src/libpanic_abort/lib.rs

   1 // Copyright 2016 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 //! Implementation of Rust panics via process aborts
  12 //!
  13 //! When compared to the implementation via unwinding, this crate is *much*
  14 //! simpler! That being said, it's not quite as versatile, but here goes!
  15
  16 #![no_std]
  17 #![unstable(feature = "panic_abort", issue = "32837")]
  18 #![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
  19        html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
  20        html_root_url = "https://doc.rust-lang.org/nightly/",
  21        issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
  22 #![deny(warnings)]
  23 #![panic_runtime]
  24 #![allow(unused_features)]
  25
  26 #![feature(core_intrinsics)]
  27 #![feature(libc)]
  28 #![feature(panic_runtime)]
  29 #![feature(staged_api)]
  30
  31 // Rust's "try" function, but if we're aborting on panics we just call the
  32 // function as there's nothing else we need to do here.
  33 #[no_mangle]
  34 pub unsafe extern fn __rust_maybe_catch_panic(f: fn(*mut u8),
  35                                               data: *mut u8,
  36                                               _data_ptr: *mut usize,
  37                                               _vtable_ptr: *mut usize) -> u32 {
  38     f(data);
  39     0
  40 }
  41
  42 // "Leak" the payload and shim to the relevant abort on the platform in
  43 // question.
  44 //
  45 // For Unix we just use `abort` from libc as it'll trigger debuggers, core
  46 // dumps, etc, as one might expect. On Windows, however, the best option we have
  47 // is the `__fastfail` intrinsics, but that's unfortunately not defined in LLVM,
  48 // and the `RaiseFailFastException` function isn't available until Windows 7
  49 // which would break compat with XP. For now just use `intrinsics::abort` which
  50 // will kill us with an illegal instruction, which will do a good enough job for
  51 // now hopefully.
  52 #[no_mangle]
  53 pub unsafe extern fn __rust_start_panic(_data: usize, _vtable: usize) -> u32 {
  54     abort();
  55
  56     #[cfg(unix)]
  57     unsafe fn abort() -> ! {
  58         extern crate libc;
  59         libc::abort();
  60     }
  61
  62     #[cfg(any(target_os = "redox",
  63               windows,
  64               all(target_arch = "wasm32", not(target_os = "emscripten"))))]
  65     unsafe fn abort() -> ! {
  66         core::intrinsics::abort();
  67     }
  68 }
  69
  70 // This... is a bit of an oddity. The tl;dr; is that this is required to link
  71 // correctly, the longer explanation is below.
  72 //
  73 // Right now the binaries of libcore/libstd that we ship are all compiled with
  74 // `-C panic=unwind`. This is done to ensure that the binaries are maximally
  75 // compatible with as many situations as possible. The compiler, however,
  76 // requires a "personality function" for all functions compiled with `-C
  77 // panic=unwind`. This personality function is hardcoded to the symbol
  78 // `rust_eh_personality` and is defined by the `eh_personality` lang item.
  79 //
  80 // So... why not just define that lang item here? Good question! The way that
  81 // panic runtimes are linked in is actually a little subtle in that they're
  82 // "sort of" in the compiler's crate store, but only actually linked if another
  83 // isn't actually linked. This ends up meaning that both this crate and the
  84 // panic_unwind crate can appear in the compiler's crate store, and if both
  85 // define the `eh_personality` lang item then that'll hit an error.
  86 //
  87 // To handle this the compiler only requires the `eh_personality` is defined if
  88 // the panic runtime being linked in is the unwinding runtime, and otherwise
  89 // it's not required to be defined (rightfully so). In this case, however, this
  90 // library just defines this symbol so there's at least some personality
  91 // somewhere.
  92 //
  93 // Essentially this symbol is just defined to get wired up to libcore/libstd
  94 // binaries, but it should never be called as we don't link in an unwinding
  95 // runtime at all.
  96 pub mod personalities {
  97     #[no_mangle]
  98     #[cfg(not(all(target_os = "windows",
  99                   target_env = "gnu",
 100                   target_arch = "x86_64")))]
 101     pub extern fn rust_eh_personality() {}
 102
 103     // On x86_64-pc-windows-gnu we use our own personality function that needs
 104     // to return `ExceptionContinueSearch` as we're passing on all our frames.
 105     #[no_mangle]
 106     #[cfg(all(target_os = "windows",
 107               target_env = "gnu",
 108               target_arch = "x86_64"))]
 109     pub extern fn rust_eh_personality(_record: usize,
 110                                       _frame: usize,
 111                                       _context: usize,
 112                                       _dispatcher: usize) -> u32 {
 113         1 // `ExceptionContinueSearch`
 114     }
 115
 116     // Similar to above, this corresponds to the `eh_unwind_resume` lang item
 117     // that's only used on Windows currently.
 118     //
 119     // Note that we don't execute landing pads, so this is never called, so it's
 120     // body is empty.
 121     #[no_mangle]
 122     #[cfg(all(target_os = "windows", target_env = "gnu"))]
 123     pub extern fn rust_eh_unwind_resume() {}
 124
 125     // These two are called by our startup objects on i686-pc-windows-gnu, but
 126     // they don't need to do anything so the bodies are nops.
 127     #[no_mangle]
 128     #[cfg(all(target_os = "windows", target_env = "gnu", target_arch = "x86"))]
 129     pub extern fn rust_eh_register_frames() {}
 130     #[no_mangle]
 131     #[cfg(all(target_os = "windows", target_env = "gnu", target_arch = "x86"))]
 132     pub extern fn rust_eh_unregister_frames() {}
 133 }