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Message-Id: <1222530242-1272-2-git-send-email-avi@redhat.com>
Date: Sat, 27 Sep 2008 18:44:00 +0300
From: Avi Kivity <avi@...hat.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: viro@...IV.linux.org.uk, linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] ioctl: generic ioctl dispatcher
ioctl handler writers currently have the following tasks:
- allocate a buffer for the data, either in memory or on the heap, depending
on the buffer size
- handle errors
- copy the data from userspace
- handle errors
- actually perform the intended operation
- copy data back to userspace
- handle errors
- free the buffer, in case it was allocated on the heap
This patch provides a dispatch_ioctl() helper, which will do all of these
things for the caller, except for performing the intended operation. The
caller need only provide a list of ioctl commands and handler functions.
Signed-off-by: Avi Kivity <avi@...hat.com>
---
fs/ioctl.c | 78 +++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/ioctl.h | 33 ++++++++++++++++++++
2 files changed, 111 insertions(+), 0 deletions(-)
diff --git a/fs/ioctl.c b/fs/ioctl.c
index 7db32b3..f63d5ce 100644
--- a/fs/ioctl.c
+++ b/fs/ioctl.c
@@ -211,3 +211,81 @@ asmlinkage long sys_ioctl(unsigned int fd, unsigned int cmd, unsigned long arg)
out:
return error;
}
+
+/**
+ * dispatch_ioctl - dispatch to an ioctl handler based on ioctl number
+ * @inode: inode to invoke ioctl method on
+ * @filp: open file to invoke ioctl method on
+ * @cmd: ioctl command to execute
+ * @arg: command-specific argument for ioctl
+ * @handlers: list of potential handlers for @cmd; null terminated;
+ * place frequently used cmds first
+ * @fallback: optional function to call if @cmd not found in @handlers
+ *
+ * Locates and calls ioctl handler in @handlers; if none exist, calls
+ * @fallback; if that does not exist, return -ENOTTY.
+ */
+long dispatch_ioctl(struct inode *inode, struct file *filp,
+ unsigned cmd, unsigned long arg,
+ const struct ioctl_handler *handlers,
+ long (*fallback)(const struct ioctl_arg *arg))
+{
+ unsigned dir, size;
+ long ret;
+ long stackbuf[IOCTL_STACK_BUF / sizeof(long)];
+ struct ioctl_arg iarg;
+ long (*handler)(const struct ioctl_arg *arg) = fallback;
+
+ /*
+ * Yes, we use a linear search. That's actually the fastest
+ * algorithm around if the list is small, or if the frequently
+ * used (and performance sensitive) items are in the front.
+ */
+ for (; handlers->handler; ++handlers)
+ if (handlers->cmd == cmd) {
+ handler = handlers->handler;
+ break;
+ }
+
+ if (!handler)
+ return -ENOTTY;
+
+ iarg.cmd = cmd;
+ iarg.file = filp;
+ iarg.inode = inode;
+ iarg.argl = arg;
+
+ size = 0;
+ dir = _IOC_DIR(cmd);
+ if (dir != _IOC_NONE)
+ size = _IOC_SIZE(cmd);
+
+ iarg.argp = stackbuf;
+ if (size > sizeof(stackbuf)) {
+ iarg.argp = kmalloc(size, GFP_KERNEL);
+ if (!iarg.argp)
+ return -ENOMEM;
+ }
+ if (dir & _IOC_WRITE)
+ if (copy_from_user(iarg.argp, (void __user *)arg, size))
+ goto out_fault;
+
+ ret = handler(&iarg);
+
+ if (ret < 0)
+ goto out;
+
+ if (dir & _IOC_READ)
+ if (copy_to_user((void __user *)arg, iarg.argp, size))
+ goto out_fault;
+out:
+ if (iarg.argp != stackbuf)
+ kfree(iarg.argp);
+
+ return ret;
+
+out_fault:
+ ret = -EFAULT;
+ goto out;
+}
+EXPORT_SYMBOL_GPL(dispatch_ioctl);
diff --git a/include/linux/ioctl.h b/include/linux/ioctl.h
index aa91eb3..881974a 100644
--- a/include/linux/ioctl.h
+++ b/include/linux/ioctl.h
@@ -3,5 +3,38 @@
#include <asm/ioctl.h>
+#ifdef __KERNEL__
+
+struct inode;
+struct file;
+
+/*
+ * for dispatch_ioctl(), how many bytes we allow to be allocated on stack.
+ * Arch may override.
+ */
+#ifndef IOCTL_STACK_BUF
+#define IOCTL_STACK_BUF 128
+#endif
+
+struct ioctl_arg {
+ unsigned cmd;
+ struct file *file;
+ struct inode *inode;
+ long argl;
+ void *argp;
+};
+
+struct ioctl_handler {
+ unsigned cmd;
+ long (*handler)(const struct ioctl_arg *arg);
+};
+
+long dispatch_ioctl(struct inode *inode, struct file *filp,
+ unsigned int cmd, unsigned long arg,
+ const struct ioctl_handler *handlers,
+ long (*fallback)(const struct ioctl_arg *arg));
+
+#endif
+
#endif /* _LINUX_IOCTL_H */
--
1.6.0.1
--
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