src/libstd/sys/windows/backtrace.rs

   1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! As always, windows has something very different than unix, we mainly want
  12 //! to avoid having to depend too much on libunwind for windows.
  13 //!
  14 //! If you google around, you'll find a fair bit of references to built-in
  15 //! functions to get backtraces on windows. It turns out that most of these are
  16 //! in an external library called dbghelp. I was unable to find this library
  17 //! via `-ldbghelp`, but it is apparently normal to do the `dlopen` equivalent
  18 //! of it.
  19 //!
  20 //! You'll also find that there's a function called CaptureStackBackTrace
  21 //! mentioned frequently (which is also easy to use), but sadly I didn't have a
  22 //! copy of that function in my mingw install (maybe it was broken?). Instead,
  23 //! this takes the route of using StackWalk64 in order to walk the stack.
  24
  25 #![allow(deprecated)] // dynamic_lib
  26
  27 use io::prelude::*;
  28
  29 use io;
  30 use libc::c_void;
  31 use mem;
  32 use ptr;
  33 use sys::c;
  34 use sys::dynamic_lib::DynamicLibrary;
  35 use sys::mutex::Mutex;
  36
  37 macro_rules! sym {
  38     ($lib:expr, $e:expr, $t:ident) => (
  39         match $lib.symbol($e) {
  40             Ok(f) => $crate::mem::transmute::<usize, $t>(f),
  41             Err(..) => return Ok(())
  42         }
  43     )
  44 }
  45
  46 #[cfg(target_env = "msvc")]
  47 #[path = "printing/msvc.rs"]
  48 mod printing;
  49
  50 #[cfg(target_env = "gnu")]
  51 #[path = "printing/gnu.rs"]
  52 mod printing;
  53
  54 type SymInitializeFn =
  55     unsafe extern "system" fn(c::HANDLE, *mut c_void,
  56                               c::BOOL) -> c::BOOL;
  57 type SymCleanupFn =
  58     unsafe extern "system" fn(c::HANDLE) -> c::BOOL;
  59
  60 type StackWalk64Fn =
  61     unsafe extern "system" fn(c::DWORD, c::HANDLE, c::HANDLE,
  62                               *mut c::STACKFRAME64, *mut c::CONTEXT,
  63                               *mut c_void, *mut c_void,
  64                               *mut c_void, *mut c_void) -> c::BOOL;
  65
  66 #[cfg(target_arch = "x86")]
  67 pub fn init_frame(frame: &mut c::STACKFRAME64,
  68                   ctx: &c::CONTEXT) -> c::DWORD {
  69     frame.AddrPC.Offset = ctx.Eip as u64;
  70     frame.AddrPC.Mode = c::ADDRESS_MODE::AddrModeFlat;
  71     frame.AddrStack.Offset = ctx.Esp as u64;
  72     frame.AddrStack.Mode = c::ADDRESS_MODE::AddrModeFlat;
  73     frame.AddrFrame.Offset = ctx.Ebp as u64;
  74     frame.AddrFrame.Mode = c::ADDRESS_MODE::AddrModeFlat;
  75     c::IMAGE_FILE_MACHINE_I386
  76 }
  77
  78 #[cfg(target_arch = "x86_64")]
  79 pub fn init_frame(frame: &mut c::STACKFRAME64,
  80                   ctx: &c::CONTEXT) -> c::DWORD {
  81     frame.AddrPC.Offset = ctx.Rip as u64;
  82     frame.AddrPC.Mode = c::ADDRESS_MODE::AddrModeFlat;
  83     frame.AddrStack.Offset = ctx.Rsp as u64;
  84     frame.AddrStack.Mode = c::ADDRESS_MODE::AddrModeFlat;
  85     frame.AddrFrame.Offset = ctx.Rbp as u64;
  86     frame.AddrFrame.Mode = c::ADDRESS_MODE::AddrModeFlat;
  87     c::IMAGE_FILE_MACHINE_AMD64
  88 }
  89
  90 struct Cleanup {
  91     handle: c::HANDLE,
  92     SymCleanup: SymCleanupFn,
  93 }
  94
  95 impl Drop for Cleanup {
  96     fn drop(&mut self) {
  97         unsafe { (self.SymCleanup)(self.handle); }
  98     }
  99 }
 100
 101 pub fn write(w: &mut Write) -> io::Result<()> {
 102     // According to windows documentation, all dbghelp functions are
 103     // single-threaded.
 104     static LOCK: Mutex = Mutex::new();
 105     unsafe {
 106         LOCK.lock();
 107         let res = _write(w);
 108         LOCK.unlock();
 109         return res
 110     }
 111 }
 112
 113 unsafe fn _write(w: &mut Write) -> io::Result<()> {
 114     let dbghelp = match DynamicLibrary::open("dbghelp.dll") {
 115         Ok(lib) => lib,
 116         Err(..) => return Ok(()),
 117     };
 118
 119     // Fetch the symbols necessary from dbghelp.dll
 120     let SymInitialize = sym!(dbghelp, "SymInitialize", SymInitializeFn);
 121     let SymCleanup = sym!(dbghelp, "SymCleanup", SymCleanupFn);
 122     let StackWalk64 = sym!(dbghelp, "StackWalk64", StackWalk64Fn);
 123
 124     // Allocate necessary structures for doing the stack walk
 125     let process = c::GetCurrentProcess();
 126     let thread = c::GetCurrentThread();
 127     let mut context: c::CONTEXT = mem::zeroed();
 128     c::RtlCaptureContext(&mut context);
 129     let mut frame: c::STACKFRAME64 = mem::zeroed();
 130     let image = init_frame(&mut frame, &context);
 131
 132     // Initialize this process's symbols
 133     let ret = SymInitialize(process, ptr::null_mut(), c::TRUE);
 134     if ret != c::TRUE { return Ok(()) }
 135     let _c = Cleanup { handle: process, SymCleanup: SymCleanup };
 136
 137     // And now that we're done with all the setup, do the stack walking!
 138     // Start from -1 to avoid printing this stack frame, which will
 139     // always be exactly the same.
 140     let mut i = -1;
 141     write!(w, "stack backtrace:\n")?;
 142     while StackWalk64(image, process, thread, &mut frame, &mut context,
 143                       ptr::null_mut(),
 144                       ptr::null_mut(),
 145                       ptr::null_mut(),
 146                       ptr::null_mut()) == c::TRUE {
 147         let addr = frame.AddrPC.Offset;
 148         if addr == frame.AddrReturn.Offset || addr == 0 ||
 149            frame.AddrReturn.Offset == 0 { break }
 150
 151         i += 1;
 152
 153         if i >= 0 {
 154             printing::print(w, i, addr - 1, process, &dbghelp)?;
 155         }
 156     }
 157
 158     Ok(())
 159 }