library/panic_abort/src/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(issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/")]
   9 #![panic_runtime]
  10 #![allow(unused_features)]
  11 #![feature(core_intrinsics)]
  12 #![feature(nll)]
  13 #![feature(panic_runtime)]
  14 #![feature(std_internals)]
  15 #![feature(staged_api)]
  16 #![feature(rustc_attrs)]
  17 #![feature(c_unwind)]
  18
  19 #[cfg(target_os = "android")]
  20 mod android;
  21
  22 use core::any::Any;
  23 use core::panic::BoxMeUp;
  24
  25 #[rustc_std_internal_symbol]
  26 #[allow(improper_ctypes_definitions)]
  27 pub unsafe extern "C" fn __rust_panic_cleanup(_: *mut u8) -> *mut (dyn Any + Send + 'static) {
  28     unreachable!()
  29 }
  30
  31 // "Leak" the payload and shim to the relevant abort on the platform in question.
  32 #[rustc_std_internal_symbol]
  33 pub unsafe extern "C-unwind" fn __rust_start_panic(_payload: *mut &mut dyn BoxMeUp) -> u32 {
  34     // Android has the ability to attach a message as part of the abort.
  35     #[cfg(target_os = "android")]
  36     android::android_set_abort_message(_payload);
  37
  38     abort();
  39
  40     cfg_if::cfg_if! {
  41         if #[cfg(unix)] {
  42             unsafe fn abort() -> ! {
  43                 libc::abort();
  44             }
  45         } else if #[cfg(any(target_os = "hermit",
  46                             target_os = "solid_asp3",
  47                             all(target_vendor = "fortanix", target_env = "sgx")
  48         ))] {
  49             unsafe fn abort() -> ! {
  50                 // call std::sys::abort_internal
  51                 extern "C" {
  52                     pub fn __rust_abort() -> !;
  53                 }
  54                 __rust_abort();
  55             }
  56         } else if #[cfg(all(windows, not(miri)))] {
  57             // On Windows, use the processor-specific __fastfail mechanism. In Windows 8
  58             // and later, this will terminate the process immediately without running any
  59             // in-process exception handlers. In earlier versions of Windows, this
  60             // sequence of instructions will be treated as an access violation,
  61             // terminating the process but without necessarily bypassing all exception
  62             // handlers.
  63             //
  64             // https://docs.microsoft.com/en-us/cpp/intrinsics/fastfail
  65             //
  66             // Note: this is the same implementation as in libstd's `abort_internal`
  67             unsafe fn abort() -> ! {
  68                 #[allow(unused)]
  69                 const FAST_FAIL_FATAL_APP_EXIT: usize = 7;
  70                 cfg_if::cfg_if! {
  71                     if #[cfg(any(target_arch = "x86", target_arch = "x86_64"))] {
  72                         core::arch::asm!("int $$0x29", in("ecx") FAST_FAIL_FATAL_APP_EXIT);
  73                     } else if #[cfg(all(target_arch = "arm", target_feature = "thumb-mode"))] {
  74                         core::arch::asm!(".inst 0xDEFB", in("r0") FAST_FAIL_FATAL_APP_EXIT);
  75                     } else if #[cfg(target_arch = "aarch64")] {
  76                         core::arch::asm!("brk 0xF003", in("x0") FAST_FAIL_FATAL_APP_EXIT);
  77                     } else {
  78                         core::intrinsics::abort();
  79                     }
  80                 }
  81                 core::intrinsics::unreachable();
  82             }
  83         } else {
  84             unsafe fn abort() -> ! {
  85                 core::intrinsics::abort();
  86             }
  87         }
  88     }
  89 }
  90
  91 // This... is a bit of an oddity. The tl;dr; is that this is required to link
  92 // correctly, the longer explanation is below.
  93 //
  94 // Right now the binaries of libcore/libstd that we ship are all compiled with
  95 // `-C panic=unwind`. This is done to ensure that the binaries are maximally
  96 // compatible with as many situations as possible. The compiler, however,
  97 // requires a "personality function" for all functions compiled with `-C
  98 // panic=unwind`. This personality function is hardcoded to the symbol
  99 // `rust_eh_personality` and is defined by the `eh_personality` lang item.
 100 //
 101 // So... why not just define that lang item here? Good question! The way that
 102 // panic runtimes are linked in is actually a little subtle in that they're
 103 // "sort of" in the compiler's crate store, but only actually linked if another
 104 // isn't actually linked. This ends up meaning that both this crate and the
 105 // panic_unwind crate can appear in the compiler's crate store, and if both
 106 // define the `eh_personality` lang item then that'll hit an error.
 107 //
 108 // To handle this the compiler only requires the `eh_personality` is defined if
 109 // the panic runtime being linked in is the unwinding runtime, and otherwise
 110 // it's not required to be defined (rightfully so). In this case, however, this
 111 // library just defines this symbol so there's at least some personality
 112 // somewhere.
 113 //
 114 // Essentially this symbol is just defined to get wired up to libcore/libstd
 115 // binaries, but it should never be called as we don't link in an unwinding
 116 // runtime at all.
 117 pub mod personalities {
 118     #[rustc_std_internal_symbol]
 119     #[cfg(not(any(
 120         all(target_family = "wasm", not(target_os = "emscripten")),
 121         all(target_os = "windows", target_env = "gnu", target_arch = "x86_64",),
 122     )))]
 123     pub extern "C" fn rust_eh_personality() {}
 124
 125     // On x86_64-pc-windows-gnu we use our own personality function that needs
 126     // to return `ExceptionContinueSearch` as we're passing on all our frames.
 127     #[rustc_std_internal_symbol]
 128     #[cfg(all(target_os = "windows", target_env = "gnu", target_arch = "x86_64"))]
 129     pub extern "C" fn rust_eh_personality(
 130         _record: usize,
 131         _frame: usize,
 132         _context: usize,
 133         _dispatcher: usize,
 134     ) -> u32 {
 135         1 // `ExceptionContinueSearch`
 136     }
 137
 138     // Similar to above, this corresponds to the `eh_catch_typeinfo` lang item
 139     // that's only used on Emscripten currently.
 140     //
 141     // Since panics don't generate exceptions and foreign exceptions are
 142     // currently UB with -C panic=abort (although this may be subject to
 143     // change), any catch_unwind calls will never use this typeinfo.
 144     #[rustc_std_internal_symbol]
 145     #[allow(non_upper_case_globals)]
 146     #[cfg(target_os = "emscripten")]
 147     static rust_eh_catch_typeinfo: [usize; 2] = [0; 2];
 148
 149     // These two are called by our startup objects on i686-pc-windows-gnu, but
 150     // they don't need to do anything so the bodies are nops.
 151     #[rustc_std_internal_symbol]
 152     #[cfg(all(target_os = "windows", target_env = "gnu", target_arch = "x86"))]
 153     pub extern "C" fn rust_eh_register_frames() {}
 154     #[rustc_std_internal_symbol]
 155     #[cfg(all(target_os = "windows", target_env = "gnu", target_arch = "x86"))]
 156     pub extern "C" fn rust_eh_unregister_frames() {}
 157 }