From a1ea208652f6046f01284ea7e7abab065d6513b1 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Thu, 1 Sep 2016 02:04:35 +0400
Subject: [PATCH] arch/x86_64: hack to work around ld64 shortcomings on OS X.

fix #35, close #36
---
 .travis.yml        |  3 +++
 src/arch/x86_64.rs | 27 ++++++++++++++++++++++++++-
 src/lib.rs         |  2 +-
 src/os/sys.rs      |  4 ++--
 4 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/.travis.yml b/.travis.yml
index 9e0985c..a6c0749 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,8 @@
 language: rust
 rust: nightly
+os:
+  - linux
+  - osx
 sudo: false
 install:
   - .travis/docs/install
diff --git a/src/arch/x86_64.rs b/src/arch/x86_64.rs
index 7290951..b4b4b1b 100644
--- a/src/arch/x86_64.rs
+++ b/src/arch/x86_64.rs
@@ -49,6 +49,7 @@ use stack::Stack;
 pub struct StackPointer(*mut usize);
 
 pub unsafe fn init(stack: &Stack, f: unsafe extern "C" fn(usize) -> !) -> StackPointer {
+  #[cfg(not(target_vendor = "apple"))]
   #[naked]
   unsafe extern "C" fn trampoline_1() {
     asm!(
@@ -77,6 +78,21 @@ pub unsafe fn init(stack: &Stack, f: unsafe extern "C" fn(usize) -> !) -> StackP
       : : "s" (trampoline_2 as usize) : "memory" : "volatile")
   }
 
+  #[cfg(target_vendor = "apple")]
+  #[naked]
+  unsafe extern "C" fn trampoline_1() {
+    asm!(
+      r#"
+        # Same as above; however, .local and .size are not supported in Mach-O.
+      __morestack:
+      .private_extern __morestack
+        .cfi_def_cfa %rbx, 0
+        .cfi_offset %rbp, -16
+        call   ${0:c}
+      "#
+      : : "s" (trampoline_2 as usize) : "memory" : "volatile")
+  }
+
   #[naked]
   unsafe extern "C" fn trampoline_2() {
     asm!(
@@ -84,7 +100,16 @@ pub unsafe fn init(stack: &Stack, f: unsafe extern "C" fn(usize) -> !) -> StackP
         # Set up the second part of our DWARF CFI.
         # When unwinding the frame corresponding to this function, a DWARF unwinder
         # will restore %rbx (and thus CFA of the first trampoline) from the stack slot.
-        .cfi_offset %rbx, 16
+        #
+        # The following is functionally equivalent to:
+        # .cfi_offset %rbx, 16
+        # however positive offsets in .cfi_offset translate to DW_CFA_offset_extended_sf,
+        # and ld64's CFI parser only supports regular DW_CFA_offset (which only supports
+        # negative offsets, with the sign being implicit), so to avoid crashing the linker
+        # on OS X, fold offset into  DW_CFA_def_offset.
+        .cfi_def_cfa_offset 24
+        .cfi_offset %rip, -24
+        .cfi_offset %rbx, 0
         # Call the provided function.
         call    *8(%rsp)
       "#
diff --git a/src/lib.rs b/src/lib.rs
index 8fd6052..02b12e7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,7 +4,7 @@
 // http://apache.org/licenses/LICENSE-2.0> or the MIT license <LICENSE-MIT or
 // http://opensource.org/licenses/MIT>, at your option. This file may not be
 // copied, modified, or distributed except according to those terms.
-#![feature(asm, naked_functions)]
+#![feature(asm, naked_functions, cfg_target_vendor)]
 #![cfg_attr(feature = "alloc", feature(alloc))]
 #![cfg_attr(test, feature(test, thread_local, const_fn))]
 #![no_std]
diff --git a/src/os/sys.rs b/src/os/sys.rs
index 748da41..2dae903 100644
--- a/src/os/sys.rs
+++ b/src/os/sys.rs
@@ -17,13 +17,13 @@ use self::libc::MAP_FAILED;
 const GUARD_PROT:  c_int = libc::PROT_NONE;
 const STACK_PROT:  c_int = libc::PROT_READ
                          | libc::PROT_WRITE;
-#[cfg(not(any(target_os = "freebsd", target_os = "dragonfly")))]
+#[cfg(not(any(target_os = "freebsd", target_os = "dragonfly", target_vendor = "apple")))]
 const STACK_FLAGS: c_int = libc::MAP_STACK
                          | libc::MAP_PRIVATE
                          | libc::MAP_ANON;
 // workaround for http://lists.freebsd.org/pipermail/freebsd-bugs/2011-July/044840.html
 // according to libgreen, DragonFlyBSD suffers from this too
-#[cfg(any(target_os = "freebsd", target_os = "dragonfly"))]
+#[cfg(any(target_os = "freebsd", target_os = "dragonfly", target_vendor = "apple"))]
 const STACK_FLAGS: c_int = libc::MAP_PRIVATE
                          | libc::MAP_ANON;