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Subject[PATCH 3/5] /dev/vring limit and base ioctls
Date
It turns out the lguest (and possibly kvm) want the addresses in the
ring buffer to only cover a certain part of memory, and be offset.

It makes sense that this be an ioctl.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
---
Documentation/ioctl-number.txt | 3 +--
drivers/char/vring.c | 37 +++++++++++++++++++++++++++++++++++--
include/linux/vring.h | 9 +++++++++
3 files changed, 45 insertions(+), 4 deletions(-)

diff -r caeeb48d478a Documentation/ioctl-number.txt
--- a/Documentation/ioctl-number.txt Fri Apr 18 13:35:17 2008 +1000
+++ b/Documentation/ioctl-number.txt Fri Apr 18 13:36:21 2008 +1000
@@ -181,8 +181,7 @@ 0xA3 90-9F linux/dtlk.h
0xA3 90-9F linux/dtlk.h
0xAB 00-1F linux/nbd.h
0xAC 00-1F linux/raw.h
-0xAD 00 Netfilter device in development:
- <mailto:rusty@rustcorp.com.au>
+0xAD 00-01 linux/vring.h
0xB0 all RATIO devices in development:
<mailto:vgo@ratio.de>
0xB1 00-1F PPPoX <mailto:mostrows@styx.uwaterloo.ca>
diff -r caeeb48d478a drivers/char/vring.c
--- a/drivers/char/vring.c Fri Apr 18 13:35:17 2008 +1000
+++ b/drivers/char/vring.c Fri Apr 18 13:36:21 2008 +1000
@@ -32,6 +32,8 @@ struct vring_info {
struct vring ring;
u16 mask;
u16 last_used;
+
+ unsigned long base, limit;

const struct vring_ops *ops;
void *ops_data;
@@ -163,6 +165,26 @@ static int vring_open(struct inode *in,

init_waitqueue_head(&vr->poll_wait);
mutex_init(&vr->lock);
+ vr->limit = -1UL;
+ vr->base = 0;
+ return 0;
+}
+
+static int vring_ioctl(struct inode *in, struct file *filp,
+ unsigned int cmd, unsigned long arg)
+{
+ struct vring_info *vr = filp->private_data;
+
+ switch (cmd) {
+ case VRINGSETBASE:
+ vr->base = arg;
+ break;
+ case VRINGSETLIMIT:
+ vr->limit = arg;
+ break;
+ default:
+ return -ENOTTY;
+ }
return 0;
}

@@ -173,6 +195,7 @@ static const struct file_operations vrin
.read = vring_read,
.write = vring_write,
.poll = vring_poll,
+ .ioctl = vring_ioctl,
};

/**
@@ -220,6 +243,8 @@ int vring_get_buffer(struct vring_info *

i = head;
do {
+ void __user *base;
+
if (unlikely(i >= vr->ring.num)) {
pr_debug("vring: bad index: %u\n", i);
return -EINVAL;
@@ -227,6 +252,14 @@ int vring_get_buffer(struct vring_info *

if (copy_from_user(&d, &vr->ring.desc[i], sizeof(d)) != 0)
return -EFAULT;
+
+ if (d.addr + d.len > vr->limit || (d.addr + d.len < d.addr)) {
+ pr_debug("vring: bad addr/len: %u@%p\n",
+ d.len, (void *)(unsigned long)d.addr);
+ return -EINVAL;
+ }
+
+ base = (void __user *)(unsigned long)d.addr + vr->base;

if (d.flags & VRING_DESC_F_WRITE) {
/* Check for length and iovec overflows */
@@ -239,7 +272,7 @@ int vring_get_buffer(struct vring_info *
return -E2BIG;
in_iov[in].iov_len = d.len;
*in_len += d.len;
- in_iov[in].iov_base = (void __user *)(long)d.addr;
+ in_iov[in].iov_base = base;
in++;
} else {
if (!num_out) {
@@ -251,7 +284,7 @@ int vring_get_buffer(struct vring_info *
return -E2BIG;
out_iov[out].iov_len = d.len;
*out_len += d.len;
- out_iov[out].iov_base = (void __user *)(long)d.addr;
+ out_iov[out].iov_base = base;
out++;
}

diff -r caeeb48d478a include/linux/vring.h
--- a/include/linux/vring.h Fri Apr 18 13:35:17 2008 +1000
+++ b/include/linux/vring.h Fri Apr 18 13:36:21 2008 +1000
@@ -18,6 +18,13 @@
*/
#ifndef _LINUX_VRING_H
#define _LINUX_VRING_H
+#include <linux/types.h>
+
+/* Ioctl defines. */
+#define VRINGSETBASE _IO(0xAD, 0)
+#define VRINGSETLIMIT _IO(0xAD, 1)
+
+#ifdef __KERNEL__

/**
* vring_ops - operations for a vring fd.
@@ -55,4 +62,6 @@ void vring_used_buffer(struct vring_info
void vring_used_buffer(struct vring_info *vr, int id, u32 len);

void vring_wake(struct vring_info *vr);
+#endif /* __KERNEL__ */
+
#endif /* _LINUX_VRING_H */

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