/*
* 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.
*/
#include <linux/kernel.h>
#include <linux/string.h>
#include <asm/backtrace.h>
#include <asm/opcode-tile.h>
#include <arch/abi.h>
#ifdef __tilegx__
#define tile_bundle_bits tilegx_bundle_bits
#define TILE_MAX_INSTRUCTIONS_PER_BUNDLE TILEGX_MAX_INSTRUCTIONS_PER_BUNDLE
#define TILE_BUNDLE_ALIGNMENT_IN_BYTES TILEGX_BUNDLE_ALIGNMENT_IN_BYTES
#define tile_decoded_instruction tilegx_decoded_instruction
#define tile_mnemonic tilegx_mnemonic
#define parse_insn_tile parse_insn_tilegx
#define TILE_OPC_IRET TILEGX_OPC_IRET
#define TILE_OPC_ADDI TILEGX_OPC_ADDI
#define TILE_OPC_ADDLI TILEGX_OPC_ADDLI
#define TILE_OPC_INFO TILEGX_OPC_INFO
#define TILE_OPC_INFOL TILEGX_OPC_INFOL
#define TILE_OPC_JRP TILEGX_OPC_JRP
#define TILE_OPC_MOVE TILEGX_OPC_MOVE
#define OPCODE_STORE TILEGX_OPC_ST
typedef long long bt_int_reg_t;
#else
#define OPCODE_STORE TILE_OPC_SW
typedef int bt_int_reg_t;
#endif
/* A decoded bundle used for backtracer analysis. */
struct BacktraceBundle {
tile_bundle_bits bits;
int num_insns;
struct tile_decoded_instruction
insns[TILE_MAX_INSTRUCTIONS_PER_BUNDLE];
};
/* Locates an instruction inside the given bundle that
* has the specified mnemonic, and whose first 'num_operands_to_match'
* operands exactly match those in 'operand_values'.
*/
static const struct tile_decoded_instruction *find_matching_insn(
const struct BacktraceBundle *bundle,
tile_mnemonic mnemonic,
const int *operand_values,
int num_operands_to_match)
{
int i, j;
bool match;
for (i = 0; i < bundle->num_insns; i++) {
const struct tile_decoded_instruction *insn =
&bundle->insns[i];
if (insn->opcode->mnemonic != mnemonic)
continue;
match = true;
for (j = 0; j < num_operands_to_match; j++) {
if (operand_values[j] != insn->operand_values[j]) {
match = false;
break;
}
}
if (match)
return insn;
}
return NULL;
}
/* Does this bundle contain an 'iret' instruction? */
static inline bool bt_has_iret(const struct BacktraceBundle *bundle)
{
return find_matching_insn(bundle, TILE_OPC_IRET, NULL, 0) != NULL;
}
/* Does this bundle contain an 'addi sp, sp, OFFSET' or
* 'addli sp, sp, OFFSET' instruction, and if so, what is OFFSET?
*/
static bool bt_has_addi_sp(const struct BacktraceBundle *bundle, int *adjust)
{
static const int vals[2] = { TREG_SP, TREG_SP };
const struct tile_decoded_instruction *insn =
find_matching_insn(bundle, TILE_OPC_ADDI, vals, 2);
if (insn == NULL)
insn = find_matching_insn(bundle, TILE_OPC_ADDLI, vals, 2);
#ifdef __tilegx__
if (insn == NULL)
insn = find_matching_insn(bundle, TILEGX_OPC_ADDXLI, vals, 2);
if (insn == NULL)
insn = find_matching_insn(bundle, TILEGX_OPC_ADDXI, vals, 2);
#endif
if (insn == NULL)
return false;
*adjust = insn->operand_values[2];
return true;
}
/* Does this bundle contain any 'info OP' or 'infol OP'
* instruction, and if so, what are their OP? Note that OP is interpreted
* as an unsigned value by this code since that's what the caller wants.
* Returns the number of info ops found.
*/
static int bt_get_info_ops(const struct BacktraceBundle *bundle,
int operands[MAX_INFO_OPS_PER_BUNDLE])
{
int num_ops = 0;
int i;
for (i = 0; i < bundle->num_insns; i++) {
const struct tile_decoded_instruction *insn =
&bundle->insns[i];
if (insn->opcode->mnemonic == TILE_OPC_INFO ||
insn->opcode->mnemonic == TILE_OPC_INFOL) {
operands[num_ops++] = insn->operand_values[0];
}
}
return num_ops;
}
/* Does this bundle contain a jrp instruction, and if so, to which
* register is it jumping?
*/
static bool bt_has_jrp(const struct BacktraceBundle *bundle, int *target_reg)
{
const struct tile_decoded_instruction *insn =
find_matching_insn(bundle, TILE_OPC_JRP, NULL, 0);
if (insn == NULL)
return false;
*target_reg = insn->operand_values[0];
return true;
}
/* Does this bundle modify the specified register in any way? */
static bool bt_modifies_reg(const struct BacktraceBundle *bundle, int reg)
{
int i, j;
for (i = 0; i < bundle->num_insns; i++) {
const struct tile_decoded_instruction *insn =
&bundle->insns[i];
if (insn->opcode->implicitly_written_register == reg)
return true;
for (j = 0; j < insn->opcode->num_operands; j++)
if (insn->operands[j]->is_dest_reg &&
insn->operand_values[j] == reg)
return true;
}
return false;
}
/* Does this bundle modify sp? */
static inline bool bt_modifies_sp(const struct BacktraceBundle *bundle)
{
return bt_modifies_reg(bundle, TREG_SP);
}
/* Does this bundle modify lr? */
static inline bool bt_modifies_lr(const struct BacktraceBundle *bundle)
{
return bt_modifies_reg(bundle, TREG_LR);
}
/* Does this bundle contain the instruction 'move fp, sp'? */
static inline bool bt_has_move_r52_sp(const struct BacktraceBundle *bundle)
{
static const int vals[2] = { 52, TREG_SP };
return find_matching_insn(bundle, TILE_OPC_MOVE, vals, 2) != NULL;
}
/* Does this bundle contain a store of lr to sp? */
static inline bool bt_has_sw_sp_lr(const struct BacktraceBundle *bundle)
{
static const int vals[2] = { TREG_SP, TREG_LR };
return find_matching_insn(bundle, OPCODE_STORE, vals, 2) != NULL;
}
#ifdef __tilegx__
/* Track moveli values placed into registers. */
static inline void bt_update_moveli(const struct BacktraceBundle *bundle,
int moveli_args[])
{
int i;
for (i = 0; i < bundle->num_insns; i++) {
const struct tile_decoded_instruction *insn =
&bundle->insns[i];
if (insn->opcode->mnemonic == TILEGX_OPC_MOVELI) {
int reg = insn->operand_values[0];
moveli_args[reg] = insn->operand_values[1];
}
}
}
/* Does this bundle contain an 'add sp, sp, reg' instruction
* from a register that we saw a moveli into, and if so, what
* is the value in the register?
*/
static bool bt_has_add_sp(const struct BacktraceBundle *bundle, int *adjust,
int moveli_args[])
{
static const int vals[2] = { TREG_SP, TREG_SP };
const struct tile_decoded_instruction *insn =
find_matching_insn(bundle, TILEGX_OPC_ADDX, vals, 2);
if (insn) {
int reg = insn->operand_values[2];
if (moveli_args[reg]) {
*adjust = moveli_args[reg];
return true;
}
}
return false;
}
#endif
/* Locates the caller's PC and SP for a program starting at the
* given address.
*/
static void find_caller_pc_and_caller_sp(CallerLocation *location,
const unsigned long start_pc,
BacktraceMemoryReader read_memory_func,
void *read_memory_func_extra)
{
/* Have we explicitly decided what the sp is,
* rather than just the default?
*/
bool sp_determined = false;
/* Has any bundle seen so far modified lr? */
bool lr_modified = false;
/* Have we seen a move from sp to fp? */
bool sp_moved_to_r52 = false;
/* Have we seen a terminating bundle? */
bool seen_terminating_bundle = false;
/* Cut down on round-trip reading overhead by reading several
* bundles at a time.
*/
tile_bundle_bits prefetched_bundles[32];
int num_bundles_prefetched = 0;
int next_bundle = 0;
unsigned long pc;
#ifdef __tilegx__
/* Naively try to track moveli values to support addx for -m32. */
int moveli_args[TILEGX_NUM_REGISTERS] = { 0 };
#endif
/* Default to assuming that the caller's sp is the current sp.
* This is necessary to handle the case where we start backtracing
* right at the end of the epilog.
*/
location->sp_location = SP_LOC_OFFSET;
location->sp_offset = 0;
/* Default to having no idea where the caller PC is. */
location->pc_location = PC_LOC_UNKNOWN;
/* Don't even try if the PC is not aligned. */
if (start_pc % TILE_BUNDLE_ALIGNMENT_IN_BYTES != 0)
return;
for (pc = start_pc;; pc += sizeof(tile_bundle_bits)) {
struct BacktraceBundle bundle;
int num_info_ops, info_operands[MAX_INFO_OPS_PER_BUNDLE];
int one_ago, jrp_reg;
bool has_jrp;
if (next_bundle >= num_bundles_prefetched) {
/* Prefetch some bytes, but don't cross a page
* boundary since that might cause a read failure we
* don't care about if we only need the first few
* bytes. Note: we don't care what the actual page
* size is; using the minimum possible page size will
* prevent any problems.
*/
unsigned int bytes_to_prefetch = 4096 - (pc & 4095);
if (bytes_to_prefetch > sizeof prefetched_bundles)
bytes_to_prefetch = sizeof prefetched_bundles;
if (!read_memory_func(prefetched_bundles, pc,
bytes_to_prefetch,
read_memory_func_extra)) {
if (pc == start_pc) {
/* The program probably called a bad
* address, such as a NULL pointer.
* So treat this as if we are at the
* start of the function prolog so the
* backtrace will show how we got here.
*/
location->pc_location = PC_LOC_IN_LR;
return;
}
/* Unreadable address. Give up. */
break;
}
next_bundle = 0;
num_bundles_prefetched =
bytes_to_prefetch / sizeof(tile_bundle_bits);
}
/* Decode the next bundle. */
bundle.bits = prefetched_bundles[next_bundle++];
bundle.num_insns =
parse_insn_tile(bundle.bits, pc, bundle.insns);
num_info_ops = bt_get_info_ops(&bundle, info_operands);
/* First look at any one_ago info ops if they are interesting,
* since they should shadow any non-one-ago info ops.
*/
for (one_ago = (pc != start_pc) ? 1 : 0;
one_ago >= 0; one_ago--) {
int i;
for (i = 0; i < num_info_ops; i++) {
int info_operand = info_operands[i];
if (info_operand < CALLER_UNKNOWN_BASE) {
/* Weird; reserved value, ignore it. */
continue;
}
/* Skip info ops which are not in the
* "one_ago" mode we want right now.
*/
if (((info_operand & ONE_BUNDLE_AGO_FLAG) != 0)
!= (one_ago != 0))
continue;
/* Clear the flag to make later checking
* easier. */
info_operand &= ~ONE_BUNDLE_AGO_FLAG;
/* Default to looking at PC_IN_LR_FLAG. */
if (info_operand & PC_IN_LR_FLAG)
location->pc_location =
PC_LOC_IN_LR;
else
location->pc_location =
PC_LOC_ON_STACK;
switch (info_operand) {
case CALLER_UNKNOWN_BASE:
location->pc_location = PC_LOC_UNKNOWN;
location->sp_location = SP_LOC_UNKNOWN;
return;
case CALLER_SP_IN_R52_BASE:
case CALLER_SP_IN_R52_BASE | PC_IN_LR_FLAG:
location->sp_location = SP_LOC_IN_R52;
return;
default:
{
const unsigned int val = info_operand
- CALLER_SP_OFFSET_BASE;
const unsigned int sp_offset =
(val >> NUM_INFO_OP_FLAGS) * 8;
if (sp_offset < 32768) {
/* This is a properly encoded
* SP offset. */
location->sp_location =
SP_LOC_OFFSET;
location->sp_offset =
sp_offset;
return;
} else {
/* This looked like an SP
* offset, but it's outside
* the legal range, so this
* must be an unrecognized
* info operand. Ignore it.
*/
}
}
break;
}
}
}
if (seen_terminating_bundle) {
/* We saw a terminating bundle during the previous
* iteration, so we were only looking for an info op.
*/
break;
}
if (bundle.bits == 0) {
/* Wacky terminating bundle. Stop looping, and hope
* we've already seen enough to find the caller.
*/
break;
}
/*
* Try to determine caller's SP.
*/
if (!sp_determined) {
int adjust;
if (bt_has_addi_sp(&bundle, &adjust)
#ifdef __tilegx__
|| bt_has_add_sp(&bundle, &adjust, moveli_args)
#endif
) {
location->sp_location = SP_LOC_OFFSET;
if (adjust <= 0) {
/* We are in prolog about to adjust
* SP. */
location->sp_offset = 0;
} else {
/* We are in epilog restoring SP. */
location->sp_offset = adjust;
}
sp_determined = true;
} else {
if (bt_has_move_r52_sp(&bundle)) {
/* Maybe in prolog, creating an
* alloca-style frame. But maybe in
* the middle of a fixed-size frame
* clobbering r52 with SP.
*/
sp_moved_to_r52 = true;
}
if (bt_modifies_sp(&bundle)) {
if (sp_moved_to_r52) {
/* We saw SP get saved into
* r52 earlier (or now), which
* must have been in the
* prolog, so we now know that
* SP is still holding the
* caller's sp value.
*/
location->sp_location =
SP_LOC_OFFSET;
location->sp_offset = 0;
} else {
/* Someone must have saved
* aside the caller's SP value
* into r52, so r52 holds the
* current value.
*/
location->sp_location =
SP_LOC_IN_R52;
}
sp_determined = true;
}
}
#ifdef __tilegx__
/* Track moveli arguments for -m32 mode. */
bt_update_moveli(&bundle, moveli_args);
#endif
}
if (bt_has_iret(&bundle)) {
/* This is a terminating bundle. */
seen_terminating_bundle = true;
continue;
}
/*
* Try to determine caller's PC.
*/
jrp_reg = -1;
has_jrp = bt_has_jrp(&bundle, &jrp_reg);
if (has_jrp)
seen_terminating_bundle = true;
if (location->pc_location == PC_LOC_UNKNOWN) {
if (has_jrp) {
if (jrp_reg == TREG_LR && !lr_modified) {
/* Looks like a leaf function, or else
* lr is already restored. */
location->pc_location =
PC_LOC_IN_LR;
} else {
location->pc_location =
PC_LOC_ON_STACK;
}
} else if (bt_has_sw_sp_lr(&bundle)) {
/* In prolog, spilling initial lr to stack. */
location->pc_location = PC_LOC_IN_LR;
} else if (bt_modifies_lr(&bundle)) {
lr_modified = true;
}
}
}
}
/* Initializes a backtracer to start from the given location.
*
* If the frame pointer cannot be determined it is set to -1.
*
* state: The state to be filled in.
* read_memory_func: A callback that reads memory.
* read_memory_func_extra: An arbitrary argument to read_memory_func.
* pc: The current PC.
* lr: The current value of the 'lr' register.
* sp: The current value of the 'sp' register.
* r52: The current value of the 'r52' register.
*/
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)
{
CallerLocation location;
unsigned long fp, initial_frame_caller_pc;
/* Find out where we are in the initial frame. */
find_caller_pc_and_caller_sp(&location, pc,
read_memory_func, read_memory_func_extra);
switch (location.sp_location) {
case SP_LOC_UNKNOWN:
/* Give up. */
fp = -1;
break;
case SP_LOC_IN_R52:
fp = r52;
break;
case SP_LOC_OFFSET:
fp = sp + location.sp_offset;
break;
default:
/* Give up. */
fp = -1;
break;
}
/* If the frame pointer is not aligned to the basic word size
* something terrible happened and we should mark it as invalid.
*/
if (fp % sizeof(bt_int_reg_t) != 0)
fp = -1;
/* -1 means "don't know initial_frame_caller_pc". */
initial_frame_caller_pc = -1;
switch (location.pc_location) {
case PC_LOC_UNKNOWN:
/* Give up. */
fp = -1;
break;
case PC_LOC_IN_LR:
if (lr == 0 || lr % TILE_BUNDLE_ALIGNMENT_IN_BYTES != 0) {
/* Give up. */
fp = -1;
} else {
initial_frame_caller_pc = lr;
}
break;
case PC_LOC_ON_STACK:
/* Leave initial_frame_caller_pc as -1,
* meaning check the stack.
*/
break;
default:
/* Give up. */
fp = -1;
break;
}
state->pc = pc;
state->sp = sp;
state->fp = fp;
state->initial_frame_caller_pc = initial_frame_caller_pc;
state->read_memory_func = read_memory_func;
state->read_memory_func_extra = read_memory_func_extra;
}
/* Handle the case where the register holds more bits than the VA. */
static bool valid_addr_reg(bt_int_reg_t reg)
{
return ((unsigned long)reg == reg);
}
/* Advances the backtracing state to the calling frame, returning
* true iff successful.
*/
bool backtrace_next(BacktraceIterator *state)
{
unsigned long next_fp, next_pc;
bt_int_reg_t next_frame[2];
if (state->fp == -1) {
/* No parent frame. */
return false;
}
/* Try to read the frame linkage data chaining to the next function. */
if (!state->read_memory_func(&next_frame, state->fp, sizeof next_frame,
state->read_memory_func_extra)) {
return false;
}
next_fp = next_frame[1];
if (!valid_addr_reg(next_frame[1]) ||
next_fp % sizeof(bt_int_reg_t) != 0) {
/* Caller's frame pointer is suspect, so give up. */
return false;
}
if (state->initial_frame_caller_pc != -1) {
/* We must be in the initial stack frame and already know the
* caller PC.
*/
next_pc = state->initial_frame_caller_pc;
/* Force reading stack next time, in case we were in the
* initial frame. We don't do this above just to paranoidly
* avoid changing the struct at all when we return false.
*/
state->initial_frame_caller_pc = -1;
} else {
/* Get the caller PC from the frame linkage area. */
next_pc = next_frame[0];
if (!valid_addr_reg(next_frame[0]) || next_pc == 0 ||
next_pc % TILE_BUNDLE_ALIGNMENT_IN_BYTES != 0) {
/* The PC is suspect, so give up. */
return false;
}
}
/* Update state to become the caller's stack frame. */
state->pc = next_pc;
state->sp = state->fp;
state->fp = next_fp;
return true;
}
