs:20 */
+  SSP_GLOBAL,   /* global canary */
+};
+
 #endif
diff --git a/gcc-4.7/gcc/config/i386/i386.c b/gcc-4.7/gcc/config/i386/i386.c
index adf911c64..c21cb81c1 100644
--- a/gcc-4.7/gcc/config/i386/i386.c
+++ b/gcc-4.7/gcc/config/i386/i386.c
@@ -3890,6 +3890,12 @@ ix86_option_override_internal (bool main_args_p)
   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;
+    }
 }
 
 /* Return TRUE if VAL is passed in register with 256bit AVX modes.  */
diff --git a/gcc-4.7/gcc/config/i386/i386.md b/gcc-4.7/gcc/config/i386/i386.md
index d8deee8da..e006cc8fb 100644
--- a/gcc-4.7/gcc/config/i386/i386.md
+++ b/gcc-4.7/gcc/config/i386/i386.md
@@ -17722,7 +17722,7 @@
 (define_expand "stack_protect_set"
   [(match_operand 0 "memory_operand" "")
    (match_operand 1 "memory_operand" "")]
-  ""
+  "ix86_stack_protector_guard == SSP_TLS"
 {
   rtx (*insn)(rtx, rtx);
 
@@ -17747,7 +17747,7 @@
 		    UNSPEC_SP_SET))
    (set (match_scratch:PTR 2 "=&r") (const_int 0))
    (clobber (reg:CC FLAGS_REG))]
-  ""
+  "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")])
 
@@ -17765,7 +17765,7 @@
   [(match_operand 0 "memory_operand" "")
    (match_operand 1 "memory_operand" "")
    (match_operand 2 "" "")]
-  ""
+  "ix86_stack_protector_guard == SSP_TLS"
 {
   rtx flags = gen_rtx_REG (CCZmode, FLAGS_REG);
 
@@ -17795,7 +17795,7 @@
 		     (match_operand:PTR 2 "memory_operand" "m")]
 		    UNSPEC_SP_TEST))
    (clobber (match_scratch:PTR 3 "=&r"))]
-  ""
+  "ix86_stack_protector_guard == SSP_TLS"
   "mov{<imodesuffix>}\t{%1, %3|%3, %1}\;xor{<imodesuffix>}\t{%2, %3|%3, %2}"
   [(set_attr "type" "multi")])
 
diff --git a/gcc-4.7/gcc/config/i386/i386.opt b/gcc-4.7/gcc/config/i386/i386.opt
index 4008fd0fe..492490f14 100644
--- a/gcc-4.7/gcc/config/i386/i386.opt
+++ b/gcc-4.7/gcc/config/i386/i386.opt
@@ -581,3 +581,18 @@ Split 32-byte AVX unaligned load
 mavx256-split-unaligned-store
 Target Report Mask(AVX256_SPLIT_UNALIGNED_STORE) Save
 Split 32-byte AVX unaligned store
+
+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)
+