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.
====
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
--
Thanks,
Andrew
