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Subject[PATCH 10/26] dynamic_debug: enlarge command/query write buffer
Date
From: Jim Cromie <jim.cromie@gmail.com>

Current write buffer is 256 bytes, on stack. Allocate it off heap,
and enlarge it to 4096 bytes, big enough for ~100 queries (at 40 bytes
each), and error out if not. This should be enough for most uses, and
others can be split into 2 writes.

This makes it play nicely with:
$> cat debug-queries-file > /dbg/dynamic_debug/control
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
---
lib/dynamic_debug.c | 16 ++++++++++++----
1 files changed, 12 insertions(+), 4 deletions(-)
diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
index 4bf27f3..2b3393f 100644
--- a/lib/dynamic_debug.c
+++ b/lib/dynamic_debug.c
@@ -590,24 +590,32 @@ __setup("ddebug_query=", ddebug_setup_query);
* File_ops->write method for <debugfs>/dynamic_debug/conrol. Gathers the
* command text from userspace, parses and executes it.
*/
+#define USER_BUF_PAGE 4095
static ssize_t ddebug_proc_write(struct file *file, const char __user *ubuf,
size_t len, loff_t *offp)
{
- char tmpbuf[256];
+ char *tmpbuf;
int ret;

if (len == 0)
return 0;
- /* we don't check *offp -- multiple writes() are allowed */
- if (len > sizeof(tmpbuf)-1)
+ if (len > USER_BUF_PAGE - 1) {
+ pr_warn("expected <%d bytes into control \n", USER_BUF_PAGE);
return -E2BIG;
- if (copy_from_user(tmpbuf, ubuf, len))
+ }
+ tmpbuf = kmalloc(len + 1, GFP_KERNEL);
+ if (!tmpbuf)
+ return -ENOMEM;
+ if (copy_from_user(tmpbuf, ubuf, len)) {
+ kfree(tmpbuf);
return -EFAULT;
+ }
tmpbuf[len] = '\0';
if (verbose)
pr_info("read %d bytes from userspace\n", (int)len);

ret = ddebug_exec_queries(tmpbuf);
+ kfree(tmpbuf);
if (ret)
return ret;

--
1.7.4.4


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