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tracing: Do not (ab)use trace_seq in event_id_read()

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event_id_read() has no reason to kmalloc "struct trace_seq"
(more than PAGE_SIZE!), it can use a small buffer instead.

Note: "if (*ppos) return 0" looks strange and even wrong,
simple_read_from_buffer() handles ppos != 0 case corrrectly.

And it seems that almost every user of trace_seq in this file
should be converted too. Unless you use seq_open(), trace_seq
buys nothing compared to the raw buffer, but it needs a bit
more memory and code.

Link: http://lkml.kernel.org/r/20130718184712.GA4786@redhat.com

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Oleg Nesterov 2013-07-18 20:47:12 +02:00 committed by Steven Rostedt
parent 7710b63995
commit cd458ba9d5
1 changed files with 4 additions and 13 deletions
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17
kernel/trace/trace_events.c
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@ -947,23 +947,14 @@ static ssize_t
event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos) event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
{ {
struct ftrace_event_call *call = filp->private_data; struct ftrace_event_call *call = filp->private_data;
struct trace_seq *s; char buf[32];
int r; int len;
if (*ppos) if (*ppos)
return 0; return 0;
s = kmalloc(sizeof(*s), GFP_KERNEL); len = sprintf(buf, "%d\n", call->event.type);
if (!s) return simple_read_from_buffer(ubuf, cnt, ppos, buf, len);
return -ENOMEM;
trace_seq_init(s);
trace_seq_printf(s, "%d\n", call->event.type);
r = simple_read_from_buffer(ubuf, cnt, ppos,
s->buffer, s->len);
kfree(s);
return r;
} }
static ssize_t static ssize_t