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-rw-r--r--arch/tile/kernel/backtrace.c682
1 files changed, 682 insertions, 0 deletions
diff --git a/arch/tile/kernel/backtrace.c b/arch/tile/kernel/backtrace.c
new file mode 100644
index 00000000000..d3c41c1ff6b
--- /dev/null
+++ b/arch/tile/kernel/backtrace.c
@@ -0,0 +1,682 @@
+/*
+ * 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 <arch/chip.h>
+
+#include <asm/opcode-tile.h>
+
+
+#define TREG_SP 54
+#define TREG_LR 55
+
+
+#if TILE_CHIP >= 10
+#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];
+};
+
+
+/* This implementation only makes sense for native tools. */
+/** Default function to read memory. */
+static bool bt_read_memory(void *result, VirtualAddress addr,
+ unsigned int size, void *extra)
+{
+ /* FIXME: this should do some horrible signal stuff to catch
+ * SEGV cleanly and fail.
+ *
+ * Or else the caller should do the setjmp for efficiency.
+ */
+
+ memcpy(result, (const void *)addr, size);
+ return true;
+}
+
+
+/** 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);
+#if TILE_CHIP >= 10
+ 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;
+}
+
+#if TILE_CHIP >= 10
+/** 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 VirtualAddress 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;
+ VirtualAddress pc;
+
+#if TILE_CHIP >= 10
+ /* 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)
+#if TILE_CHIP >= 10
+ || 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;
+ }
+ }
+
+#if TILE_CHIP >= 10
+ /* 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;
+ }
+ }
+ }
+}
+
+void backtrace_init(BacktraceIterator *state,
+ BacktraceMemoryReader read_memory_func,
+ void *read_memory_func_extra,
+ VirtualAddress pc, VirtualAddress lr,
+ VirtualAddress sp, VirtualAddress r52)
+{
+ CallerLocation location;
+ VirtualAddress fp, initial_frame_caller_pc;
+
+ if (read_memory_func == NULL) {
+ read_memory_func = bt_read_memory;
+ }
+
+ /* 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 ((VirtualAddress)reg == reg);
+}
+
+bool backtrace_next(BacktraceIterator *state)
+{
+ VirtualAddress 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;
+}
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