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dynamic_debug: enlarge command/query write buffer 

Current query write buffer is 256 bytes, on stack.  In comparison, the
ddebug_query boot-arg is 1024.  Allocate the buffer off heap, and
enlarge it to 4096 bytes, big enough for ~100 queries (at 40 bytes
each), and error out if not.  This makes it play nicely with large
query sets (to be added later).  The buffer should be enough for most
uses, and others should probably be split into subsets.

[jbaron@redhat.com: changed USER_BUF_PAGE from 4095 -> 4096 ]
Signed-off-by: Jim Cromie <jim.cromie@gmail.com>
Signed-off-by: Jason Baron <jbaron@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Jim Cromie 2011-12-19 17:13:07 -05:00 committed by Greg Kroah-Hartman
parent 8bd6026e88
commit 7281491c59
1 changed files with 12 additions and 4 deletions
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16
lib/dynamic_debug.c
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@ -570,24 +570,32 @@ __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 4096
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_query(tmpbuf);
kfree(tmpbuf);
if (ret)
return ret;