Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 884 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
new file mode 100644
index 000000000..02436f80e
--- /dev/null
+++ b/arch/powerpc/kernel/hw_breakpoint.c
@@ -0,0 +1,884 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers. Derived from
+ * "arch/x86/kernel/hw_breakpoint.c"
+ *
+ * Copyright 2010 IBM Corporation
+ * Author: K.Prasad <prasad@linux.vnet.ibm.com>
+ */
+
+#include <linux/hw_breakpoint.h>
+#include <linux/notifier.h>
+#include <linux/kprobes.h>
+#include <linux/percpu.h>
+#include <linux/kernel.h>
+#include <linux/sched.h>
+#include <linux/smp.h>
+#include <linux/spinlock.h>
+#include <linux/debugfs.h>
+#include <linux/init.h>
+
+#include <asm/hw_breakpoint.h>
+#include <asm/processor.h>
+#include <asm/sstep.h>
+#include <asm/debug.h>
+#include <asm/hvcall.h>
+#include <asm/inst.h>
+#include <linux/uaccess.h>
+
+/*
+ * Stores the breakpoints currently in use on each breakpoint address
+ * register for every cpu
+ */
+static DEFINE_PER_CPU(struct perf_event *, bp_per_reg[HBP_NUM_MAX]);
+
+/*
+ * Returns total number of data or instruction breakpoints available.
+ */
+int hw_breakpoint_slots(int type)
+{
+	if (type == TYPE_DATA)
+		return nr_wp_slots();
+	return 0;		/* no instruction breakpoints available */
+}
+
+static bool single_step_pending(void)
+{
+	int i;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (current->thread.last_hit_ubp[i])
+			return true;
+	}
+	return false;
+}
+
+/*
+ * Install a perf counter breakpoint.
+ *
+ * We seek a free debug address register and use it for this
+ * breakpoint.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
+ */
+int arch_install_hw_breakpoint(struct perf_event *bp)
+{
+	struct arch_hw_breakpoint *info = counter_arch_bp(bp);
+	struct perf_event **slot;
+	int i;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		slot = this_cpu_ptr(&bp_per_reg[i]);
+		if (!*slot) {
+			*slot = bp;
+			break;
+		}
+	}
+
+	if (WARN_ONCE(i == nr_wp_slots(), "Can't find any breakpoint slot"))
+		return -EBUSY;
+
+	/*
+	 * Do not install DABR values if the instruction must be single-stepped.
+	 * If so, DABR will be populated in single_step_dabr_instruction().
+	 */
+	if (!single_step_pending())
+		__set_breakpoint(i, info);
+
+	return 0;
+}
+
+/*
+ * Uninstall the breakpoint contained in the given counter.
+ *
+ * First we search the debug address register it uses and then we disable
+ * it.
+ *
+ * Atomic: we hold the counter->ctx->lock and we only handle variables
+ * and registers local to this cpu.
+ */
+void arch_uninstall_hw_breakpoint(struct perf_event *bp)
+{
+	struct arch_hw_breakpoint null_brk = {0};
+	struct perf_event **slot;
+	int i;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		slot = this_cpu_ptr(&bp_per_reg[i]);
+		if (*slot == bp) {
+			*slot = NULL;
+			break;
+		}
+	}
+
+	if (WARN_ONCE(i == nr_wp_slots(), "Can't find any breakpoint slot"))
+		return;
+
+	__set_breakpoint(i, &null_brk);
+}
+
+static bool is_ptrace_bp(struct perf_event *bp)
+{
+	return bp->overflow_handler == ptrace_triggered;
+}
+
+struct breakpoint {
+	struct list_head list;
+	struct perf_event *bp;
+	bool ptrace_bp;
+};
+
+/*
+ * While kernel/events/hw_breakpoint.c does its own synchronization, we cannot
+ * rely on it safely synchronizing internals here; however, we can rely on it
+ * not requesting more breakpoints than available.
+ */
+static DEFINE_SPINLOCK(cpu_bps_lock);
+static DEFINE_PER_CPU(struct breakpoint *, cpu_bps[HBP_NUM_MAX]);
+static DEFINE_SPINLOCK(task_bps_lock);
+static LIST_HEAD(task_bps);
+
+static struct breakpoint *alloc_breakpoint(struct perf_event *bp)
+{
+	struct breakpoint *tmp;
+
+	tmp = kzalloc(sizeof(*tmp), GFP_KERNEL);
+	if (!tmp)
+		return ERR_PTR(-ENOMEM);
+	tmp->bp = bp;
+	tmp->ptrace_bp = is_ptrace_bp(bp);
+	return tmp;
+}
+
+static bool bp_addr_range_overlap(struct perf_event *bp1, struct perf_event *bp2)
+{
+	__u64 bp1_saddr, bp1_eaddr, bp2_saddr, bp2_eaddr;
+
+	bp1_saddr = ALIGN_DOWN(bp1->attr.bp_addr, HW_BREAKPOINT_SIZE);
+	bp1_eaddr = ALIGN(bp1->attr.bp_addr + bp1->attr.bp_len, HW_BREAKPOINT_SIZE);
+	bp2_saddr = ALIGN_DOWN(bp2->attr.bp_addr, HW_BREAKPOINT_SIZE);
+	bp2_eaddr = ALIGN(bp2->attr.bp_addr + bp2->attr.bp_len, HW_BREAKPOINT_SIZE);
+
+	return (bp1_saddr < bp2_eaddr && bp1_eaddr > bp2_saddr);
+}
+
+static bool alternate_infra_bp(struct breakpoint *b, struct perf_event *bp)
+{
+	return is_ptrace_bp(bp) ? !b->ptrace_bp : b->ptrace_bp;
+}
+
+static bool can_co_exist(struct breakpoint *b, struct perf_event *bp)
+{
+	return !(alternate_infra_bp(b, bp) && bp_addr_range_overlap(b->bp, bp));
+}
+
+static int task_bps_add(struct perf_event *bp)
+{
+	struct breakpoint *tmp;
+
+	tmp = alloc_breakpoint(bp);
+	if (IS_ERR(tmp))
+		return PTR_ERR(tmp);
+
+	spin_lock(&task_bps_lock);
+	list_add(&tmp->list, &task_bps);
+	spin_unlock(&task_bps_lock);
+	return 0;
+}
+
+static void task_bps_remove(struct perf_event *bp)
+{
+	struct list_head *pos, *q;
+
+	spin_lock(&task_bps_lock);
+	list_for_each_safe(pos, q, &task_bps) {
+		struct breakpoint *tmp = list_entry(pos, struct breakpoint, list);
+
+		if (tmp->bp == bp) {
+			list_del(&tmp->list);
+			kfree(tmp);
+			break;
+		}
+	}
+	spin_unlock(&task_bps_lock);
+}
+
+/*
+ * If any task has breakpoint from alternate infrastructure,
+ * return true. Otherwise return false.
+ */
+static bool all_task_bps_check(struct perf_event *bp)
+{
+	struct breakpoint *tmp;
+	bool ret = false;
+
+	spin_lock(&task_bps_lock);
+	list_for_each_entry(tmp, &task_bps, list) {
+		if (!can_co_exist(tmp, bp)) {
+			ret = true;
+			break;
+		}
+	}
+	spin_unlock(&task_bps_lock);
+	return ret;
+}
+
+/*
+ * If same task has breakpoint from alternate infrastructure,
+ * return true. Otherwise return false.
+ */
+static bool same_task_bps_check(struct perf_event *bp)
+{
+	struct breakpoint *tmp;
+	bool ret = false;
+
+	spin_lock(&task_bps_lock);
+	list_for_each_entry(tmp, &task_bps, list) {
+		if (tmp->bp->hw.target == bp->hw.target &&
+		    !can_co_exist(tmp, bp)) {
+			ret = true;
+			break;
+		}
+	}
+	spin_unlock(&task_bps_lock);
+	return ret;
+}
+
+static int cpu_bps_add(struct perf_event *bp)
+{
+	struct breakpoint **cpu_bp;
+	struct breakpoint *tmp;
+	int i = 0;
+
+	tmp = alloc_breakpoint(bp);
+	if (IS_ERR(tmp))
+		return PTR_ERR(tmp);
+
+	spin_lock(&cpu_bps_lock);
+	cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (!cpu_bp[i]) {
+			cpu_bp[i] = tmp;
+			break;
+		}
+	}
+	spin_unlock(&cpu_bps_lock);
+	return 0;
+}
+
+static void cpu_bps_remove(struct perf_event *bp)
+{
+	struct breakpoint **cpu_bp;
+	int i = 0;
+
+	spin_lock(&cpu_bps_lock);
+	cpu_bp = per_cpu_ptr(cpu_bps, bp->cpu);
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (!cpu_bp[i])
+			continue;
+
+		if (cpu_bp[i]->bp == bp) {
+			kfree(cpu_bp[i]);
+			cpu_bp[i] = NULL;
+			break;
+		}
+	}
+	spin_unlock(&cpu_bps_lock);
+}
+
+static bool cpu_bps_check(int cpu, struct perf_event *bp)
+{
+	struct breakpoint **cpu_bp;
+	bool ret = false;
+	int i;
+
+	spin_lock(&cpu_bps_lock);
+	cpu_bp = per_cpu_ptr(cpu_bps, cpu);
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (cpu_bp[i] && !can_co_exist(cpu_bp[i], bp)) {
+			ret = true;
+			break;
+		}
+	}
+	spin_unlock(&cpu_bps_lock);
+	return ret;
+}
+
+static bool all_cpu_bps_check(struct perf_event *bp)
+{
+	int cpu;
+
+	for_each_online_cpu(cpu) {
+		if (cpu_bps_check(cpu, bp))
+			return true;
+	}
+	return false;
+}
+
+int arch_reserve_bp_slot(struct perf_event *bp)
+{
+	int ret;
+
+	/* ptrace breakpoint */
+	if (is_ptrace_bp(bp)) {
+		if (all_cpu_bps_check(bp))
+			return -ENOSPC;
+
+		if (same_task_bps_check(bp))
+			return -ENOSPC;
+
+		return task_bps_add(bp);
+	}
+
+	/* perf breakpoint */
+	if (is_kernel_addr(bp->attr.bp_addr))
+		return 0;
+
+	if (bp->hw.target && bp->cpu == -1) {
+		if (same_task_bps_check(bp))
+			return -ENOSPC;
+
+		return task_bps_add(bp);
+	} else if (!bp->hw.target && bp->cpu != -1) {
+		if (all_task_bps_check(bp))
+			return -ENOSPC;
+
+		return cpu_bps_add(bp);
+	}
+
+	if (same_task_bps_check(bp))
+		return -ENOSPC;
+
+	ret = cpu_bps_add(bp);
+	if (ret)
+		return ret;
+	ret = task_bps_add(bp);
+	if (ret)
+		cpu_bps_remove(bp);
+
+	return ret;
+}
+
+void arch_release_bp_slot(struct perf_event *bp)
+{
+	if (!is_kernel_addr(bp->attr.bp_addr)) {
+		if (bp->hw.target)
+			task_bps_remove(bp);
+		if (bp->cpu != -1)
+			cpu_bps_remove(bp);
+	}
+}
+
+/*
+ * Perform cleanup of arch-specific counters during unregistration
+ * of the perf-event
+ */
+void arch_unregister_hw_breakpoint(struct perf_event *bp)
+{
+	/*
+	 * If the breakpoint is unregistered between a hw_breakpoint_handler()
+	 * and the single_step_dabr_instruction(), then cleanup the breakpoint
+	 * restoration variables to prevent dangling pointers.
+	 * FIXME, this should not be using bp->ctx at all! Sayeth peterz.
+	 */
+	if (bp->ctx && bp->ctx->task && bp->ctx->task != ((void *)-1L)) {
+		int i;
+
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (bp->ctx->task->thread.last_hit_ubp[i] == bp)
+				bp->ctx->task->thread.last_hit_ubp[i] = NULL;
+		}
+	}
+}
+
+/*
+ * Check for virtual address in kernel space.
+ */
+int arch_check_bp_in_kernelspace(struct arch_hw_breakpoint *hw)
+{
+	return is_kernel_addr(hw->address);
+}
+
+int arch_bp_generic_fields(int type, int *gen_bp_type)
+{
+	*gen_bp_type = 0;
+	if (type & HW_BRK_TYPE_READ)
+		*gen_bp_type |= HW_BREAKPOINT_R;
+	if (type & HW_BRK_TYPE_WRITE)
+		*gen_bp_type |= HW_BREAKPOINT_W;
+	if (*gen_bp_type == 0)
+		return -EINVAL;
+	return 0;
+}
+
+/*
+ * Watchpoint match range is always doubleword(8 bytes) aligned on
+ * powerpc. If the given range is crossing doubleword boundary, we
+ * need to increase the length such that next doubleword also get
+ * covered. Ex,
+ *
+ *          address   len = 6 bytes
+ *                |=========.
+ *   |------------v--|------v--------|
+ *   | | | | | | | | | | | | | | | | |
+ *   |---------------|---------------|
+ *    <---8 bytes--->
+ *
+ * In this case, we should configure hw as:
+ *   start_addr = address & ~(HW_BREAKPOINT_SIZE - 1)
+ *   len = 16 bytes
+ *
+ * @start_addr is inclusive but @end_addr is exclusive.
+ */
+static int hw_breakpoint_validate_len(struct arch_hw_breakpoint *hw)
+{
+	u16 max_len = DABR_MAX_LEN;
+	u16 hw_len;
+	unsigned long start_addr, end_addr;
+
+	start_addr = ALIGN_DOWN(hw->address, HW_BREAKPOINT_SIZE);
+	end_addr = ALIGN(hw->address + hw->len, HW_BREAKPOINT_SIZE);
+	hw_len = end_addr - start_addr;
+
+	if (dawr_enabled()) {
+		max_len = DAWR_MAX_LEN;
+		/* DAWR region can't cross 512 bytes boundary on p10 predecessors */
+		if (!cpu_has_feature(CPU_FTR_ARCH_31) &&
+		    (ALIGN_DOWN(start_addr, SZ_512) != ALIGN_DOWN(end_addr - 1, SZ_512)))
+			return -EINVAL;
+	} else if (IS_ENABLED(CONFIG_PPC_8xx)) {
+		/* 8xx can setup a range without limitation */
+		max_len = U16_MAX;
+	}
+
+	if (hw_len > max_len)
+		return -EINVAL;
+
+	hw->hw_len = hw_len;
+	return 0;
+}
+
+/*
+ * Validate the arch-specific HW Breakpoint register settings
+ */
+int hw_breakpoint_arch_parse(struct perf_event *bp,
+			     const struct perf_event_attr *attr,
+			     struct arch_hw_breakpoint *hw)
+{
+	int ret = -EINVAL;
+
+	if (!bp || !attr->bp_len)
+		return ret;
+
+	hw->type = HW_BRK_TYPE_TRANSLATE;
+	if (attr->bp_type & HW_BREAKPOINT_R)
+		hw->type |= HW_BRK_TYPE_READ;
+	if (attr->bp_type & HW_BREAKPOINT_W)
+		hw->type |= HW_BRK_TYPE_WRITE;
+	if (hw->type == HW_BRK_TYPE_TRANSLATE)
+		/* must set alteast read or write */
+		return ret;
+	if (!attr->exclude_user)
+		hw->type |= HW_BRK_TYPE_USER;
+	if (!attr->exclude_kernel)
+		hw->type |= HW_BRK_TYPE_KERNEL;
+	if (!attr->exclude_hv)
+		hw->type |= HW_BRK_TYPE_HYP;
+	hw->address = attr->bp_addr;
+	hw->len = attr->bp_len;
+
+	if (!ppc_breakpoint_available())
+		return -ENODEV;
+
+	return hw_breakpoint_validate_len(hw);
+}
+
+/*
+ * Restores the breakpoint on the debug registers.
+ * Invoke this function if it is known that the execution context is
+ * about to change to cause loss of MSR_SE settings.
+ */
+void thread_change_pc(struct task_struct *tsk, struct pt_regs *regs)
+{
+	struct arch_hw_breakpoint *info;
+	int i;
+
+	preempt_disable();
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (unlikely(tsk->thread.last_hit_ubp[i]))
+			goto reset;
+	}
+	goto out;
+
+reset:
+	regs_set_return_msr(regs, regs->msr & ~MSR_SE);
+	for (i = 0; i < nr_wp_slots(); i++) {
+		info = counter_arch_bp(__this_cpu_read(bp_per_reg[i]));
+		__set_breakpoint(i, info);
+		tsk->thread.last_hit_ubp[i] = NULL;
+	}
+
+out:
+	preempt_enable();
+}
+
+static bool is_larx_stcx_instr(int type)
+{
+	return type == LARX || type == STCX;
+}
+
+static bool is_octword_vsx_instr(int type, int size)
+{
+	return ((type == LOAD_VSX || type == STORE_VSX) && size == 32);
+}
+
+/*
+ * We've failed in reliably handling the hw-breakpoint. Unregister
+ * it and throw a warning message to let the user know about it.
+ */
+static void handler_error(struct perf_event *bp, struct arch_hw_breakpoint *info)
+{
+	WARN(1, "Unable to handle hardware breakpoint. Breakpoint at 0x%lx will be disabled.",
+	     info->address);
+	perf_event_disable_inatomic(bp);
+}
+
+static void larx_stcx_err(struct perf_event *bp, struct arch_hw_breakpoint *info)
+{
+	printk_ratelimited("Breakpoint hit on instruction that can't be emulated. Breakpoint at 0x%lx will be disabled.\n",
+			   info->address);
+	perf_event_disable_inatomic(bp);
+}
+
+static bool stepping_handler(struct pt_regs *regs, struct perf_event **bp,
+			     struct arch_hw_breakpoint **info, int *hit,
+			     ppc_inst_t instr)
+{
+	int i;
+	int stepped;
+
+	/* Do not emulate user-space instructions, instead single-step them */
+	if (user_mode(regs)) {
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (!hit[i])
+				continue;
+			current->thread.last_hit_ubp[i] = bp[i];
+			info[i] = NULL;
+		}
+		regs_set_return_msr(regs, regs->msr | MSR_SE);
+		return false;
+	}
+
+	stepped = emulate_step(regs, instr);
+	if (!stepped) {
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (!hit[i])
+				continue;
+			handler_error(bp[i], info[i]);
+			info[i] = NULL;
+		}
+		return false;
+	}
+	return true;
+}
+
+static void handle_p10dd1_spurious_exception(struct arch_hw_breakpoint **info,
+					     int *hit, unsigned long ea)
+{
+	int i;
+	unsigned long hw_end_addr;
+
+	/*
+	 * Handle spurious exception only when any bp_per_reg is set.
+	 * Otherwise this might be created by xmon and not actually a
+	 * spurious exception.
+	 */
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (!info[i])
+			continue;
+
+		hw_end_addr = ALIGN(info[i]->address + info[i]->len, HW_BREAKPOINT_SIZE);
+
+		/*
+		 * Ending address of DAWR range is less than starting
+		 * address of op.
+		 */
+		if ((hw_end_addr - 1) >= ea)
+			continue;
+
+		/*
+		 * Those addresses need to be in the same or in two
+		 * consecutive 512B blocks;
+		 */
+		if (((hw_end_addr - 1) >> 10) != (ea >> 10))
+			continue;
+
+		/*
+		 * 'op address + 64B' generates an address that has a
+		 * carry into bit 52 (crosses 2K boundary).
+		 */
+		if ((ea & 0x800) == ((ea + 64) & 0x800))
+			continue;
+
+		break;
+	}
+
+	if (i == nr_wp_slots())
+		return;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (info[i]) {
+			hit[i] = 1;
+			info[i]->type |= HW_BRK_TYPE_EXTRANEOUS_IRQ;
+		}
+	}
+}
+
+/*
+ * Handle a DABR or DAWR exception.
+ *
+ * Called in atomic context.
+ */
+int hw_breakpoint_handler(struct die_args *args)
+{
+	bool err = false;
+	int rc = NOTIFY_STOP;
+	struct perf_event *bp[HBP_NUM_MAX] = { NULL };
+	struct pt_regs *regs = args->regs;
+	struct arch_hw_breakpoint *info[HBP_NUM_MAX] = { NULL };
+	int i;
+	int hit[HBP_NUM_MAX] = {0};
+	int nr_hit = 0;
+	bool ptrace_bp = false;
+	ppc_inst_t instr = ppc_inst(0);
+	int type = 0;
+	int size = 0;
+	unsigned long ea;
+
+	/* Disable breakpoints during exception handling */
+	hw_breakpoint_disable();
+
+	/*
+	 * The counter may be concurrently released but that can only
+	 * occur from a call_rcu() path. We can then safely fetch
+	 * the breakpoint, use its callback, touch its counter
+	 * while we are in an rcu_read_lock() path.
+	 */
+	rcu_read_lock();
+
+	if (!IS_ENABLED(CONFIG_PPC_8xx))
+		wp_get_instr_detail(regs, &instr, &type, &size, &ea);
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		bp[i] = __this_cpu_read(bp_per_reg[i]);
+		if (!bp[i])
+			continue;
+
+		info[i] = counter_arch_bp(bp[i]);
+		info[i]->type &= ~HW_BRK_TYPE_EXTRANEOUS_IRQ;
+
+		if (wp_check_constraints(regs, instr, ea, type, size, info[i])) {
+			if (!IS_ENABLED(CONFIG_PPC_8xx) &&
+			    ppc_inst_equal(instr, ppc_inst(0))) {
+				handler_error(bp[i], info[i]);
+				info[i] = NULL;
+				err = 1;
+				continue;
+			}
+
+			if (is_ptrace_bp(bp[i]))
+				ptrace_bp = true;
+			hit[i] = 1;
+			nr_hit++;
+		}
+	}
+
+	if (err)
+		goto reset;
+
+	if (!nr_hit) {
+		/* Workaround for Power10 DD1 */
+		if (!IS_ENABLED(CONFIG_PPC_8xx) && mfspr(SPRN_PVR) == 0x800100 &&
+		    is_octword_vsx_instr(type, size)) {
+			handle_p10dd1_spurious_exception(info, hit, ea);
+		} else {
+			rc = NOTIFY_DONE;
+			goto out;
+		}
+	}
+
+	/*
+	 * Return early after invoking user-callback function without restoring
+	 * DABR if the breakpoint is from ptrace which always operates in
+	 * one-shot mode. The ptrace-ed process will receive the SIGTRAP signal
+	 * generated in do_dabr().
+	 */
+	if (ptrace_bp) {
+		for (i = 0; i < nr_wp_slots(); i++) {
+			if (!hit[i])
+				continue;
+			perf_bp_event(bp[i], regs);
+			info[i] = NULL;
+		}
+		rc = NOTIFY_DONE;
+		goto reset;
+	}
+
+	if (!IS_ENABLED(CONFIG_PPC_8xx)) {
+		if (is_larx_stcx_instr(type)) {
+			for (i = 0; i < nr_wp_slots(); i++) {
+				if (!hit[i])
+					continue;
+				larx_stcx_err(bp[i], info[i]);
+				info[i] = NULL;
+			}
+			goto reset;
+		}
+
+		if (!stepping_handler(regs, bp, info, hit, instr))
+			goto reset;
+	}
+
+	/*
+	 * As a policy, the callback is invoked in a 'trigger-after-execute'
+	 * fashion
+	 */
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (!hit[i])
+			continue;
+		if (!(info[i]->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
+			perf_bp_event(bp[i], regs);
+	}
+
+reset:
+	for (i = 0; i < nr_wp_slots(); i++) {
+		if (!info[i])
+			continue;
+		__set_breakpoint(i, info[i]);
+	}
+
+out:
+	rcu_read_unlock();
+	return rc;
+}
+NOKPROBE_SYMBOL(hw_breakpoint_handler);
+
+/*
+ * Handle single-step exceptions following a DABR hit.
+ *
+ * Called in atomic context.
+ */
+static int single_step_dabr_instruction(struct die_args *args)
+{
+	struct pt_regs *regs = args->regs;
+	struct perf_event *bp = NULL;
+	struct arch_hw_breakpoint *info;
+	int i;
+	bool found = false;
+
+	/*
+	 * Check if we are single-stepping as a result of a
+	 * previous HW Breakpoint exception
+	 */
+	for (i = 0; i < nr_wp_slots(); i++) {
+		bp = current->thread.last_hit_ubp[i];
+
+		if (!bp)
+			continue;
+
+		found = true;
+		info = counter_arch_bp(bp);
+
+		/*
+		 * We shall invoke the user-defined callback function in the
+		 * single stepping handler to confirm to 'trigger-after-execute'
+		 * semantics
+		 */
+		if (!(info->type & HW_BRK_TYPE_EXTRANEOUS_IRQ))
+			perf_bp_event(bp, regs);
+		current->thread.last_hit_ubp[i] = NULL;
+	}
+
+	if (!found)
+		return NOTIFY_DONE;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		bp = __this_cpu_read(bp_per_reg[i]);
+		if (!bp)
+			continue;
+
+		info = counter_arch_bp(bp);
+		__set_breakpoint(i, info);
+	}
+
+	/*
+	 * If the process was being single-stepped by ptrace, let the
+	 * other single-step actions occur (e.g. generate SIGTRAP).
+	 */
+	if (test_thread_flag(TIF_SINGLESTEP))
+		return NOTIFY_DONE;
+
+	return NOTIFY_STOP;
+}
+NOKPROBE_SYMBOL(single_step_dabr_instruction);
+
+/*
+ * Handle debug exception notifications.
+ *
+ * Called in atomic context.
+ */
+int hw_breakpoint_exceptions_notify(
+		struct notifier_block *unused, unsigned long val, void *data)
+{
+	int ret = NOTIFY_DONE;
+
+	switch (val) {
+	case DIE_DABR_MATCH:
+		ret = hw_breakpoint_handler(data);
+		break;
+	case DIE_SSTEP:
+		ret = single_step_dabr_instruction(data);
+		break;
+	}
+
+	return ret;
+}
+NOKPROBE_SYMBOL(hw_breakpoint_exceptions_notify);
+
+/*
+ * Release the user breakpoints used by ptrace
+ */
+void flush_ptrace_hw_breakpoint(struct task_struct *tsk)
+{
+	int i;
+	struct thread_struct *t = &tsk->thread;
+
+	for (i = 0; i < nr_wp_slots(); i++) {
+		unregister_hw_breakpoint(t->ptrace_bps[i]);
+		t->ptrace_bps[i] = NULL;
+	}
+}
+
+void hw_breakpoint_pmu_read(struct perf_event *bp)
+{
+	/* TODO */
+}
+
+void ptrace_triggered(struct perf_event *bp,
+		      struct perf_sample_data *data, struct pt_regs *regs)
+{
+	struct perf_event_attr attr;
+
+	/*
+	 * Disable the breakpoint request here since ptrace has defined a
+	 * one-shot behaviour for breakpoint exceptions in PPC64.
+	 * The SIGTRAP signal is generated automatically for us in do_dabr().
+	 * We don't have to do anything about that here
+	 */
+	attr = bp->attr;
+	attr.disabled = true;
+	modify_user_hw_breakpoint(bp, &attr);
+}