Split out probestack impl for Apple platforms

Author: tmandry

src/probestack.rs

@@ -43,13 +43,21 @@
 
 #![cfg(not(windows))] // Windows already has builtins to do this
 
+#[cfg(all(
+    any(target_arch = "x86_64", target_arch = "x86"),
+    not(target_vendor = "apple")
+))]
 extern "C" {
     pub fn __rust_probestack();
 }
 
 #[naked]
 #[no_mangle]
-#[cfg(all(target_arch = "x86_64", not(feature = "mangled-names")))]
+#[cfg(all(
+    target_arch = "x86_64",
+    not(target_vendor = "apple"),
+    not(feature = "mangled-names")
+))]
 pub unsafe extern "C" fn __rust_probestack_wrapper() {
     // Our goal here is to touch each page between %rsp+8 and %rsp+8-%rax,
     // ensuring that if any pages are unmapped we'll make a page fault.
@@ -128,7 +136,11 @@ pub unsafe extern "C" fn __rust_probestack_wrapper() {
 
 #[naked]
 #[no_mangle]
-#[cfg(all(target_arch = "x86", not(feature = "mangled-names")))]
+#[cfg(all(
+    target_arch = "x86",
+    not(target_vendor = "apple"),
+    not(feature = "mangled-names")
+))]
 pub unsafe extern "C" fn __rust_probestack_wrapper() {
     // This is the same as x86_64 above, only translated for 32-bit sizes. Note
     // that on Unix we're expected to restore everything as it was, this
@@ -179,3 +191,81 @@ pub unsafe extern "C" fn __rust_probestack_wrapper() {
     " ::: "memory" : "volatile");
     ::core::intrinsics::unreachable();
 }
+
+#[naked]
+#[no_mangle]
+#[cfg(all(
+    target_arch = "x86_64",
+    target_vendor = "apple",
+    not(feature = "mangled-names")
+))]
+pub unsafe extern "C" fn __rust_probestack() {
+    // Same as above, but without the CFI tricks. The assembler for Apple
+    // devices doesn't support the directives we were using to define
+    // __rust_probestack.
+    asm!("
+        pushq  %rbp
+        movq   %rsp, %rbp
+
+        mov    %rax,%r11
+
+        cmp    $$0x1000,%r11
+        jna    3f
+    2:
+        sub    $$0x1000,%rsp
+        test   %rsp,8(%rsp)
+        sub    $$0x1000,%r11
+        cmp    $$0x1000,%r11
+        ja     2b
+
+    3:
+        sub    %r11,%rsp
+        test   %rsp,8(%rsp)
+
+        add    %rax,%rsp
+
+        leave
+        ret
+    " ::: "memory" : "volatile");
+    ::core::intrinsics::unreachable();
+}
+
+#[naked]
+#[no_mangle]
+#[cfg(all(
+    target_arch = "x86",
+    target_vendor = "apple",
+    not(feature = "mangled-names")
+))]
+pub unsafe extern "C" fn __rust_probestack() {
+    // This is the same as x86_64 above, only translated for 32-bit sizes. Note
+    // that on Unix we're expected to restore everything as it was, this
+    // function basically can't tamper with anything.
+    //
+    // The ABI here is the same as x86_64, except everything is 32-bits large.
+    asm!("
+        push   %ebp
+        mov    %esp, %ebp
+        push   %ecx
+        mov    %eax,%ecx
+
+        cmp    $$0x1000,%ecx
+        jna    3f
+    2:
+        sub    $$0x1000,%esp
+        test   %esp,8(%esp)
+        sub    $$0x1000,%ecx
+        cmp    $$0x1000,%ecx
+        ja     2b
+
+    3:
+        sub    %ecx,%esp
+        test   %esp,8(%esp)
+
+        add    %eax,%esp
+        pop    %ecx
+        leave
+        ret
+    " ::: "memory" : "volatile");
+    ::core::intrinsics::unreachable();
+}