From e0f2d48196d0c4e8ed0bbd14c108efc716474c8d Mon Sep 17 00:00:00 2001
From: edef <edef@edef.eu>
Date: Wed, 24 Dec 2014 06:48:49 +0100
Subject: [PATCH] sneak an extra argument in by using rbx for the jump target

---
 src/arch.rs |  4 ++--
 src/arch.s  | 11 ++++++-----
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/src/arch.rs b/src/arch.rs
index f768b56..b32d1cc 100644
--- a/src/arch.rs
+++ b/src/arch.rs
@@ -62,11 +62,11 @@ pub fn initialise_call_frame(stack: &mut Stack, init: uintptr_t, args: &[uintptr
     rbp: 0,
     rsp: sp as uintptr_t,
     ip: bootstrap as uintptr_t,
-    r12: init,
+    rbx: init,
     .. Registers::new()
   };
 
-  match into_fields!(regs { rdi, r13, r14, r15 } <- args.iter().cloned()) {
+  match into_fields!(regs { rdi, r12, r13, r14, r15 } <- args.iter().cloned()) {
     Some(mut args) => if args.next().is_some() {
       panic!("too many arguments")
     },
diff --git a/src/arch.s b/src/arch.s
index 7326511..a360fca 100644
--- a/src/arch.s
+++ b/src/arch.s
@@ -84,11 +84,12 @@ lwt_bootstrap:
 ;; places the parameters in unrelated registers, and we frob them into place
 ;; out here, in assembly-land. below are the parameter registers in order,
 ;; along with the alternative register used in parentheses, if there is one.
-;; rdi, rsi (r13), rdx (r14), rcx (r15), r8, r9
-  mov rsi, r13
-  mov rdx, r14
-  mov rcx, r15
-  jmp r12
+;; rdi, rsi (r12), rdx (r13), rcx (r14), r8(r15), r9
+  mov rsi, r12
+  mov rdx, r13
+  mov rcx, r14
+  mov r8, r15
+  jmp rbx
 
 
 ;; Rust stores a stack limit at [fs:0x70]. These two functions set and retrieve