/* Copyright (c) 2011-2021, 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

#ifdef __cplusplus
extern "C" {
#endif

#define DEBUG_BREAK_USE_TRAP_INSTRUCTION  1
#define DEBUG_BREAK_USE_BUILTIN_TRAP      2
#define DEBUG_BREAK_USE_SIGTRAP           3
#define DEBUG_BREAK_USE_BUILTIN_DEBUGTRAP 4

#if defined(__i386__) || defined(__x86_64__)
	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
__inline__ static void trap_instruction(void)
{
	__asm__ volatile("int $0x03");
}
#elif defined(__thumb__)
	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
/* FIXME: handle __THUMB_INTERWORK__ */
__attribute__((always_inline))
__inline__ static void 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' would keep getting stuck on the same instruction.
	 *
	 * Workaround: use the new GDB commands 'debugbreak-step' and
	 * 'debugbreak-continue' that become available
	 * after you source the script from GDB:
	 *
	 * $ gdb -x debugbreak-gdb.py <... USUAL ARGUMENTS ...>
	 *
	 * 'debugbreak-step' would jump over the breakpoint instruction with
	 * roughly equivalent of:
	 * (gdb) set $instruction_len = 2
	 * (gdb) tbreak *($pc + $instruction_len)
	 * (gdb) jump   *($pc + $instruction_len)
	 */
}
#elif defined(__arm__) && !defined(__thumb__)
	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
__attribute__((always_inline))
__inline__ static void trap_instruction(void)
{
	/* See 'arm-linux-tdep.c' in GDB source,
	 * 'eabi_linux_arm_le_breakpoint' */
	__asm__ volatile(".inst 0xe7f001f0");
	/* Known problem:
	 * Same problem and workaround as Thumb mode */
}
#elif defined(__aarch64__) && defined(__APPLE__)
	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_BUILTIN_DEBUGTRAP
#elif defined(__aarch64__)
	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
__attribute__((always_inline))
__inline__ static void trap_instruction(void)
{
	/* See 'aarch64-tdep.c' in GDB source,
	 * 'aarch64_default_breakpoint' */
	__asm__ volatile(".inst 0xd4200000");
}
#elif defined(__powerpc__)
	/* PPC 32 or 64-bit, big or little endian */
	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
__attribute__((always_inline))
__inline__ static void trap_instruction(void)
{
	/* See 'rs6000-tdep.c' in GDB source,
	 * 'rs6000_breakpoint' */
	__asm__ volatile(".4byte 0x7d821008");

	/* Known problem:
	 * After a breakpoint hit, can't 'stepi', 'step', or 'continue' in GDB.
	 * 'step' stuck on the same instruction ("twge r2,r2").
	 *
	 * The workaround is the same as ARM Thumb mode: use debugbreak-gdb.py
	 * or manually jump over the instruction. */
}
#elif defined(__riscv)
	/* RISC-V 32 or 64-bit, whether the "C" extension
	 * for compressed, 16-bit instructions are supported or not */
	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_TRAP_INSTRUCTION
__attribute__((always_inline))
__inline__ static void trap_instruction(void)
{
	/* See 'riscv-tdep.c' in GDB source,
	 * 'riscv_sw_breakpoint_from_kind' */
	__asm__ volatile(".4byte 0x00100073");
}
#else
	#define DEBUG_BREAK_IMPL DEBUG_BREAK_USE_SIGTRAP
#endif


#ifndef DEBUG_BREAK_IMPL
#error "debugbreak.h is not supported on this target"
#elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_TRAP_INSTRUCTION
__attribute__((always_inline))
__inline__ static void debug_break(void)
{
	trap_instruction();
}
#elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_BUILTIN_DEBUGTRAP
__attribute__((always_inline))
__inline__ static void debug_break(void)
{
	__builtin_debugtrap();
}
#elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_BUILTIN_TRAP
__attribute__((always_inline))
__inline__ static void debug_break(void)
{
	__builtin_trap();
}
#elif DEBUG_BREAK_IMPL == DEBUG_BREAK_USE_SIGTRAP
#include <signal.h>
__attribute__((always_inline))
__inline__ static void debug_break(void)
{
	raise(SIGTRAP);
}
#else
#error "invalid DEBUG_BREAK_IMPL value"
#endif

#ifdef __cplusplus
}
#endif

#endif /* ifdef _MSC_VER */

#endif /* ifndef DEBUG_BREAK_H */
