dynamic_debug: enlarge command/query write buffer (7281491c) · Commits · 戴 / test

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>

lib/dynamic_debug.c

+12 −4

Original line number	Diff line number	Diff line
		@@ -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;

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