| // 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); |
| } |
| |
| /* |
| * 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; |
| |
| /* 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; |
| |
| 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; |
| |
| 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; |
| } |
| |
| |