When enabled, dump_on_panic will dump the content of the trace remote buffer if the system panics.
Signed-off-by: Vincent Donnefort <[email protected]> diff --git a/kernel/trace/trace_remote.c b/kernel/trace/trace_remote.c index b0404ad8981d..cf99752e1cd5 100644 --- a/kernel/trace/trace_remote.c +++ b/kernel/trace/trace_remote.c @@ -7,6 +7,7 @@ #include <linux/kstrtox.h> #include <linux/lockdep.h> #include <linux/mutex.h> +#include <linux/panic_notifier.h> #include <linux/tracefs.h> #include <linux/trace_remote.h> #include <linux/trace_seq.h> @@ -22,6 +23,7 @@ enum tri_type { TRI_CONSUMING, TRI_NONCONSUMING, TRI_DMESG, + TRI_PANIC, }; struct trace_remote_iterator { @@ -60,6 +62,9 @@ struct trace_remote { struct delayed_work poll_work; unsigned int poll_cnt; bool tracing_on; + bool panic_on; + struct notifier_block panic_notifier; + struct trace_remote_iterator *panic_iter; }; static DEFINE_MUTEX(trace_remotes_lock); @@ -71,10 +76,15 @@ static bool trace_remote_loaded(struct trace_remote *remote) return !!remote->trace_buffer; } +static void trace_remote_unload(struct trace_remote *remote); +static int trace_remote_panic_load(struct trace_remote *remote); +static void trace_remote_panic_unload(struct trace_remote *remote); + static int trace_remote_load(struct trace_remote *remote) { struct ring_buffer_remote *rb_remote = &remote->rb_remote; struct trace_buffer_desc *desc; + int ret = 0; lockdep_assert_held(&remote->lock); @@ -89,15 +99,28 @@ static int trace_remote_load(struct trace_remote *remote) rb_remote->swap_reader_page = remote->cbs->swap_reader_page; rb_remote->priv = remote->priv; rb_remote->reset = remote->cbs->reset; + remote->trace_buffer_desc = desc; remote->trace_buffer = ring_buffer_alloc_remote(rb_remote); if (!remote->trace_buffer) { remote->cbs->unload_trace_buffer(desc, remote->priv); return -ENOMEM; } - remote->trace_buffer_desc = desc; + if (remote->panic_on) { + ret = trace_remote_panic_load(remote); + if (ret) + trace_remote_unload(remote); + } - return 0; + return ret; +} + +static void trace_remote_unload(struct trace_remote *remote) +{ + trace_remote_panic_unload(remote); + ring_buffer_free(remote->trace_buffer); + remote->trace_buffer = NULL; + remote->cbs->unload_trace_buffer(remote->trace_buffer_desc, remote->priv); } static void trace_remote_try_unload(struct trace_remote *remote) @@ -115,9 +138,7 @@ static void trace_remote_try_unload(struct trace_remote *remote) if (!ring_buffer_empty(remote->trace_buffer)) return; - ring_buffer_free(remote->trace_buffer); - remote->trace_buffer = NULL; - remote->cbs->unload_trace_buffer(remote->trace_buffer_desc, remote->priv); + trace_remote_unload(remote); } static int trace_remote_enable_tracing(struct trace_remote *remote) @@ -434,58 +455,68 @@ static void trace_remote_dec_poll(struct trace_remote *remote) static struct trace_remote_iterator *trace_remote_iter(struct trace_remote *remote, int cpu, enum tri_type type) { - struct trace_remote_iterator *iter = NULL; + struct trace_remote_iterator *iter __free(kfree) = kzalloc_obj(*iter); int ret; lockdep_assert_held(&remote->lock); - if (type == TRI_NONCONSUMING && !trace_remote_loaded(remote)) - return NULL; + if (!iter) + return ERR_PTR(-ENOMEM); - ret = trace_remote_get(remote, cpu); - if (ret) - return ERR_PTR(ret); + switch (type) { + case TRI_NONCONSUMING: + if (!trace_remote_loaded(remote)) + return NULL; + fallthrough; + case TRI_CONSUMING: + case TRI_DMESG: + ret = trace_remote_get(remote, cpu); + if (ret) + return ERR_PTR(ret); + break; + case TRI_PANIC: + break; + } if (!trace_remote_has_cpu(remote, cpu)) { ret = -ENODEV; goto err; } - iter = kzalloc_obj(*iter); - if (iter) { - iter->remote = remote; - iter->cpu = cpu; - iter->type = type; - trace_seq_init(&iter->seq); + iter->remote = remote; + iter->cpu = cpu; + iter->type = type; + trace_seq_init(&iter->seq); - switch (type) { - case TRI_DMESG: - /* only one printk iter allowed */ - if (WARN_ON_ONCE(remote->dmesg)) { - ret = -EBUSY; - break; - } - smp_store_release(&remote->dmesg, iter); - fallthrough; - case TRI_CONSUMING: - trace_remote_inc_poll(remote); - break; - case TRI_NONCONSUMING: - ret = __alloc_ring_buffer_iter(iter, cpu); - break; + switch (type) { + case TRI_DMESG: + /* only one dmesg iter allowed */ + if (WARN_ON_ONCE(remote->dmesg)) { + ret = -EBUSY; + goto err; } - + smp_store_release(&remote->dmesg, iter); + fallthrough; + case TRI_CONSUMING: + trace_remote_inc_poll(remote); + break; + case TRI_PANIC: + case TRI_NONCONSUMING: + ret = __alloc_ring_buffer_iter(iter, cpu); if (ret) goto err; - - return iter; + break; } - ret = -ENOMEM; -err: - kfree(iter); - trace_remote_put(remote); + return no_free_ptr(iter); +err: + switch (type) { + case TRI_PANIC: + break; + default: + trace_remote_put(remote); + } return ERR_PTR(ret); } @@ -508,14 +539,18 @@ static void trace_remote_iter_free(struct trace_remote_iterator *iter) fallthrough; case TRI_CONSUMING: trace_remote_dec_poll(remote); + trace_remote_put(remote); break; case TRI_NONCONSUMING: + trace_remote_put(remote); + __free_ring_buffer_iter(iter, iter->cpu); + break; + case TRI_PANIC: __free_ring_buffer_iter(iter, iter->cpu); break; } kfree(iter); - trace_remote_put(remote); } static bool trace_remote_iter_is_consuming(struct trace_remote_iterator *iter) @@ -988,6 +1023,116 @@ static int dmesg_show(struct seq_file *s, void *unused) } DEFINE_TRACE_REMOTE_ATTRIBUTE(dmesg); +static int trace_remote_panic_handler(struct notifier_block *self, unsigned long ev, void *v) +{ + struct trace_remote *remote = container_of(self, struct trace_remote, panic_notifier); + struct trace_remote_iterator *iter = smp_load_acquire(&remote->panic_iter); + int cpu; + + if (!iter) { + pr_warn("Unexpected error: no panic iterator for the trace remote\n"); + return NOTIFY_DONE; + } + + for_each_possible_cpu(cpu) { + if (iter->rb_iters[cpu]) { + /* No RING_BUFFER_ALL_CPUS to avoid taking cpu_read_lock() */ + ring_buffer_read_remote_meta_page(remote->trace_buffer, cpu); + ring_buffer_iter_reset(iter->rb_iters[cpu]); + } + } + + while (trace_remote_iter_read_event(iter)) { + trace_seq_init(&iter->seq); + + trace_remote_iter_print_event(iter); + pr_emerg("%s", iter->seq.buffer); + + trace_remote_iter_move(iter); + } + + return NOTIFY_DONE; +} + +static int trace_remote_panic_load(struct trace_remote *remote) +{ + struct notifier_block *notifier = &remote->panic_notifier; + struct trace_remote_iterator *iter; + + lockdep_assert_held(&remote->lock); + + if (remote->panic_iter) + return 0; + + iter = trace_remote_iter(remote, RING_BUFFER_ALL_CPUS, TRI_PANIC); + if (IS_ERR(iter)) + return PTR_ERR(iter); + + smp_store_release(&remote->panic_iter, iter); + + notifier->notifier_call = trace_remote_panic_handler; + notifier->priority = INT_MAX - 1; + atomic_notifier_chain_register(&panic_notifier_list, notifier); + + return 0; +} + +static void trace_remote_panic_unload(struct trace_remote *remote) +{ + struct trace_remote_iterator *iter = remote->panic_iter; + + lockdep_assert_held(&remote->lock); + + if (!iter) + return; + + atomic_notifier_chain_unregister(&panic_notifier_list, &remote->panic_notifier); + smp_store_release(&remote->panic_iter, NULL); + trace_remote_iter_free(iter); +} + +static ssize_t dump_on_panic_write(struct file *filp, const char __user *ubuf, + size_t cnt, loff_t *ppos) +{ + struct seq_file *seq = filp->private_data; + struct trace_remote *remote = seq->private; + bool enable; + int ret; + + ret = kstrtobool_from_user(ubuf, cnt, &enable); + if (ret) + return ret; + + guard(mutex)(&remote->lock); + + if (enable == remote->panic_on) + return cnt; + + if (trace_remote_loaded(remote)) { + if (enable) { + ret = trace_remote_panic_load(remote); + if (ret) + return ret; + } else { + trace_remote_panic_unload(remote); + } + } + + remote->panic_on = enable; + + return cnt; +} + +static int dump_on_panic_show(struct seq_file *s, void *unused) +{ + struct trace_remote *remote = s->private; + + seq_printf(s, "%d\n", remote->panic_on); + + return 0; +} +DEFINE_TRACE_REMOTE_ATTRIBUTE(dump_on_panic); + static int trace_remote_init_tracefs(const char *name, struct trace_remote *remote) { struct dentry *remote_d, *percpu_d, *d; @@ -1015,6 +1160,11 @@ static int trace_remote_init_tracefs(const char *name, struct trace_remote *remo if (!d) goto err; + d = trace_create_file("dump_on_panic", TRACEFS_MODE_WRITE, remote_d, remote, + &dump_on_panic_fops); + if (!d) + goto err; + d = trace_create_file("buffer_size_kb", TRACEFS_MODE_WRITE, remote_d, remote, &buffer_size_kb_fops); if (!d) -- 2.54.0.1032.g2f8565e1d1-goog
