diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index fd1d91017b99b..b144da7d80394 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1719,8 +1719,8 @@ DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry); extern void perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs); extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs); extern struct perf_callchain_entry * -get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, - u32 max_stack, bool crosstask, bool add_mark); +get_perf_callchain(struct pt_regs *regs, struct perf_callchain_entry *external_entry, + bool kernel, bool user, u32 max_stack, bool crosstask, bool add_mark); extern int get_callchain_buffers(int max_stack); extern void put_callchain_buffers(void); extern struct perf_callchain_entry *get_callchain_entry(int *rctx); diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 4d53cdd1374cf..3513077c57d5a 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -31,6 +31,52 @@ struct bpf_stack_map { struct stack_map_bucket *buckets[] __counted_by(n_buckets); }; +struct bpf_perf_callchain_entry { + u64 nr; + u64 ip[PERF_MAX_STACK_DEPTH]; +}; + +#define MAX_PERF_CALLCHAIN_PREEMPT 3 +static DEFINE_PER_CPU(struct bpf_perf_callchain_entry[MAX_PERF_CALLCHAIN_PREEMPT], + bpf_perf_callchain_entries); +static DEFINE_PER_CPU(int, bpf_perf_callchain_preempt_cnt); + +static int bpf_get_perf_callchain_or_entry(struct perf_callchain_entry **entry, + struct pt_regs *regs, bool kernel, + bool user, u32 max_stack, bool crosstack, + bool add_mark, bool get_callchain) +{ + struct bpf_perf_callchain_entry *bpf_entry; + struct perf_callchain_entry *perf_entry; + int preempt_cnt; + + preempt_cnt = this_cpu_inc_return(bpf_perf_callchain_preempt_cnt); + if (WARN_ON_ONCE(preempt_cnt > MAX_PERF_CALLCHAIN_PREEMPT)) { + this_cpu_dec(bpf_perf_callchain_preempt_cnt); + return -EBUSY; + } + + bpf_entry = this_cpu_ptr(&bpf_perf_callchain_entries[preempt_cnt - 1]); + if (!get_callchain) { + *entry = (struct perf_callchain_entry *)bpf_entry; + return 0; + } + + perf_entry = get_perf_callchain(regs, (struct perf_callchain_entry *)bpf_entry, + kernel, user, max_stack, + crosstack, add_mark); + *entry = perf_entry; + + return 0; +} + +static void bpf_put_perf_callchain(void) +{ + if (WARN_ON_ONCE(this_cpu_read(bpf_perf_callchain_preempt_cnt) == 0)) + return; + this_cpu_dec(bpf_perf_callchain_preempt_cnt); +} + static inline bool stack_map_use_build_id(struct bpf_map *map) { return (map->map_flags & BPF_F_STACK_BUILD_ID); @@ -192,11 +238,11 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth) { #ifdef CONFIG_STACKTRACE struct perf_callchain_entry *entry; - int rctx; - - entry = get_callchain_entry(&rctx); + int ret; - if (!entry) + ret = bpf_get_perf_callchain_or_entry(&entry, NULL, false, false, 0, false, false, + false); + if (ret) return NULL; entry->nr = stack_trace_save_tsk(task, (unsigned long *)entry->ip, @@ -216,7 +262,7 @@ get_callchain_entry_for_task(struct task_struct *task, u32 max_depth) to[i] = (u64)(from[i]); } - put_callchain_entry(rctx); + bpf_put_perf_callchain(); return entry; #else /* CONFIG_STACKTRACE */ @@ -305,6 +351,7 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, bool user = flags & BPF_F_USER_STACK; struct perf_callchain_entry *trace; bool kernel = !user; + int err; if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) @@ -314,14 +361,15 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, if (max_depth > sysctl_perf_event_max_stack) max_depth = sysctl_perf_event_max_stack; - trace = get_perf_callchain(regs, kernel, user, max_depth, - false, false); + err = bpf_get_perf_callchain_or_entry(&trace, regs, kernel, user, max_depth, + false, false, true); + if (err) + return err; - if (unlikely(!trace)) - /* couldn't fetch the stack trace */ - return -EFAULT; + err = __bpf_get_stackid(map, trace, flags); + bpf_put_perf_callchain(); - return __bpf_get_stackid(map, trace, flags); + return err; } const struct bpf_func_proto bpf_get_stackid_proto = { @@ -443,20 +491,23 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, if (sysctl_perf_event_max_stack < max_depth) max_depth = sysctl_perf_event_max_stack; - if (may_fault) - rcu_read_lock(); /* need RCU for perf's callchain below */ - if (trace_in) trace = trace_in; - else if (kernel && task) + else if (kernel && task) { trace = get_callchain_entry_for_task(task, max_depth); - else - trace = get_perf_callchain(regs, kernel, user, max_depth, - crosstask, false); + } else { + err = bpf_get_perf_callchain_or_entry(&trace, regs, kernel, user, max_depth, + false, false, true); + if (err) + return err; + } + + if (unlikely(!trace)) + goto err_fault; - if (unlikely(!trace) || trace->nr < skip) { - if (may_fault) - rcu_read_unlock(); + if (trace->nr < skip) { + if (!trace_in) + bpf_put_perf_callchain(); goto err_fault; } @@ -475,9 +526,8 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, memcpy(buf, ips, copy_len); } - /* trace/ips should not be dereferenced after this point */ - if (may_fault) - rcu_read_unlock(); + if (!trace_in) + bpf_put_perf_callchain(); if (user_build_id) stack_map_get_build_id_offset(buf, trace_nr, user, may_fault); diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index 808c0d7a31faf..851e8f9d026f5 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -217,8 +217,8 @@ static void fixup_uretprobe_trampoline_entries(struct perf_callchain_entry *entr } struct perf_callchain_entry * -get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, - u32 max_stack, bool crosstask, bool add_mark) +get_perf_callchain(struct pt_regs *regs, struct perf_callchain_entry *external_entry, + bool kernel, bool user, u32 max_stack, bool crosstask, bool add_mark) { struct perf_callchain_entry *entry; struct perf_callchain_entry_ctx ctx; @@ -228,7 +228,11 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, if (crosstask && user && !kernel) return NULL; - entry = get_callchain_entry(&rctx); + if (external_entry) + entry = external_entry; + else + entry = get_callchain_entry(&rctx); + if (!entry) return NULL; @@ -260,7 +264,8 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, } exit_put: - put_callchain_entry(rctx); + if (!external_entry) + put_callchain_entry(rctx); return entry; } diff --git a/kernel/events/core.c b/kernel/events/core.c index 7541f6f85fcb0..5d8e146003ac3 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8217,7 +8217,7 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs) if (!kernel && !user) return &__empty_callchain; - callchain = get_perf_callchain(regs, kernel, user, + callchain = get_perf_callchain(regs, NULL, kernel, user, max_stack, crosstask, true); return callchain ?: &__empty_callchain; }