auto merge of #6249 : crabtw/rust/arm, r=brson

It uses the private field of TCB head to store stack limit. I tested on my Raspberry PI. A simple hello world program ran without any problem. However, for a more complex program, it segfaulted as #6231.

src/librustc/back/arm.rs

@@ -64,7 +64,7 @@ pub fn get_target_strs(target_os: session::os) -> target_strs::t {
         target_triple: match target_os {
           session::os_macos => ~"arm-apple-darwin",
           session::os_win32 => ~"arm-pc-mingw32",
-          session::os_linux => ~"arm-unknown-linux",
+          session::os_linux => ~"arm-unknown-linux-gnueabihf",
           session::os_android => ~"arm-linux-androideabi",
           session::os_freebsd => ~"arm-unknown-freebsd"
         },

src/rt/arch/arm/record_sp.S

@@ -15,13 +15,21 @@
 
 record_sp_limit:
 	mrc p15, #0, r3, c13, c0, #3
+#if __ANDROID__
 	add r3, r3, #252
+#elif __linux__
+	add r3, r3, #4
+#endif
 	str r0, [r3]
 	mov pc, lr
 
 get_sp_limit:
 	mrc p15, #0, r3, c13, c0, #3
+#if __ANDROID__
 	add r3, r3, #252
+#elif __linux__
+	add r3, r3, #4
+#endif
 	ldr r0, [r3]
 	mov pc, lr
 

src/rt/rust_task.h

@@ -146,6 +146,9 @@
 #ifdef __mips__
 #define RED_ZONE_SIZE RZ_MAC_32
 #endif
+#ifdef __arm__
+#define RED_ZONE_SIZE RZ_LINUX_32
+#endif
 #endif
 #ifdef __APPLE__
 #ifdef __i386__