/*
* 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.
*/
/*
* 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/smp.h>
#include <linux/hw_breakpoint.h>
#include <asm/processor.h>
#ifdef CONFIG_X86
#include <asm/debugreg.h>
#endif
/*
* 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, 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(task_bp_pinned, cpu);
for (i = HBP_NUM -1; i >= 0; i--) {
if (tsk_pinned[i] > 0)
return i + 1;
}
return 0;
}
/*
* 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, int cpu)
{
if (cpu >= 0) {
slots->pinned = per_cpu(nr_cpu_bp_pinned, cpu);
slots->pinned += max_task_bp_pinned(cpu);
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);
nr += max_task_bp_pinned(cpu);
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)
{
int count = 0;
struct perf_event *bp;
struct perf_event_context *ctx = tsk->perf_event_ctxp;
unsigned int *task_bp_pinned;
struct list_head *list;
unsigned long flags;
if (WARN_ONCE(!ctx, "No perf context for this task"))
return;
list = &ctx->event_list;
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++;
}
spin_unlock_irqrestore(&ctx->lock, flags);
if (WARN_ONCE(count < 0, "No breakpoint counter found in the counter list"))
return;
task_bp_pinned = per_cpu(task_bp_pinned, cpu);
if (enable) {
task_bp_pinned[count]++;
if (count > 0)
task_bp_pinned[count-1]--;
} else {
task_bp_pinned[count]--;
if (count > 0)
task_bp_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(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(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(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(task_bp_pinned, *))) < HBP_NUM
*/
int reserve_bp_slot(struct perf_event *bp)
{
struct bp_busy_slots slots = {0};
int ret = 0;
mutex_lock(&nr_bp_mutex);
fetch_bp_busy_slots(&slots, bp->cpu);
/* Flexible counters need to keep at least one slot */
if (slots.pinned + (!!slots.flexible) == HBP_NUM) {
ret = -ENOSPC;
goto end;
}
toggle_bp_slot(bp, true);
end:
mutex_unlock(&nr_bp_mutex);
return ret;
}
void release_bp_slot(struct perf_event *bp)
{
mutex_lock(&nr_bp_mutex);
toggle_bp_slot(bp, false);
mutex_unlock(&nr_bp_mutex);
}
int __register_perf_hw_breakpoint(struct perf_event *bp)
{
int ret;
ret = reserve_bp_slot(bp);
if (ret)
return ret;
if (!bp->attr.disabled)
ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
return ret;
}
int register_perf_hw_breakpoint(struct perf_event *bp)
{
bp->callback = perf_bp_event;
return __register_perf_hw_breakpoint(bp);
}
/*
* Register a breakpoint bound to a task and a given cpu.
* If cpu is -1, the breakpoint is active for the task in every cpu
* If the task is -1, the breakpoint is active for every tasks in the given
* cpu.
*/
static struct perf_event *
register_user_hw_breakpoint_cpu(unsigned long addr,
int len,
int type,
perf_callback_t triggered,
pid_t pid,
int cpu,
bool active)
{
struct perf_event_attr *attr;
struct perf_event *bp;
attr = kzalloc(sizeof(*attr), GFP_KERNEL);
if (!attr)
return ERR_PTR(-ENOMEM);
attr->type = PERF_TYPE_BREAKPOINT;
attr->size = sizeof(*attr);
attr->bp_addr = addr;
attr->bp_len = len;
attr->bp_type = type;
/*
* Such breakpoints are used by debuggers to trigger signals when
* we hit the excepted memory op. We can't miss such events, they
* must be pinned.
*/
attr->pinned = 1;
if (!active)
attr->disabled = 1;
bp = perf_event_create_kernel_counter(attr, cpu, pid, triggered);
kfree(attr);
return bp;
}
/**
* register_user_hw_breakpoint - register a hardware breakpoint for user space
* @addr: is the memory address that triggers the breakpoint
* @len: the length of the access to the memory (1 byte, 2 bytes etc...)
* @type: the type of the access to the memory (read/write/exec)
* @triggered: callback to trigger when we hit the breakpoint
* @tsk: pointer to 'task_struct' of the process to which the address belongs
* @active: should we activate it while registering it
*
*/
struct perf_event *
register_user_hw_breakpoint(unsigned long addr,
int len,
int type,
perf_callback_t triggered,
struct task_struct *tsk,
bool active)
{
return register_user_hw_breakpoint_cpu(addr, len, type, triggered,
tsk->pid, -1, active);
}
EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
/**
* modify_user_hw_breakpoint - modify a user-space hardware breakpoint
* @bp: the breakpoint structure to modify
* @addr: is the memory address that triggers the breakpoint
* @len: the length of the access to the memory (1 byte, 2 bytes etc...)
* @type: the type of the access to the memory (read/write/exec)
* @triggered: callback to trigger when we hit the breakpoint
* @tsk: pointer to 'task_struct' of the process to which the address belongs
* @active: should we activate it while registering it
*/
struct perf_event *
modify_user_hw_breakpoint(struct perf_event *bp,
unsigned long addr,
int len,
int type,
perf_callback_t triggered,
struct task_struct *tsk,
bool active)
{
/*
* FIXME: do it without unregistering
* - We don't want to lose our slot
* - If the new bp is incorrect, don't lose the older one
*/
unregister_hw_breakpoint(bp);
return register_user_hw_breakpoint(addr, len, type, triggered,
tsk, active);
}
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);
static struct perf_event *
register_kernel_hw_breakpoint_cpu(unsigned long addr,
int len,
int type,
perf_callback_t triggered,
int cpu,
bool active)
{
return register_user_hw_breakpoint_cpu(addr, len, type, triggered,
-1, cpu, active);
}
/**
* register_wide_hw_breakpoint - register a wide breakpoint in the kernel
* @addr: is the memory address that triggers the breakpoint
* @len: the length of the access to the memory (1 byte, 2 bytes etc...)
* @type: the type of the access to the memory (read/write/exec)
* @triggered: callback to trigger when we hit the breakpoint
* @active: should we activate it while registering it
*
* @return a set of per_cpu pointers to perf events
*/
struct perf_event **
register_wide_hw_breakpoint(unsigned long addr,
int len,
int type,
perf_callback_t triggered,
bool active)
{
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);
for_each_possible_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
bp = register_kernel_hw_breakpoint_cpu(addr, len, type,
triggered, cpu, active);
*pevent = bp;
if (IS_ERR(bp) || !bp) {
err = PTR_ERR(bp);
goto fail;
}
}
return cpu_events;
fail:
for_each_possible_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
if (IS_ERR(*pevent) || !*pevent)
break;
unregister_hw_breakpoint(*pevent);
}
free_percpu(cpu_events);
/* return the error if any */
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
};
