// SPDX-License-Identifier: GPL-2.0+
|
/*
|
* 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/list.h>
|
#include <linux/cpu.h>
|
#include <linux/smp.h>
|
#include <linux/bug.h>
|
|
#include <linux/hw_breakpoint.h>
|
/*
|
* Constraints data
|
*/
|
struct bp_cpuinfo {
|
/* Number of pinned cpu breakpoints in a cpu */
|
unsigned int cpu_pinned;
|
/* tsk_pinned[n] is the number of tasks having n+1 breakpoints */
|
unsigned int *tsk_pinned;
|
/* Number of non-pinned cpu/task breakpoints in a cpu */
|
unsigned int flexible; /* XXX: placeholder, see fetch_this_slot() */
|
};
|
|
static DEFINE_PER_CPU(struct bp_cpuinfo, bp_cpuinfo[TYPE_MAX]);
|
static int nr_slots[TYPE_MAX];
|
|
static struct bp_cpuinfo *get_bp_info(int cpu, enum bp_type_idx type)
|
{
|
return per_cpu_ptr(bp_cpuinfo + type, cpu);
|
}
|
|
/* Keep track of the breakpoints attached to tasks */
|
static LIST_HEAD(bp_task_head);
|
|
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(u64 bp_type)
|
{
|
if (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)
|
{
|
unsigned int *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned;
|
int i;
|
|
for (i = nr_slots[type] - 1; i >= 0; i--) {
|
if (tsk_pinned[i] > 0)
|
return i + 1;
|
}
|
|
return 0;
|
}
|
|
/*
|
* Count the number of breakpoints of the same type and same task.
|
* The given event must be not on the list.
|
*/
|
static int task_bp_pinned(int cpu, struct perf_event *bp, enum bp_type_idx type)
|
{
|
struct task_struct *tsk = bp->hw.target;
|
struct perf_event *iter;
|
int count = 0;
|
|
list_for_each_entry(iter, &bp_task_head, hw.bp_list) {
|
if (iter->hw.target == tsk &&
|
find_slot_idx(iter->attr.bp_type) == type &&
|
(iter->cpu < 0 || cpu == iter->cpu))
|
count += hw_breakpoint_weight(iter);
|
}
|
|
return count;
|
}
|
|
static const struct cpumask *cpumask_of_bp(struct perf_event *bp)
|
{
|
if (bp->cpu >= 0)
|
return cpumask_of(bp->cpu);
|
return cpu_possible_mask;
|
}
|
|
/*
|
* 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)
|
{
|
const struct cpumask *cpumask = cpumask_of_bp(bp);
|
int cpu;
|
|
for_each_cpu(cpu, cpumask) {
|
struct bp_cpuinfo *info = get_bp_info(cpu, type);
|
int nr;
|
|
nr = info->cpu_pinned;
|
if (!bp->hw.target)
|
nr += max_task_bp_pinned(cpu, type);
|
else
|
nr += task_bp_pinned(cpu, bp, type);
|
|
if (nr > slots->pinned)
|
slots->pinned = nr;
|
|
nr = info->flexible;
|
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 perf_event *bp, int cpu,
|
enum bp_type_idx type, int weight)
|
{
|
unsigned int *tsk_pinned = get_bp_info(cpu, type)->tsk_pinned;
|
int old_idx, new_idx;
|
|
old_idx = task_bp_pinned(cpu, bp, type) - 1;
|
new_idx = old_idx + weight;
|
|
if (old_idx >= 0)
|
tsk_pinned[old_idx]--;
|
if (new_idx >= 0)
|
tsk_pinned[new_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)
|
{
|
const struct cpumask *cpumask = cpumask_of_bp(bp);
|
int cpu;
|
|
if (!enable)
|
weight = -weight;
|
|
/* Pinned counter cpu profiling */
|
if (!bp->hw.target) {
|
get_bp_info(bp->cpu, type)->cpu_pinned += weight;
|
return;
|
}
|
|
/* Pinned counter task profiling */
|
for_each_cpu(cpu, cpumask)
|
toggle_bp_task_slot(bp, cpu, type, weight);
|
|
if (enable)
|
list_add_tail(&bp->hw.bp_list, &bp_task_head);
|
else
|
list_del(&bp->hw.bp_list);
|
}
|
|
__weak int arch_reserve_bp_slot(struct perf_event *bp)
|
{
|
return 0;
|
}
|
|
__weak void arch_release_bp_slot(struct perf_event *bp)
|
{
|
}
|
|
/*
|
* Function to perform processor-specific cleanup during unregistration
|
*/
|
__weak void arch_unregister_hw_breakpoint(struct perf_event *bp)
|
{
|
/*
|
* A weak stub function here for those archs that don't define
|
* it inside arch/.../kernel/hw_breakpoint.c
|
*/
|
}
|
|
/*
|
* Constraints 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(info->flexible, cpu) || (per_cpu(info->cpu_pinned, cpu)
|
* + max(per_cpu(info->tsk_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(info->flexible, *) || (max(per_cpu(info->cpu_pinned, *))
|
* + max(per_cpu(info->tsk_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(info->flexible, cpu) > 1) + per_cpu(info->cpu_pinned, cpu)
|
* + max(per_cpu(info->tsk_pinned, cpu))) < HBP_NUM
|
*
|
* -> Same checks as before. But now the info->flexible, if any, must keep
|
* one register at least (or they will never be fed).
|
*
|
* - If attached to every cpus, check:
|
*
|
* ((per_cpu(info->flexible, *) > 1) + max(per_cpu(info->cpu_pinned, *))
|
* + max(per_cpu(info->tsk_pinned, *))) < HBP_NUM
|
*/
|
static int __reserve_bp_slot(struct perf_event *bp, u64 bp_type)
|
{
|
struct bp_busy_slots slots = {0};
|
enum bp_type_idx type;
|
int weight;
|
int ret;
|
|
/* We couldn't initialize breakpoint constraints on boot */
|
if (!constraints_initialized)
|
return -ENOMEM;
|
|
/* Basic checks */
|
if (bp_type == HW_BREAKPOINT_EMPTY ||
|
bp_type == HW_BREAKPOINT_INVALID)
|
return -EINVAL;
|
|
type = find_slot_idx(bp_type);
|
weight = hw_breakpoint_weight(bp);
|
|
fetch_bp_busy_slots(&slots, bp, type);
|
/*
|
* Simulate the addition of this breakpoint to the constraints
|
* and see the result.
|
*/
|
fetch_this_slot(&slots, weight);
|
|
/* Flexible counters need to keep at least one slot */
|
if (slots.pinned + (!!slots.flexible) > nr_slots[type])
|
return -ENOSPC;
|
|
ret = arch_reserve_bp_slot(bp);
|
if (ret)
|
return ret;
|
|
toggle_bp_slot(bp, true, type, weight);
|
|
return 0;
|
}
|
|
int reserve_bp_slot(struct perf_event *bp)
|
{
|
int ret;
|
|
mutex_lock(&nr_bp_mutex);
|
|
ret = __reserve_bp_slot(bp, bp->attr.bp_type);
|
|
mutex_unlock(&nr_bp_mutex);
|
|
return ret;
|
}
|
|
static void __release_bp_slot(struct perf_event *bp, u64 bp_type)
|
{
|
enum bp_type_idx type;
|
int weight;
|
|
arch_release_bp_slot(bp);
|
|
type = find_slot_idx(bp_type);
|
weight = hw_breakpoint_weight(bp);
|
toggle_bp_slot(bp, false, type, weight);
|
}
|
|
void release_bp_slot(struct perf_event *bp)
|
{
|
mutex_lock(&nr_bp_mutex);
|
|
arch_unregister_hw_breakpoint(bp);
|
__release_bp_slot(bp, bp->attr.bp_type);
|
|
mutex_unlock(&nr_bp_mutex);
|
}
|
|
static int __modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type)
|
{
|
int err;
|
|
__release_bp_slot(bp, old_type);
|
|
err = __reserve_bp_slot(bp, new_type);
|
if (err) {
|
/*
|
* Reserve the old_type slot back in case
|
* there's no space for the new type.
|
*
|
* This must succeed, because we just released
|
* the old_type slot in the __release_bp_slot
|
* call above. If not, something is broken.
|
*/
|
WARN_ON(__reserve_bp_slot(bp, old_type));
|
}
|
|
return err;
|
}
|
|
static int modify_bp_slot(struct perf_event *bp, u64 old_type, u64 new_type)
|
{
|
int ret;
|
|
mutex_lock(&nr_bp_mutex);
|
ret = __modify_bp_slot(bp, old_type, new_type);
|
mutex_unlock(&nr_bp_mutex);
|
return ret;
|
}
|
|
/*
|
* Allow the kernel debugger to reserve breakpoint slots without
|
* taking a lock using the dbg_* variant of for the reserve and
|
* release breakpoint slots.
|
*/
|
int dbg_reserve_bp_slot(struct perf_event *bp)
|
{
|
if (mutex_is_locked(&nr_bp_mutex))
|
return -1;
|
|
return __reserve_bp_slot(bp, bp->attr.bp_type);
|
}
|
|
int dbg_release_bp_slot(struct perf_event *bp)
|
{
|
if (mutex_is_locked(&nr_bp_mutex))
|
return -1;
|
|
__release_bp_slot(bp, bp->attr.bp_type);
|
|
return 0;
|
}
|
|
static int hw_breakpoint_parse(struct perf_event *bp,
|
const struct perf_event_attr *attr,
|
struct arch_hw_breakpoint *hw)
|
{
|
int err;
|
|
err = hw_breakpoint_arch_parse(bp, attr, hw);
|
if (err)
|
return err;
|
|
if (arch_check_bp_in_kernelspace(hw)) {
|
if (attr->exclude_kernel)
|
return -EINVAL;
|
/*
|
* Don't let unprivileged users set a breakpoint in the trap
|
* path to avoid trap recursion attacks.
|
*/
|
if (!capable(CAP_SYS_ADMIN))
|
return -EPERM;
|
}
|
|
return 0;
|
}
|
|
int register_perf_hw_breakpoint(struct perf_event *bp)
|
{
|
struct arch_hw_breakpoint hw = { };
|
int err;
|
|
err = reserve_bp_slot(bp);
|
if (err)
|
return err;
|
|
err = hw_breakpoint_parse(bp, &bp->attr, &hw);
|
if (err) {
|
release_bp_slot(bp);
|
return err;
|
}
|
|
bp->hw.info = hw;
|
|
return 0;
|
}
|
|
/**
|
* register_user_hw_breakpoint - register a hardware breakpoint for user space
|
* @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
|
*/
|
struct perf_event *
|
register_user_hw_breakpoint(struct perf_event_attr *attr,
|
perf_overflow_handler_t triggered,
|
void *context,
|
struct task_struct *tsk)
|
{
|
return perf_event_create_kernel_counter(attr, -1, tsk, triggered,
|
context);
|
}
|
EXPORT_SYMBOL_GPL(register_user_hw_breakpoint);
|
|
static void hw_breakpoint_copy_attr(struct perf_event_attr *to,
|
struct perf_event_attr *from)
|
{
|
to->bp_addr = from->bp_addr;
|
to->bp_type = from->bp_type;
|
to->bp_len = from->bp_len;
|
to->disabled = from->disabled;
|
}
|
|
int
|
modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *attr,
|
bool check)
|
{
|
struct arch_hw_breakpoint hw = { };
|
int err;
|
|
err = hw_breakpoint_parse(bp, attr, &hw);
|
if (err)
|
return err;
|
|
if (check) {
|
struct perf_event_attr old_attr;
|
|
old_attr = bp->attr;
|
hw_breakpoint_copy_attr(&old_attr, attr);
|
if (memcmp(&old_attr, attr, sizeof(*attr)))
|
return -EINVAL;
|
}
|
|
if (bp->attr.bp_type != attr->bp_type) {
|
err = modify_bp_slot(bp, bp->attr.bp_type, attr->bp_type);
|
if (err)
|
return err;
|
}
|
|
hw_breakpoint_copy_attr(&bp->attr, attr);
|
bp->hw.info = hw;
|
|
return 0;
|
}
|
|
/**
|
* modify_user_hw_breakpoint - modify a user-space hardware breakpoint
|
* @bp: the breakpoint structure to modify
|
* @attr: new breakpoint attributes
|
*/
|
int modify_user_hw_breakpoint(struct perf_event *bp, struct perf_event_attr *attr)
|
{
|
int err;
|
|
/*
|
* modify_user_hw_breakpoint can be invoked with IRQs disabled and hence it
|
* will not be possible to raise IPIs that invoke __perf_event_disable.
|
* So call the function directly after making sure we are targeting the
|
* current task.
|
*/
|
if (irqs_disabled() && bp->ctx && bp->ctx->task == current)
|
perf_event_disable_local(bp);
|
else
|
perf_event_disable(bp);
|
|
err = modify_user_hw_breakpoint_check(bp, attr, false);
|
|
if (!bp->attr.disabled)
|
perf_event_enable(bp);
|
|
return err;
|
}
|
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);
|
|
/**
|
* register_wide_hw_breakpoint - register a wide breakpoint in the kernel
|
* @attr: breakpoint attributes
|
* @triggered: callback to trigger when we hit the breakpoint
|
*
|
* @return a set of per_cpu pointers to perf events
|
*/
|
struct perf_event * __percpu *
|
register_wide_hw_breakpoint(struct perf_event_attr *attr,
|
perf_overflow_handler_t triggered,
|
void *context)
|
{
|
struct perf_event * __percpu *cpu_events, *bp;
|
long err = 0;
|
int cpu;
|
|
cpu_events = alloc_percpu(typeof(*cpu_events));
|
if (!cpu_events)
|
return (void __percpu __force *)ERR_PTR(-ENOMEM);
|
|
get_online_cpus();
|
for_each_online_cpu(cpu) {
|
bp = perf_event_create_kernel_counter(attr, cpu, NULL,
|
triggered, context);
|
if (IS_ERR(bp)) {
|
err = PTR_ERR(bp);
|
break;
|
}
|
|
per_cpu(*cpu_events, cpu) = bp;
|
}
|
put_online_cpus();
|
|
if (likely(!err))
|
return cpu_events;
|
|
unregister_wide_hw_breakpoint(cpu_events);
|
return (void __percpu __force *)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 * __percpu *cpu_events)
|
{
|
int cpu;
|
|
for_each_possible_cpu(cpu)
|
unregister_hw_breakpoint(per_cpu(*cpu_events, cpu));
|
|
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 void bp_perf_event_destroy(struct perf_event *event)
|
{
|
release_bp_slot(event);
|
}
|
|
static int hw_breakpoint_event_init(struct perf_event *bp)
|
{
|
int err;
|
|
if (bp->attr.type != PERF_TYPE_BREAKPOINT)
|
return -ENOENT;
|
|
/*
|
* no branch sampling for breakpoint events
|
*/
|
if (has_branch_stack(bp))
|
return -EOPNOTSUPP;
|
|
err = register_perf_hw_breakpoint(bp);
|
if (err)
|
return err;
|
|
bp->destroy = bp_perf_event_destroy;
|
|
return 0;
|
}
|
|
static int hw_breakpoint_add(struct perf_event *bp, int flags)
|
{
|
if (!(flags & PERF_EF_START))
|
bp->hw.state = PERF_HES_STOPPED;
|
|
if (is_sampling_event(bp)) {
|
bp->hw.last_period = bp->hw.sample_period;
|
perf_swevent_set_period(bp);
|
}
|
|
return arch_install_hw_breakpoint(bp);
|
}
|
|
static void hw_breakpoint_del(struct perf_event *bp, int flags)
|
{
|
arch_uninstall_hw_breakpoint(bp);
|
}
|
|
static void hw_breakpoint_start(struct perf_event *bp, int flags)
|
{
|
bp->hw.state = 0;
|
}
|
|
static void hw_breakpoint_stop(struct perf_event *bp, int flags)
|
{
|
bp->hw.state = PERF_HES_STOPPED;
|
}
|
|
static struct pmu perf_breakpoint = {
|
.task_ctx_nr = perf_sw_context, /* could eventually get its own */
|
|
.event_init = hw_breakpoint_event_init,
|
.add = hw_breakpoint_add,
|
.del = hw_breakpoint_del,
|
.start = hw_breakpoint_start,
|
.stop = hw_breakpoint_stop,
|
.read = hw_breakpoint_pmu_read,
|
};
|
|
int __init init_hw_breakpoint(void)
|
{
|
int cpu, err_cpu;
|
int i;
|
|
for (i = 0; i < TYPE_MAX; i++)
|
nr_slots[i] = hw_breakpoint_slots(i);
|
|
for_each_possible_cpu(cpu) {
|
for (i = 0; i < TYPE_MAX; i++) {
|
struct bp_cpuinfo *info = get_bp_info(cpu, i);
|
|
info->tsk_pinned = kcalloc(nr_slots[i], sizeof(int),
|
GFP_KERNEL);
|
if (!info->tsk_pinned)
|
goto err_alloc;
|
}
|
}
|
|
constraints_initialized = 1;
|
|
perf_pmu_register(&perf_breakpoint, "breakpoint", PERF_TYPE_BREAKPOINT);
|
|
return register_die_notifier(&hw_breakpoint_exceptions_nb);
|
|
err_alloc:
|
for_each_possible_cpu(err_cpu) {
|
for (i = 0; i < TYPE_MAX; i++)
|
kfree(get_bp_info(err_cpu, i)->tsk_pinned);
|
if (err_cpu == cpu)
|
break;
|
}
|
|
return -ENOMEM;
|
}
|
