1 files changed, 40 insertions, 13 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index dade4c9559cc..37824d98ae71 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4123,6 +4123,30 @@ static const char readme_msg[] =
 	"\t\t\t  traces\n"
 #endif
 #endif /* CONFIG_STACK_TRACER */
+#ifdef CONFIG_KPROBE_EVENT
+	"  kprobe_events\t\t- Add/remove/show the kernel dynamic events\n"
+	"\t\t\t  Write into this file to define/undefine new trace events.\n"
+#endif
+#ifdef CONFIG_UPROBE_EVENT
+	"  uprobe_events\t\t- Add/remove/show the userspace dynamic events\n"
+	"\t\t\t  Write into this file to define/undefine new trace events.\n"
+#endif
+#if defined(CONFIG_KPROBE_EVENT) || defined(CONFIG_UPROBE_EVENT)
+	"\t  accepts: event-definitions (one definition per line)\n"
+	"\t   Format: p|r[:[<group>/]<event>] <place> [<args>]\n"
+	"\t           -:[<group>/]<event>\n"
+#ifdef CONFIG_KPROBE_EVENT
+	"\t    place: [<module>:]<symbol>[+<offset>]|<memaddr>\n"
+#endif
+#ifdef CONFIG_UPROBE_EVENT
+	"\t    place: <path>:<offset>\n"
+#endif
+	"\t     args: <name>=fetcharg[:type]\n"
+	"\t fetcharg: %<register>, @<address>, @<symbol>[+|-<offset>],\n"
+	"\t           $stack<index>, $stack, $retval, $comm\n"
+	"\t     type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string,\n"
+	"\t           b<bit-width>@<bit-offset>/<container-size>\n"
+#endif
 	"  events/\t\t- Directory containing all trace event subsystems:\n"
 	"      enable\t\t- Write 0/1 to enable/disable tracing of all events\n"
 	"  events/<system>/\t- Directory containing all trace events for <system>:\n"
@@ -5124,19 +5148,20 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
 	struct trace_iterator *iter = filp->private_data;
 	ssize_t sret;
 
-	/* return any leftover data */
-	sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
-	if (sret != -EBUSY)
-		return sret;
-
-	trace_seq_init(&iter->seq);
-
 	/*
 	 * Avoid more than one consumer on a single file descriptor
 	 * This is just a matter of traces coherency, the ring buffer itself
 	 * is protected.
 	 */
 	mutex_lock(&iter->mutex);
+
+	/* return any leftover data */
+	sret = trace_seq_to_user(&iter->seq, ubuf, cnt);
+	if (sret != -EBUSY)
+		goto out;
+
+	trace_seq_init(&iter->seq);
+
 	if (iter->trace->read) {
 		sret = iter->trace->read(iter, filp, ubuf, cnt, ppos);
 		if (sret)
@@ -6163,9 +6188,6 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 		return -EBUSY;
 #endif
 
-	if (splice_grow_spd(pipe, &spd))
-		return -ENOMEM;
-
 	if (*ppos & (PAGE_SIZE - 1))
 		return -EINVAL;
 
@@ -6175,6 +6197,9 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 		len &= PAGE_MASK;
 	}
 
+	if (splice_grow_spd(pipe, &spd))
+		return -ENOMEM;
+
  again:
 	trace_access_lock(iter->cpu_file);
 	entries = ring_buffer_entries_cpu(iter->trace_buffer->buffer, iter->cpu_file);
@@ -6232,19 +6257,21 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
 	/* did we read anything? */
 	if (!spd.nr_pages) {
 		if (ret)
-			return ret;
+			goto out;
 
+		ret = -EAGAIN;
 		if ((file->f_flags & O_NONBLOCK) || (flags & SPLICE_F_NONBLOCK))
-			return -EAGAIN;
+			goto out;
 
 		ret = wait_on_pipe(iter, true);
 		if (ret)
-			return ret;
+			goto out;
 
 		goto again;
 	}
 
 	ret = splice_to_pipe(pipe, &spd);
+out:
 	splice_shrink_spd(&spd);
 
 	return ret;