diff --git a/src/libcore/rt/context.rs b/src/libcore/rt/context.rs
index de96a7d1793..dfb7bdf04c3 100644
--- a/src/libcore/rt/context.rs
+++ b/src/libcore/rt/context.rs
@@ -65,42 +65,6 @@ extern {
     fn swap_registers(out_regs: *mut Registers, in_regs: *Registers);
 }
 
-// Definitions of these registers are in rt/arch/x86_64/regs.h
-#[cfg(target_arch = "x86_64")]
-type Registers = [uint * 22];
-
-#[cfg(target_arch = "x86_64")]
-fn new_regs() -> ~Registers { ~[0, .. 22] }
-
-#[cfg(target_arch = "x86_64")]
-fn initialize_call_frame(regs: &mut Registers,
-                         fptr: *c_void, arg: *c_void, sp: *mut uint) {
-
-    // Redefinitions from regs.h
-    const RUSTRT_ARG0: uint = 3;
-    const RUSTRT_RSP: uint = 1;
-    const RUSTRT_IP: uint = 8;
-    const RUSTRT_RBP: uint = 2;
-
-    let sp = align_down(sp);
-    let sp = mut_offset(sp, -1);
-
-    // The final return address. 0 indicates the bottom of the stack
-    unsafe { *sp = 0; }
-
-    rtdebug!("creating call frame");
-    rtdebug!("fptr %x", fptr as uint);
-    rtdebug!("arg %x", arg as uint);
-    rtdebug!("sp %x", sp as uint);
-
-    regs[RUSTRT_ARG0] = arg as uint;
-    regs[RUSTRT_RSP] = sp as uint;
-    regs[RUSTRT_IP] = fptr as uint;
-
-    // Last base pointer on the stack should be 0
-    regs[RUSTRT_RBP] = 0;
-}
-
 #[cfg(target_arch = "x86")]
 struct Registers {
     eax: u32, ebx: u32, ecx: u32, edx: u32,
@@ -137,6 +101,79 @@ fn initialize_call_frame(regs: &mut Registers,
     regs.ebp = 0;
 }
 
+#[cfg(target_arch = "x86_64")]
+type Registers = [uint * 22];
+
+#[cfg(target_arch = "x86_64")]
+fn new_regs() -> ~Registers { ~[0, .. 22] }
+
+#[cfg(target_arch = "x86_64")]
+fn initialize_call_frame(regs: &mut Registers,
+                         fptr: *c_void, arg: *c_void, sp: *mut uint) {
+
+    // Redefinitions from regs.h
+    const RUSTRT_ARG0: uint = 3;
+    const RUSTRT_RSP: uint = 1;
+    const RUSTRT_IP: uint = 8;
+    const RUSTRT_RBP: uint = 2;
+
+    let sp = align_down(sp);
+    let sp = mut_offset(sp, -1);
+
+    // The final return address. 0 indicates the bottom of the stack
+    unsafe { *sp = 0; }
+
+    rtdebug!("creating call frame");
+    rtdebug!("fptr %x", fptr as uint);
+    rtdebug!("arg %x", arg as uint);
+    rtdebug!("sp %x", sp as uint);
+
+    regs[RUSTRT_ARG0] = arg as uint;
+    regs[RUSTRT_RSP] = sp as uint;
+    regs[RUSTRT_IP] = fptr as uint;
+
+    // Last base pointer on the stack should be 0
+    regs[RUSTRT_RBP] = 0;
+}
+
+#[cfg(target_arch = "arm")]
+type Registers = [uint * 32];
+
+#[cfg(target_arch = "arm")]
+fn new_regs() -> ~Registers { ~[0, .. 32] }
+
+#[cfg(target_arch = "arm")]
+fn initialize_call_frame(regs: &mut Registers,
+                         fptr: *c_void, arg: *c_void, sp: *mut uint) {
+    let sp = mut_offset(sp, -1);
+
+    // The final return address. 0 indicates the bottom of the stack
+    unsafe { *sp = 0; }
+
+    regs[0] = arg as uint;   // r0
+    regs[13] = sp as uint;   // #53 sp, r13
+    regs[14] = fptr as uint; // #60 pc, r15 --> lr
+}
+
+#[cfg(target_arch = "mips")]
+type Registers = [uint * 32];
+
+#[cfg(target_arch = "mips")]
+fn new_regs() -> ~Registers { ~[0, .. 32] }
+
+#[cfg(target_arch = "mips")]
+fn initialize_call_frame(regs: &mut Registers,
+                         fptr: *c_void, arg: *c_void, sp: *mut uint) {
+    let sp = mut_offset(sp, -1);
+
+    // The final return address. 0 indicates the bottom of the stack
+    unsafe { *sp = 0; }
+
+    regs[4] = arg as uint;
+    regs[29] = sp as uint;
+    regs[31] = fptr as uint;
+}
+
 fn align_down(sp: *mut uint) -> *mut uint {
     unsafe {
         let sp = transmute::<*mut uint, uint>(sp);
diff --git a/src/libcore/rt/mod.rs b/src/libcore/rt/mod.rs
index 772690c8dcd..9feb588e592 100644
--- a/src/libcore/rt/mod.rs
+++ b/src/libcore/rt/mod.rs
@@ -8,11 +8,6 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// XXX: Missing some implementation for other architectures
-#[cfg(target_os = "linux")];
-#[cfg(target_os = "mac")];
-#[cfg(target_os = "win32")];
-
 // Some basic logging
 macro_rules! rtdebug (
     ($( $arg:expr),+) => ( {