* 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>
*/
/*
#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>
-#include <asm/processor.h>
+/*
+ * Constraints data
+ */
+
+/* Number of pinned cpu breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_cpu_bp_pinned);
-#ifdef CONFIG_X86
-#include <asm/debugreg.h>
-#endif
+/* Number of pinned task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_task_bp_pinned[HBP_NUM]);
-static atomic_t bp_slot;
+/* Number of non-pinned cpu/task breakpoints in a cpu */
+static DEFINE_PER_CPU(unsigned int, nr_bp_flexible);
-int reserve_bp_slot(struct perf_event *bp)
+/* 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)
{
- if (atomic_inc_return(&bp_slot) == HBP_NUM) {
- atomic_dec(&bp_slot);
+ int i;
+ unsigned int *tsk_pinned = per_cpu(nr_task_bp_pinned, cpu);
- return -ENOSPC;
+ for (i = HBP_NUM -1; i >= 0; i--) {
+ if (tsk_pinned[i] > 0)
+ return i + 1;
}
return 0;
}
-void release_bp_slot(struct perf_event *bp)
+static int task_bp_pinned(struct task_struct *tsk)
{
- atomic_dec(&bp_slot);
+ 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;
}
-int __register_perf_hw_breakpoint(struct perf_event *bp)
+/*
+ * 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 ret;
+ int cpu = bp->cpu;
+ struct task_struct *tsk = bp->ctx->task;
- ret = reserve_bp_slot(bp);
- if (ret)
- return ret;
+ 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);
- if (!bp->attr.disabled)
- ret = arch_validate_hwbkpt_settings(bp, bp->ctx->task);
+ return;
+ }
- return ret;
+ 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;
+ }
}
-int register_perf_hw_breakpoint(struct perf_event *bp)
+/*
+ * 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)
{
- bp->callback = perf_bp_event;
+ 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;
+ }
- return __register_perf_hw_breakpoint(bp);
+ /* Pinned counter cpu profiling */
+ if (enable)
+ per_cpu(nr_cpu_bp_pinned, bp->cpu)++;
+ else
+ per_cpu(nr_cpu_bp_pinned, bp->cpu)--;
}
/*
- * 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.
+ * 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 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)
+int reserve_bp_slot(struct perf_event *bp)
{
- struct perf_event_attr *attr;
- struct perf_event *bp;
+ struct bp_busy_slots slots = {0};
+ int ret = 0;
- attr = kzalloc(sizeof(*attr), GFP_KERNEL);
- if (!attr)
- return ERR_PTR(-ENOMEM);
+ mutex_lock(&nr_bp_mutex);
- 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;
+ fetch_bp_busy_slots(&slots, bp);
- if (!active)
- attr->disabled = 1;
+ /* 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);
- bp = perf_event_create_kernel_counter(attr, cpu, pid, triggered);
- kfree(attr);
+end:
+ mutex_unlock(&nr_bp_mutex);
- return bp;
+ 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;
+
+ /*
+ * 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);
+
+ return ret;
}
/**
* 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)
+ * @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
- * @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)
+register_user_hw_breakpoint(struct perf_event_attr *attr,
+ perf_overflow_handler_t triggered,
+ struct task_struct *tsk)
{
- return register_user_hw_breakpoint_cpu(addr, len, type, triggered,
- tsk->pid, -1, active);
+ 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
- * @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)
+ * @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
- * @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)
+int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
{
- /*
- * 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);
+ 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;
- return register_user_hw_breakpoint(addr, len, type, triggered,
- tsk, active);
+ 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);
}
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)
+ * @attr: breakpoint attributes
* @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)
+register_wide_hw_breakpoint(struct perf_event_attr *attr,
+ perf_overflow_handler_t triggered)
{
struct perf_event **cpu_events, **pevent, *bp;
long err;
if (!cpu_events)
return ERR_PTR(-ENOMEM);
- for_each_possible_cpu(cpu) {
+ get_online_cpus();
+ for_each_online_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
- bp = register_kernel_hw_breakpoint_cpu(addr, len, type,
- triggered, cpu, active);
+ bp = perf_event_create_kernel_counter(attr, cpu, -1, triggered);
*pevent = bp;
- if (IS_ERR(bp) || !bp) {
+ if (IS_ERR(bp)) {
err = PTR_ERR(bp);
goto fail;
}
}
+ put_online_cpus();
return cpu_events;
fail:
- for_each_possible_cpu(cpu) {
+ for_each_online_cpu(cpu) {
pevent = per_cpu_ptr(cpu_events, cpu);
- if (IS_ERR(*pevent) || !*pevent)
+ if (IS_ERR(*pevent))
break;
unregister_hw_breakpoint(*pevent);
}
+ put_online_cpus();
+
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
}
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,
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff