1 files changed, 579 insertions, 293 deletions

diff --git a/arch/arm/kernel/hw_breakpoint.c b/arch/arm/kernel/hw_breakpoint.c
index 21e3a4ab3b8..4d963fb66e3 100644
--- a/arch/arm/kernel/hw_breakpoint.c
+++ b/arch/arm/kernel/hw_breakpoint.c
@@ -24,17 +24,19 @@
 #define pr_fmt(fmt) "hw-breakpoint: " fmt
 
 #include <linux/errno.h>
+#include <linux/hardirq.h>
 #include <linux/perf_event.h>
 #include <linux/hw_breakpoint.h>
 #include <linux/smp.h>
+#include <linux/cpu_pm.h>
 
 #include <asm/cacheflush.h>
 #include <asm/cputype.h>
 #include <asm/current.h>
 #include <asm/hw_breakpoint.h>
 #include <asm/kdebug.h>
-#include <asm/system.h>
 #include <asm/traps.h>
+#include <asm/hardware/coresight.h>
 
 /* Breakpoint currently in use for each BRP. */
 static DEFINE_PER_CPU(struct perf_event *, bp_on_reg[ARM_MAX_BRP]);
@@ -49,98 +51,20 @@ static int core_num_wrps;
 /* Debug architecture version. */
 static u8 debug_arch;
 
+/* Does debug architecture support OS Save and Restore? */
+static bool has_ossr;
+
 /* Maximum supported watchpoint length. */
 static u8 max_watchpoint_len;
 
-/* Determine number of BRP registers available. */
-static int get_num_brps(void)
-{
-	u32 didr;
-	ARM_DBG_READ(c0, 0, didr);
-	return ((didr >> 24) & 0xf) + 1;
-}
-
-/* Determine number of WRP registers available. */
-static int get_num_wrps(void)
-{
-	/*
-	 * FIXME: When a watchpoint fires, the only way to work out which
-	 * watchpoint it was is by disassembling the faulting instruction
-	 * and working out the address of the memory access.
-	 *
-	 * Furthermore, we can only do this if the watchpoint was precise
-	 * since imprecise watchpoints prevent us from calculating register
-	 * based addresses.
-	 *
-	 * For the time being, we only report 1 watchpoint register so we
-	 * always know which watchpoint fired. In the future we can either
-	 * add a disassembler and address generation emulator, or we can
-	 * insert a check to see if the DFAR is set on watchpoint exception
-	 * entry [the ARM ARM states that the DFAR is UNKNOWN, but
-	 * experience shows that it is set on some implementations].
-	 */
-
-#if 0
-	u32 didr, wrps;
-	ARM_DBG_READ(c0, 0, didr);
-	return ((didr >> 28) & 0xf) + 1;
-#endif
-
-	return 1;
-}
-
-int hw_breakpoint_slots(int type)
-{
-	/*
-	 * We can be called early, so don't rely on
-	 * our static variables being initialised.
-	 */
-	switch (type) {
-	case TYPE_INST:
-		return get_num_brps();
-	case TYPE_DATA:
-		return get_num_wrps();
-	default:
-		pr_warning("unknown slot type: %d\n", type);
-		return 0;
-	}
-}
-
-/* Determine debug architecture. */
-static u8 get_debug_arch(void)
-{
-	u32 didr;
-
-	/* Do we implement the extended CPUID interface? */
-	if (((read_cpuid_id() >> 16) & 0xf) != 0xf) {
-		pr_warning("CPUID feature registers not supported. "
-				"Assuming v6 debug is present.\n");
-		return ARM_DEBUG_ARCH_V6;
-	}
-
-	ARM_DBG_READ(c0, 0, didr);
-	return (didr >> 16) & 0xf;
-}
-
-/* Does this core support mismatch breakpoints? */
-static int core_has_mismatch_bps(void)
-{
-	return debug_arch >= ARM_DEBUG_ARCH_V7_ECP14 && core_num_brps > 1;
-}
-
-u8 arch_get_debug_arch(void)
-{
-	return debug_arch;
-}
-
-#define READ_WB_REG_CASE(OP2, M, VAL)		\
-	case ((OP2 << 4) + M):			\
-		ARM_DBG_READ(c ## M, OP2, VAL); \
+#define READ_WB_REG_CASE(OP2, M, VAL)			\
+	case ((OP2 << 4) + M):				\
+		ARM_DBG_READ(c0, c ## M, OP2, VAL);	\
 		break
 
-#define WRITE_WB_REG_CASE(OP2, M, VAL)		\
-	case ((OP2 << 4) + M):			\
-		ARM_DBG_WRITE(c ## M, OP2, VAL);\
+#define WRITE_WB_REG_CASE(OP2, M, VAL)			\
+	case ((OP2 << 4) + M):				\
+		ARM_DBG_WRITE(c0, c ## M, OP2, VAL);	\
 		break
 
 #define GEN_READ_WB_REG_CASES(OP2, VAL)		\
@@ -210,49 +134,167 @@ static void write_wb_reg(int n, u32 val)
 	isb();
 }
 
+/* Determine debug architecture. */
+static u8 get_debug_arch(void)
+{
+	u32 didr;
+
+	/* Do we implement the extended CPUID interface? */
+	if (((read_cpuid_id() >> 16) & 0xf) != 0xf) {
+		pr_warn_once("CPUID feature registers not supported. "
+			     "Assuming v6 debug is present.\n");
+		return ARM_DEBUG_ARCH_V6;
+	}
+
+	ARM_DBG_READ(c0, c0, 0, didr);
+	return (didr >> 16) & 0xf;
+}
+
+u8 arch_get_debug_arch(void)
+{
+	return debug_arch;
+}
+
+static int debug_arch_supported(void)
+{
+	u8 arch = get_debug_arch();
+
+	/* We don't support the memory-mapped interface. */
+	return (arch >= ARM_DEBUG_ARCH_V6 && arch <= ARM_DEBUG_ARCH_V7_ECP14) ||
+		arch >= ARM_DEBUG_ARCH_V7_1;
+}
+
+/* Can we determine the watchpoint access type from the fsr? */
+static int debug_exception_updates_fsr(void)
+{
+	return get_debug_arch() >= ARM_DEBUG_ARCH_V8;
+}
+
+/* Determine number of WRP registers available. */
+static int get_num_wrp_resources(void)
+{
+	u32 didr;
+	ARM_DBG_READ(c0, c0, 0, didr);
+	return ((didr >> 28) & 0xf) + 1;
+}
+
+/* Determine number of BRP registers available. */
+static int get_num_brp_resources(void)
+{
+	u32 didr;
+	ARM_DBG_READ(c0, c0, 0, didr);
+	return ((didr >> 24) & 0xf) + 1;
+}
+
+/* Does this core support mismatch breakpoints? */
+static int core_has_mismatch_brps(void)
+{
+	return (get_debug_arch() >= ARM_DEBUG_ARCH_V7_ECP14 &&
+		get_num_brp_resources() > 1);
+}
+
+/* Determine number of usable WRPs available. */
+static int get_num_wrps(void)
+{
+	/*
+	 * On debug architectures prior to 7.1, when a watchpoint fires, the
+	 * only way to work out which watchpoint it was is by disassembling
+	 * the faulting instruction and working out the address of the memory
+	 * access.
+	 *
+	 * Furthermore, we can only do this if the watchpoint was precise
+	 * since imprecise watchpoints prevent us from calculating register
+	 * based addresses.
+	 *
+	 * Providing we have more than 1 breakpoint register, we only report
+	 * a single watchpoint register for the time being. This way, we always
+	 * know which watchpoint fired. In the future we can either add a
+	 * disassembler and address generation emulator, or we can insert a
+	 * check to see if the DFAR is set on watchpoint exception entry
+	 * [the ARM ARM states that the DFAR is UNKNOWN, but experience shows
+	 * that it is set on some implementations].
+	 */
+	if (get_debug_arch() < ARM_DEBUG_ARCH_V7_1)
+		return 1;
+
+	return get_num_wrp_resources();
+}
+
+/* Determine number of usable BRPs available. */
+static int get_num_brps(void)
+{
+	int brps = get_num_brp_resources();
+	return core_has_mismatch_brps() ? brps - 1 : brps;
+}
+
 /*
  * In order to access the breakpoint/watchpoint control registers,
  * we must be running in debug monitor mode. Unfortunately, we can
  * be put into halting debug mode at any time by an external debugger
  * but there is nothing we can do to prevent that.
  */
-static int enable_monitor_mode(void)
+static int monitor_mode_enabled(void)
 {
 	u32 dscr;
-	int ret = 0;
+	ARM_DBG_READ(c0, c1, 0, dscr);
+	return !!(dscr & ARM_DSCR_MDBGEN);
+}
 
-	ARM_DBG_READ(c1, 0, dscr);
+static int enable_monitor_mode(void)
+{
+	u32 dscr;
+	ARM_DBG_READ(c0, c1, 0, dscr);
 
-	/* Ensure that halting mode is disabled. */
-	if (WARN_ONCE(dscr & ARM_DSCR_HDBGEN, "halting debug mode enabled."
-				"Unable to access hardware resources.")) {
-		ret = -EPERM;
+	/* If monitor mode is already enabled, just return. */
+	if (dscr & ARM_DSCR_MDBGEN)
 		goto out;
-	}
 
 	/* Write to the corresponding DSCR. */
-	switch (debug_arch) {
+	switch (get_debug_arch()) {
 	case ARM_DEBUG_ARCH_V6:
 	case ARM_DEBUG_ARCH_V6_1:
-		ARM_DBG_WRITE(c1, 0, (dscr | ARM_DSCR_MDBGEN));
+		ARM_DBG_WRITE(c0, c1, 0, (dscr | ARM_DSCR_MDBGEN));
 		break;
 	case ARM_DEBUG_ARCH_V7_ECP14:
-		ARM_DBG_WRITE(c2, 2, (dscr | ARM_DSCR_MDBGEN));
+	case ARM_DEBUG_ARCH_V7_1:
+	case ARM_DEBUG_ARCH_V8:
+		ARM_DBG_WRITE(c0, c2, 2, (dscr | ARM_DSCR_MDBGEN));
+		isb();
 		break;
 	default:
-		ret = -ENODEV;
-		goto out;
+		return -ENODEV;
 	}
 
 	/* Check that the write made it through. */
-	ARM_DBG_READ(c1, 0, dscr);
-	if (WARN_ONCE(!(dscr & ARM_DSCR_MDBGEN),
-				"failed to enable monitor mode.")) {
-		ret = -EPERM;
+	ARM_DBG_READ(c0, c1, 0, dscr);
+	if (!(dscr & ARM_DSCR_MDBGEN)) {
+		pr_warn_once("Failed to enable monitor mode on CPU %d.\n",
+				smp_processor_id());
+		return -EPERM;
 	}
 
 out:
-	return ret;
+	return 0;
+}
+
+int hw_breakpoint_slots(int type)
+{
+	if (!debug_arch_supported())
+		return 0;
+
+	/*
+	 * We can be called early, so don't rely on
+	 * our static variables being initialised.
+	 */
+	switch (type) {
+	case TYPE_INST:
+		return get_num_brps();
+	case TYPE_DATA:
+		return get_num_wrps();
+	default:
+		pr_warning("unknown slot type: %d\n", type);
+		return 0;
+	}
 }
 
 /*
@@ -268,9 +310,6 @@ static u8 get_max_wp_len(void)
 	if (debug_arch < ARM_DEBUG_ARCH_V7_ECP14)
 		goto out;
 
-	if (enable_monitor_mode())
-		goto out;
-
 	memset(&ctrl, 0, sizeof(ctrl));
 	ctrl.len = ARM_BREAKPOINT_LEN_8;
 	ctrl_reg = encode_ctrl_reg(ctrl);
@@ -290,54 +329,29 @@ u8 arch_get_max_wp_len(void)
 }
 
 /*
- * Handler for reactivating a suspended watchpoint when the single
- * step `mismatch' breakpoint is triggered.
- */
-static void wp_single_step_handler(struct perf_event *bp, int unused,
-				   struct perf_sample_data *data,
-				   struct pt_regs *regs)
-{
-	perf_event_enable(counter_arch_bp(bp)->suspended_wp);
-	unregister_hw_breakpoint(bp);
-}
-
-static int bp_is_single_step(struct perf_event *bp)
-{
-	return bp->overflow_handler == wp_single_step_handler;
-}
-
-/*
  * Install a perf counter breakpoint.
  */
 int arch_install_hw_breakpoint(struct perf_event *bp)
 {
 	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 	struct perf_event **slot, **slots;
-	int i, max_slots, ctrl_base, val_base, ret = 0;
+	int i, max_slots, ctrl_base, val_base;
+	u32 addr, ctrl;
 
-	/* Ensure that we are in monitor mode and halting mode is disabled. */
-	ret = enable_monitor_mode();
-	if (ret)
-		goto out;
+	addr = info->address;
+	ctrl = encode_ctrl_reg(info->ctrl) | 0x1;
 
 	if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
 		/* Breakpoint */
 		ctrl_base = ARM_BASE_BCR;
 		val_base = ARM_BASE_BVR;
-		slots = __get_cpu_var(bp_on_reg);
-		max_slots = core_num_brps - 1;
-
-		if (bp_is_single_step(bp)) {
-			info->ctrl.mismatch = 1;
-			i = max_slots;
-			slots[i] = bp;
-			goto setup;
-		}
+		slots = this_cpu_ptr(bp_on_reg);
+		max_slots = core_num_brps;
 	} else {
 		/* Watchpoint */
 		ctrl_base = ARM_BASE_WCR;
 		val_base = ARM_BASE_WVR;
-		slots = __get_cpu_var(wp_on_reg);
+		slots = this_cpu_ptr(wp_on_reg);
 		max_slots = core_num_wrps;
 	}
 
@@ -350,20 +364,28 @@ int arch_install_hw_breakpoint(struct perf_event *bp)
 		}
 	}
 
-	if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot")) {
-		ret = -EBUSY;
-		goto out;
+	if (i == max_slots) {
+		pr_warning("Can't find any breakpoint slot\n");
+		return -EBUSY;
+	}
+
+	/* Override the breakpoint data with the step data. */
+	if (info->step_ctrl.enabled) {
+		addr = info->trigger & ~0x3;
+		ctrl = encode_ctrl_reg(info->step_ctrl);
+		if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE) {
+			i = 0;
+			ctrl_base = ARM_BASE_BCR + core_num_brps;
+			val_base = ARM_BASE_BVR + core_num_brps;
+		}
 	}
 
-setup:
 	/* Setup the address register. */
-	write_wb_reg(val_base + i, info->address);
+	write_wb_reg(val_base + i, addr);
 
 	/* Setup the control register. */
-	write_wb_reg(ctrl_base + i, encode_ctrl_reg(info->ctrl) | 0x1);
-
-out:
-	return ret;
+	write_wb_reg(ctrl_base + i, ctrl);
+	return 0;
 }
 
 void arch_uninstall_hw_breakpoint(struct perf_event *bp)
@@ -375,18 +397,12 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 	if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE) {
 		/* Breakpoint */
 		base = ARM_BASE_BCR;
-		slots = __get_cpu_var(bp_on_reg);
-		max_slots = core_num_brps - 1;
-
-		if (bp_is_single_step(bp)) {
-			i = max_slots;
-			slots[i] = NULL;
-			goto reset;
-		}
+		slots = this_cpu_ptr(bp_on_reg);
+		max_slots = core_num_brps;
 	} else {
 		/* Watchpoint */
 		base = ARM_BASE_WCR;
-		slots = __get_cpu_var(wp_on_reg);
+		slots = this_cpu_ptr(wp_on_reg);
 		max_slots = core_num_wrps;
 	}
 
@@ -400,10 +416,18 @@ void arch_uninstall_hw_breakpoint(struct perf_event *bp)
 		}
 	}
 
-	if (WARN_ONCE(i == max_slots, "Can't find any breakpoint slot"))
+	if (i == max_slots) {
+		pr_warning("Can't find any breakpoint slot\n");
 		return;
+	}
+
+	/* Ensure that we disable the mismatch breakpoint. */
+	if (info->ctrl.type != ARM_BREAKPOINT_EXECUTE &&
+	    info->step_ctrl.enabled) {
+		i = 0;
+		base = ARM_BASE_BCR + core_num_brps;
+	}
 
-reset:
 	/* Reset the control register. */
 	write_wb_reg(base + i, 0);
 }
@@ -537,12 +561,23 @@ static int arch_build_bp_info(struct perf_event *bp)
 		return -EINVAL;
 	}
 
+	/*
+	 * Breakpoints must be of length 2 (thumb) or 4 (ARM) bytes.
+	 * Watchpoints can be of length 1, 2, 4 or 8 bytes if supported
+	 * by the hardware and must be aligned to the appropriate number of
+	 * bytes.
+	 */
+	if (info->ctrl.type == ARM_BREAKPOINT_EXECUTE &&
+	    info->ctrl.len != ARM_BREAKPOINT_LEN_2 &&
+	    info->ctrl.len != ARM_BREAKPOINT_LEN_4)
+		return -EINVAL;
+
 	/* Address */
 	info->address = bp->attr.bp_addr;
 
 	/* Privilege */
 	info->ctrl.privilege = ARM_BREAKPOINT_USER;
-	if (arch_check_bp_in_kernelspace(bp) && !bp_is_single_step(bp))
+	if (arch_check_bp_in_kernelspace(bp))
 		info->ctrl.privilege |= ARM_BREAKPOINT_PRIV;
 
 	/* Enabled? */
@@ -561,7 +596,11 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
 {
 	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 	int ret = 0;
-	u32 bytelen, max_len, offset, alignment_mask = 0x3;
+	u32 offset, alignment_mask = 0x3;
+
+	/* Ensure that we are in monitor debug mode. */
+	if (!monitor_mode_enabled())
+		return -ENODEV;
 
 	/* Build the arch_hw_breakpoint. */
 	ret = arch_build_bp_info(bp);
@@ -571,111 +610,187 @@ int arch_validate_hwbkpt_settings(struct perf_event *bp)
 	/* Check address alignment. */
 	if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
 		alignment_mask = 0x7;
-	if (info->address & alignment_mask) {
+	offset = info->address & alignment_mask;
+	switch (offset) {
+	case 0:
+		/* Aligned */
+		break;
+	case 1:
+	case 2:
+		/* Allow halfword watchpoints and breakpoints. */
+		if (info->ctrl.len == ARM_BREAKPOINT_LEN_2)
+			break;
+	case 3:
+		/* Allow single byte watchpoint. */
+		if (info->ctrl.len == ARM_BREAKPOINT_LEN_1)
+			break;
+	default:
+		ret = -EINVAL;
+		goto out;
+	}
+
+	info->address &= ~alignment_mask;
+	info->ctrl.len <<= offset;
+
+	if (!bp->overflow_handler) {
 		/*
-		 * Try to fix the alignment. This may result in a length
-		 * that is too large, so we must check for that.
+		 * Mismatch breakpoints are required for single-stepping
+		 * breakpoints.
 		 */
-		bytelen = get_hbp_len(info->ctrl.len);
-		max_len = info->ctrl.type == ARM_BREAKPOINT_EXECUTE ? 4 :
-				max_watchpoint_len;
-
-		if (max_len >= 8)
-			offset = info->address & 0x7;
-		else
-			offset = info->address & 0x3;
-
-		if (bytelen > (1 << ((max_len - (offset + 1)) >> 1))) {
-			ret = -EFBIG;
-			goto out;
-		}
+		if (!core_has_mismatch_brps())
+			return -EINVAL;
 
-		info->ctrl.len <<= offset;
-		info->address &= ~offset;
+		/* We don't allow mismatch breakpoints in kernel space. */
+		if (arch_check_bp_in_kernelspace(bp))
+			return -EPERM;
 
-		pr_debug("breakpoint alignment fixup: length = 0x%x, "
-			"address = 0x%x\n", info->ctrl.len, info->address);
-	}
+		/*
+		 * Per-cpu breakpoints are not supported by our stepping
+		 * mechanism.
+		 */
+		if (!bp->hw.bp_target)
+			return -EINVAL;
 
-	/*
-	 * Currently we rely on an overflow handler to take
-	 * care of single-stepping the breakpoint when it fires.
-	 * In the case of userspace breakpoints on a core with V7 debug,
-	 * we can use the mismatch feature as a poor-man's hardware single-step.
-	 */
-	if (WARN_ONCE(!bp->overflow_handler &&
-		(arch_check_bp_in_kernelspace(bp) || !core_has_mismatch_bps()),
-			"overflow handler required but none found")) {
-		ret = -EINVAL;
-		goto out;
+		/*
+		 * We only support specific access types if the fsr
+		 * reports them.
+		 */
+		if (!debug_exception_updates_fsr() &&
+		    (info->ctrl.type == ARM_BREAKPOINT_LOAD ||
+		     info->ctrl.type == ARM_BREAKPOINT_STORE))
+			return -EINVAL;
 	}
+
 out:
 	return ret;
 }
 
-static void update_mismatch_flag(int idx, int flag)
+/*
+ * Enable/disable single-stepping over the breakpoint bp at address addr.
+ */
+static void enable_single_step(struct perf_event *bp, u32 addr)
 {
-	struct perf_event *bp = __get_cpu_var(bp_on_reg[idx]);
-	struct arch_hw_breakpoint *info;
-
-	if (bp == NULL)
-		return;
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
 
-	info = counter_arch_bp(bp);
+	arch_uninstall_hw_breakpoint(bp);
+	info->step_ctrl.mismatch  = 1;
+	info->step_ctrl.len	  = ARM_BREAKPOINT_LEN_4;
+	info->step_ctrl.type	  = ARM_BREAKPOINT_EXECUTE;
+	info->step_ctrl.privilege = info->ctrl.privilege;
+	info->step_ctrl.enabled	  = 1;
+	info->trigger		  = addr;
+	arch_install_hw_breakpoint(bp);
+}
 
-	/* Update the mismatch field to enter/exit `single-step' mode */
-	if (!bp->overflow_handler && info->ctrl.mismatch != flag) {
-		info->ctrl.mismatch = flag;
-		write_wb_reg(ARM_BASE_BCR + idx, encode_ctrl_reg(info->ctrl) | 0x1);
-	}
+static void disable_single_step(struct perf_event *bp)
+{
+	arch_uninstall_hw_breakpoint(bp);
+	counter_arch_bp(bp)->step_ctrl.enabled = 0;
+	arch_install_hw_breakpoint(bp);
 }
 
-static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs)
+static void watchpoint_handler(unsigned long addr, unsigned int fsr,
+			       struct pt_regs *regs)
 {
-	int i;
-	struct perf_event *bp, **slots = __get_cpu_var(wp_on_reg);
+	int i, access;
+	u32 val, ctrl_reg, alignment_mask;
+	struct perf_event *wp, **slots;
 	struct arch_hw_breakpoint *info;
-	struct perf_event_attr attr;
-
-	/* Without a disassembler, we can only handle 1 watchpoint. */
-	BUG_ON(core_num_wrps > 1);
+	struct arch_hw_breakpoint_ctrl ctrl;
 
-	hw_breakpoint_init(&attr);
-	attr.bp_addr	= regs->ARM_pc & ~0x3;
-	attr.bp_len	= HW_BREAKPOINT_LEN_4;
-	attr.bp_type	= HW_BREAKPOINT_X;
+	slots = this_cpu_ptr(wp_on_reg);
 
 	for (i = 0; i < core_num_wrps; ++i) {
 		rcu_read_lock();
 
-		if (slots[i] == NULL) {
-			rcu_read_unlock();
-			continue;
-		}
+		wp = slots[i];
 
+		if (wp == NULL)
+			goto unlock;
+
+		info = counter_arch_bp(wp);
 		/*
-		 * The DFAR is an unknown value. Since we only allow a
-		 * single watchpoint, we can set the trigger to the lowest
-		 * possible faulting address.
+		 * The DFAR is an unknown value on debug architectures prior
+		 * to 7.1. Since we only allow a single watchpoint on these
+		 * older CPUs, we can set the trigger to the lowest possible
+		 * faulting address.
 		 */
-		info = counter_arch_bp(slots[i]);
-		info->trigger = slots[i]->attr.bp_addr;
+		if (debug_arch < ARM_DEBUG_ARCH_V7_1) {
+			BUG_ON(i > 0);
+			info->trigger = wp->attr.bp_addr;
+		} else {
+			if (info->ctrl.len == ARM_BREAKPOINT_LEN_8)
+				alignment_mask = 0x7;
+			else
+				alignment_mask = 0x3;
+
+			/* Check if the watchpoint value matches. */
+			val = read_wb_reg(ARM_BASE_WVR + i);
+			if (val != (addr & ~alignment_mask))
+				goto unlock;
+
+			/* Possible match, check the byte address select. */
+			ctrl_reg = read_wb_reg(ARM_BASE_WCR + i);
+			decode_ctrl_reg(ctrl_reg, &ctrl);
+			if (!((1 << (addr & alignment_mask)) & ctrl.len))
+				goto unlock;
+
+			/* Check that the access type matches. */
+			if (debug_exception_updates_fsr()) {
+				access = (fsr & ARM_FSR_ACCESS_MASK) ?
+					  HW_BREAKPOINT_W : HW_BREAKPOINT_R;
+				if (!(access & hw_breakpoint_type(wp)))
+					goto unlock;
+			}
+
+			/* We have a winner. */
+			info->trigger = addr;
+		}
+
 		pr_debug("watchpoint fired: address = 0x%x\n", info->trigger);
-		perf_bp_event(slots[i], regs);
+		perf_bp_event(wp, regs);
 
 		/*
 		 * If no overflow handler is present, insert a temporary
 		 * mismatch breakpoint so we can single-step over the
 		 * watchpoint trigger.
 		 */
-		if (!slots[i]->overflow_handler) {
-			bp = register_user_hw_breakpoint(&attr,
-							 wp_single_step_handler,
-							 current);
-			counter_arch_bp(bp)->suspended_wp = slots[i];
-			perf_event_disable(slots[i]);
-		}
+		if (!wp->overflow_handler)
+			enable_single_step(wp, instruction_pointer(regs));
 
+unlock:
+		rcu_read_unlock();
+	}
+}
+
+static void watchpoint_single_step_handler(unsigned long pc)
+{
+	int i;
+	struct perf_event *wp, **slots;
+	struct arch_hw_breakpoint *info;
+
+	slots = this_cpu_ptr(wp_on_reg);
+
+	for (i = 0; i < core_num_wrps; ++i) {
+		rcu_read_lock();
+
+		wp = slots[i];
+
+		if (wp == NULL)
+			goto unlock;
+
+		info = counter_arch_bp(wp);
+		if (!info->step_ctrl.enabled)
+			goto unlock;
+
+		/*
+		 * Restore the original watchpoint if we've completed the
+		 * single-step.
+		 */
+		if (info->trigger != pc)
+			disable_single_step(wp);
+
+unlock:
 		rcu_read_unlock();
 	}
 }
@@ -683,64 +798,73 @@ static void watchpoint_handler(unsigned long unknown, struct pt_regs *regs)
 static void breakpoint_handler(unsigned long unknown, struct pt_regs *regs)
 {
 	int i;
-	int mismatch;
 	u32 ctrl_reg, val, addr;
-	struct perf_event *bp, **slots = __get_cpu_var(bp_on_reg);
+	struct perf_event *bp, **slots;
 	struct arch_hw_breakpoint *info;
 	struct arch_hw_breakpoint_ctrl ctrl;
 
+	slots = this_cpu_ptr(bp_on_reg);
+
 	/* The exception entry code places the amended lr in the PC. */
 	addr = regs->ARM_pc;
 
+	/* Check the currently installed breakpoints first. */
 	for (i = 0; i < core_num_brps; ++i) {
 		rcu_read_lock();
 
 		bp = slots[i];
 
-		if (bp == NULL) {
-			rcu_read_unlock();
-			continue;
-		}
+		if (bp == NULL)
+			goto unlock;
 
-		mismatch = 0;
+		info = counter_arch_bp(bp);
 
 		/* Check if the breakpoint value matches. */
 		val = read_wb_reg(ARM_BASE_BVR + i);
 		if (val != (addr & ~0x3))
-			goto unlock;
+			goto mismatch;
 
 		/* Possible match, check the byte address select to confirm. */
 		ctrl_reg = read_wb_reg(ARM_BASE_BCR + i);
 		decode_ctrl_reg(ctrl_reg, &ctrl);
 		if ((1 << (addr & 0x3)) & ctrl.len) {
-			mismatch = 1;
-			info = counter_arch_bp(bp);
 			info->trigger = addr;
-		}
-
-unlock:
-		if ((mismatch && !info->ctrl.mismatch) || bp_is_single_step(bp)) {
 			pr_debug("breakpoint fired: address = 0x%x\n", addr);
 			perf_bp_event(bp, regs);
+			if (!bp->overflow_handler)
+				enable_single_step(bp, addr);
+			goto unlock;
 		}
 
-		update_mismatch_flag(i, mismatch);
+mismatch:
+		/* If we're stepping a breakpoint, it can now be restored. */
+		if (info->step_ctrl.enabled)
+			disable_single_step(bp);
+unlock:
 		rcu_read_unlock();
 	}
+
+	/* Handle any pending watchpoint single-step breakpoints. */
+	watchpoint_single_step_handler(addr);
 }
 
 /*
  * Called from either the Data Abort Handler [watchpoint] or the
- * Prefetch Abort Handler [breakpoint].
+ * Prefetch Abort Handler [breakpoint] with interrupts disabled.
  */
 static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
 				 struct pt_regs *regs)
 {
-	int ret = 1; /* Unhandled fault. */
+	int ret = 0;
 	u32 dscr;
 
+	preempt_disable();
+
+	if (interrupts_enabled(regs))
+		local_irq_enable();
+
 	/* We only handle watchpoints and hardware breakpoints. */
-	ARM_DBG_READ(c1, 0, dscr);
+	ARM_DBG_READ(c0, c1, 0, dscr);
 
 	/* Perform perf callbacks. */
 	switch (ARM_DSCR_MOE(dscr)) {
@@ -750,28 +874,130 @@ static int hw_breakpoint_pending(unsigned long addr, unsigned int fsr,
 	case ARM_ENTRY_ASYNC_WATCHPOINT:
 		WARN(1, "Asynchronous watchpoint exception taken. Debugging results may be unreliable\n");
 	case ARM_ENTRY_SYNC_WATCHPOINT:
-		watchpoint_handler(addr, regs);
+		watchpoint_handler(addr, fsr, regs);
 		break;
 	default:
-		goto out;
+		ret = 1; /* Unhandled fault. */
 	}
 
-	ret = 0;
-out:
+	preempt_enable();
+
 	return ret;
 }
 
 /*
  * One-time initialisation.
  */
-static void __init reset_ctrl_regs(void *unused)
+static cpumask_t debug_err_mask;
+
+static int debug_reg_trap(struct pt_regs *regs, unsigned int instr)
 {
-	int i;
+	int cpu = smp_processor_id();
 
-	if (enable_monitor_mode())
+	pr_warning("Debug register access (0x%x) caused undefined instruction on CPU %d\n",
+		   instr, cpu);
+
+	/* Set the error flag for this CPU and skip the faulting instruction. */
+	cpumask_set_cpu(cpu, &debug_err_mask);
+	instruction_pointer(regs) += 4;
+	return 0;
+}
+
+static struct undef_hook debug_reg_hook = {
+	.instr_mask	= 0x0fe80f10,
+	.instr_val	= 0x0e000e10,
+	.fn		= debug_reg_trap,
+};
+
+/* Does this core support OS Save and Restore? */
+static bool core_has_os_save_restore(void)
+{
+	u32 oslsr;
+
+	switch (get_debug_arch()) {
+	case ARM_DEBUG_ARCH_V7_1:
+		return true;
+	case ARM_DEBUG_ARCH_V7_ECP14:
+		ARM_DBG_READ(c1, c1, 4, oslsr);
+		if (oslsr & ARM_OSLSR_OSLM0)
+			return true;
+	default:
+		return false;
+	}
+}
+
+static void reset_ctrl_regs(void *unused)
+{
+	int i, raw_num_brps, err = 0, cpu = smp_processor_id();
+	u32 val;
+
+	/*
+	 * v7 debug contains save and restore registers so that debug state
+	 * can be maintained across low-power modes without leaving the debug
+	 * logic powered up. It is IMPLEMENTATION DEFINED whether we can access
+	 * the debug registers out of reset, so we must unlock the OS Lock
+	 * Access Register to avoid taking undefined instruction exceptions
+	 * later on.
+	 */
+	switch (debug_arch) {
+	case ARM_DEBUG_ARCH_V6:
+	case ARM_DEBUG_ARCH_V6_1:
+		/* ARMv6 cores clear the registers out of reset. */
+		goto out_mdbgen;
+	case ARM_DEBUG_ARCH_V7_ECP14:
+		/*
+		 * Ensure sticky power-down is clear (i.e. debug logic is
+		 * powered up).
+		 */
+		ARM_DBG_READ(c1, c5, 4, val);
+		if ((val & 0x1) == 0)
+			err = -EPERM;
+
+		if (!has_ossr)
+			goto clear_vcr;
+		break;
+	case ARM_DEBUG_ARCH_V7_1:
+		/*
+		 * Ensure the OS double lock is clear.
+		 */
+		ARM_DBG_READ(c1, c3, 4, val);
+		if ((val & 0x1) == 1)
+			err = -EPERM;
+		break;
+	}
+
+	if (err) {
+		pr_warn_once("CPU %d debug is powered down!\n", cpu);
+		cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
 		return;
+	}
 
-	for (i = 0; i < core_num_brps; ++i) {
+	/*
+	 * Unconditionally clear the OS lock by writing a value
+	 * other than CS_LAR_KEY to the access register.
+	 */
+	ARM_DBG_WRITE(c1, c0, 4, ~CS_LAR_KEY);
+	isb();
+
+	/*
+	 * Clear any configured vector-catch events before
+	 * enabling monitor mode.
+	 */
+clear_vcr:
+	ARM_DBG_WRITE(c0, c7, 0, 0);
+	isb();
+
+	if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
+		pr_warn_once("CPU %d failed to disable vector catch\n", cpu);
+		return;
+	}
+
+	/*
+	 * The control/value register pairs are UNKNOWN out of reset so
+	 * clear them to avoid spurious debug events.
+	 */
+	raw_num_brps = get_num_brp_resources();
+	for (i = 0; i < raw_num_brps; ++i) {
 		write_wb_reg(ARM_BASE_BCR + i, 0UL);
 		write_wb_reg(ARM_BASE_BVR + i, 0UL);
 	}
@@ -780,57 +1006,117 @@ static void __init reset_ctrl_regs(void *unused)
 		write_wb_reg(ARM_BASE_WCR + i, 0UL);
 		write_wb_reg(ARM_BASE_WVR + i, 0UL);
 	}
+
+	if (cpumask_intersects(&debug_err_mask, cpumask_of(cpu))) {
+		pr_warn_once("CPU %d failed to clear debug register pairs\n", cpu);
+		return;
+	}
+
+	/*
+	 * Have a crack at enabling monitor mode. We don't actually need
+	 * it yet, but reporting an error early is useful if it fails.
+	 */
+out_mdbgen:
+	if (enable_monitor_mode())
+		cpumask_or(&debug_err_mask, &debug_err_mask, cpumask_of(cpu));
 }
 
-static int __init arch_hw_breakpoint_init(void)
+static int dbg_reset_notify(struct notifier_block *self,
+				      unsigned long action, void *cpu)
 {
-	int ret = 0;
-	u32 dscr;
+	if ((action & ~CPU_TASKS_FROZEN) == CPU_ONLINE)
+		smp_call_function_single((int)cpu, reset_ctrl_regs, NULL, 1);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block dbg_reset_nb = {
+	.notifier_call = dbg_reset_notify,
+};
+
+#ifdef CONFIG_CPU_PM
+static int dbg_cpu_pm_notify(struct notifier_block *self, unsigned long action,
+			     void *v)
+{
+	if (action == CPU_PM_EXIT)
+		reset_ctrl_regs(NULL);
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block dbg_cpu_pm_nb = {
+	.notifier_call = dbg_cpu_pm_notify,
+};
+
+static void __init pm_init(void)
+{
+	cpu_pm_register_notifier(&dbg_cpu_pm_nb);
+}
+#else
+static inline void pm_init(void)
+{
+}
+#endif
 
+static int __init arch_hw_breakpoint_init(void)
+{
 	debug_arch = get_debug_arch();
 
-	if (debug_arch > ARM_DEBUG_ARCH_V7_ECP14) {
+	if (!debug_arch_supported()) {
 		pr_info("debug architecture 0x%x unsupported.\n", debug_arch);
-		ret = -ENODEV;
-		goto out;
+		return 0;
 	}
 
+	has_ossr = core_has_os_save_restore();
+
 	/* Determine how many BRPs/WRPs are available. */
 	core_num_brps = get_num_brps();
 	core_num_wrps = get_num_wrps();
 
-	pr_info("found %d breakpoint and %d watchpoint registers.\n",
-			core_num_brps, core_num_wrps);
-
-	if (core_has_mismatch_bps())
-		pr_info("1 breakpoint reserved for watchpoint single-step.\n");
+	cpu_notifier_register_begin();
 
-	ARM_DBG_READ(c1, 0, dscr);
-	if (dscr & ARM_DSCR_HDBGEN) {
-		pr_warning("halting debug mode enabled. Assuming maximum "
-				"watchpoint size of 4 bytes.");
-	} else {
-		/* Work out the maximum supported watchpoint length. */
-		max_watchpoint_len = get_max_wp_len();
-		pr_info("maximum watchpoint size is %u bytes.\n",
-				max_watchpoint_len);
+	/*
+	 * We need to tread carefully here because DBGSWENABLE may be
+	 * driven low on this core and there isn't an architected way to
+	 * determine that.
+	 */
+	register_undef_hook(&debug_reg_hook);
 
-		/*
-		 * Reset the breakpoint resources. We assume that a halting
-		 * debugger will leave the world in a nice state for us.
-		 */
-		smp_call_function(reset_ctrl_regs, NULL, 1);
-		reset_ctrl_regs(NULL);
+	/*
+	 * Reset the breakpoint resources. We assume that a halting
+	 * debugger will leave the world in a nice state for us.
+	 */
+	on_each_cpu(reset_ctrl_regs, NULL, 1);
+	unregister_undef_hook(&debug_reg_hook);
+	if (!cpumask_empty(&debug_err_mask)) {
+		core_num_brps = 0;
+		core_num_wrps = 0;
+		cpu_notifier_register_done();
+		return 0;
 	}
 
+	pr_info("found %d " "%s" "breakpoint and %d watchpoint registers.\n",
+		core_num_brps, core_has_mismatch_brps() ? "(+1 reserved) " :
+		"", core_num_wrps);
+
+	/* Work out the maximum supported watchpoint length. */
+	max_watchpoint_len = get_max_wp_len();
+	pr_info("maximum watchpoint size is %u bytes.\n",
+			max_watchpoint_len);
+
 	/* Register debug fault handler. */
-	hook_fault_code(2, hw_breakpoint_pending, SIGTRAP, TRAP_HWBKPT,
-			"watchpoint debug exception");
-	hook_ifault_code(2, hw_breakpoint_pending, SIGTRAP, TRAP_HWBKPT,
-			"breakpoint debug exception");
+	hook_fault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
+			TRAP_HWBKPT, "watchpoint debug exception");
+	hook_ifault_code(FAULT_CODE_DEBUG, hw_breakpoint_pending, SIGTRAP,
+			TRAP_HWBKPT, "breakpoint debug exception");
 
-out:
-	return ret;
+	/* Register hotplug and PM notifiers. */
+	__register_cpu_notifier(&dbg_reset_nb);
+
+	cpu_notifier_register_done();
+
+	pm_init();
+	return 0;
 }
 arch_initcall(arch_hw_breakpoint_init);