[PATCH 2/8] ksym_tracer: Rewrite ksym_trace_filter_read()

Li Zefan
2009-07-07T05:52:56Z

Reading ksym_trace_filter gave me some arbitrary characters,
when it should show nothing. It's because buf is not initialized
when there's no filter.

Also reduce stack usage by about 512 bytes.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
kernel/trace/trace_ksym.c | 29 ++++++++++++++++++-----------
1 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/kernel/trace/trace_ksym.c b/kernel/trace/trace_ksym.c
index 085ff05..b6710d3 100644
--- a/kernel/trace/trace_ksym.c
+++ b/kernel/trace/trace_ksym.c
@@ -35,7 +35,6 @@
#define KSYM_TRACER_MAX HBP_NUM

#define KSYM_TRACER_OP_LEN 3 /* rw- */
-#define KSYM_FILTER_ENTRY_LEN (KSYM_NAME_LEN + KSYM_TRACER_OP_LEN + 1)

struct trace_ksym {
struct hw_breakpoint *ksym_hbp;
@@ -230,25 +229,33 @@ static ssize_t ksym_trace_filter_read(struct file *filp, char __user *ubuf,
{
struct trace_ksym *entry;
struct hlist_node *node;
- char buf[KSYM_FILTER_ENTRY_LEN * KSYM_TRACER_MAX];
- ssize_t ret, cnt = 0;
+ struct trace_seq *s;
+ ssize_t cnt = 0;
+ int ret;
+
+ s = kmalloc(sizeof(*s), GFP_KERNEL);
+ if (!s)
+ return -ENOMEM;
+ trace_seq_init(s);

mutex_lock(&ksym_tracer_mutex);

hlist_for_each_entry(entry, node, &ksym_filter_head, ksym_hlist) {
- cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt, "%s:",
- entry->ksym_hbp->info.name);
+ ret = trace_seq_printf(s, "%s:", entry->ksym_hbp->info.name);
if (entry->ksym_hbp->info.type == HW_BREAKPOINT_WRITE)
- cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt,
- "-w-\n");
+ ret = trace_seq_puts(s, "-w-\n");
else if (entry->ksym_hbp->info.type == HW_BREAKPOINT_RW)
- cnt += snprintf(&buf[cnt], KSYM_FILTER_ENTRY_LEN - cnt,
- "rw-\n");
+ ret = trace_seq_puts(s, "rw-\n");
+ WARN_ON_ONCE(!ret);
}
- ret = simple_read_from_buffer(ubuf, count, ppos, buf, strlen(buf));
+
+ cnt = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
+
mutex_unlock(&ksym_tracer_mutex);

- return ret;
+ kfree(s);
+
+ return cnt;
}

static ssize_t ksym_trace_filter_write(struct file *file,
--
1.5.4.rc3