// Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.

use libc;
use core::prelude::*;
use self::imp::{make_handler, drop_handler};

pub use self::imp::{init, cleanup};

pub struct Handler {
    _data: *mut libc::c_void
}

impl Handler {
    pub unsafe fn new() -> Handler {
        make_handler()
    }
}

impl Drop for Handler {
    fn drop(&mut self) {
        unsafe {
            drop_handler(self);
        }
    }
}

#[cfg(any(target_os = "linux",
          target_os = "macos",
          target_os = "bitrig",
          target_os = "netbsd",
          target_os = "openbsd"))]
mod imp {
    use sys_common::stack;

    use super::Handler;
    use rt::util::report_overflow;
    use mem;
    use ptr;
    use intrinsics;
    use sys::c::{siginfo, sigaction, SIGBUS, SIG_DFL,
                 SA_SIGINFO, SA_ONSTACK, sigaltstack,
                 SIGSTKSZ, sighandler_t, raise};
    use libc;
    use libc::funcs::posix88::mman::{mmap, munmap};
    use libc::funcs::posix01::signal::signal;
    use libc::consts::os::posix88::{SIGSEGV,
                                    PROT_READ,
                                    PROT_WRITE,
                                    MAP_PRIVATE,
                                    MAP_ANON,
                                    MAP_FAILED};

    use sys_common::thread_info;


    // This is initialized in init() and only read from after
    static mut PAGE_SIZE: usize = 0;

    #[no_stack_check]
    unsafe extern fn signal_handler(signum: libc::c_int,
                                     info: *mut siginfo,
                                     _data: *mut libc::c_void) {

        // We can not return from a SIGSEGV or SIGBUS signal.
        // See: https://www.gnu.org/software/libc/manual/html_node/Handler-Returns.html

        unsafe fn term(signum: libc::c_int) -> ! {
            use core::mem::transmute;

            signal(signum, transmute(SIG_DFL));
            raise(signum);
            intrinsics::abort();
        }

        // We're calling into functions with stack checks
        stack::record_sp_limit(0);

        let guard = thread_info::stack_guard().unwrap_or(0);
        let addr = (*info).si_addr as usize;

        if guard == 0 || addr < guard - PAGE_SIZE || addr >= guard {
            term(signum);
        }

        report_overflow();

        intrinsics::abort()
    }

    static mut MAIN_ALTSTACK: *mut libc::c_void = 0 as *mut libc::c_void;

    pub unsafe fn init() {
        let psize = libc::sysconf(libc::consts::os::sysconf::_SC_PAGESIZE);
        if psize == -1 {
            panic!("failed to get page size");
        }

        PAGE_SIZE = psize as usize;

        let mut action: sigaction = mem::zeroed();
        action.sa_flags = SA_SIGINFO | SA_ONSTACK;
        action.sa_sigaction = signal_handler as sighandler_t;
        sigaction(SIGSEGV, &action, ptr::null_mut());
        sigaction(SIGBUS, &action, ptr::null_mut());

        let handler = make_handler();
        MAIN_ALTSTACK = handler._data;
        mem::forget(handler);
    }

    pub unsafe fn cleanup() {
        Handler { _data: MAIN_ALTSTACK };
    }

    pub unsafe fn make_handler() -> Handler {
        let alt_stack = mmap(ptr::null_mut(),
                             SIGSTKSZ,
                             PROT_READ | PROT_WRITE,
                             MAP_PRIVATE | MAP_ANON,
                             -1,
                             0);
        if alt_stack == MAP_FAILED {
            panic!("failed to allocate an alternative stack");
        }

        let mut stack: sigaltstack = mem::zeroed();

        stack.ss_sp = alt_stack;
        stack.ss_flags = 0;
        stack.ss_size = SIGSTKSZ;

        sigaltstack(&stack, ptr::null_mut());

        Handler { _data: alt_stack }
    }

    pub unsafe fn drop_handler(handler: &mut Handler) {
        munmap(handler._data, SIGSTKSZ);
    }
}

#[cfg(not(any(target_os = "linux",
              target_os = "macos",
              target_os = "bitrig",
              target_os = "netbsd",
              target_os = "openbsd")))]
mod imp {
    use libc;

    pub unsafe fn init() {
    }

    pub unsafe fn cleanup() {
    }

    pub unsafe fn make_handler() -> super::Handler {
        super::Handler { _data: 0 as *mut libc::c_void }
    }

    pub unsafe fn drop_handler(_handler: &mut super::Handler) {
    }
}