/*
* 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.bp_target;
struct perf_event *iter;
int count = 0;
list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
if (iter->hw.bp_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.bp_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.bp_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;
}
