fix ksm.h breakage of nommu build
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / hw_breakpoint.c
blobdbcbf6a33a08d4f3a0d9b50469fa15162d81787b
1 /*
2 * This program is free software; you can redistribute it and/or modify
3 * it under the terms of the GNU General Public License as published by
4 * the Free Software Foundation; either version 2 of the License, or
5 * (at your option) any later version.
7 * This program is distributed in the hope that it will be useful,
8 * but WITHOUT ANY WARRANTY; without even the implied warranty of
9 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
10 * GNU General Public License for more details.
12 * You should have received a copy of the GNU General Public License
13 * along with this program; if not, write to the Free Software
14 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
16 * Copyright (C) 2007 Alan Stern
17 * Copyright (C) IBM Corporation, 2009
18 * Copyright (C) 2009, Frederic Weisbecker <fweisbec@gmail.com>
20 * Thanks to Ingo Molnar for his many suggestions.
22 * Authors: Alan Stern <stern@rowland.harvard.edu>
23 * K.Prasad <prasad@linux.vnet.ibm.com>
24 * Frederic Weisbecker <fweisbec@gmail.com>
28 * HW_breakpoint: a unified kernel/user-space hardware breakpoint facility,
29 * using the CPU's debug registers.
30 * This file contains the arch-independent routines.
33 #include <linux/irqflags.h>
34 #include <linux/kallsyms.h>
35 #include <linux/notifier.h>
36 #include <linux/kprobes.h>
37 #include <linux/kdebug.h>
38 #include <linux/kernel.h>
39 #include <linux/module.h>
40 #include <linux/percpu.h>
41 #include <linux/sched.h>
42 #include <linux/init.h>
43 #include <linux/smp.h>
45 #include <linux/hw_breakpoint.h>
48 * Constraints data
51 /* Number of pinned cpu breakpoints in a cpu */
52 static DEFINE_PER_CPU(unsigned int, nr_cpu_bp_pinned);
54 /* Number of pinned task breakpoints in a cpu */
55 static DEFINE_PER_CPU(unsigned int, nr_task_bp_pinned[HBP_NUM]);
57 /* Number of non-pinned cpu/task breakpoints in a cpu */
58 static DEFINE_PER_CPU(unsigned int, nr_bp_flexible);
60 /* Gather the number of total pinned and un-pinned bp in a cpuset */
61 struct bp_busy_slots {
62 unsigned int pinned;
63 unsigned int flexible;
66 /* Serialize accesses to the above constraints */
67 static DEFINE_MUTEX(nr_bp_mutex);
70 * Report the maximum number of pinned breakpoints a task
71 * have in this cpu
73 static unsigned int max_task_bp_pinned(int cpu)
75 int i;
76 unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned, cpu);
78 for (i = HBP_NUM -1; i >= 0; i--) {
79 if (tsk_pinned[i] > 0)
80 return i + 1;
83 return 0;
86 static int task_bp_pinned(struct task_struct *tsk)
88 struct perf_event_context *ctx = tsk->perf_event_ctxp;
89 struct list_head *list;
90 struct perf_event *bp;
91 unsigned long flags;
92 int count = 0;
94 if (WARN_ONCE(!ctx, "No perf context for this task"))
95 return 0;
97 list = &ctx->event_list;
99 raw_spin_lock_irqsave(&ctx->lock, flags);
102 * The current breakpoint counter is not included in the list
103 * at the open() callback time
105 list_for_each_entry(bp, list, event_entry) {
106 if (bp->attr.type == PERF_TYPE_BREAKPOINT)
107 count++;
110 raw_spin_unlock_irqrestore(&ctx->lock, flags);
112 return count;
116 * Report the number of pinned/un-pinned breakpoints we have in
117 * a given cpu (cpu > -1) or in all of them (cpu = -1).
119 static void
120 fetch_bp_busy_slots(struct bp_busy_slots *slots, struct perf_event *bp)
122 int cpu = bp->cpu;
123 struct task_struct *tsk = bp->ctx->task;
125 if (cpu >= 0) {
126 slots->pinned = per_cpu(nr_cpu_bp_pinned, cpu);
127 if (!tsk)
128 slots->pinned += max_task_bp_pinned(cpu);
129 else
130 slots->pinned += task_bp_pinned(tsk);
131 slots->flexible = per_cpu(nr_bp_flexible, cpu);
133 return;
136 for_each_online_cpu(cpu) {
137 unsigned int nr;
139 nr = per_cpu(nr_cpu_bp_pinned, cpu);
140 if (!tsk)
141 nr += max_task_bp_pinned(cpu);
142 else
143 nr += task_bp_pinned(tsk);
145 if (nr > slots->pinned)
146 slots->pinned = nr;
148 nr = per_cpu(nr_bp_flexible, cpu);
150 if (nr > slots->flexible)
151 slots->flexible = nr;
156 * Add a pinned breakpoint for the given task in our constraint table
158 static void toggle_bp_task_slot(struct task_struct *tsk, int cpu, bool enable)
160 unsigned int *tsk_pinned;
161 int count = 0;
163 count = task_bp_pinned(tsk);
165 tsk_pinned = per_cpu(nr_task_bp_pinned, cpu);
166 if (enable) {
167 tsk_pinned[count]++;
168 if (count > 0)
169 tsk_pinned[count-1]--;
170 } else {
171 tsk_pinned[count]--;
172 if (count > 0)
173 tsk_pinned[count-1]++;
178 * Add/remove the given breakpoint in our constraint table
180 static void toggle_bp_slot(struct perf_event *bp, bool enable)
182 int cpu = bp->cpu;
183 struct task_struct *tsk = bp->ctx->task;
185 /* Pinned counter task profiling */
186 if (tsk) {
187 if (cpu >= 0) {
188 toggle_bp_task_slot(tsk, cpu, enable);
189 return;
192 for_each_online_cpu(cpu)
193 toggle_bp_task_slot(tsk, cpu, enable);
194 return;
197 /* Pinned counter cpu profiling */
198 if (enable)
199 per_cpu(nr_cpu_bp_pinned, bp->cpu)++;
200 else
201 per_cpu(nr_cpu_bp_pinned, bp->cpu)--;
205 * Contraints to check before allowing this new breakpoint counter:
207 * == Non-pinned counter == (Considered as pinned for now)
209 * - If attached to a single cpu, check:
211 * (per_cpu(nr_bp_flexible, cpu) || (per_cpu(nr_cpu_bp_pinned, cpu)
212 * + max(per_cpu(nr_task_bp_pinned, cpu)))) < HBP_NUM
214 * -> If there are already non-pinned counters in this cpu, it means
215 * there is already a free slot for them.
216 * Otherwise, we check that the maximum number of per task
217 * breakpoints (for this cpu) plus the number of per cpu breakpoint
218 * (for this cpu) doesn't cover every registers.
220 * - If attached to every cpus, check:
222 * (per_cpu(nr_bp_flexible, *) || (max(per_cpu(nr_cpu_bp_pinned, *))
223 * + max(per_cpu(nr_task_bp_pinned, *)))) < HBP_NUM
225 * -> This is roughly the same, except we check the number of per cpu
226 * bp for every cpu and we keep the max one. Same for the per tasks
227 * breakpoints.
230 * == Pinned counter ==
232 * - If attached to a single cpu, check:
234 * ((per_cpu(nr_bp_flexible, cpu) > 1) + per_cpu(nr_cpu_bp_pinned, cpu)
235 * + max(per_cpu(nr_task_bp_pinned, cpu))) < HBP_NUM
237 * -> Same checks as before. But now the nr_bp_flexible, if any, must keep
238 * one register at least (or they will never be fed).
240 * - If attached to every cpus, check:
242 * ((per_cpu(nr_bp_flexible, *) > 1) + max(per_cpu(nr_cpu_bp_pinned, *))
243 * + max(per_cpu(nr_task_bp_pinned, *))) < HBP_NUM
245 int reserve_bp_slot(struct perf_event *bp)
247 struct bp_busy_slots slots = {0};
248 int ret = 0;
250 mutex_lock(&nr_bp_mutex);
252 fetch_bp_busy_slots(&slots, bp);
254 /* Flexible counters need to keep at least one slot */
255 if (slots.pinned + (!!slots.flexible) == HBP_NUM) {
256 ret = -ENOSPC;
257 goto end;
260 toggle_bp_slot(bp, true);
262 end:
263 mutex_unlock(&nr_bp_mutex);
265 return ret;
268 void release_bp_slot(struct perf_event *bp)
270 mutex_lock(&nr_bp_mutex);
272 toggle_bp_slot(bp, false);
274 mutex_unlock(&nr_bp_mutex);
278 int register_perf_hw_breakpoint(struct perf_event *bp)
280 int ret;
282 ret = reserve_bp_slot(bp);
283 if (ret)
284 return ret;
287 * Ptrace breakpoints can be temporary perf events only
288 * meant to reserve a slot. In this case, it is created disabled and
289 * we don't want to check the params right now (as we put a null addr)
290 * But perf tools create events as disabled and we want to check
291 * the params for them.
292 * This is a quick hack that will be removed soon, once we remove
293 * the tmp breakpoints from ptrace
295 if (!bp->attr.disabled || !bp->overflow_handler)
296 ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
298 return ret;
302 * register_user_hw_breakpoint - register a hardware breakpoint for user space
303 * @attr: breakpoint attributes
304 * @triggered: callback to trigger when we hit the breakpoint
305 * @tsk: pointer to 'task_struct' of the process to which the address belongs
307 struct perf_event *
308 register_user_hw_breakpoint(struct perf_event_attr *attr,
309 perf_overflow_handler_t triggered,
310 struct task_struct *tsk)
312 return perf_event_create_kernel_counter(attr, -1, tsk->pid, triggered);
314 EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
317 * modify_user_hw_breakpoint - modify a user-space hardware breakpoint
318 * @bp: the breakpoint structure to modify
319 * @attr: new breakpoint attributes
320 * @triggered: callback to trigger when we hit the breakpoint
321 * @tsk: pointer to 'task_struct' of the process to which the address belongs
323 int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
325 u64 old_addr = bp->attr.bp_addr;
326 int old_type = bp->attr.bp_type;
327 int old_len = bp->attr.bp_len;
328 int err = 0;
330 perf_event_disable(bp);
332 bp->attr.bp_addr = attr->bp_addr;
333 bp->attr.bp_type = attr->bp_type;
334 bp->attr.bp_len = attr->bp_len;
336 if (attr->disabled)
337 goto end;
339 err = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
340 if (!err)
341 perf_event_enable(bp);
343 if (err) {
344 bp->attr.bp_addr = old_addr;
345 bp->attr.bp_type = old_type;
346 bp->attr.bp_len = old_len;
347 if (!bp->attr.disabled)
348 perf_event_enable(bp);
350 return err;
353 end:
354 bp->attr.disabled = attr->disabled;
356 return 0;
358 EXPORT_SYMBOL_GPL(modify_user_hw_breakpoint);
361 * unregister_hw_breakpoint - unregister a user-space hardware breakpoint
362 * @bp: the breakpoint structure to unregister
364 void unregister_hw_breakpoint(struct perf_event *bp)
366 if (!bp)
367 return;
368 perf_event_release_kernel(bp);
370 EXPORT_SYMBOL_GPL(unregister_hw_breakpoint);
373 * register_wide_hw_breakpoint - register a wide breakpoint in the kernel
374 * @attr: breakpoint attributes
375 * @triggered: callback to trigger when we hit the breakpoint
377 * @return a set of per_cpu pointers to perf events
379 struct perf_event **
380 register_wide_hw_breakpoint(struct perf_event_attr *attr,
381 perf_overflow_handler_t triggered)
383 struct perf_event **cpu_events, **pevent, *bp;
384 long err;
385 int cpu;
387 cpu_events = alloc_percpu(typeof(*cpu_events));
388 if (!cpu_events)
389 return ERR_PTR(-ENOMEM);
391 for_each_possible_cpu(cpu) {
392 pevent = per_cpu_ptr(cpu_events, cpu);
393 bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);
395 *pevent = bp;
397 if (IS_ERR(bp)) {
398 err = PTR_ERR(bp);
399 goto fail;
403 return cpu_events;
405 fail:
406 for_each_possible_cpu(cpu) {
407 pevent = per_cpu_ptr(cpu_events, cpu);
408 if (IS_ERR(*pevent))
409 break;
410 unregister_hw_breakpoint(*pevent);
412 free_percpu(cpu_events);
413 /* return the error if any */
414 return ERR_PTR(err);
416 EXPORT_SYMBOL_GPL(register_wide_hw_breakpoint);
419 * unregister_wide_hw_breakpoint - unregister a wide breakpoint in the kernel
420 * @cpu_events: the per cpu set of events to unregister
422 void unregister_wide_hw_breakpoint(struct perf_event **cpu_events)
424 int cpu;
425 struct perf_event **pevent;
427 for_each_possible_cpu(cpu) {
428 pevent = per_cpu_ptr(cpu_events, cpu);
429 unregister_hw_breakpoint(*pevent);
431 free_percpu(cpu_events);
433 EXPORT_SYMBOL_GPL(unregister_wide_hw_breakpoint);
435 static struct notifier_block hw_breakpoint_exceptions_nb = {
436 .notifier_call = hw_breakpoint_exceptions_notify,
437 /* we need to be notified first */
438 .priority = 0x7fffffff
441 static int __init init_hw_breakpoint(void)
443 return register_die_notifier(&hw_breakpoint_exceptions_nb);
445 core_initcall(init_hw_breakpoint);
448 struct pmu perf_ops_bp = {
449 .enable = arch_install_hw_breakpoint,
450 .disable = arch_uninstall_hw_breakpoint,
451 .read = hw_breakpoint_pmu_read,
452 .unthrottle = hw_breakpoint_pmu_unthrottle