--- /dev/null
+/*
+ * 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; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * 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. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
+ *
+ * Copyright (C) 2007 Alan Stern
+ * Copyright (C) IBM Corporation, 2009
+ * Copyright (C) 2009, Frederic Weisbecker <fweisbec@gmail.com>
+ *
+ * Thanks to Ingo Molnar for his many suggestions.
+ *
+ * Authors: Alan Stern <stern@rowland.harvard.edu>
+ * K.Prasad <prasad@linux.vnet.ibm.com>
+ * Frederic Weisbecker <fweisbec@gmail.com>
+ */
+
+/*
+ * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
+ * using the CPU's debug registers.
+ * This file contains the arch-independent routines.
+ */
+
+#include <linux/irqflags.h>
+#include <linux/kallsyms.h>
+#include <linux/notifier.h>
+#include <linux/kprobes.h>
+#include <linux/kdebug.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/percpu.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/list.h>
+#include <linux/cpu.h>
+#include <linux/smp.h>
+
+#include <linux/hw_breakpoint.h>
+/*
+ * Constraints data
+ */
+struct bp_cpuinfo {
+ /* Number of pinned cpu breakpoints in a cpu */
+ unsigned int cpu_pinned;
+ /* tsk_pinned[n] is the number of tasks having n+1 breakpoints */
+ unsigned int *tsk_pinned;
+ /* Number of non-pinned cpu/task breakpoints in a cpu */
+ unsigned int flexible; /* XXX: placeholder, see fetch_this_slot() */
+};
+
+static DEFINE_PER_CPU(struct bp_cpuinfo, bp_cpuinfo[TYPE_MAX]);
+static int nr_slots[TYPE_MAX];
+
+static struct bp_cpuinfo *get_bp_info(int cpu, enum bp_type_idx type)
+{
+ return per_cpu_ptr(bp_cpuinfo + type, cpu);
+}
+
+/* Keep track of the breakpoints attached to tasks */
+static LIST_HEAD(bp_task_head);
+
+static int constraints_initialized;
+
+/* Gather the number of total pinned and un-pinned bp in a cpuset */
+struct bp_busy_slots {
+ unsigned int pinned;
+ unsigned int flexible;
+};
+
+/* Serialize accesses to the above constraints */
+static DEFINE_MUTEX(nr_bp_mutex);
+
+__weak int hw_breakpoint_weight(struct perf_event *bp)
+{
+ return 1;
+}
+
+static inline enum bp_type_idx find_slot_idx(struct perf_event *bp)
+{
+ if (bp->attr.bp_type & HW_BREAKPOINT_RW)
+ return TYPE_DATA;
+
+ return TYPE_INST;
+}
+
+/*
+ * Report the maximum number of pinned breakpoints a task
+ * have in this cpu
+ */
+static unsigned int max_task_bp_pinned(int cpu, enum bp_type_idx type)
+{
+ unsigned int *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned;
+ int i;
+
+ for (i = nr_slots[type] - 1; i >= 0; i--) {
+ if (tsk_pinned[i] > 0)
+ return i + 1;
+ }
+
+ return 0;
+}
+
+/*
+ * Count the number of breakpoints of the same type and same task.
+ * The given event must be not on the list.
+ */
+static int task_bp_pinned(int cpu, struct perf_event *bp, enum bp_type_idx type)
+{
+ struct task_struct *tsk = bp->hw.target;
+ struct perf_event *iter;
+ int count = 0;
+
+ list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
+ if (iter->hw.target == tsk &&
+ find_slot_idx(iter) == type &&
+ (iter->cpu < 0 || cpu == iter->cpu))
+ count += hw_breakpoint_weight(iter);
+ }
+
+ return count;
+}
+
+static const struct cpumask *cpumask_of_bp(struct perf_event *bp)
+{
+ if (bp->cpu >= 0)
+ return cpumask_of(bp->cpu);
+ return cpu_possible_mask;
+}
+
+/*
+ * Report the number of pinned/un-pinned breakpoints we have in
+ * a given cpu (cpu > -1) or in all of them (cpu = -1).
+ */
+static void
+fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp,
+ enum bp_type_idx type)
+{
+ const struct cpumask *cpumask = cpumask_of_bp(bp);
+ int cpu;
+
+ for_each_cpu(cpu, cpumask) {
+ struct bp_cpuinfo *info = get_bp_info(cpu, type);
+ int nr;
+
+ nr = info->cpu_pinned;
+ if (!bp->hw.target)
+ nr += max_task_bp_pinned(cpu, type);
+ else
+ nr += task_bp_pinned(cpu, bp, type);
+
+ if (nr > slots->pinned)
+ slots->pinned = nr;
+
+ nr = info->flexible;
+ if (nr > slots->flexible)
+ slots->flexible = nr;
+ }
+}
+
+/*
+ * For now, continue to consider flexible as pinned, until we can
+ * ensure no flexible event can ever be scheduled before a pinned event
+ * in a same cpu.
+ */
+static void
+fetch_this_slot(struct bp_busy_slots *slots, int weight)
+{
+ slots->pinned += weight;
+}
+
+/*
+ * Add a pinned breakpoint for the given task in our constraint table
+ */
+static void toggle_bp_task_slot(struct perf_event *bp, int cpu,
+ enum bp_type_idx type, int weight)
+{
+ unsigned int *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned;
+ int old_idx, new_idx;
+
+ old_idx = task_bp_pinned(cpu, bp, type) - 1;
+ new_idx = old_idx + weight;
+
+ if (old_idx >= 0)
+ tsk_pinned[old_idx]--;
+ if (new_idx >= 0)
+ tsk_pinned[new_idx]++;
+}
+
+/*
+ * Add/remove the given breakpoint in our constraint table
+ */
+static void
+toggle_bp_slot(struct perf_event *bp, bool enable, enum bp_type_idx type,
+ int weight)
+{
+ const struct cpumask *cpumask = cpumask_of_bp(bp);
+ int cpu;
+
+ if (!enable)
+ weight = -weight;
+
+ /* Pinned counter cpu profiling */
+ if (!bp->hw.target) {
+ get_bp_info(bp->cpu, type)->cpu_pinned += weight;
+ return;
+ }
+
+ /* Pinned counter task profiling */
+ for_each_cpu(cpu, cpumask)
+ toggle_bp_task_slot(bp, cpu, type, weight);
+
+ if (enable)
+ list_add_tail(&bp->hw.bp_list, &bp_task_head);
+ else
+ list_del(&bp->hw.bp_list);
+}
+
+/*
+ * Function to perform processor-specific cleanup during unregistration
+ */
+__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
+{
+ /*
+ * A weak stub function here for those archs that don't define
+ * it inside arch/.../kernel/hw_breakpoint.c
+ */
+}
+
+/*
+ * Contraints to check before allowing this new breakpoint counter:
+ *
+ * == Non-pinned counter == (Considered as pinned for now)
+ *
+ * - If attached to a single cpu, check:
+ *
+ * (per_cpu(info->flexible, cpu) || (per_cpu(info->cpu_pinned, cpu)
+ * + max(per_cpu(info->tsk_pinned, cpu)))) < HBP_NUM
+ *
+ * -> If there are already non-pinned counters in this cpu, it means
+ * there is already a free slot for them.
+ * Otherwise, we check that the maximum number of per task
+ * breakpoints (for this cpu) plus the number of per cpu breakpoint
+ * (for this cpu) doesn't cover every registers.
+ *
+ * - If attached to every cpus, check:
+ *
+ * (per_cpu(info->flexible, *) || (max(per_cpu(info->cpu_pinned, *))
+ * + max(per_cpu(info->tsk_pinned, *)))) < HBP_NUM
+ *
+ * -> This is roughly the same, except we check the number of per cpu
+ * bp for every cpu and we keep the max one. Same for the per tasks
+ * breakpoints.
+ *
+ *
+ * == Pinned counter ==
+ *
+ * - If attached to a single cpu, check:
+ *
+ * ((per_cpu(info->flexible, cpu) > 1) + per_cpu(info->cpu_pinned, cpu)
+ * + max(per_cpu(info->tsk_pinned, cpu))) < HBP_NUM
+ *
+ * -> Same checks as before. But now the info->flexible, if any, must keep
+ * one register at least (or they will never be fed).
+ *
+ * - If attached to every cpus, check:
+ *
+ * ((per_cpu(info->flexible, *) > 1) + max(per_cpu(info->cpu_pinned, *))
+ * + max(per_cpu(info->tsk_pinned, *))) < HBP_NUM
+ */
+static int __reserve_bp_slot(struct perf_event *bp)
+{
+ struct bp_busy_slots slots = {0};
+ enum bp_type_idx type;
+ int weight;
+
+ /* We couldn't initialize breakpoint constraints on boot */
+ if (!constraints_initialized)
+ return -ENOMEM;
+
+ /* Basic checks */
+ if (bp->attr.bp_type == HW_BREAKPOINT_EMPTY ||
+ bp->attr.bp_type == HW_BREAKPOINT_INVALID)
+ return -EINVAL;
+
+ type = find_slot_idx(bp);
+ weight = hw_breakpoint_weight(bp);
+
+ fetch_bp_busy_slots(&slots, bp, type);
+ /*
+ * Simulate the addition of this breakpoint to the constraints
+ * and see the result.
+ */
+ fetch_this_slot(&slots, weight);
+
+ /* Flexible counters need to keep at least one slot */
+ if (slots.pinned + (!!slots.flexible) > nr_slots[type])
+ return -ENOSPC;
+
+ toggle_bp_slot(bp, true, type, weight);
+
+ return 0;
+}
+
+int reserve_bp_slot(struct perf_event *bp)
+{
+ int ret;
+
+ mutex_lock(&nr_bp_mutex);
+
+ ret = __reserve_bp_slot(bp);
+
+ mutex_unlock(&nr_bp_mutex);
+
+ return ret;
+}
+
+static void __release_bp_slot(struct perf_event *bp)
+{
+ enum bp_type_idx type;
+ int weight;
+
+ type = find_slot_idx(bp);
+ weight = hw_breakpoint_weight(bp);
+ toggle_bp_slot(bp, false, type, weight);
+}
+
+void release_bp_slot(struct perf_event *bp)
+{
+ mutex_lock(&nr_bp_mutex);
+
+ arch_unregister_hw_breakpoint(bp);
+ __release_bp_slot(bp);
+
+ mutex_unlock(&nr_bp_mutex);
+}
+
+/*
+ * Allow the kernel debugger to reserve breakpoint slots without
+ * taking a lock using the dbg_* variant of for the reserve and
+ * release breakpoint slots.
+ */
+int dbg_reserve_bp_slot(struct perf_event *bp)
+{
+ if (mutex_is_locked(&nr_bp_mutex))
+ return -1;
+
+ return __reserve_bp_slot(bp);
+}
+
+int dbg_release_bp_slot(struct perf_event *bp)
+{
+ if (mutex_is_locked(&nr_bp_mutex))
+ return -1;
+
+ __release_bp_slot(bp);
+
+ return 0;
+}
+
+static int validate_hw_breakpoint(struct perf_event *bp)
+{
+ int ret;
+
+ ret = arch_validate_hwbkpt_settings(bp);
+ if (ret)
+ return ret;
+
+ if (arch_check_bp_in_kernelspace(bp)) {
+ if (bp->attr.exclude_kernel)
+ return -EINVAL;
+ /*
+ * Don't let unprivileged users set a breakpoint in the trap
+ * path to avoid trap recursion attacks.
+ */
+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+ }
+
+ return 0;
+}
+
+int register_perf_hw_breakpoint(struct perf_event *bp)
+{
+ int ret;
+
+ ret = reserve_bp_slot(bp);
+ if (ret)
+ return ret;
+
+ ret = validate_hw_breakpoint(bp);
+
+ /* if arch_validate_hwbkpt_settings() fails then release bp slot */
+ if (ret)
+ release_bp_slot(bp);
+
+ return ret;
+}
+
+/**
+ * register_user_hw_breakpoint - register a hardware breakpoint for user space
+ * @attr: breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ */
+struct perf_event *
+register_user_hw_breakpoint(struct perf_event_attr *attr,
+ perf_overflow_handler_t triggered,
+ void *context,
+ struct task_struct *tsk)
+{
+ return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
+ context);
+}
+EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
+
+/**
+ * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
+ * @bp: the breakpoint structure to modify
+ * @attr: new breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ * @tsk: pointer to 'task_struct' of the process to which the address belongs
+ */
+int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
+{
+ u64 old_addr = bp->attr.bp_addr;
+ u64 old_len = bp->attr.bp_len;
+ int old_type = bp->attr.bp_type;
+ int err = 0;
+
+ /*
+ * modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it
+ * will not be possible to raise IPIs that invoke __perf_event_disable.
+ * So call the function directly after making sure we are targeting the
+ * current task.
+ */
+ if (irqs_disabled() && bp->ctx && bp->ctx->task == current)
+ __perf_event_disable(bp);
+ else
+ perf_event_disable(bp);
+
+ bp->attr.bp_addr = attr->bp_addr;
+ bp->attr.bp_type = attr->bp_type;
+ bp->attr.bp_len = attr->bp_len;
+
+ if (attr->disabled)
+ goto end;
+
+ err = validate_hw_breakpoint(bp);
+ if (!err)
+ perf_event_enable(bp);
+
+ if (err) {
+ bp->attr.bp_addr = old_addr;
+ bp->attr.bp_type = old_type;
+ bp->attr.bp_len = old_len;
+ if (!bp->attr.disabled)
+ perf_event_enable(bp);
+
+ return err;
+ }
+
+end:
+ bp->attr.disabled = attr->disabled;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
+
+/**
+ * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
+ * @bp: the breakpoint structure to unregister
+ */
+void unregister_hw_breakpoint(struct perf_event *bp)
+{
+ if (!bp)
+ return;
+ perf_event_release_kernel(bp);
+}
+EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
+
+/**
+ * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
+ * @attr: breakpoint attributes
+ * @triggered: callback to trigger when we hit the breakpoint
+ *
+ * @return a set of per_cpu pointers to perf events
+ */
+struct perf_event * __percpu *
+register_wide_hw_breakpoint(struct perf_event_attr *attr,
+ perf_overflow_handler_t triggered,
+ void *context)
+{
+ struct perf_event * __percpu *cpu_events, *bp;
+ long err = 0;
+ int cpu;
+
+ cpu_events = alloc_percpu(typeof(*cpu_events));
+ if (!cpu_events)
+ return (void __percpu __force *)ERR_PTR(-ENOMEM);
+
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
+ bp = perf_event_create_kernel_counter(attr, cpu, NULL,
+ triggered, context);
+ if (IS_ERR(bp)) {
+ err = PTR_ERR(bp);
+ break;
+ }
+
+ per_cpu(*cpu_events, cpu) = bp;
+ }
+ put_online_cpus();
+
+ if (likely(!err))
+ return cpu_events;
+
+ unregister_wide_hw_breakpoint(cpu_events);
+ return (void __percpu __force *)ERR_PTR(err);
+}
+EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
+
+/**
+ * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
+ * @cpu_events: the per cpu set of events to unregister
+ */
+void unregister_wide_hw_breakpoint(struct perf_event * __percpu *cpu_events)
+{
+ int cpu;
+
+ for_each_possible_cpu(cpu)
+ unregister_hw_breakpoint(per_cpu(*cpu_events, cpu));
+
+ free_percpu(cpu_events);
+}
+EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
+
+static struct notifier_block hw_breakpoint_exceptions_nb = {
+ .notifier_call = hw_breakpoint_exceptions_notify,
+ /* we need to be notified first */
+ .priority = 0x7fffffff
+};
+
+static void bp_perf_event_destroy(struct perf_event *event)
+{
+ release_bp_slot(event);
+}
+
+static int hw_breakpoint_event_init(struct perf_event *bp)
+{
+ int err;
+
+ if (bp->attr.type != PERF_TYPE_BREAKPOINT)
+ return -ENOENT;
+
+ /*
+ * no branch sampling for breakpoint events
+ */
+ if (has_branch_stack(bp))
+ return -EOPNOTSUPP;
+
+ err = register_perf_hw_breakpoint(bp);
+ if (err)
+ return err;
+
+ bp->destroy = bp_perf_event_destroy;
+
+ return 0;
+}
+
+static int hw_breakpoint_add(struct perf_event *bp, int flags)
+{
+ if (!(flags & PERF_EF_START))
+ bp->hw.state = PERF_HES_STOPPED;
+
+ if (is_sampling_event(bp)) {
+ bp->hw.last_period = bp->hw.sample_period;
+ perf_swevent_set_period(bp);
+ }
+
+ return arch_install_hw_breakpoint(bp);
+}
+
+static void hw_breakpoint_del(struct perf_event *bp, int flags)
+{
+ arch_uninstall_hw_breakpoint(bp);
+}
+
+static void hw_breakpoint_start(struct perf_event *bp, int flags)
+{
+ bp->hw.state = 0;
+}
+
+static void hw_breakpoint_stop(struct perf_event *bp, int flags)
+{
+ bp->hw.state = PERF_HES_STOPPED;
+}
+
+static struct pmu perf_breakpoint = {
+ .task_ctx_nr = perf_sw_context, /* could eventually get its own */
+
+ .event_init = hw_breakpoint_event_init,
+ .add = hw_breakpoint_add,
+ .del = hw_breakpoint_del,
+ .start = hw_breakpoint_start,
+ .stop = hw_breakpoint_stop,
+ .read = hw_breakpoint_pmu_read,
+};
+
+int __init init_hw_breakpoint(void)
+{
+ int cpu, err_cpu;
+ int i;
+
+ for (i = 0; i < TYPE_MAX; i++)
+ nr_slots[i] = hw_breakpoint_slots(i);
+
+ for_each_possible_cpu(cpu) {
+ for (i = 0; i < TYPE_MAX; i++) {
+ struct bp_cpuinfo *info = get_bp_info(cpu, i);
+
+ info->tsk_pinned = kcalloc(nr_slots[i], sizeof(int),
+ GFP_KERNEL);
+ if (!info->tsk_pinned)
+ goto err_alloc;
+ }
+ }
+
+ constraints_initialized = 1;
+
+ perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
+
+ return register_die_notifier(&hw_breakpoint_exceptions_nb);
+
+ err_alloc:
+ for_each_possible_cpu(err_cpu) {
+ for (i = 0; i < TYPE_MAX; i++)
+ kfree(get_bp_info(err_cpu, i)->tsk_pinned);
+ if (err_cpu == cpu)
+ break;
+ }
+
+ return -ENOMEM;
+}
+
+
Code Review / kvmfornfv.git / blobdiff