Add control flow information to __rust_probestack

Author: tmandry

src/probestack.rs

@@ -43,18 +43,36 @@
 
 #![cfg(not(windows))] // Windows already has builtins to do this
 
+extern "C" {
+    pub fn __rust_probestack();
+}
+
 #[naked]
 #[no_mangle]
 #[cfg(all(target_arch = "x86_64", not(feature = "mangled-names")))]
-pub unsafe extern "C" fn __rust_probestack() {
+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.
     //
-    // The ABI here is that the stack frame size is located in `%eax`. Upon
-    // return we're not supposed to modify `%esp` or `%eax`.
+    // The ABI here is that the stack frame size is located in `%rax`. Upon
+    // return we're not supposed to modify `%rsp` or `%rax`.
     asm!("
+        // We are about to define a 'function within a function.' Because the
+        // compiler will have emitted a .cfi_startproc at the beginning of
+        // __rust_probestack_wrapper, we need .cfi_endproc before we can define
+        // the contents of __rust_probestack.
+        .cfi_endproc
+
+        .pushsection .text.__rust_probestack
+        .globl __rust_probestack
+        .type  __rust_probestack, @function
+    __rust_probestack:
+        .cfi_startproc
         pushq  %rbp
+        .cfi_adjust_cfa_offset 8
+        .cfi_offset %rbp, -16
         movq   %rsp, %rbp
+        .cfi_def_cfa_register %rbp
 
         mov    %rax,%r11        // duplicate %rax as we're clobbering %r11
 
@@ -93,23 +111,43 @@ pub unsafe extern "C" fn __rust_probestack() {
         add    %rax,%rsp
 
         leave
+        .cfi_def_cfa_register %rsp
+        .cfi_adjust_cfa_offset -8
         ret
+        .cfi_endproc
+
+        .size __rust_probestack, . - __rust_probestack
+        .popsection
+
+        // Similar to above, we add .cfi_startproc here to match the
+        // .cfi_endproc emitted at the end of __rust_probestack_wrapper.
+        .cfi_startproc
     " ::: "memory" : "volatile");
     ::core::intrinsics::unreachable();
 }
 
 #[naked]
 #[no_mangle]
 #[cfg(all(target_arch = "x86", not(feature = "mangled-names")))]
-pub unsafe extern "C" fn __rust_probestack() {
+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
     // function basically can't tamper with anything.
     //
     // The ABI here is the same as x86_64, except everything is 32-bits large.
     asm!("
+        .cfi_endproc
+
+        .pushsection .text.__rust_probestack
+        .globl __rust_probestack
+        .type  __rust_probestack, @function
+    __rust_probestack:
+        .cfi_startproc
         push   %ebp
+        .cfi_adjust_cfa_offset 4
+        .cfi_offset %ebp, -8
         mov    %esp, %ebp
+        .cfi_def_cfa_register %ebp
         push   %ecx
         mov    %eax,%ecx
 
@@ -129,7 +167,15 @@ pub unsafe extern "C" fn __rust_probestack() {
         add    %eax,%esp
         pop    %ecx
         leave
+        .cfi_def_cfa_register %esp
+        .cfi_adjust_cfa_offset -4
         ret
+        .cfi_endproc
+
+        .size __rust_probestack, . - __rust_probestack
+        .popsection
+
+        .cfi_startproc
     " ::: "memory" : "volatile");
     ::core::intrinsics::unreachable();
 }