/*
* 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>
*/
/*
* 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
static atomic_t bp_slot;
int reserve_bp_slot(struct perf_event *bp)
{
if (atomic_inc_return(&bp_slot) == HBP_NUM) {
atomic_dec(&bp_slot);
return -ENOSPC;
}
return 0;
}
void release_bp_slot(struct perf_event *bp)
{
atomic_dec(&bp_slot);
}
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);
}
/**
* 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);
}
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
};
