[PATCH] CONFIG_PACKET_MMAP should depend on MMU

[PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Aubrey Li]

The option CONFIG_PACKET_MMAP should depend on MMU.

Signed-off-by: Aubrey.Li <aubreylee@gmail.com>
---
 net/packet/Kconfig |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/net/packet/Kconfig b/net/packet/Kconfig
index 34ff93f..959c272 100644
--- a/net/packet/Kconfig
+++ b/net/packet/Kconfig
@@ -17,7 +17,7 @@ config PACKET

 config PACKET_MMAP
 	bool "Packet socket: mmapped IO"
-	depends on PACKET
+	depends on PACKET && MMU
 	help
 	  If you say Y here, the Packet protocol driver will use an IO
 	  mechanism that results in faster communication.
-- 
1.5.1

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Wu, Bryan]

On Mon, 2007-04-09 at 11:01 +0800, Aubrey Li wrote:
> The option CONFIG_PACKET_MMAP should depend on MMU.
> 
> Signed-off-by: Aubrey.Li <aubreylee@gmail.com>
> ---
>  net/packet/Kconfig |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/packet/Kconfig b/net/packet/Kconfig
> index 34ff93f..959c272 100644
> --- a/net/packet/Kconfig
> +++ b/net/packet/Kconfig
> @@ -17,7 +17,7 @@ config PACKET
> 
>  config PACKET_MMAP
>  	bool "Packet socket: mmapped IO"
> -	depends on PACKET
> +	depends on PACKET && MMU
>  	help
>  	  If you say Y here, the Packet protocol driver will use an IO
>  	  mechanism that results in faster communication.

Yeah, this is a bug found on blackfin arch and it is also for other
NOMMU arch. Is there any solution for this? We think Aubrey's idea
works.

Thanks
-Bryan

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Robin Getz]

On Mon 9 Apr 2007 05:50, Wu, Bryan pondered:
> On Mon, 2007-04-09 at 11:01 +0800, Aubrey Li wrote:
> > The option CONFIG_PACKET_MMAP should depend on MMU.
> >
> > Signed-off-by: Aubrey.Li <aubreylee@gmail.com>
> > ---
> >  net/packet/Kconfig |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/net/packet/Kconfig b/net/packet/Kconfig
> > index 34ff93f..959c272 100644
> > --- a/net/packet/Kconfig
> > +++ b/net/packet/Kconfig
> > @@ -17,7 +17,7 @@ config PACKET
> >
> >  config PACKET_MMAP
> >  	bool "Packet socket: mmapped IO"
> > -	depends on PACKET
> > +	depends on PACKET && MMU
> >  	help
> >  	  If you say Y here, the Packet protocol driver will use an IO
> >  	  mechanism that results in faster communication.
>
> Yeah, this is a bug found on blackfin arch and it is also for other
> NOMMU arch. Is there any solution for this? We think Aubrey's idea
> works.
>

I would hardly say that disabling a feature should be classified as "works". 

"works" would be re-writing packet/af_packet.c:packet_mmap() so it doesn't use 
vm_insert_page (which I think is the major/only problem) or putting some 
proper #ifdef MMU to get the intended functionality.

David - I know you have been reworking the noMMU vma handling - is there a 
solution to vm_insert_page?

-Robin

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Howells]

Robin Getz <rgetz@blackfin.uclinux.org> wrote:

> David - I know you have been reworking the noMMU vma handling - is there a 
> solution to vm_insert_page?

The reason vm_insert_page() is being called, I imagine, is because
packet_mmap() has to insert mappings to an already existing buffer.  All it
does is munge the PTEs in that virtual region to point to the buffer.

As long as the buffer is completely contiguous (which I don't know for
certain), then this function can be trivially reduced in NOMMU-mode to
something that just returns the address of the requested part of the buffer.
No remapping would be required.

However...  If the buffer is *not* completely contiguous, then you can still
perform mmaps of it - but only where the desired part _is_ contiguous.
Alternatively, you can arrange for the buffer to be completely contiguous
upfront.

Looking at alloc_pg_vec() in af_packet.c, I will place my bets on the latter
case.  I don't know that this is a problem; it depends on how things work, and
that I don't know offhand.  If someone can give me a simple test program, I
would be able to evaluate it better.

David

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Robin Getz]

On Tue 10 Apr 2007 08:55, David Howells pondered:
> Looking at alloc_pg_vec() in af_packet.c, I will place my bets on the
> latter case.  I don't know that this is a problem; it depends on how things
> work, and that I don't know offhand.  If someone can give me a simple test
> program, I would be able to evaluate it better.

Hmm - the only think I have used in the past is tcpdump/libpcap from
http://public.lanl.gov/cpw/

Documentation/networking/packet_mmap.txt also seems to be a little dated, but 
does have some code snippets if you wanted to make something lightweight...

Does anyone else on netdev have a small test app?

-Robin

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Aubrey Li]

[-- Attachment #1: Type: text/plain, Size: 846 bytes --]

On 4/11/07, Robin Getz <rgetz@blackfin.uclinux.org> wrote:
> On Tue 10 Apr 2007 08:55, David Howells pondered:
> > Looking at alloc_pg_vec() in af_packet.c, I will place my bets on the
> > latter case.  I don't know that this is a problem; it depends on how things
> > work, and that I don't know offhand.  If someone can give me a simple test
> > program, I would be able to evaluate it better.
>
> Hmm - the only think I have used in the past is tcpdump/libpcap from
> http://public.lanl.gov/cpw/
>
> Documentation/networking/packet_mmap.txt also seems to be a little dated, but
> does have some code snippets if you wanted to make something lightweight...
>
> Does anyone else on netdev have a small test app?
>
Here, in the attachment I wrote a small test app. Please correct if
there is anything wrong, and feel free to improve it.

-Aubrey

[-- Attachment #2: packet-mmap.tar.gz --]
[-- Type: application/x-gzip, Size: 947 bytes --]

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Robin Getz]

On Tue 17 Apr 2007 06:36, Aubrey Li pondered:
> Here, in the attachment I wrote a small test app. Please correct if
> there is anything wrong, and feel free to improve it.

Thanks. 

David - Does this give you what you need?

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Howells]

Robin Getz <rgetz@blackfin.uclinux.org> wrote:

> David - Does this give you what you need?

Possibly.  I'll have a look at it tomorrow.

David

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Howells]

Aubrey Li <aubreylee@gmail.com> wrote:

> Here, in the attachment I wrote a small test app. Please correct if
> there is anything wrong, and feel free to improve it.

Okay... I have that working... probably.  I don't know what output it's
supposed to produce, but I see this:

	# /packet-mmap/sample_packet_mmap
	00-00-00-01-00-00-00-8a-00-00-00-8a-00-42-00-50-
	38-43-13-a0-00-07-ff-3c-00-00-00-00-00-00-00-00-
	00-11-08-00-00-00-00-01-00-01-00-06-00-d0-b7-de-
	32-7b-00-00-00-00-00-00-00-00-00-00-00-00-00-00-
	00-00-00-90-cc-a2-75-6b-00-d0-b7-de-32-7b-08-00-
	45-00-00-7c-00-00-40-00-40-11-b4-13-c0-a8-02-80-
	c0-a8-02-8d-08-01-03-20-00-68-8e-65-7f-5b-7e-03-
	00-00-00-01-00-00-00-00-00-00-00-00-00-00-00-00-
	00-00-00-00-00-00-00-00-00-00-00-01-00-00-81-a4-
	00-00-00-01-00-00-00-00-00-00-00-00-00-1d-b8-86-
	00-00-10-00-ff-ff-ff-ff-00-00-0e-f0-00-00-09-02-
	01-cb-03-16-46-26-38-0d-00-00-00-00-46-26-38-1e-
	00-00-00-00-46-26-38-1e-00-00-00-00-00-00-00-00-
	00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00- [repeated]

Does that look reasonable?

I've attached the preliminary patch.  Note four things about it:

 (1) I've had to add the get_unmapped_area() op to the proto_ops struct, but
     I've only done it for CONFIG_MMU=n as making it available for CONFIG_MMU=y
     could cause problems.

 (2) There's a race between packet_get_unmapped_area() being called and
     packet_mmap() being called.

 (3) I've added an extra check into packet_set_ring() to make sure the caller
     isn't asking for a combination of buffer size and count that will exceed
     ULONG_MAX.  This protects a multiply done elsewhere.

 (4) The entire data buffer is allocated as one contiguous lump in NOMMU-mode.

David

---
[PATCH] NOMMU: Support mmap() on AF_PACKET sockets

From: David Howells <dhowells@redhat.com>

Support mmap() on AF_PACKET sockets in NOMMU-mode kernels.

Signed-Off-By: David Howells <dhowells@redhat.com>
---

 include/linux/net.h    |    7 +++
 include/net/sock.h     |    8 +++
 net/core/sock.c        |   10 ++++
 net/packet/af_packet.c |  118 ++++++++++++++++++++++++++++++++++++++++++++++++
 net/socket.c           |   77 +++++++++++++++++++++++++++++++
 5 files changed, 219 insertions(+), 1 deletions(-)

diff --git a/include/linux/net.h b/include/linux/net.h
index 4db21e6..9e77cf6 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -161,6 +161,11 @@ struct proto_ops {
 	int		(*recvmsg)   (struct kiocb *iocb, struct socket *sock,
 				      struct msghdr *m, size_t total_len,
 				      int flags);
+#ifndef CONFIG_MMU
+	unsigned long	(*get_unmapped_area)(struct file *file, struct socket *sock,
+					     unsigned long addr, unsigned long len,
+					     unsigned long pgoff, unsigned long flags);
+#endif
 	int		(*mmap)	     (struct file *file, struct socket *sock,
 				      struct vm_area_struct * vma);
 	ssize_t		(*sendpage)  (struct socket *sock, struct page *page,
@@ -191,6 +196,8 @@ extern int   	     sock_sendmsg(struct socket *sock, struct msghdr *msg,
 extern int	     sock_recvmsg(struct socket *sock, struct msghdr *msg,
 				  size_t size, int flags);
 extern int 	     sock_map_fd(struct socket *sock);
+extern void	     sock_make_mappable(struct socket *sock,
+					unsigned long prot);
 extern struct socket *sockfd_lookup(int fd, int *err);
 #define		     sockfd_put(sock) fput(sock->file)
 extern int	     net_ratelimit(void);
diff --git a/include/net/sock.h b/include/net/sock.h
index 2c7d60c..d91edea 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -841,6 +841,14 @@ extern int                      sock_no_sendmsg(struct kiocb *, struct socket *,
 						struct msghdr *, size_t);
 extern int                      sock_no_recvmsg(struct kiocb *, struct socket *,
 						struct msghdr *, size_t, int);
+#ifndef CONFIG_MMU
+extern unsigned long		sock_no_get_unmapped_area(struct file *,
+							  struct socket *,
+							  unsigned long,
+							  unsigned long,
+							  unsigned long,
+							  unsigned long);
+#endif
 extern int			sock_no_mmap(struct file *file,
 					     struct socket *sock,
 					     struct vm_area_struct *vma);
diff --git a/net/core/sock.c b/net/core/sock.c
index 27c4f62..b288799 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1364,6 +1364,15 @@ int sock_no_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *m,
 	return -EOPNOTSUPP;
 }
 
+#ifndef CONFIG_MMU
+unsigned long sock_no_get_unmapped_area(struct file *file, struct socket *sock,
+					unsigned long addr, unsigned long len,
+					unsigned long pgoff, unsigned long flags)
+{
+	return (unsigned long) -ENODEV;
+}
+#endif
+
 int sock_no_mmap(struct file *file, struct socket *sock, struct vm_area_struct *vma)
 {
 	/* Mirror missing mmap method error code */
@@ -1943,6 +1952,7 @@ EXPORT_SYMBOL(sock_no_getname);
 EXPORT_SYMBOL(sock_no_getsockopt);
 EXPORT_SYMBOL(sock_no_ioctl);
 EXPORT_SYMBOL(sock_no_listen);
+EXPORT_SYMBOL(sock_no_get_unmapped_area);
 EXPORT_SYMBOL(sock_no_mmap);
 EXPORT_SYMBOL(sock_no_poll);
 EXPORT_SYMBOL(sock_no_recvmsg);
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 28d47e8..12d970a 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -78,6 +78,7 @@
 #include <linux/poll.h>
 #include <linux/module.h>
 #include <linux/init.h>
+#include <asm/mman.h>
 
 #ifdef CONFIG_INET
 #include <net/inet_common.h>
@@ -1023,6 +1024,7 @@ static int packet_create(struct socket *sock, int protocol)
 		sock->ops = &packet_ops_spkt;
 #endif
 	sock_init_data(sock, sk);
+	sock_make_mappable(sock, PROT_READ | PROT_WRITE);
 
 	po = pkt_sk(sk);
 	sk->sk_family = PF_PACKET;
@@ -1629,6 +1631,7 @@ static inline struct page *pg_vec_endpage(char *one_pg_vec, unsigned int order)
 	return virt_to_page(one_pg_vec + (PAGE_SIZE << order) - 1);
 }
 
+#ifdef CONFIG_MMU
 static void free_pg_vec(char **pg_vec, unsigned int order, unsigned int len)
 {
 	int i;
@@ -1671,6 +1674,45 @@ out_free_pgvec:
 	goto out;
 }
 
+#else
+/*
+ * free the buffer pointer block and all the buffers for NOMMU
+ */
+static void free_pg_vec(char **pg_vec, unsigned int order, unsigned int len)
+{
+	kfree(pg_vec[0]);
+	kfree(pg_vec);
+}
+
+/*
+ * allocate the buffer pointer block and all the buffer blocks for the mappable
+ * AF_PACKET buffers for NOMMU mode
+ * - in NOMMU mode the buffers must be contiguous with each other
+ */
+static char **alloc_pg_vec(struct tpacket_req *req, int order)
+{
+	char *buffers;
+	char **ptrblock;
+	int loop;
+
+	buffers = kcalloc(req->tp_block_size, req->tp_block_nr, GFP_KERNEL);
+	if (!buffers)
+		return ERR_PTR(-ENOMEM);
+	ptrblock = kmalloc(sizeof(char *) * req->tp_block_nr, GFP_KERNEL);
+	if (!ptrblock) {
+		kfree(buffers);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	for (loop = 0; loop < req->tp_block_nr; loop++) {
+		ptrblock[loop] = buffers;
+		buffers += req->tp_block_size;
+	}
+
+	return ptrblock;
+}
+#endif
+
 static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing)
 {
 	char **pg_vec = NULL;
@@ -1695,6 +1737,8 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing
 			return -EINVAL;
 		if (unlikely(req->tp_frame_size & (TPACKET_ALIGNMENT - 1)))
 			return -EINVAL;
+		if (unlikely(ULONG_MAX / req->tp_block_size < req->tp_block_nr))
+			return -ENOMEM;
 
 		po->frames_per_block = req->tp_block_size/req->tp_frame_size;
 		if (unlikely(po->frames_per_block <= 0))
@@ -1783,6 +1827,7 @@ out:
 	return err;
 }
 
+#ifdef CONFIG_MMU
 static int packet_mmap(struct file *file, struct socket *sock, struct vm_area_struct *vma)
 {
 	struct sock *sk = sock->sk;
@@ -1823,7 +1868,72 @@ out:
 	release_sock(sk);
 	return err;
 }
-#endif
+
+#else
+/*
+ * find out where the socket buffers are so that NOMMU mmap can return the
+ * address directly
+ */
+static unsigned long packet_get_unmapped_area(struct file *file,
+					      struct socket *sock,
+					      unsigned long addr,
+					      unsigned long len,
+					      unsigned long pgoff,
+					      unsigned long flags)
+{
+	struct sock *sk = sock->sk;
+	struct packet_sock *po = pkt_sk(sk);
+
+	/* check that they want to map the whole buffer */
+	if (pgoff)
+		return (unsigned long) -EINVAL;
+
+	lock_sock(sk);
+	if (!po->pg_vec ||
+	    len != po->pg_vec_len * po->pg_vec_pages * PAGE_SIZE)
+		addr = (unsigned long) -EINVAL;
+	else
+		addr = (unsigned long) po->pg_vec[0];
+	release_sock(sk);
+	return addr;
+}
+
+/*
+ * set the mapping of a packet socket buffer for NOMMU mmap
+ */
+static int packet_mmap(struct file *file, struct socket *sock,
+		       struct vm_area_struct *vma)
+{
+	struct sock *sk = sock->sk;
+	struct packet_sock *po = pkt_sk(sk);
+	unsigned long len;
+	int ret;
+
+	if (vma->vm_pgoff)
+		return -EINVAL;
+
+	lock_sock(sk);
+
+	/* check that they want to map the whole buffer */
+	len = vma->vm_end - vma->vm_start;
+	if (!po->pg_vec ||
+	    len != po->pg_vec_len * po->pg_vec_pages * PAGE_SIZE) {
+		ret = -EINVAL;
+	} else if (vma->vm_start != (unsigned long) po->pg_vec[0]) {
+		/* someone found the gap between get_unmapped_area and mmap */
+		ret = -ESTALE;
+	} else {
+		atomic_inc(&po->mapped);
+		vma->vm_ops = &packet_mmap_ops;
+		ret = 0;
+	}
+
+	release_sock(sk);
+	return ret;
+}
+
+#endif /* CONFIG_MMU */
+#endif /* CONFIG_PACKET_MMAP */
 
 
 #ifdef CONFIG_SOCK_PACKET
@@ -1844,6 +1954,9 @@ static const struct proto_ops packet_ops_spkt = {
 	.getsockopt =	sock_no_getsockopt,
 	.sendmsg =	packet_sendmsg_spkt,
 	.recvmsg =	packet_recvmsg,
+#ifndef CONFIG_MMU
+	.get_unmapped_area = sock_no_get_unmapped_area,
+#endif
 	.mmap =		sock_no_mmap,
 	.sendpage =	sock_no_sendpage,
 };
@@ -1866,6 +1979,9 @@ static const struct proto_ops packet_ops = {
 	.getsockopt =	packet_getsockopt,
 	.sendmsg =	packet_sendmsg,
 	.recvmsg =	packet_recvmsg,
+#ifndef CONFIG_MMU
+	.get_unmapped_area = packet_get_unmapped_area,
+#endif
 	.mmap =		packet_mmap,
 	.sendpage =	sock_no_sendpage,
 };
diff --git a/net/socket.c b/net/socket.c
index ea8f81a..4109db6 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -87,6 +87,7 @@
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
+#include <asm/mman.h>
 
 #include <net/compat.h>
 
@@ -98,6 +99,13 @@ static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
 			 unsigned long nr_segs, loff_t pos);
 static ssize_t sock_aio_write(struct kiocb *iocb, const struct iovec *iov,
 			  unsigned long nr_segs, loff_t pos);
+#ifndef CONFIG_MMU
+static unsigned long sock_get_unmapped_area(struct file *file,
+					    unsigned long addr,
+					    unsigned long len,
+					    unsigned long pgoff,
+					    unsigned long flags);
+#endif
 static int sock_mmap(struct file *file, struct vm_area_struct *vma);
 
 static int sock_close(struct inode *inode, struct file *file);
@@ -127,6 +135,9 @@ static const struct file_operations socket_file_ops = {
 #ifdef CONFIG_COMPAT
 	.compat_ioctl = compat_sock_ioctl,
 #endif
+#ifndef CONFIG_MMU
+	.get_unmapped_area = sock_get_unmapped_area,
+#endif
 	.mmap =		sock_mmap,
 	.open =		sock_no_open,	/* special open code to disallow open via /proc */
 	.release =	sock_close,
@@ -136,6 +147,26 @@ static const struct file_operations socket_file_ops = {
 };
 
 /*
+ * capabilities for non-mappable sockets
+ * - does not permit mmap at all
+ * - no readahead or I/O queue unplugging required
+ */
+struct backing_dev_info non_mappable_socket_bdi = {
+	.capabilities	= 0,
+};
+
+/*
+ * capabilities for read/write mappable sockets
+ * - permits shared-mmap for read and write only
+ * - does not permit private mmap
+ * - no readahead or I/O queue unplugging required
+ */
+struct backing_dev_info rw_mappable_socket_bdi = {
+	.capabilities	= (BDI_CAP_MAP_DIRECT | BDI_CAP_READ_MAP |
+			   BDI_CAP_WRITE_MAP),
+};
+
+/*
  *	The protocol list. Each protocol is registered in here.
  */
 
@@ -415,6 +446,34 @@ static struct socket *sock_from_file(struct file *file, int *err)
 }
 
 /**
+ *	sock_make_mappable -	Change the mmappability of a socket
+ *	@sock: The socket to alter
+ *	@prot: The mmap protection to permit
+ *
+ *	The nominated socket has its backing device information selection
+ *	changed to indicate to mmap() what sort of mappings are available on
+ *	this socket.
+ */
+void sock_make_mappable(struct socket *sock, unsigned long prot)
+{
+	struct address_space *mapping = &SOCK_INODE(sock)->i_data;
+
+	switch (prot) {
+	case 0:
+		mapping->backing_dev_info = &non_mappable_socket_bdi;
+		break;
+	case PROT_READ | PROT_WRITE:
+		mapping->backing_dev_info = &rw_mappable_socket_bdi;
+		break;
+	case PROT_READ:
+	case PROT_WRITE:
+	default:
+		BUG();
+		break;
+	}
+}
+
+/**
  *	sockfd_lookup	- 	Go from a file number to its socket slot
  *	@fd: file handle
  *	@err: pointer to an error code return
@@ -482,6 +541,7 @@ static struct socket *sock_alloc(void)
 	inode->i_mode = S_IFSOCK | S_IRWXUGO;
 	inode->i_uid = current->fsuid;
 	inode->i_gid = current->fsgid;
+	inode->i_data.backing_dev_info = &non_mappable_socket_bdi;
 
 	get_cpu_var(sockets_in_use)++;
 	put_cpu_var(sockets_in_use);
@@ -918,6 +978,22 @@ static unsigned int sock_poll(struct file *file, poll_table *wait)
 	return sock->ops->poll(file, sock, wait);
 }
 
+#ifndef CONFIG_MMU
+static unsigned long sock_get_unmapped_area(struct file *file,
+					    unsigned long addr,
+					    unsigned long len,
+					    unsigned long pgoff,
+					    unsigned long flags)
+{
+	struct socket *sock = file->private_data;
+
+	if (!sock->ops->get_unmapped_area)
+		return -ENOSYS;
+	return sock->ops->get_unmapped_area(file, sock,
+					    addr, len, pgoff, flags);
+}
+#endif
+
 static int sock_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct socket *sock = file->private_data;
@@ -2288,6 +2364,7 @@ EXPORT_SYMBOL(sock_create);
 EXPORT_SYMBOL(sock_create_kern);
 EXPORT_SYMBOL(sock_create_lite);
 EXPORT_SYMBOL(sock_map_fd);
+EXPORT_SYMBOL(sock_make_mappable);
 EXPORT_SYMBOL(sock_recvmsg);
 EXPORT_SYMBOL(sock_register);
 EXPORT_SYMBOL(sock_release);

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Aubrey Li]

On 4/18/07, David Howells <dhowells@redhat.com> wrote:
> Aubrey Li <aubreylee@gmail.com> wrote:
>
> > Here, in the attachment I wrote a small test app. Please correct if
> > there is anything wrong, and feel free to improve it.
>
> Okay... I have that working... probably.  I don't know what output it's
> supposed to produce, but I see this:
>
>         # /packet-mmap/sample_packet_mmap
>         00-00-00-01-00-00-00-8a-00-00-00-8a-00-42-00-50-
>         38-43-13-a0-00-07-ff-3c-00-00-00-00-00-00-00-00-
>         00-11-08-00-00-00-00-01-00-01-00-06-00-d0-b7-de-
>         32-7b-00-00-00-00-00-00-00-00-00-00-00-00-00-00-
>         00-00-00-90-cc-a2-75-6b-00-d0-b7-de-32-7b-08-00-
>         45-00-00-7c-00-00-40-00-40-11-b4-13-c0-a8-02-80-
>         c0-a8-02-8d-08-01-03-20-00-68-8e-65-7f-5b-7e-03-
>         00-00-00-01-00-00-00-00-00-00-00-00-00-00-00-00-
>         00-00-00-00-00-00-00-00-00-00-00-01-00-00-81-a4-
>         00-00-00-01-00-00-00-00-00-00-00-00-00-1d-b8-86-
>         00-00-10-00-ff-ff-ff-ff-00-00-0e-f0-00-00-09-02-
>         01-cb-03-16-46-26-38-0d-00-00-00-00-46-26-38-1e-
>         00-00-00-00-46-26-38-1e-00-00-00-00-00-00-00-00-
>         00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00- [repeated]
>
> Does that look reasonable?

Yes, it's reasonable for me, as long as your
         host IP is 192.168.2.128
and
         target IP is 192.168.2.141
See below

>         00-90-cc-a2-75-6b-|___ MAC Address
>         00-d0-b7-de-32-7b-|
>         08-00------------------------Type: IP
>         45-00------------------------Ver, IHL, TOS
>         00-7c------------------------IP.total.length
>         00-00-
>         40-00-
>         40----------------------------TTL
>         11----------------------------UDP protocol
>         b4-13------------------------Checksum
>         c0-a8-02-80---------------Source IP: 192.168.2.128
>         c0-a8-02-8d---------------Dest IP:     192.168.2.141
------------snip--------------

>
> I've attached the preliminary patch.

Thanks, I'll take a look and try to see if I can give some feedback.

-Aubrey

> Note four things about it:
>
>  (1) I've had to add the get_unmapped_area() op to the proto_ops struct, but
>      I've only done it for CONFIG_MMU=n as making it available for CONFIG_MMU=y
>      could cause problems.
>
>  (2) There's a race between packet_get_unmapped_area() being called and
>      packet_mmap() being called.
>
>  (3) I've added an extra check into packet_set_ring() to make sure the caller
>      isn't asking for a combination of buffer size and count that will exceed
>      ULONG_MAX.  This protects a multiply done elsewhere.
>
>  (4) The entire data buffer is allocated as one contiguous lump in NOMMU-mode.
>
> David
>
> ---
> [PATCH] NOMMU: Support mmap() on AF_PACKET sockets
>
> From: David Howells <dhowells@redhat.com>
>
> Support mmap() on AF_PACKET sockets in NOMMU-mode kernels.
>
> Signed-Off-By: David Howells <dhowells@redhat.com>
> ---
>
>  include/linux/net.h    |    7 +++
>  include/net/sock.h     |    8 +++
>  net/core/sock.c        |   10 ++++
>  net/packet/af_packet.c |  118 ++++++++++++++++++++++++++++++++++++++++++++++++
>  net/socket.c           |   77 +++++++++++++++++++++++++++++++
>  5 files changed, 219 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/net.h b/include/linux/net.h
> index 4db21e6..9e77cf6 100644
> --- a/include/linux/net.h
> +++ b/include/linux/net.h
> @@ -161,6 +161,11 @@ struct proto_ops {
>         int             (*recvmsg)   (struct kiocb *iocb, struct socket *sock,
>                                       struct msghdr *m, size_t total_len,
>                                       int flags);
> +#ifndef CONFIG_MMU
> +       unsigned long   (*get_unmapped_area)(struct file *file, struct socket *sock,
> +                                            unsigned long addr, unsigned long len,
> +                                            unsigned long pgoff, unsigned long flags);
> +#endif
>         int             (*mmap)      (struct file *file, struct socket *sock,
>                                       struct vm_area_struct * vma);
>         ssize_t         (*sendpage)  (struct socket *sock, struct page *page,
> @@ -191,6 +196,8 @@ extern int               sock_sendmsg(struct socket *sock, struct msghdr *msg,
>  extern int          sock_recvmsg(struct socket *sock, struct msghdr *msg,
>                                   size_t size, int flags);
>  extern int          sock_map_fd(struct socket *sock);
> +extern void         sock_make_mappable(struct socket *sock,
> +                                       unsigned long prot);
>  extern struct socket *sockfd_lookup(int fd, int *err);
>  #define                     sockfd_put(sock) fput(sock->file)
>  extern int          net_ratelimit(void);
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 2c7d60c..d91edea 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -841,6 +841,14 @@ extern int                      sock_no_sendmsg(struct kiocb *, struct socket *,
>                                                 struct msghdr *, size_t);
>  extern int                      sock_no_recvmsg(struct kiocb *, struct socket *,
>                                                 struct msghdr *, size_t, int);
> +#ifndef CONFIG_MMU
> +extern unsigned long           sock_no_get_unmapped_area(struct file *,
> +                                                         struct socket *,
> +                                                         unsigned long,
> +                                                         unsigned long,
> +                                                         unsigned long,
> +                                                         unsigned long);
> +#endif
>  extern int                     sock_no_mmap(struct file *file,
>                                              struct socket *sock,
>                                              struct vm_area_struct *vma);
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 27c4f62..b288799 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1364,6 +1364,15 @@ int sock_no_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *m,
>         return -EOPNOTSUPP;
>  }
>
> +#ifndef CONFIG_MMU
> +unsigned long sock_no_get_unmapped_area(struct file *file, struct socket *sock,
> +                                       unsigned long addr, unsigned long len,
> +                                       unsigned long pgoff, unsigned long flags)
> +{
> +       return (unsigned long) -ENODEV;
> +}
> +#endif
> +
>  int sock_no_mmap(struct file *file, struct socket *sock, struct vm_area_struct *vma)
>  {
>         /* Mirror missing mmap method error code */
> @@ -1943,6 +1952,7 @@ EXPORT_SYMBOL(sock_no_getname);
>  EXPORT_SYMBOL(sock_no_getsockopt);
>  EXPORT_SYMBOL(sock_no_ioctl);
>  EXPORT_SYMBOL(sock_no_listen);
> +EXPORT_SYMBOL(sock_no_get_unmapped_area);
>  EXPORT_SYMBOL(sock_no_mmap);
>  EXPORT_SYMBOL(sock_no_poll);
>  EXPORT_SYMBOL(sock_no_recvmsg);
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 28d47e8..12d970a 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -78,6 +78,7 @@
>  #include <linux/poll.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> +#include <asm/mman.h>
>
>  #ifdef CONFIG_INET
>  #include <net/inet_common.h>
> @@ -1023,6 +1024,7 @@ static int packet_create(struct socket *sock, int protocol)
>                 sock->ops = &packet_ops_spkt;
>  #endif
>         sock_init_data(sock, sk);
> +       sock_make_mappable(sock, PROT_READ | PROT_WRITE);
>
>         po = pkt_sk(sk);
>         sk->sk_family = PF_PACKET;
> @@ -1629,6 +1631,7 @@ static inline struct page *pg_vec_endpage(char *one_pg_vec, unsigned int order)
>         return virt_to_page(one_pg_vec + (PAGE_SIZE << order) - 1);
>  }
>
> +#ifdef CONFIG_MMU
>  static void free_pg_vec(char **pg_vec, unsigned int order, unsigned int len)
>  {
>         int i;
> @@ -1671,6 +1674,45 @@ out_free_pgvec:
>         goto out;
>  }
>
> +#else
> +/*
> + * free the buffer pointer block and all the buffers for NOMMU
> + */
> +static void free_pg_vec(char **pg_vec, unsigned int order, unsigned int len)
> +{
> +       kfree(pg_vec[0]);
> +       kfree(pg_vec);
> +}
> +
> +/*
> + * allocate the buffer pointer block and all the buffer blocks for the mappable
> + * AF_PACKET buffers for NOMMU mode
> + * - in NOMMU mode the buffers must be contiguous with each other
> + */
> +static char **alloc_pg_vec(struct tpacket_req *req, int order)
> +{
> +       char *buffers;
> +       char **ptrblock;
> +       int loop;
> +
> +       buffers = kcalloc(req->tp_block_size, req->tp_block_nr, GFP_KERNEL);
> +       if (!buffers)
> +               return ERR_PTR(-ENOMEM);
> +       ptrblock = kmalloc(sizeof(char *) * req->tp_block_nr, GFP_KERNEL);
> +       if (!ptrblock) {
> +               kfree(buffers);
> +               return ERR_PTR(-ENOMEM);
> +       }
> +
> +       for (loop = 0; loop < req->tp_block_nr; loop++) {
> +               ptrblock[loop] = buffers;
> +               buffers += req->tp_block_size;
> +       }
> +
> +       return ptrblock;
> +}
> +#endif
> +
>  static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing)
>  {
>         char **pg_vec = NULL;
> @@ -1695,6 +1737,8 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing
>                         return -EINVAL;
>                 if (unlikely(req->tp_frame_size & (TPACKET_ALIGNMENT - 1)))
>                         return -EINVAL;
> +               if (unlikely(ULONG_MAX / req->tp_block_size < req->tp_block_nr))
> +                       return -ENOMEM;
>
>                 po->frames_per_block = req->tp_block_size/req->tp_frame_size;
>                 if (unlikely(po->frames_per_block <= 0))
> @@ -1783,6 +1827,7 @@ out:
>         return err;
>  }
>
> +#ifdef CONFIG_MMU
>  static int packet_mmap(struct file *file, struct socket *sock, struct vm_area_struct *vma)
>  {
>         struct sock *sk = sock->sk;
> @@ -1823,7 +1868,72 @@ out:
>         release_sock(sk);
>         return err;
>  }
> -#endif
> +
> +#else
> +/*
> + * find out where the socket buffers are so that NOMMU mmap can return the
> + * address directly
> + */
> +static unsigned long packet_get_unmapped_area(struct file *file,
> +                                             struct socket *sock,
> +                                             unsigned long addr,
> +                                             unsigned long len,
> +                                             unsigned long pgoff,
> +                                             unsigned long flags)
> +{
> +       struct sock *sk = sock->sk;
> +       struct packet_sock *po = pkt_sk(sk);
> +
> +       /* check that they want to map the whole buffer */
> +       if (pgoff)
> +               return (unsigned long) -EINVAL;
> +
> +       lock_sock(sk);
> +       if (!po->pg_vec ||
> +           len != po->pg_vec_len * po->pg_vec_pages * PAGE_SIZE)
> +               addr = (unsigned long) -EINVAL;
> +       else
> +               addr = (unsigned long) po->pg_vec[0];
> +       release_sock(sk);
> +       return addr;
> +}
> +
> +/*
> + * set the mapping of a packet socket buffer for NOMMU mmap
> + */
> +static int packet_mmap(struct file *file, struct socket *sock,
> +                      struct vm_area_struct *vma)
> +{
> +       struct sock *sk = sock->sk;
> +       struct packet_sock *po = pkt_sk(sk);
> +       unsigned long len;
> +       int ret;
> +
> +       if (vma->vm_pgoff)
> +               return -EINVAL;
> +
> +       lock_sock(sk);
> +
> +       /* check that they want to map the whole buffer */
> +       len = vma->vm_end - vma->vm_start;
> +       if (!po->pg_vec ||
> +           len != po->pg_vec_len * po->pg_vec_pages * PAGE_SIZE) {
> +               ret = -EINVAL;
> +       } else if (vma->vm_start != (unsigned long) po->pg_vec[0]) {
> +               /* someone found the gap between get_unmapped_area and mmap */
> +               ret = -ESTALE;
> +       } else {
> +               atomic_inc(&po->mapped);
> +               vma->vm_ops = &packet_mmap_ops;
> +               ret = 0;
> +       }
> +
> +       release_sock(sk);
> +       return ret;
> +}
> +
> +#endif /* CONFIG_MMU */
> +#endif /* CONFIG_PACKET_MMAP */
>
>
>  #ifdef CONFIG_SOCK_PACKET
> @@ -1844,6 +1954,9 @@ static const struct proto_ops packet_ops_spkt = {
>         .getsockopt =   sock_no_getsockopt,
>         .sendmsg =      packet_sendmsg_spkt,
>         .recvmsg =      packet_recvmsg,
> +#ifndef CONFIG_MMU
> +       .get_unmapped_area = sock_no_get_unmapped_area,
> +#endif
>         .mmap =         sock_no_mmap,
>         .sendpage =     sock_no_sendpage,
>  };
> @@ -1866,6 +1979,9 @@ static const struct proto_ops packet_ops = {
>         .getsockopt =   packet_getsockopt,
>         .sendmsg =      packet_sendmsg,
>         .recvmsg =      packet_recvmsg,
> +#ifndef CONFIG_MMU
> +       .get_unmapped_area = packet_get_unmapped_area,
> +#endif
>         .mmap =         packet_mmap,
>         .sendpage =     sock_no_sendpage,
>  };
> diff --git a/net/socket.c b/net/socket.c
> index ea8f81a..4109db6 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -87,6 +87,7 @@
>
>  #include <asm/uaccess.h>
>  #include <asm/unistd.h>
> +#include <asm/mman.h>
>
>  #include <net/compat.h>
>
> @@ -98,6 +99,13 @@ static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
>                          unsigned long nr_segs, loff_t pos);
>  static ssize_t sock_aio_write(struct kiocb *iocb, const struct iovec *iov,
>                           unsigned long nr_segs, loff_t pos);
> +#ifndef CONFIG_MMU
> +static unsigned long sock_get_unmapped_area(struct file *file,
> +                                           unsigned long addr,
> +                                           unsigned long len,
> +                                           unsigned long pgoff,
> +                                           unsigned long flags);
> +#endif
>  static int sock_mmap(struct file *file, struct vm_area_struct *vma);
>
>  static int sock_close(struct inode *inode, struct file *file);
> @@ -127,6 +135,9 @@ static const struct file_operations socket_file_ops = {
>  #ifdef CONFIG_COMPAT
>         .compat_ioctl = compat_sock_ioctl,
>  #endif
> +#ifndef CONFIG_MMU
> +       .get_unmapped_area = sock_get_unmapped_area,
> +#endif
>         .mmap =         sock_mmap,
>         .open =         sock_no_open,   /* special open code to disallow open via /proc */
>         .release =      sock_close,
> @@ -136,6 +147,26 @@ static const struct file_operations socket_file_ops = {
>  };
>
>  /*
> + * capabilities for non-mappable sockets
> + * - does not permit mmap at all
> + * - no readahead or I/O queue unplugging required
> + */
> +struct backing_dev_info non_mappable_socket_bdi = {
> +       .capabilities   = 0,
> +};
> +
> +/*
> + * capabilities for read/write mappable sockets
> + * - permits shared-mmap for read and write only
> + * - does not permit private mmap
> + * - no readahead or I/O queue unplugging required
> + */
> +struct backing_dev_info rw_mappable_socket_bdi = {
> +       .capabilities   = (BDI_CAP_MAP_DIRECT | BDI_CAP_READ_MAP |
> +                          BDI_CAP_WRITE_MAP),
> +};
> +
> +/*
>   *     The protocol list. Each protocol is registered in here.
>   */
>
> @@ -415,6 +446,34 @@ static struct socket *sock_from_file(struct file *file, int *err)
>  }
>
>  /**
> + *     sock_make_mappable -    Change the mmappability of a socket
> + *     @sock: The socket to alter
> + *     @prot: The mmap protection to permit
> + *
> + *     The nominated socket has its backing device information selection
> + *     changed to indicate to mmap() what sort of mappings are available on
> + *     this socket.
> + */
> +void sock_make_mappable(struct socket *sock, unsigned long prot)
> +{
> +       struct address_space *mapping = &SOCK_INODE(sock)->i_data;
> +
> +       switch (prot) {
> +       case 0:
> +               mapping->backing_dev_info = &non_mappable_socket_bdi;
> +               break;
> +       case PROT_READ | PROT_WRITE:
> +               mapping->backing_dev_info = &rw_mappable_socket_bdi;
> +               break;
> +       case PROT_READ:
> +       case PROT_WRITE:
> +       default:
> +               BUG();
> +               break;
> +       }
> +}
> +
> +/**
>   *     sockfd_lookup   -       Go from a file number to its socket slot
>   *     @fd: file handle
>   *     @err: pointer to an error code return
> @@ -482,6 +541,7 @@ static struct socket *sock_alloc(void)
>         inode->i_mode = S_IFSOCK | S_IRWXUGO;
>         inode->i_uid = current->fsuid;
>         inode->i_gid = current->fsgid;
> +       inode->i_data.backing_dev_info = &non_mappable_socket_bdi;
>
>         get_cpu_var(sockets_in_use)++;
>         put_cpu_var(sockets_in_use);
> @@ -918,6 +978,22 @@ static unsigned int sock_poll(struct file *file, poll_table *wait)
>         return sock->ops->poll(file, sock, wait);
>  }
>
> +#ifndef CONFIG_MMU
> +static unsigned long sock_get_unmapped_area(struct file *file,
> +                                           unsigned long addr,
> +                                           unsigned long len,
> +                                           unsigned long pgoff,
> +                                           unsigned long flags)
> +{
> +       struct socket *sock = file->private_data;
> +
> +       if (!sock->ops->get_unmapped_area)
> +               return -ENOSYS;
> +       return sock->ops->get_unmapped_area(file, sock,
> +                                           addr, len, pgoff, flags);
> +}
> +#endif
> +
>  static int sock_mmap(struct file *file, struct vm_area_struct *vma)
>  {
>         struct socket *sock = file->private_data;
> @@ -2288,6 +2364,7 @@ EXPORT_SYMBOL(sock_create);
>  EXPORT_SYMBOL(sock_create_kern);
>  EXPORT_SYMBOL(sock_create_lite);
>  EXPORT_SYMBOL(sock_map_fd);
> +EXPORT_SYMBOL(sock_make_mappable);
>  EXPORT_SYMBOL(sock_recvmsg);
>  EXPORT_SYMBOL(sock_register);
>  EXPORT_SYMBOL(sock_release);
>

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Howells]

Aubrey Li <aubreylee@gmail.com> wrote:

> Yes, it's reasonable for me, as long as your
>         host IP is 192.168.2.128
> and
>         target IP is 192.168.2.141

That is correct, yes:-)

I expect it's an NFS packet as my board is using an NFS root at the moment.

David

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Aubrey Li]

On 4/18/07, David Howells <dhowells@redhat.com> wrote:
> Aubrey Li <aubreylee@gmail.com> wrote:
>
> > Here, in the attachment I wrote a small test app. Please correct if
> > there is anything wrong, and feel free to improve it.
>
> Okay... I have that working... probably.  I don't know what output it's
> supposed to produce, but I see this:
>
>         # /packet-mmap/sample_packet_mmap
>         00-00-00-01-00-00-00-8a-00-00-00-8a-00-42-00-50-
>         38-43-13-a0-00-07-ff-3c-00-00-00-00-00-00-00-00-
>         00-11-08-00-00-00-00-01-00-01-00-06-00-d0-b7-de-
>         32-7b-00-00-00-00-00-00-00-00-00-00-00-00-00-00-
>         00-00-00-90-cc-a2-75-6b-00-d0-b7-de-32-7b-08-00-
>         45-00-00-7c-00-00-40-00-40-11-b4-13-c0-a8-02-80-
>         c0-a8-02-8d-08-01-03-20-00-68-8e-65-7f-5b-7e-03-
>         00-00-00-01-00-00-00-00-00-00-00-00-00-00-00-00-
>         00-00-00-00-00-00-00-00-00-00-00-01-00-00-81-a4-
>         00-00-00-01-00-00-00-00-00-00-00-00-00-1d-b8-86-
>         00-00-10-00-ff-ff-ff-ff-00-00-0e-f0-00-00-09-02-
>         01-cb-03-16-46-26-38-0d-00-00-00-00-46-26-38-1e-
>         00-00-00-00-46-26-38-1e-00-00-00-00-00-00-00-00-
>         00-00-00-00-00-00-00-00-00-00-00-00-00-00-00-00- [repeated]
>
> Does that look reasonable?
>
> I've attached the preliminary patch.  Note four things about it:
>
>  (1) I've had to add the get_unmapped_area() op to the proto_ops struct, but
>      I've only done it for CONFIG_MMU=n as making it available for CONFIG_MMU=y
>      could cause problems.
>
>  (2) There's a race between packet_get_unmapped_area() being called and
>      packet_mmap() being called.
>
>  (3) I've added an extra check into packet_set_ring() to make sure the caller
>      isn't asking for a combination of buffer size and count that will exceed
>      ULONG_MAX.  This protects a multiply done elsewhere.
>
>  (4) The entire data buffer is allocated as one contiguous lump in NOMMU-mode.
>
> David
>
> ---
> [PATCH] NOMMU: Support mmap() on AF_PACKET sockets
>
> From: David Howells <dhowells@redhat.com>
>
> Support mmap() on AF_PACKET sockets in NOMMU-mode kernels.
>
> Signed-Off-By: David Howells <dhowells@redhat.com>
> ---
>
>  include/linux/net.h    |    7 +++
>  include/net/sock.h     |    8 +++
>  net/core/sock.c        |   10 ++++
>  net/packet/af_packet.c |  118 ++++++++++++++++++++++++++++++++++++++++++++++++
>  net/socket.c           |   77 +++++++++++++++++++++++++++++++
>  5 files changed, 219 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/net.h b/include/linux/net.h
> index 4db21e6..9e77cf6 100644
> --- a/include/linux/net.h
> +++ b/include/linux/net.h
> @@ -161,6 +161,11 @@ struct proto_ops {
>         int             (*recvmsg)   (struct kiocb *iocb, struct socket *sock,
>                                       struct msghdr *m, size_t total_len,
>                                       int flags);
> +#ifndef CONFIG_MMU
> +       unsigned long   (*get_unmapped_area)(struct file *file, struct socket *sock,
> +                                            unsigned long addr, unsigned long len,
> +                                            unsigned long pgoff, unsigned long flags);
> +#endif
>         int             (*mmap)      (struct file *file, struct socket *sock,
>                                       struct vm_area_struct * vma);
>         ssize_t         (*sendpage)  (struct socket *sock, struct page *page,
> @@ -191,6 +196,8 @@ extern int               sock_sendmsg(struct socket *sock, struct msghdr *msg,
>  extern int          sock_recvmsg(struct socket *sock, struct msghdr *msg,
>                                   size_t size, int flags);
>  extern int          sock_map_fd(struct socket *sock);
> +extern void         sock_make_mappable(struct socket *sock,
> +                                       unsigned long prot);
>  extern struct socket *sockfd_lookup(int fd, int *err);
>  #define                     sockfd_put(sock) fput(sock->file)
>  extern int          net_ratelimit(void);
> diff --git a/include/net/sock.h b/include/net/sock.h
> index 2c7d60c..d91edea 100644
> --- a/include/net/sock.h
> +++ b/include/net/sock.h
> @@ -841,6 +841,14 @@ extern int                      sock_no_sendmsg(struct kiocb *, struct socket *,
>                                                 struct msghdr *, size_t);
>  extern int                      sock_no_recvmsg(struct kiocb *, struct socket *,
>                                                 struct msghdr *, size_t, int);
> +#ifndef CONFIG_MMU
> +extern unsigned long           sock_no_get_unmapped_area(struct file *,
> +                                                         struct socket *,
> +                                                         unsigned long,
> +                                                         unsigned long,
> +                                                         unsigned long,
> +                                                         unsigned long);
> +#endif
>  extern int                     sock_no_mmap(struct file *file,
>                                              struct socket *sock,
>                                              struct vm_area_struct *vma);
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 27c4f62..b288799 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1364,6 +1364,15 @@ int sock_no_recvmsg(struct kiocb *iocb, struct socket *sock, struct msghdr *m,
>         return -EOPNOTSUPP;
>  }
>
> +#ifndef CONFIG_MMU
> +unsigned long sock_no_get_unmapped_area(struct file *file, struct socket *sock,
> +                                       unsigned long addr, unsigned long len,
> +                                       unsigned long pgoff, unsigned long flags)
> +{
> +       return (unsigned long) -ENODEV;
> +}
> +#endif
> +
>  int sock_no_mmap(struct file *file, struct socket *sock, struct vm_area_struct *vma)
>  {
>         /* Mirror missing mmap method error code */
> @@ -1943,6 +1952,7 @@ EXPORT_SYMBOL(sock_no_getname);
>  EXPORT_SYMBOL(sock_no_getsockopt);
>  EXPORT_SYMBOL(sock_no_ioctl);
>  EXPORT_SYMBOL(sock_no_listen);
> +EXPORT_SYMBOL(sock_no_get_unmapped_area);
>  EXPORT_SYMBOL(sock_no_mmap);
>  EXPORT_SYMBOL(sock_no_poll);
>  EXPORT_SYMBOL(sock_no_recvmsg);
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index 28d47e8..12d970a 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -78,6 +78,7 @@
>  #include <linux/poll.h>
>  #include <linux/module.h>
>  #include <linux/init.h>
> +#include <asm/mman.h>
>
>  #ifdef CONFIG_INET
>  #include <net/inet_common.h>
> @@ -1023,6 +1024,7 @@ static int packet_create(struct socket *sock, int protocol)
>                 sock->ops = &packet_ops_spkt;
>  #endif
>         sock_init_data(sock, sk);
> +       sock_make_mappable(sock, PROT_READ | PROT_WRITE);
>
>         po = pkt_sk(sk);
>         sk->sk_family = PF_PACKET;
> @@ -1629,6 +1631,7 @@ static inline struct page *pg_vec_endpage(char *one_pg_vec, unsigned int order)
>         return virt_to_page(one_pg_vec + (PAGE_SIZE << order) - 1);
>  }
>
> +#ifdef CONFIG_MMU
>  static void free_pg_vec(char **pg_vec, unsigned int order, unsigned int len)
>  {
>         int i;
> @@ -1671,6 +1674,45 @@ out_free_pgvec:
>         goto out;
>  }
>
> +#else
> +/*
> + * free the buffer pointer block and all the buffers for NOMMU
> + */
> +static void free_pg_vec(char **pg_vec, unsigned int order, unsigned int len)
> +{
> +       kfree(pg_vec[0]);
> +       kfree(pg_vec);
> +}
> +
> +/*
> + * allocate the buffer pointer block and all the buffer blocks for the mappable
> + * AF_PACKET buffers for NOMMU mode
> + * - in NOMMU mode the buffers must be contiguous with each other
> + */
> +static char **alloc_pg_vec(struct tpacket_req *req, int order)
> +{
> +       char *buffers;
> +       char **ptrblock;
> +       int loop;
> +
> +       buffers = kcalloc(req->tp_block_size, req->tp_block_nr, GFP_KERNEL);
> +       if (!buffers)
> +               return ERR_PTR(-ENOMEM);
> +       ptrblock = kmalloc(sizeof(char *) * req->tp_block_nr, GFP_KERNEL);
> +       if (!ptrblock) {
> +               kfree(buffers);
> +               return ERR_PTR(-ENOMEM);
> +       }
> +
> +       for (loop = 0; loop < req->tp_block_nr; loop++) {
> +               ptrblock[loop] = buffers;
> +               buffers += req->tp_block_size;
> +       }
> +
> +       return ptrblock;
> +}
> +#endif
> +
>  static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing)
>  {
>         char **pg_vec = NULL;
> @@ -1695,6 +1737,8 @@ static int packet_set_ring(struct sock *sk, struct tpacket_req *req, int closing
>                         return -EINVAL;
>                 if (unlikely(req->tp_frame_size & (TPACKET_ALIGNMENT - 1)))
>                         return -EINVAL;
> +               if (unlikely(ULONG_MAX / req->tp_block_size < req->tp_block_nr))
> +                       return -ENOMEM;
>
>                 po->frames_per_block = req->tp_block_size/req->tp_frame_size;
>                 if (unlikely(po->frames_per_block <= 0))
> @@ -1783,6 +1827,7 @@ out:
>         return err;
>  }
>
> +#ifdef CONFIG_MMU
>  static int packet_mmap(struct file *file, struct socket *sock, struct vm_area_struct *vma)
>  {
>         struct sock *sk = sock->sk;
> @@ -1823,7 +1868,72 @@ out:
>         release_sock(sk);
>         return err;
>  }
> -#endif
> +
> +#else
> +/*
> + * find out where the socket buffers are so that NOMMU mmap can return the
> + * address directly
> + */
> +static unsigned long packet_get_unmapped_area(struct file *file,
> +                                             struct socket *sock,
> +                                             unsigned long addr,
> +                                             unsigned long len,
> +                                             unsigned long pgoff,
> +                                             unsigned long flags)
> +{
> +       struct sock *sk = sock->sk;
> +       struct packet_sock *po = pkt_sk(sk);
> +
> +       /* check that they want to map the whole buffer */
> +       if (pgoff)
> +               return (unsigned long) -EINVAL;
> +
> +       lock_sock(sk);
> +       if (!po->pg_vec ||
> +           len != po->pg_vec_len * po->pg_vec_pages * PAGE_SIZE)
> +               addr = (unsigned long) -EINVAL;
> +       else
> +               addr = (unsigned long) po->pg_vec[0];
> +       release_sock(sk);
> +       return addr;
> +}
> +
> +/*
> + * set the mapping of a packet socket buffer for NOMMU mmap
> + */
> +static int packet_mmap(struct file *file, struct socket *sock,
> +                      struct vm_area_struct *vma)
> +{
> +       struct sock *sk = sock->sk;
> +       struct packet_sock *po = pkt_sk(sk);
> +       unsigned long len;
> +       int ret;
> +
> +       if (vma->vm_pgoff)
> +               return -EINVAL;
> +
> +       lock_sock(sk);
> +
> +       /* check that they want to map the whole buffer */
> +       len = vma->vm_end - vma->vm_start;
> +       if (!po->pg_vec ||
> +           len != po->pg_vec_len * po->pg_vec_pages * PAGE_SIZE) {
> +               ret = -EINVAL;
> +       } else if (vma->vm_start != (unsigned long) po->pg_vec[0]) {
> +               /* someone found the gap between get_unmapped_area and mmap */
> +               ret = -ESTALE;
> +       } else {
> +               atomic_inc(&po->mapped);
> +               vma->vm_ops = &packet_mmap_ops;
> +               ret = 0;
> +       }
> +
> +       release_sock(sk);
> +       return ret;
> +}
> +
> +#endif /* CONFIG_MMU */
> +#endif /* CONFIG_PACKET_MMAP */
>
>
>  #ifdef CONFIG_SOCK_PACKET
> @@ -1844,6 +1954,9 @@ static const struct proto_ops packet_ops_spkt = {
>         .getsockopt =   sock_no_getsockopt,
>         .sendmsg =      packet_sendmsg_spkt,
>         .recvmsg =      packet_recvmsg,
> +#ifndef CONFIG_MMU
> +       .get_unmapped_area = sock_no_get_unmapped_area,
> +#endif
>         .mmap =         sock_no_mmap,
>         .sendpage =     sock_no_sendpage,
>  };
> @@ -1866,6 +1979,9 @@ static const struct proto_ops packet_ops = {
>         .getsockopt =   packet_getsockopt,
>         .sendmsg =      packet_sendmsg,
>         .recvmsg =      packet_recvmsg,
> +#ifndef CONFIG_MMU
> +       .get_unmapped_area = packet_get_unmapped_area,
> +#endif
>         .mmap =         packet_mmap,
>         .sendpage =     sock_no_sendpage,
>  };
> diff --git a/net/socket.c b/net/socket.c
> index ea8f81a..4109db6 100644
> --- a/net/socket.c
> +++ b/net/socket.c
> @@ -87,6 +87,7 @@
>
>  #include <asm/uaccess.h>
>  #include <asm/unistd.h>
> +#include <asm/mman.h>
>
>  #include <net/compat.h>
>
> @@ -98,6 +99,13 @@ static ssize_t sock_aio_read(struct kiocb *iocb, const struct iovec *iov,
>                          unsigned long nr_segs, loff_t pos);
>  static ssize_t sock_aio_write(struct kiocb *iocb, const struct iovec *iov,
>                           unsigned long nr_segs, loff_t pos);
> +#ifndef CONFIG_MMU
> +static unsigned long sock_get_unmapped_area(struct file *file,
> +                                           unsigned long addr,
> +                                           unsigned long len,
> +                                           unsigned long pgoff,
> +                                           unsigned long flags);
> +#endif
>  static int sock_mmap(struct file *file, struct vm_area_struct *vma);
>
>  static int sock_close(struct inode *inode, struct file *file);
> @@ -127,6 +135,9 @@ static const struct file_operations socket_file_ops = {
>  #ifdef CONFIG_COMPAT
>         .compat_ioctl = compat_sock_ioctl,
>  #endif
> +#ifndef CONFIG_MMU
> +       .get_unmapped_area = sock_get_unmapped_area,
> +#endif
>         .mmap =         sock_mmap,
>         .open =         sock_no_open,   /* special open code to disallow open via /proc */
>         .release =      sock_close,
> @@ -136,6 +147,26 @@ static const struct file_operations socket_file_ops = {
>  };
>
>  /*
> + * capabilities for non-mappable sockets
> + * - does not permit mmap at all
> + * - no readahead or I/O queue unplugging required
> + */
> +struct backing_dev_info non_mappable_socket_bdi = {
> +       .capabilities   = 0,
> +};
> +
> +/*
> + * capabilities for read/write mappable sockets
> + * - permits shared-mmap for read and write only
> + * - does not permit private mmap
> + * - no readahead or I/O queue unplugging required
> + */
> +struct backing_dev_info rw_mappable_socket_bdi = {
> +       .capabilities   = (BDI_CAP_MAP_DIRECT | BDI_CAP_READ_MAP |
> +                          BDI_CAP_WRITE_MAP),
> +};
> +
> +/*
>   *     The protocol list. Each protocol is registered in here.
>   */
>
> @@ -415,6 +446,34 @@ static struct socket *sock_from_file(struct file *file, int *err)
>  }
>
>  /**
> + *     sock_make_mappable -    Change the mmappability of a socket
> + *     @sock: The socket to alter
> + *     @prot: The mmap protection to permit
> + *
> + *     The nominated socket has its backing device information selection
> + *     changed to indicate to mmap() what sort of mappings are available on
> + *     this socket.
> + */
> +void sock_make_mappable(struct socket *sock, unsigned long prot)
> +{
> +       struct address_space *mapping = &SOCK_INODE(sock)->i_data;
> +
> +       switch (prot) {
> +       case 0:
> +               mapping->backing_dev_info = &non_mappable_socket_bdi;
> +               break;
> +       case PROT_READ | PROT_WRITE:
> +               mapping->backing_dev_info = &rw_mappable_socket_bdi;
> +               break;
> +       case PROT_READ:
> +       case PROT_WRITE:
> +       default:
> +               BUG();
> +               break;
> +       }
> +}
> +
> +/**
>   *     sockfd_lookup   -       Go from a file number to its socket slot
>   *     @fd: file handle
>   *     @err: pointer to an error code return
> @@ -482,6 +541,7 @@ static struct socket *sock_alloc(void)
>         inode->i_mode = S_IFSOCK | S_IRWXUGO;
>         inode->i_uid = current->fsuid;
>         inode->i_gid = current->fsgid;
> +       inode->i_data.backing_dev_info = &non_mappable_socket_bdi;
>
>         get_cpu_var(sockets_in_use)++;
>         put_cpu_var(sockets_in_use);
> @@ -918,6 +978,22 @@ static unsigned int sock_poll(struct file *file, poll_table *wait)
>         return sock->ops->poll(file, sock, wait);
>  }
>
> +#ifndef CONFIG_MMU
> +static unsigned long sock_get_unmapped_area(struct file *file,
> +                                           unsigned long addr,
> +                                           unsigned long len,
> +                                           unsigned long pgoff,
> +                                           unsigned long flags)
> +{
> +       struct socket *sock = file->private_data;
> +
> +       if (!sock->ops->get_unmapped_area)
> +               return -ENOSYS;
> +       return sock->ops->get_unmapped_area(file, sock,
> +                                           addr, len, pgoff, flags);
> +}
> +#endif
> +
>  static int sock_mmap(struct file *file, struct vm_area_struct *vma)
>  {
>         struct socket *sock = file->private_data;
> @@ -2288,6 +2364,7 @@ EXPORT_SYMBOL(sock_create);
>  EXPORT_SYMBOL(sock_create_kern);
>  EXPORT_SYMBOL(sock_create_lite);
>  EXPORT_SYMBOL(sock_map_fd);
> +EXPORT_SYMBOL(sock_make_mappable);
>  EXPORT_SYMBOL(sock_recvmsg);
>  EXPORT_SYMBOL(sock_register);
>  EXPORT_SYMBOL(sock_release);
>

The patch works properly on my side. But
1) I'm not sure why you re-wrote alloc/free_pg_vec function, doesn't
the current implement work for NOMMU? I know you want to allocate the
entire data buffer as one contiguous lump, but is it really necessary?

2) So the mapped pages doesn't count into NR_FILE_MAPPED, is it a problem?

-Aubrey

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Howells]

Aubrey Li <aubreylee@gmail.com> wrote:

> The patch works properly on my side. But
> 1) I'm not sure why you re-wrote alloc/free_pg_vec function, doesn't
> the current implement work for NOMMU? I know you want to allocate the
> entire data buffer as one contiguous lump, but is it really necessary?

Yes.  It's not possible to map the whole buffer otherwise.  Think about it!
mmap() returns _one_ reference address.  In MMU-mode, the non-contiguous
physical buffers can be made to appear virtually contiguous by fudging the
page tables and using the MMU.  This is not possible in NOMMU-mode.  The app
will expect the buffer to be one contiguous lump in its address space, and
will not be able to locate the other segments of the buffer.

Actually, what I said is not quite true.  It is possible to map the whole
buffer otherwise: I could lift the restriction that requires that you map the
whole buffer or not at all, and then userspace could stitch the whole lot
together itself.  This would then require userspace to be bimodal.

> 2) So the mapped pages doesn't count into NR_FILE_MAPPED, is it a problem?

Not really, no - there are no pagetables.

Furthermore, issuing the PACKET_RX_RING sockopt does the entire allocation.
Any subsequent mmaps on it have little effect.

We could do that accounting though if you think it'd be better.  I don't
suppose it hurts.

David

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Aubrey Li]

On 4/20/07, David Howells <dhowells@redhat.com> wrote:
> Aubrey Li <aubreylee@gmail.com> wrote:
>
> > The patch works properly on my side. But
> > 1) I'm not sure why you re-wrote alloc/free_pg_vec function, doesn't
> > the current implement work for NOMMU? I know you want to allocate the
> > entire data buffer as one contiguous lump, but is it really necessary?
>
> Yes.  It's not possible to map the whole buffer otherwise.  Think about it!
> mmap() returns _one_ reference address.  In MMU-mode, the non-contiguous
> physical buffers can be made to appear virtually contiguous by fudging the
> page tables and using the MMU.  This is not possible in NOMMU-mode.  The app
> will expect the buffer to be one contiguous lump in its address space, and
> will not be able to locate the other segments of the buffer.

Great explanation, thanks, :-)

>
> Actually, what I said is not quite true.  It is possible to map the whole
> buffer otherwise: I could lift the restriction that requires that you map the
> whole buffer or not at all, and then userspace could stitch the whole lot
> together itself.  This would then require userspace to be bimodal.
>
> > 2) So the mapped pages doesn't count into NR_FILE_MAPPED, is it a problem?
>
> Not really, no - there are no pagetables.
>
> Furthermore, issuing the PACKET_RX_RING sockopt does the entire allocation.
> Any subsequent mmaps on it have little effect.
>
> We could do that accounting though if you think it'd be better.  I don't
> suppose it hurts.
>
as checked in packet_set_ring, buffer size must be a multiple of PAGE_SIZE,
--------------------packet_set_ring------------------------
if (unlikely(req->tp_block_size & (PAGE_SIZE - 1)))

So why not use __get_free_pages rather than kmalloc, so that we have
pagetables to count?

-Aubrey

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Howells]

Aubrey Li <aubreylee@gmail.com> wrote:

> as checked in packet_set_ring, buffer size must be a multiple of PAGE_SIZE,
> --------------------packet_set_ring------------------------
> if (unlikely(req->tp_block_size & (PAGE_SIZE - 1)))
> 
> So why not use __get_free_pages rather than kmalloc,

Because kmalloc() may be able to get us a smaller chunk of memory.  Actually,
calling __get_free_pages() might be a better, and then release the excess
pages.

> so that we have pagetables to count?

There are no pagetables in NOMMU-mode.

David

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Eric Dumazet]

On Fri, 20 Apr 2007 09:58:52 +0100
David Howells <dhowells@redhat.com> wrote:
> 
> Because kmalloc() may be able to get us a smaller chunk of memory.  Actually,
> calling __get_free_pages() might be a better, and then release the excess
> pages.

Interesting, that rings a bell here.

I wonder why we dont use this in alloc_large_system_hash().

(if __get_free_pages(GFP_ATOMIC, order) is used instead of alloc_bootmem() or __vmalloc())

We currently loose 1/4 of space on tcp hash table for example, because sizeof(inet_ehash_bucket) is not a power of 2.

Is it really possible to allocate an order-10 page, then release part of it (say an order-8 subpage) ?

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Howells]

Eric Dumazet <dada1@cosmosbay.com> wrote:

> Is it really possible to allocate an order-10 page, then release part of it
> (say an order-8 subpage) ?

Yes.

David

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Aubrey Li]

On 4/20/07, David Howells <dhowells@redhat.com> wrote:
> Aubrey Li <aubreylee@gmail.com> wrote:
>
> > as checked in packet_set_ring, buffer size must be a multiple of PAGE_SIZE,
> > --------------------packet_set_ring------------------------
> > if (unlikely(req->tp_block_size & (PAGE_SIZE - 1)))
> >
> > So why not use __get_free_pages rather than kmalloc,
>
> Because kmalloc() may be able to get us a smaller chunk of memory.  Actually,
> calling __get_free_pages() might be a better, and then release the excess
> pages.
>

>> so that we have pagetables to count?

>There are no pagetables in NOMMU-mode.

Hmm..., I'm thinking some codes in memory reclaim depend on
NR_FILE_MMAPED like follows
----snip----
if (zone_page_state(zone, NR_FILE_PAGES) -
                        zone_page_state(zone, NR_FILE_MAPPED) >
                        zone->min_unmapped_pages)
----snip----
Since we are enabling packet mmap feature, we should take its mapped
pages into count of NR_FILE_MAPPED.

-Aubrey

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Miller]

From: "Wu, Bryan" <bryan.wu@analog.com>
Date: Mon, 09 Apr 2007 17:50:22 +0800

> On Mon, 2007-04-09 at 11:01 +0800, Aubrey Li wrote:
> > The option CONFIG_PACKET_MMAP should depend on MMU.
> > 
> > Signed-off-by: Aubrey.Li <aubreylee@gmail.com>
> > ---
> >  net/packet/Kconfig |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> > 
> > diff --git a/net/packet/Kconfig b/net/packet/Kconfig
> > index 34ff93f..959c272 100644
> > --- a/net/packet/Kconfig
> > +++ b/net/packet/Kconfig
> > @@ -17,7 +17,7 @@ config PACKET
> > 
> >  config PACKET_MMAP
> >  	bool "Packet socket: mmapped IO"
> > -	depends on PACKET
> > +	depends on PACKET && MMU
> >  	help
> >  	  If you say Y here, the Packet protocol driver will use an IO
> >  	  mechanism that results in faster communication.
> 
> Yeah, this is a bug found on blackfin arch and it is also for other
> NOMMU arch. Is there any solution for this? We think Aubrey's idea
> works.

I will apply this patch.

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[David Miller]

From: David Miller <davem@davemloft.net>
Date: Mon, 09 Apr 2007 09:55:23 -0700 (PDT)

> From: "Wu, Bryan" <bryan.wu@analog.com>
> Date: Mon, 09 Apr 2007 17:50:22 +0800
> 
> > On Mon, 2007-04-09 at 11:01 +0800, Aubrey Li wrote:
> > > The option CONFIG_PACKET_MMAP should depend on MMU.
> > > 
> > > Signed-off-by: Aubrey.Li <aubreylee@gmail.com>
> > > ---
> > >  net/packet/Kconfig |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > > 
> > > diff --git a/net/packet/Kconfig b/net/packet/Kconfig
> > > index 34ff93f..959c272 100644
> > > --- a/net/packet/Kconfig
> > > +++ b/net/packet/Kconfig
> > > @@ -17,7 +17,7 @@ config PACKET
> > > 
> > >  config PACKET_MMAP
> > >  	bool "Packet socket: mmapped IO"
> > > -	depends on PACKET
> > > +	depends on PACKET && MMU
> > >  	help
> > >  	  If you say Y here, the Packet protocol driver will use an IO
> > >  	  mechanism that results in faster communication.
> > 
> > Yeah, this is a bug found on blackfin arch and it is also for other
> > NOMMU arch. Is there any solution for this? We think Aubrey's idea
> > works.
> 
> I will apply this patch.

Actually I won't, the other comments in this thread make a lot
of sense, we should try to make it build and work just as we
do for other similar things on no-MMU.

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Robin Getz]

On Mon 9 Apr 2007 14:43, David Miller pondered:
> From: David Miller <davem@davemloft.net>
> Date: Mon, 09 Apr 2007 09:55:23 -0700 (PDT)
> >
> > I will apply this patch.
>
> Actually I won't, the other comments in this thread make a lot
> of sense, we should try to make it build and work just as we
> do for other similar things on no-MMU.

Great. Any pointers in the right direction to remove the requirement of 
vm_insert_page() in the noMMU case?

Thanks
-Robin

Re: [PATCH] CONFIG_PACKET_MMAP should depend on MMU

[Wu, Bryan]

On Mon, 2007-04-09 at 16:08 -0400, Robin Getz wrote:
> On Mon 9 Apr 2007 14:43, David Miller pondered:
> > From: David Miller <davem@davemloft.net>
> > Date: Mon, 09 Apr 2007 09:55:23 -0700 (PDT)
> > >
> > > I will apply this patch.
> >
> > Actually I won't, the other comments in this thread make a lot
> > of sense, we should try to make it build and work just as we
> > do for other similar things on no-MMU.
> 
> Great. Any pointers in the right direction to remove the requirement of 
> vm_insert_page() in the noMMU case?
> 
> Thanks
> -Robin

OK, we will try to find other way to fix this bug according Robin's
comments.

Thanks
-Bryan