arch/tile: core support for Tilera 32-bit chips.

This change is the core kernel support for TILEPro and TILE64 chips.
No driver support (except the console driver) is included yet.

This includes the relevant Linux headers in asm/; the low-level
low-level "Tile architecture" headers in arch/, which are
shared with the hypervisor, etc., and are build-system agnostic;
and the relevant hypervisor headers in hv/.

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Reviewed-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 634 insertions, 0 deletions

diff --git a/arch/tile/kernel/backtrace.c b/arch/tile/kernel/backtrace.c
new file mode 100644
index 00000000000..1b0a410ef5e
--- /dev/null
+++ b/arch/tile/kernel/backtrace.c
@@ -0,0 +1,634 @@
+/*
+ * 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>
+
+#if TILE_CHIP < 10
+
+
+#include <asm/opcode-tile.h>
+
+
+#define TREG_SP 54
+#define TREG_LR 55
+
+
+/** A decoded bundle used for backtracer analysis. */
+typedef struct {
+	tile_bundle_bits bits;
+	int num_insns;
+	struct tile_decoded_instruction
+	insns[TILE_MAX_INSTRUCTIONS_PER_BUNDLE];
+} BacktraceBundle;
+
+
+/* This implementation only makes sense for native tools. */
+/** Default function to read memory. */
+static bool
+bt_read_memory(void *result, VirtualAddress addr, size_t 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 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 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 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 (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 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 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 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 BacktraceBundle *bundle)
+{
+	return bt_modifies_reg(bundle, TREG_SP);
+}
+
+/** Does this bundle modify lr? */
+static inline bool
+bt_modifies_lr(const 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 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 the instruction 'sw sp, lr'? */
+static inline bool
+bt_has_sw_sp_lr(const BacktraceBundle *bundle)
+{
+	static const int vals[2] = { TREG_SP, TREG_LR };
+	return find_matching_insn(bundle, TILE_OPC_SW, vals, 2) != NULL;
+}
+
+/** 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;
+
+	/* 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)) {
+
+		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)) {
+				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 (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;
+	}
+
+	/* The frame pointer should theoretically be aligned mod 8. If
+	 * it's not even aligned mod 4 then something terrible happened
+	 * and we should mark it as invalid.
+	 */
+	if (fp % 4 != 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;
+}
+
+bool
+backtrace_next(BacktraceIterator *state)
+{
+	VirtualAddress next_fp, next_pc, 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 (next_fp % 4 != 0) {
+		/* Caller's frame pointer is suspect, so give up.
+		 * Technically it should be aligned mod 8, but we will
+		 * be forgiving here.
+		 */
+		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 (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;
+}
+
+#else /* TILE_CHIP < 10 */
+
+void
+backtrace_init(BacktraceIterator *state,
+	       BacktraceMemoryReader read_memory_func,
+	       void *read_memory_func_extra,
+	       VirtualAddress pc, VirtualAddress lr,
+	       VirtualAddress sp, VirtualAddress r52)
+{
+	state->pc = pc;
+	state->sp = sp;
+	state->fp = -1;
+	state->initial_frame_caller_pc = -1;
+	state->read_memory_func = read_memory_func;
+	state->read_memory_func_extra = read_memory_func_extra;
+}
+
+bool backtrace_next(BacktraceIterator *state) { return false; }
+
+#endif /* TILE_CHIP < 10 */