// 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 * @context: context data could be used in the triggered callback * @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 * @context: context data could be used in the triggered callback * * @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); cpus_read_lock(); 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; } cpus_read_unlock(); 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; }