tracing: Keep track of set_ftrace_filter position and allow lseek again
This patch keeps track of the index within the elements of
set_ftrace_filter and if the position goes backwards, it nicely
resets and starts from the beginning again.
This allows for lseek and pread to work properly now.
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
index c8db0db..2d51166 100644
--- a/kernel/trace/ftrace.c
+++ b/kernel/trace/ftrace.c
@@ -1368,6 +1368,7 @@
#define FTRACE_BUFF_MAX (KSYM_SYMBOL_LEN+4) /* room for wildcards */
struct ftrace_iterator {
+ loff_t pos;
loff_t func_pos;
struct ftrace_page *pg;
struct dyn_ftrace *func;
@@ -1385,9 +1386,8 @@
struct hlist_node *hnd = NULL;
struct hlist_head *hhd;
- WARN_ON(!(iter->flags & FTRACE_ITER_HASH));
-
(*pos)++;
+ iter->pos = *pos;
if (iter->probe)
hnd = &iter->probe->node;
@@ -1427,14 +1427,9 @@
void *p = NULL;
loff_t l;
- if (!(iter->flags & FTRACE_ITER_HASH))
- iter->func_pos = *pos;
-
if (iter->func_pos > *pos)
return NULL;
- iter->flags |= FTRACE_ITER_HASH;
-
iter->hidx = 0;
for (l = 0; l <= (*pos - iter->func_pos); ) {
p = t_hash_next(m, &l);
@@ -1444,6 +1439,9 @@
if (!p)
return NULL;
+ /* Only set this if we have an item */
+ iter->flags |= FTRACE_ITER_HASH;
+
return iter;
}
@@ -1478,6 +1476,8 @@
return t_hash_next(m, pos);
(*pos)++;
+ iter->pos = *pos;
+ iter->func_pos = *pos;
if (iter->flags & FTRACE_ITER_PRINTALL)
return NULL;
@@ -1517,6 +1517,13 @@
return iter;
}
+static void reset_iter_read(struct ftrace_iterator *iter)
+{
+ iter->pos = 0;
+ iter->func_pos = 0;
+ iter->flags &= ~(FTRACE_ITER_PRINTALL & FTRACE_ITER_HASH);
+}
+
static void *t_start(struct seq_file *m, loff_t *pos)
{
struct ftrace_iterator *iter = m->private;
@@ -1525,6 +1532,12 @@
mutex_lock(&ftrace_lock);
/*
+ * If an lseek was done, then reset and start from beginning.
+ */
+ if (*pos < iter->pos)
+ reset_iter_read(iter);
+
+ /*
* For set_ftrace_filter reading, if we have the filter
* off, we can short cut and just print out that all
* functions are enabled.
@@ -1541,6 +1554,11 @@
if (iter->flags & FTRACE_ITER_HASH)
return t_hash_start(m, pos);
+ /*
+ * Unfortunately, we need to restart at ftrace_pages_start
+ * every time we let go of the ftrace_mutex. This is because
+ * those pointers can change without the lock.
+ */
iter->pg = ftrace_pages_start;
iter->idx = 0;
for (l = 0; l <= *pos; ) {
@@ -2447,7 +2465,7 @@
.open = ftrace_filter_open,
.read = seq_read,
.write = ftrace_filter_write,
- .llseek = no_llseek,
+ .llseek = ftrace_regex_lseek,
.release = ftrace_filter_release,
};
