/* Copyright (c) 2011-2015, Scott Tsai
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice,
 *    this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright notice,
 *    this list of conditions and the following disclaimer in the documentation
 *    and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef DEBUG_BREAK_H
#define DEBUG_BREAK_H

#ifdef _MSC_VER

#define debug_break __debugbreak

#else

#include <signal.h>

#ifdef __cplusplus
extern "C" {
#endif

enum {
    /* gcc optimizers consider code after __builtin_trap() dead.
     * Making __builtin_trap() unsuitable for breaking into the debugger */
    DEBUG_BREAK_PREFER_BUILTIN_TRAP_TO_SIGTRAP = 0,
};

#if defined(__i386__) || defined(__x86_64__)
enum { HAVE_TRAP_INSTRUCTION = 1, };
__attribute__((gnu_inline, always_inline))
static void __inline__ trap_instruction(void)
{
    __asm__ volatile("int $0x03");
}
#elif defined(__thumb__)
enum { HAVE_TRAP_INSTRUCTION = 1, };
/* FIXME: handle __THUMB_INTERWORK__ */
__attribute__((gnu_inline, always_inline))
static void __inline__ trap_instruction(void)
{
    /* See 'arm-linux-tdep.c' in GDB source.
     * Both instruction sequences below work. */
#if 1
    /* 'eabi_linux_thumb_le_breakpoint' */
    __asm__ volatile(".inst 0xde01");
#else
    /* 'eabi_linux_thumb2_le_breakpoint' */
    __asm__ volatile(".inst.w 0xf7f0a000");
#endif

    /* Known problem:
     * After a breakpoint hit, can't stepi, step, or continue in GDB.
     * 'step' stuck on the same instruction.
     *
     * Workaround: a new GDB command,
     * 'debugbreak-step' is defined in debugbreak-gdb.py
     * that does:
     * (gdb) set $instruction_len = 2
     * (gdb) tbreak *($pc + $instruction_len)
     * (gdb) jump   *($pc + $instruction_len)
     */
}
#elif defined(__arm__) && !defined(__thumb__)
enum { HAVE_TRAP_INSTRUCTION = 1, };
__attribute__((gnu_inline, always_inline))
static void __inline__ trap_instruction(void)
{
    /* See 'arm-linux-tdep.c' in GDB source,
     * 'eabi_linux_arm_le_breakpoint' */
    __asm__ volatile(".inst 0xe7f001f0");
    /* Has same known problem and workaround
     * as Thumb mode */
}
#elif defined(__aarch64__)
enum { HAVE_TRAP_INSTRUCTION = 1, };
__attribute__((gnu_inline, always_inline))
static void __inline__ trap_instruction(void)
{
    /* See 'aarch64-tdep.c' in GDB source,
     * 'aarch64_default_breakpoint' */
    __asm__ volatile(".inst 0xd4200000");
}
#else
enum { HAVE_TRAP_INSTRUCTION = 0, };
#endif

__attribute__((gnu_inline, always_inline))
static void __inline__ debug_break(void)
{
    if (HAVE_TRAP_INSTRUCTION) {
        trap_instruction();
    } else if (DEBUG_BREAK_PREFER_BUILTIN_TRAP_TO_SIGTRAP) {
         /* raises SIGILL on Linux x86{,-64}, to continue in gdb:
          * (gdb) handle SIGILL stop nopass
          * */
        __builtin_trap();
    } else {
        #if defined(_WIN32) || defined(_WIN64)
        /* SIGTRAP available only on POSIX-compliant operating systems
         * use builtin trap instead */
            __builtin_trap();
        #else
            raise(SIGTRAP);
        #endif
    }
}

#ifdef __cplusplus
}
#endif

#endif

#endif