tilegx: support KGDB

Enter kernel debugger at boot with:
  --hvd UART_1=1 --hvx kgdbwait --hvx kgdboc=ttyS1,115200
or at runtime with:
  echo ttyS1,115200 > /sys/module/kgdboc/parameters/kgdboc
  echo g > /proc/sysrq-trigger

Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>

3 files changed, 505 insertions, 0 deletions

diff --git a/arch/tile/kernel/Makefile b/arch/tile/kernel/Makefile
index b7c8b5e19d57..27a2bf39dae8 100644
--- a/arch/tile/kernel/Makefile
+++ b/arch/tile/kernel/Makefile
@@ -29,5 +29,6 @@ obj-$(CONFIG_TILE_USB)		+= usb.o
 obj-$(CONFIG_TILE_HVGLUE_TRACE)	+= hvglue_trace.o
 obj-$(CONFIG_FUNCTION_TRACER)	+= ftrace.o mcount_64.o
 obj-$(CONFIG_KPROBES)		+= kprobes.o
+obj-$(CONFIG_KGDB)		+= kgdb.o
 
 obj-y				+= vdso/
diff --git a/arch/tile/kernel/kgdb.c b/arch/tile/kernel/kgdb.c
new file mode 100644
index 000000000000..4cd88381a83e
--- /dev/null
+++ b/arch/tile/kernel/kgdb.c
@@ -0,0 +1,499 @@
+/*
+ * Copyright 2013 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.
+ *
+ * TILE-Gx KGDB support.
+ */
+
+#include <linux/ptrace.h>
+#include <linux/kgdb.h>
+#include <linux/kdebug.h>
+#include <linux/uaccess.h>
+#include <linux/module.h>
+#include <asm/cacheflush.h>
+
+static tile_bundle_bits singlestep_insn = TILEGX_BPT_BUNDLE | DIE_SSTEPBP;
+static unsigned long stepped_addr;
+static tile_bundle_bits stepped_instr;
+
+struct dbg_reg_def_t dbg_reg_def[DBG_MAX_REG_NUM] = {
+	{ "r0", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[0])},
+	{ "r1", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[1])},
+	{ "r2", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[2])},
+	{ "r3", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[3])},
+	{ "r4", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[4])},
+	{ "r5", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[5])},
+	{ "r6", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[6])},
+	{ "r7", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[7])},
+	{ "r8", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[8])},
+	{ "r9", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[9])},
+	{ "r10", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[10])},
+	{ "r11", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[11])},
+	{ "r12", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[12])},
+	{ "r13", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[13])},
+	{ "r14", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[14])},
+	{ "r15", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[15])},
+	{ "r16", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[16])},
+	{ "r17", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[17])},
+	{ "r18", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[18])},
+	{ "r19", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[19])},
+	{ "r20", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[20])},
+	{ "r21", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[21])},
+	{ "r22", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[22])},
+	{ "r23", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[23])},
+	{ "r24", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[24])},
+	{ "r25", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[25])},
+	{ "r26", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[26])},
+	{ "r27", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[27])},
+	{ "r28", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[28])},
+	{ "r29", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[29])},
+	{ "r30", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[30])},
+	{ "r31", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[31])},
+	{ "r32", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[32])},
+	{ "r33", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[33])},
+	{ "r34", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[34])},
+	{ "r35", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[35])},
+	{ "r36", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[36])},
+	{ "r37", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[37])},
+	{ "r38", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[38])},
+	{ "r39", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[39])},
+	{ "r40", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[40])},
+	{ "r41", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[41])},
+	{ "r42", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[42])},
+	{ "r43", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[43])},
+	{ "r44", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[44])},
+	{ "r45", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[45])},
+	{ "r46", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[46])},
+	{ "r47", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[47])},
+	{ "r48", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[48])},
+	{ "r49", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[49])},
+	{ "r50", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[50])},
+	{ "r51", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[51])},
+	{ "r52", GDB_SIZEOF_REG, offsetof(struct pt_regs, regs[52])},
+	{ "tp", GDB_SIZEOF_REG, offsetof(struct pt_regs, tp)},
+	{ "sp", GDB_SIZEOF_REG, offsetof(struct pt_regs, sp)},
+	{ "lr", GDB_SIZEOF_REG, offsetof(struct pt_regs, lr)},
+	{ "sn", GDB_SIZEOF_REG, -1},
+	{ "idn0", GDB_SIZEOF_REG, -1},
+	{ "idn1", GDB_SIZEOF_REG, -1},
+	{ "udn0", GDB_SIZEOF_REG, -1},
+	{ "udn1", GDB_SIZEOF_REG, -1},
+	{ "udn2", GDB_SIZEOF_REG, -1},
+	{ "udn3", GDB_SIZEOF_REG, -1},
+	{ "zero", GDB_SIZEOF_REG, -1},
+	{ "pc", GDB_SIZEOF_REG, offsetof(struct pt_regs, pc)},
+	{ "faultnum", GDB_SIZEOF_REG, offsetof(struct pt_regs, faultnum)},
+};
+
+char *dbg_get_reg(int regno, void *mem, struct pt_regs *regs)
+{
+	if (regno >= DBG_MAX_REG_NUM || regno < 0)
+		return NULL;
+
+	if (dbg_reg_def[regno].offset != -1)
+		memcpy(mem, (void *)regs + dbg_reg_def[regno].offset,
+		       dbg_reg_def[regno].size);
+	else
+		memset(mem, 0, dbg_reg_def[regno].size);
+	return dbg_reg_def[regno].name;
+}
+
+int dbg_set_reg(int regno, void *mem, struct pt_regs *regs)
+{
+	if (regno >= DBG_MAX_REG_NUM || regno < 0)
+		return -EINVAL;
+
+	if (dbg_reg_def[regno].offset != -1)
+		memcpy((void *)regs + dbg_reg_def[regno].offset, mem,
+		       dbg_reg_def[regno].size);
+	return 0;
+}
+
+/*
+ * Similar to pt_regs_to_gdb_regs() except that process is sleeping and so
+ * we may not be able to get all the info.
+ */
+void
+sleeping_thread_to_gdb_regs(unsigned long *gdb_regs, struct task_struct *task)
+{
+	int reg;
+	struct pt_regs *thread_regs;
+	unsigned long *ptr = gdb_regs;
+
+	if (task == NULL)
+		return;
+
+	/* Initialize to zero. */
+	memset(gdb_regs, 0, NUMREGBYTES);
+
+	thread_regs = task_pt_regs(task);
+	for (reg = 0; reg <= TREG_LAST_GPR; reg++)
+		*(ptr++) = thread_regs->regs[reg];
+
+	gdb_regs[TILEGX_PC_REGNUM] = thread_regs->pc;
+	gdb_regs[TILEGX_FAULTNUM_REGNUM] = thread_regs->faultnum;
+}
+
+void kgdb_arch_set_pc(struct pt_regs *regs, unsigned long pc)
+{
+	regs->pc = pc;
+}
+
+static void kgdb_call_nmi_hook(void *ignored)
+{
+	kgdb_nmicallback(raw_smp_processor_id(), NULL);
+}
+
+void kgdb_roundup_cpus(unsigned long flags)
+{
+	local_irq_enable();
+	smp_call_function(kgdb_call_nmi_hook, NULL, 0);
+	local_irq_disable();
+}
+
+/*
+ * Convert a kernel address to the writable kernel text mapping.
+ */
+static unsigned long writable_address(unsigned long addr)
+{
+	unsigned long ret = 0;
+
+	if (core_kernel_text(addr))
+		ret = addr - MEM_SV_START + PAGE_OFFSET;
+	else if (is_module_text_address(addr))
+		ret = addr;
+	else
+		pr_err("Unknown virtual address 0x%lx\n", addr);
+
+	return ret;
+}
+
+/*
+ * Calculate the new address for after a step.
+ */
+static unsigned long get_step_address(struct pt_regs *regs)
+{
+	int src_reg;
+	int jump_off;
+	int br_off;
+	unsigned long addr;
+	unsigned int opcode;
+	tile_bundle_bits bundle;
+
+	/* Move to the next instruction by default. */
+	addr = regs->pc + TILEGX_BUNDLE_SIZE_IN_BYTES;
+	bundle = *(unsigned long *)instruction_pointer(regs);
+
+	/* 0: X mode, Otherwise: Y mode. */
+	if (bundle & TILEGX_BUNDLE_MODE_MASK) {
+		if (get_Opcode_Y1(bundle) == RRR_1_OPCODE_Y1 &&
+		    get_RRROpcodeExtension_Y1(bundle) ==
+		    UNARY_RRR_1_OPCODE_Y1) {
+			opcode = get_UnaryOpcodeExtension_Y1(bundle);
+
+			switch (opcode) {
+			case JALR_UNARY_OPCODE_Y1:
+			case JALRP_UNARY_OPCODE_Y1:
+			case JR_UNARY_OPCODE_Y1:
+			case JRP_UNARY_OPCODE_Y1:
+				src_reg = get_SrcA_Y1(bundle);
+				dbg_get_reg(src_reg, &addr, regs);
+				break;
+			}
+		}
+	} else if (get_Opcode_X1(bundle) == RRR_0_OPCODE_X1) {
+		if (get_RRROpcodeExtension_X1(bundle) ==
+		    UNARY_RRR_0_OPCODE_X1) {
+			opcode = get_UnaryOpcodeExtension_X1(bundle);
+
+			switch (opcode) {
+			case JALR_UNARY_OPCODE_X1:
+			case JALRP_UNARY_OPCODE_X1:
+			case JR_UNARY_OPCODE_X1:
+			case JRP_UNARY_OPCODE_X1:
+				src_reg = get_SrcA_X1(bundle);
+				dbg_get_reg(src_reg, &addr, regs);
+				break;
+			}
+		}
+	} else if (get_Opcode_X1(bundle) == JUMP_OPCODE_X1) {
+		opcode = get_JumpOpcodeExtension_X1(bundle);
+
+		switch (opcode) {
+		case JAL_JUMP_OPCODE_X1:
+		case J_JUMP_OPCODE_X1:
+			jump_off = sign_extend(get_JumpOff_X1(bundle), 27);
+			addr = regs->pc +
+				(jump_off << TILEGX_LOG2_BUNDLE_SIZE_IN_BYTES);
+			break;
+		}
+	} else if (get_Opcode_X1(bundle) == BRANCH_OPCODE_X1) {
+		br_off = 0;
+		opcode = get_BrType_X1(bundle);
+
+		switch (opcode) {
+		case BEQZT_BRANCH_OPCODE_X1:
+		case BEQZ_BRANCH_OPCODE_X1:
+			if (get_SrcA_X1(bundle) == 0)
+				br_off = get_BrOff_X1(bundle);
+			break;
+		case BGEZT_BRANCH_OPCODE_X1:
+		case BGEZ_BRANCH_OPCODE_X1:
+			if (get_SrcA_X1(bundle) >= 0)
+				br_off = get_BrOff_X1(bundle);
+			break;
+		case BGTZT_BRANCH_OPCODE_X1:
+		case BGTZ_BRANCH_OPCODE_X1:
+			if (get_SrcA_X1(bundle) > 0)
+				br_off = get_BrOff_X1(bundle);
+			break;
+		case BLBCT_BRANCH_OPCODE_X1:
+		case BLBC_BRANCH_OPCODE_X1:
+			if (!(get_SrcA_X1(bundle) & 1))
+				br_off = get_BrOff_X1(bundle);
+			break;
+		case BLBST_BRANCH_OPCODE_X1:
+		case BLBS_BRANCH_OPCODE_X1:
+			if (get_SrcA_X1(bundle) & 1)
+				br_off = get_BrOff_X1(bundle);
+			break;
+		case BLEZT_BRANCH_OPCODE_X1:
+		case BLEZ_BRANCH_OPCODE_X1:
+			if (get_SrcA_X1(bundle) <= 0)
+				br_off = get_BrOff_X1(bundle);
+			break;
+		case BLTZT_BRANCH_OPCODE_X1:
+		case BLTZ_BRANCH_OPCODE_X1:
+			if (get_SrcA_X1(bundle) < 0)
+				br_off = get_BrOff_X1(bundle);
+			break;
+		case BNEZT_BRANCH_OPCODE_X1:
+		case BNEZ_BRANCH_OPCODE_X1:
+			if (get_SrcA_X1(bundle) != 0)
+				br_off = get_BrOff_X1(bundle);
+			break;
+		}
+
+		if (br_off != 0) {
+			br_off = sign_extend(br_off, 17);
+			addr = regs->pc +
+				(br_off << TILEGX_LOG2_BUNDLE_SIZE_IN_BYTES);
+		}
+	}
+
+	return addr;
+}
+
+/*
+ * Replace the next instruction after the current instruction with a
+ * breakpoint instruction.
+ */
+static void do_single_step(struct pt_regs *regs)
+{
+	unsigned long addr_wr;
+
+	/* Determine where the target instruction will send us to. */
+	stepped_addr = get_step_address(regs);
+	probe_kernel_read((char *)&stepped_instr, (char *)stepped_addr,
+			  BREAK_INSTR_SIZE);
+
+	addr_wr = writable_address(stepped_addr);
+	probe_kernel_write((char *)addr_wr, (char *)&singlestep_insn,
+			   BREAK_INSTR_SIZE);
+	smp_wmb();
+	flush_icache_range(stepped_addr, stepped_addr + BREAK_INSTR_SIZE);
+}
+
+static void undo_single_step(struct pt_regs *regs)
+{
+	unsigned long addr_wr;
+
+	if (stepped_instr == 0)
+		return;
+
+	addr_wr = writable_address(stepped_addr);
+	probe_kernel_write((char *)addr_wr, (char *)&stepped_instr,
+			   BREAK_INSTR_SIZE);
+	stepped_instr = 0;
+	smp_wmb();
+	flush_icache_range(stepped_addr, stepped_addr + BREAK_INSTR_SIZE);
+}
+
+/*
+ * Calls linux_debug_hook before the kernel dies. If KGDB is enabled,
+ * then try to fall into the debugger.
+ */
+static int
+kgdb_notify(struct notifier_block *self, unsigned long cmd, void *ptr)
+{
+	int ret;
+	unsigned long flags;
+	struct die_args *args = (struct die_args *)ptr;
+	struct pt_regs *regs = args->regs;
+
+#ifdef CONFIG_KPROBES
+	/*
+	 * Return immediately if the kprobes fault notifier has set
+	 * DIE_PAGE_FAULT.
+	 */
+	if (cmd == DIE_PAGE_FAULT)
+		return NOTIFY_DONE;
+#endif /* CONFIG_KPROBES */
+
+	switch (cmd) {
+	case DIE_BREAK:
+	case DIE_COMPILED_BPT:
+		break;
+	case DIE_SSTEPBP:
+		local_irq_save(flags);
+		kgdb_handle_exception(0, SIGTRAP, 0, regs);
+		local_irq_restore(flags);
+		return NOTIFY_STOP;
+	default:
+		/* Userspace events, ignore. */
+		if (user_mode(regs))
+			return NOTIFY_DONE;
+	}
+
+	local_irq_save(flags);
+	ret = kgdb_handle_exception(args->trapnr, args->signr, args->err, regs);
+	local_irq_restore(flags);
+	if (ret)
+		return NOTIFY_DONE;
+
+	return NOTIFY_STOP;
+}
+
+static struct notifier_block kgdb_notifier = {
+	.notifier_call = kgdb_notify,
+};
+
+/*
+ * kgdb_arch_handle_exception - Handle architecture specific GDB packets.
+ * @vector: The error vector of the exception that happened.
+ * @signo: The signal number of the exception that happened.
+ * @err_code: The error code of the exception that happened.
+ * @remcom_in_buffer: The buffer of the packet we have read.
+ * @remcom_out_buffer: The buffer of %BUFMAX bytes to write a packet into.
+ * @regs: The &struct pt_regs of the current process.
+ *
+ * This function MUST handle the 'c' and 's' command packets,
+ * as well packets to set / remove a hardware breakpoint, if used.
+ * If there are additional packets which the hardware needs to handle,
+ * they are handled here. The code should return -1 if it wants to
+ * process more packets, and a %0 or %1 if it wants to exit from the
+ * kgdb callback.
+ */
+int kgdb_arch_handle_exception(int vector, int signo, int err_code,
+			       char *remcom_in_buffer, char *remcom_out_buffer,
+			       struct pt_regs *regs)
+{
+	char *ptr;
+	unsigned long address;
+
+	/* Undo any stepping we may have done. */
+	undo_single_step(regs);
+
+	switch (remcom_in_buffer[0]) {
+	case 'c':
+	case 's':
+	case 'D':
+	case 'k':
+		/*
+		 * Try to read optional parameter, pc unchanged if no parm.
+		 * If this was a compiled-in breakpoint, we need to move
+		 * to the next instruction or we will just breakpoint
+		 * over and over again.
+		 */
+		ptr = &remcom_in_buffer[1];
+		if (kgdb_hex2long(&ptr, &address))
+			regs->pc = address;
+		else if (*(unsigned long *)regs->pc == compiled_bpt)
+			regs->pc += BREAK_INSTR_SIZE;
+
+		if (remcom_in_buffer[0] == 's') {
+			do_single_step(regs);
+			kgdb_single_step = 1;
+			atomic_set(&kgdb_cpu_doing_single_step,
+				   raw_smp_processor_id());
+		} else
+			atomic_set(&kgdb_cpu_doing_single_step, -1);
+
+		return 0;
+	}
+
+	return -1; /* this means that we do not want to exit from the handler */
+}
+
+struct kgdb_arch arch_kgdb_ops;
+
+/*
+ * kgdb_arch_init - Perform any architecture specific initalization.
+ *
+ * This function will handle the initalization of any architecture
+ * specific callbacks.
+ */
+int kgdb_arch_init(void)
+{
+	tile_bundle_bits bundle = TILEGX_BPT_BUNDLE;
+
+	memcpy(arch_kgdb_ops.gdb_bpt_instr, &bundle, BREAK_INSTR_SIZE);
+	return register_die_notifier(&kgdb_notifier);
+}
+
+/*
+ * kgdb_arch_exit - Perform any architecture specific uninitalization.
+ *
+ * This function will handle the uninitalization of any architecture
+ * specific callbacks, for dynamic registration and unregistration.
+ */
+void kgdb_arch_exit(void)
+{
+	unregister_die_notifier(&kgdb_notifier);
+}
+
+int kgdb_arch_set_breakpoint(struct kgdb_bkpt *bpt)
+{
+	int err;
+	unsigned long addr_wr = writable_address(bpt->bpt_addr);
+
+	if (addr_wr == 0)
+		return -1;
+
+	err = probe_kernel_read(bpt->saved_instr, (char *)bpt->bpt_addr,
+				BREAK_INSTR_SIZE);
+	if (err)
+		return err;
+
+	err = probe_kernel_write((char *)addr_wr, arch_kgdb_ops.gdb_bpt_instr,
+				 BREAK_INSTR_SIZE);
+	smp_wmb();
+	flush_icache_range((unsigned long)bpt->bpt_addr,
+			   (unsigned long)bpt->bpt_addr + BREAK_INSTR_SIZE);
+	return err;
+}
+
+int kgdb_arch_remove_breakpoint(struct kgdb_bkpt *bpt)
+{
+	int err;
+	unsigned long addr_wr = writable_address(bpt->bpt_addr);
+
+	if (addr_wr == 0)
+		return -1;
+
+	err = probe_kernel_write((char *)addr_wr, (char *)bpt->saved_instr,
+				 BREAK_INSTR_SIZE);
+	smp_wmb();
+	flush_icache_range((unsigned long)bpt->bpt_addr,
+			   (unsigned long)bpt->bpt_addr + BREAK_INSTR_SIZE);
+	return err;
+}
diff --git a/arch/tile/kernel/traps.c b/arch/tile/kernel/traps.c
index 628661f6a929..a937365b3429 100644
--- a/arch/tile/kernel/traps.c
+++ b/arch/tile/kernel/traps.c
@@ -240,6 +240,11 @@ static int do_bpt(struct pt_regs *regs)
 		notify_die(DIE_BREAK, "debug", regs, bundle,
 			INT_ILL, SIGTRAP);
 		break;
+	/* compiled_bpt */
+	case DIE_COMPILED_BPT:
+		notify_die(DIE_COMPILED_BPT, "debug", regs, bundle,
+			INT_ILL, SIGTRAP);
+		break;
 	/* breakpoint2_insn */
 	case DIE_SSTEPBP:
 		notify_die(DIE_SSTEPBP, "single_step", regs, bundle,