/*
* 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/cpu.h>
#include <linux/smp.h>
#include <linux/hw_breakpoint.h>
/*
* Constraints data
*/
/* Number of pinned cpu breakpoints in a cpu */
static DEFINE_PER_CPU(unsigned int, nr_cpu_bp_pinned);
/* Number of pinned task breakpoints in a cpu */
static DEFINE_PER_CPU(unsigned int, nr_task_bp_pinned[HBP_NUM]);
/* Number of non-pinned cpu/task breakpoints in a cpu */
static DEFINE_PER_CPU(unsigned int, nr_bp_flexible);
/* 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);
/*
* Report the maximum number of pinned breakpoints a task
* have in this cpu
*/
static unsigned int max_task_bp_pinned(int cpu)
{
int i;
unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned, cpu);
for (i = HBP_NUM -1; i >= 0; i--) {
if (tsk_pinned[i] > 0)
return i + 1;
}
return 0;
}
static int task_bp_pinned(struct task_struct *tsk)
{
struct perf_event_context *ctx = tsk->perf_event_ctxp;
struct list_head *list;
struct perf_event *bp;
unsigned long flags;
int count = 0;
if (WARN_ONCE(!ctx, "No perf context for this task"))
return 0;
list = &ctx->event_list;
raw_spin_lock_irqsave(&ctx->lock, flags);
/*
* The current breakpoint counter is not included in the list
* at the open() callback time
*/
list_for_each_entry(bp, list, event_entry) {
if (bp->attr.type == PERF_TYPE_BREAKPOINT)
count++;
}
raw_spin_unlock_irqrestore(&ctx->lock, flags);
return count;
}
/*
* 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)
{
int cpu = bp->cpu;
struct task_struct *tsk = bp->ctx->task;
if (cpu >= 0) {
slots->pinned = per_cpu(nr_cpu_bp_pinned, cpu);
if (!tsk)
slots->pinned += max_task_bp_pinned(cpu);
else
slots->pinned += task_bp_pinned(tsk);
slots->flexible = per_cpu(nr_bp_flexible, cpu);
return;
}
for_each_online_cpu(cpu) {
unsigned int nr;
nr = per_cpu(nr_cpu_bp_pinned, cpu);
if (!tsk)
nr += max_task_bp_pinned(cpu);
else
nr += task_bp_pinned(tsk);
if (nr > slots->pinned)
slots->pinned = nr;
nr = per_cpu(nr_bp_flexible, cpu);
if (nr > slots->flexible)
slots->flexible = nr;
}
}
/*
* Add a pinned breakpoint for the given task in our constraint table
*/
static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable)
{
unsigned int *tsk_pinned;
int count = 0;
count = task_bp_pinned(tsk);
tsk_pinned = per_cpu(nr_task_bp_pinned, cpu);
if (enable) {
tsk_pinned[count]++;
if (count > 0)
tsk_pinned[count-1]--;
} else {
tsk_pinned[count]--;
if (count > 0)
tsk_pinned[count-1]++;
}
}
/*
* Add/remove the given breakpoint in our constraint table
*/
static void toggle_bp_slot(struct perf_event *bp, bool enable)
{
int cpu = bp->cpu;
struct task_struct *tsk = bp->ctx->task;
/* Pinned counter task profiling */
if (tsk) {
if (cpu >= 0) {
toggle_bp_task_slot(tsk, cpu, enable);
return;
}
for_each_online_cpu(cpu)
toggle_bp_task_slot(tsk, cpu, enable);
return;
}
/* Pinned counter cpu profiling */
if (enable)
per_cpu(nr_cpu_bp_pinned, bp->cpu)++;
else
per_cpu(nr_cpu_bp_pinned, bp->cpu)--;
}
/*
* 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(nr_bp_flexible, cpu) || (per_cpu(nr_cpu_bp_pinned, cpu)
* + max(per_cpu(nr_task_bp_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(nr_bp_flexible, *) || (max(per_cpu(nr_cpu_bp_pinned, *))
* + max(per_cpu(nr_task_bp_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(nr_bp_flexible, cpu) > 1) + per_cpu(nr_cpu_bp_pinned, cpu)
* + max(per_cpu(nr_task_bp_pinned, cpu))) < HBP_NUM
*
* -> Same checks as before. But now the nr_bp_flexible, if any, must keep
* one register at least (or they will never be fed).
*
* - If attached to every cpus, check:
*
* ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
* + max(per_cpu(nr_task_bp_pinned, *))) < HBP_NUM
*/
static int __reserve_bp_slot(struct perf_event *bp)
{
struct bp_busy_slots slots = {0};
fetch_bp_busy_slots(&slots, bp);
/* Flexible counters need to keep at least one slot */
if (slots.pinned + (!!slots.flexible) == HBP_NUM)
return -ENOSPC;
toggle_bp_slot(bp, true);
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)
{
toggle_bp_slot(bp, false);
}
void release_bp_slot(struct perf_event *bp)
{
mutex_lock(&nr_bp_mutex);
__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;
}
int register_perf_hw_breakpoint(struct perf_event *bp)
{
int ret;
ret = reserve_bp_slot(bp);
if (ret)
return ret;
/*
* Ptrace breakpoints can be temporary perf events only
* meant to reserve a slot. In this case, it is created disabled and
* we don't want to check the params right now (as we put a null addr)
* But perf tools create events as disabled and we want to check
* the params for them.
* This is a quick hack that will be removed soon, once we remove
* the tmp breakpoints from ptrace
*/
if (!bp->attr.disabled || !bp->overflow_handler)
ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
/* 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,
struct task_struct *tsk)
{
return perf_event_create_kernel_counter(attr, -1, tsk->pid, triggered);
}
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;
int old_type = bp->attr.bp_type;
int old_len = bp->attr.bp_len;
int err = 0;
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 = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
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 **
register_wide_hw_breakpoint(struct perf_event_attr *attr,
perf_overflow_handler_t triggered)
{
struct perf_event **cpu_events, **pevent, *bp;
long err;
int cpu;
cpu_events = alloc_percpu(typeof(*cpu_events));
if (!cpu_events)
return ERR_PTR(-ENOMEM);
get_online_cpus();
for_each_online_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);
*pevent = bp;
if (IS_ERR(bp)) {
err = PTR_ERR(bp);
goto fail;
}
}
put_online_cpus();
return cpu_events;
fail:
for_each_online_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
if (IS_ERR(*pevent))
break;
unregister_hw_breakpoint(*pevent);
}
put_online_cpus();
free_percpu(cpu_events);
return 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 **cpu_events)
{
int cpu;
struct perf_event **pevent;
for_each_possible_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
unregister_hw_breakpoint(*pevent);
}
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 int __init init_hw_breakpoint(void)
{
return register_die_notifier(&hw_breakpoint_exceptions_nb);
}
core_initcall(init_hw_breakpoint);
struct pmu perf_ops_bp = {
.enable = arch_install_hw_breakpoint,
.disable = arch_uninstall_hw_breakpoint,
.read = hw_breakpoint_pmu_read,
.unthrottle = hw_breakpoint_pmu_unthrottle
};
