/*
* Copyright 2010 Tilera Corporation. All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation, version 2.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
* NON INFRINGEMENT. See the GNU General Public License for
* more details.
*/

#ifndef _ASM_TILE_BACKTRACE_H
#define _ASM_TILE_BACKTRACE_H

#include <linux/types.h>

/* Reads 'size' bytes from 'address' and writes the data to 'result'.
* Returns true if successful, else false (e.g. memory not readable).
*/
typedef bool (*BacktraceMemoryReader)(void *result,
unsigned long address,
unsigned int size,
void *extra);

typedef struct {
/* Current PC. */
unsigned long pc;

/* Current stack pointer value. */
unsigned long sp;

/* Current frame pointer value (i.e. caller's stack pointer) */
unsigned long fp;

/* Internal use only: caller's PC for first frame. */
unsigned long initial_frame_caller_pc;

/* Internal use only: callback to read memory. */
BacktraceMemoryReader read_memory_func;

/* Internal use only: arbitrary argument to read_memory_func. */
void *read_memory_func_extra;

} BacktraceIterator;


typedef enum {

/* We have no idea what the caller's pc is. */
PC_LOC_UNKNOWN,

/* The caller's pc is currently in lr. */
PC_LOC_IN_LR,

/* The caller's pc can be found by dereferencing the caller's sp. */
PC_LOC_ON_STACK

} CallerPCLocation;


typedef enum {

/* We have no idea what the caller's sp is. */
SP_LOC_UNKNOWN,

/* The caller's sp is currently in r52. */
SP_LOC_IN_R52,

/* The caller's sp can be found by adding a certain constant
* to the current value of sp.
*/
SP_LOC_OFFSET

} CallerSPLocation;


/* Bit values ORed into CALLER_* values for info ops. */
enum {
/* Setting the low bit on any of these values means the info op
* applies only to one bundle ago.
*/
ONE_BUNDLE_AGO_FLAG = 1,

/* Setting this bit on a CALLER_SP_* value means the PC is in LR.
* If not set, PC is on the stack.
*/
PC_IN_LR_FLAG = 2,

/* This many of the low bits of a CALLER_SP_* value are for the
* flag bits above.
*/
NUM_INFO_OP_FLAGS = 2,

/* We cannot have one in the memory pipe so this is the maximum. */
MAX_INFO_OPS_PER_BUNDLE = 2
};


/* Internal constants used to define 'info' operands. */
enum {
/* 0 and 1 are reserved, as are all negative numbers. */

CALLER_UNKNOWN_BASE = 2,

CALLER_SP_IN_R52_BASE = 4,

CALLER_SP_OFFSET_BASE = 8,
};


/* Current backtracer state describing where it thinks the caller is. */
typedef struct {
/*
* Public fields
*/

/* How do we find the caller's PC? */
CallerPCLocation pc_location : 8;

/* How do we find the caller's SP? */
CallerSPLocation sp_location : 8;

/* If sp_location == SP_LOC_OFFSET, then caller_sp == sp +
* loc->sp_offset. Else this field is undefined.
*/
uint16_t sp_offset;

/* In the most recently visited bundle a terminating bundle? */
bool at_terminating_bundle;

/*
* Private fields
*/

/* Will the forward scanner see someone clobbering sp
* (i.e. changing it with something other than addi sp, sp, N?)
*/
bool sp_clobber_follows;

/* Operand to next "visible" info op (no more than one bundle past
* the next terminating bundle), or -32768 if none.
*/
int16_t next_info_operand;

/* Is the info of in next_info_op in the very next bundle? */
bool is_next_info_operand_adjacent;

} CallerLocation;

extern void backtrace_init(BacktraceIterator *state,
BacktraceMemoryReader read_memory_func,
void *read_memory_func_extra,
unsigned long pc, unsigned long lr,
unsigned long sp, unsigned long r52);


extern bool backtrace_next(BacktraceIterator *state);

#endif /* _ASM_TILE_BACKTRACE_H */