src/libpanic_abort/lib.rs

   1 //! Implementation of Rust panics via process aborts
   2 //!
   3 //! When compared to the implementation via unwinding, this crate is *much*
   4 //! simpler! That being said, it's not quite as versatile, but here goes!
   5
   6 #![no_std]
   7 #![unstable(feature = "panic_abort", issue = "32837")]
   8 #![doc(
   9     html_root_url = "https://doc.rust-lang.org/nightly/",
  10     issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/"
  11 )]
  12 #![panic_runtime]
  13 #![allow(unused_features)]
  14 #![feature(core_intrinsics)]
  15 #![feature(libc)]
  16 #![feature(nll)]
  17 #![feature(panic_runtime)]
  18 #![feature(staged_api)]
  19 #![feature(rustc_attrs)]
  20
  21 use core::any::Any;
  22
  23 #[rustc_std_internal_symbol]
  24 pub unsafe extern "C" fn __rust_panic_cleanup(_: *mut u8) -> *mut (dyn Any + Send + 'static) {
  25     unreachable!()
  26 }
  27
  28 // "Leak" the payload and shim to the relevant abort on the platform in
  29 // question.
  30 //
  31 // For Unix we just use `abort` from libc as it'll trigger debuggers, core
  32 // dumps, etc, as one might expect. On Windows, however, the best option we have
  33 // is the `__fastfail` intrinsics, but that's unfortunately not defined in LLVM,
  34 // and the `RaiseFailFastException` function isn't available until Windows 7
  35 // which would break compat with XP. For now just use `intrinsics::abort` which
  36 // will kill us with an illegal instruction, which will do a good enough job for
  37 // now hopefully.
  38 #[rustc_std_internal_symbol]
  39 pub unsafe extern "C" fn __rust_start_panic(_payload: usize) -> u32 {
  40     abort();
  41
  42     #[cfg(any(unix, target_os = "cloudabi"))]
  43     unsafe fn abort() -> ! {
  44         libc::abort();
  45     }
  46
  47     #[cfg(any(windows, all(target_arch = "wasm32", not(target_os = "emscripten"))))]
  48     unsafe fn abort() -> ! {
  49         core::intrinsics::abort();
  50     }
  51
  52     #[cfg(any(target_os = "hermit", all(target_vendor = "fortanix", target_env = "sgx")))]
  53     unsafe fn abort() -> ! {
  54         // call std::sys::abort_internal
  55         extern "C" {
  56             pub fn __rust_abort() -> !;
  57         }
  58         __rust_abort();
  59     }
  60 }
  61
  62 // This... is a bit of an oddity. The tl;dr; is that this is required to link
  63 // correctly, the longer explanation is below.
  64 //
  65 // Right now the binaries of libcore/libstd that we ship are all compiled with
  66 // `-C panic=unwind`. This is done to ensure that the binaries are maximally
  67 // compatible with as many situations as possible. The compiler, however,
  68 // requires a "personality function" for all functions compiled with `-C
  69 // panic=unwind`. This personality function is hardcoded to the symbol
  70 // `rust_eh_personality` and is defined by the `eh_personality` lang item.
  71 //
  72 // So... why not just define that lang item here? Good question! The way that
  73 // panic runtimes are linked in is actually a little subtle in that they're
  74 // "sort of" in the compiler's crate store, but only actually linked if another
  75 // isn't actually linked. This ends up meaning that both this crate and the
  76 // panic_unwind crate can appear in the compiler's crate store, and if both
  77 // define the `eh_personality` lang item then that'll hit an error.
  78 //
  79 // To handle this the compiler only requires the `eh_personality` is defined if
  80 // the panic runtime being linked in is the unwinding runtime, and otherwise
  81 // it's not required to be defined (rightfully so). In this case, however, this
  82 // library just defines this symbol so there's at least some personality
  83 // somewhere.
  84 //
  85 // Essentially this symbol is just defined to get wired up to libcore/libstd
  86 // binaries, but it should never be called as we don't link in an unwinding
  87 // runtime at all.
  88 pub mod personalities {
  89     #[rustc_std_internal_symbol]
  90     #[cfg(not(any(
  91         all(target_arch = "wasm32", not(target_os = "emscripten"),),
  92         all(target_os = "windows", target_env = "gnu", target_arch = "x86_64",),
  93     )))]
  94     pub extern "C" fn rust_eh_personality() {}
  95
  96     // On x86_64-pc-windows-gnu we use our own personality function that needs
  97     // to return `ExceptionContinueSearch` as we're passing on all our frames.
  98     #[rustc_std_internal_symbol]
  99     #[cfg(all(target_os = "windows", target_env = "gnu", target_arch = "x86_64"))]
 100     pub extern "C" fn rust_eh_personality(
 101         _record: usize,
 102         _frame: usize,
 103         _context: usize,
 104         _dispatcher: usize,
 105     ) -> u32 {
 106         1 // `ExceptionContinueSearch`
 107     }
 108
 109     // Similar to above, this corresponds to the `eh_unwind_resume` lang item
 110     // that's only used on Windows currently.
 111     //
 112     // Note that we don't execute landing pads, so this is never called, so it's
 113     // body is empty.
 114     #[rustc_std_internal_symbol]
 115     #[cfg(all(bootstrap, target_os = "windows", target_env = "gnu"))]
 116     pub extern "C" fn rust_eh_unwind_resume() {}
 117
 118     // These two are called by our startup objects on i686-pc-windows-gnu, but
 119     // they don't need to do anything so the bodies are nops.
 120     #[rustc_std_internal_symbol]
 121     #[cfg(all(target_os = "windows", target_env = "gnu", target_arch = "x86"))]
 122     pub extern "C" fn rust_eh_register_frames() {}
 123     #[rustc_std_internal_symbol]
 124     #[cfg(all(target_os = "windows", target_env = "gnu", target_arch = "x86"))]
 125     pub extern "C" fn rust_eh_unregister_frames() {}
 126 }