sgx_panic_abort/lib.rs

//! Implementation of Rust panics via process aborts
//!
//! When compared to the implementation via unwinding, this crate is *much*
//! simpler! That being said, it's not quite as versatile, but here goes!

#![no_std]
#![unstable(feature = "panic_abort", issue = "32837")]
#![panic_runtime]
#![allow(unused_features)]

#![feature(core_intrinsics)]
#![feature(nll)]
#![feature(panic_runtime)]
#![feature(staged_api)]
#![feature(rustc_attrs)]

use core::any::Any;

#[rustc_std_internal_symbol]
#[allow(improper_ctypes_definitions)]
pub unsafe extern "C" fn __rust_panic_cleanup(_: *mut u8) -> *mut (dyn Any + Send + 'static) {
    unreachable!()
}

// "Leak" the payload and shim to the relevant abort on the platform in
// question.
//
// For Unix we just use `abort` from libc as it'll trigger debuggers, core
// dumps, etc, as one might expect. On Windows, however, the best option we have
// is the `__fastfail` intrinsics, but that's unfortunately not defined in LLVM,
// and the `RaiseFailFastException` function isn't available until Windows 7
// which would break compat with XP. For now just use `intrinsics::abort` which
// will kill us with an illegal instruction, which will do a good enough job for
// now hopefully.
#[rustc_std_internal_symbol]
pub unsafe extern "C" fn __rust_start_panic(_payload: usize) -> u32 {
    sgx_abort();

    #[link(name = "sgx_trts")]
    extern "C" {
        pub fn abort() -> !;
    }

    fn sgx_abort() -> ! {
        unsafe { abort() }
    }
}

// This... is a bit of an oddity. The tl;dr; is that this is required to link
// correctly, the longer explanation is below.
//
// Right now the binaries of libcore/libstd that we ship are all compiled with
// `-C panic=unwind`. This is done to ensure that the binaries are maximally
// compatible with as many situations as possible. The compiler, however,
// requires a "personality function" for all functions compiled with `-C
// panic=unwind`. This personality function is hardcoded to the symbol
// `rust_eh_personality` and is defined by the `eh_personality` lang item.
//
// So... why not just define that lang item here? Good question! The way that
// panic runtimes are linked in is actually a little subtle in that they're
// "sort of" in the compiler's crate store, but only actually linked if another
// isn't actually linked. This ends up meaning that both this crate and the
// panic_unwind crate can appear in the compiler's crate store, and if both
// define the `eh_personality` lang item then that'll hit an error.
//
// To handle this the compiler only requires the `eh_personality` is defined if
// the panic runtime being linked in is the unwinding runtime, and otherwise
// it's not required to be defined (rightfully so). In this case, however, this
// library just defines this symbol so there's at least some personality
// somewhere.
//
// Essentially this symbol is just defined to get wired up to libcore/libstd
// binaries, but it should never be called as we don't link in an unwinding
// runtime at all.
pub mod personalities {
    #[rustc_std_internal_symbol]
    pub extern "C" fn rust_eh_personality() {}
}