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/*
* 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/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[TYPE_MAX]);
/* Number of pinned task breakpoints in a cpu */
static DEFINE_PER_CPU(unsigned int *, nr_task_bp_pinned[TYPE_MAX]);
/* Number of non-pinned cpu/task breakpoints in a cpu */
static DEFINE_PER_CPU(unsigned int, nr_bp_flexible[TYPE_MAX]);
static int nr_slots[TYPE_MAX];
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)
{
int i;
unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);
for (i = nr_slots[type] - 1; i >= 0; i--) {
if (tsk_pinned[i] > 0)
return i + 1;
}
return 0;
}
static int task_bp_pinned(struct task_struct *tsk, enum bp_type_idx type)
{
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)
if (find_slot_idx(bp) == type)
count += hw_breakpoint_weight(bp);
}
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,
enum bp_type_idx type)
{
int cpu = bp->cpu;
struct task_struct *tsk = bp->ctx->task;
if (cpu >= 0) {
slots->pinned = per_cpu(nr_cpu_bp_pinned[type], cpu);
if (!tsk)
slots->pinned += max_task_bp_pinned(cpu, type);
else
slots->pinned += task_bp_pinned(tsk, type);
slots->flexible = per_cpu(nr_bp_flexible[type], cpu);
return;
}
for_each_online_cpu(cpu) {
unsigned int nr;
nr = per_cpu(nr_cpu_bp_pinned[type], cpu);
if (!tsk)
nr += max_task_bp_pinned(cpu, type);
else
nr += task_bp_pinned(tsk, type);
if (nr > slots->pinned)
slots->pinned = nr;
nr = per_cpu(nr_bp_flexible[type], cpu);
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 task_struct *tsk, int cpu, bool enable,
enum bp_type_idx type, int weight)
{
unsigned int *tsk_pinned;
int old_count = 0;
int old_idx = 0;
int idx = 0;
old_count = task_bp_pinned(tsk, type);
old_idx = old_count - 1;
idx = old_idx + weight;
tsk_pinned = per_cpu(nr_task_bp_pinned[type], cpu);
if (enable) {
tsk_pinned[idx]++;
if (old_count > 0)
tsk_pinned[old_idx]--;
} else {
tsk_pinned[idx]--;
if (old_count > 0)
tsk_pinned[old_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)
{
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, type, weight);
return;
}
for_each_online_cpu(cpu)
toggle_bp_task_slot(tsk, cpu, enable, type, weight);
return;
}
/* Pinned counter cpu profiling */
if (enable)
per_cpu(nr_cpu_bp_pinned[type], bp->cpu) += weight;
else
per_cpu(nr_cpu_bp_pinned[type], bp->cpu) -= weight;
}
/*
* 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};
enum bp_type_idx type;
int weight;
/* We couldn't initialize breakpoint constraints on boot */
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