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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v2 5/7] Mini-OS: add 9pfs transport layer
Add the transport layer of 9pfs. This is basically the infrastructure
to send requests to the backend and to receive the related answers via
the rings.
As a first example add the version and attach requests of the 9pfs
protocol when mounting a new 9pfs device. For the version use the
"9P2000.u" variant, as it is the smallest subset supported by the qemu
based backend.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2:
- add more comments (Samuel Thibault)
- log short copy (Samuel Thibault)
- send event after consuming response (Samuel Thibault)
- reaturn EAGAIN in case no free request could be got (Samuel Thibault)
---
9pfront.c | 478 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 478 insertions(+)
diff --git a/9pfront.c b/9pfront.c
index 89ecb3a1..0b8d5461 100644
--- a/9pfront.c
+++ b/9pfront.c
@@ -7,6 +7,8 @@
#include <mini-os/lib.h>
#include <mini-os/events.h>
#include <mini-os/gnttab.h>
+#include <mini-os/semaphore.h>
+#include <mini-os/wait.h>
#include <mini-os/xenbus.h>
#include <mini-os/xmalloc.h>
#include <errno.h>
@@ -14,6 +16,9 @@
#include <mini-os/9pfront.h>
#ifdef HAVE_LIBC
+
+#define N_REQS 64
+
struct dev_9pfs {
int id;
char nodename[20];
@@ -22,6 +27,7 @@ struct dev_9pfs {
char *tag;
const char *mnt;
+ unsigned int msize_max;
struct xen_9pfs_data_intf *intf;
struct xen_9pfs_data data;
@@ -32,14 +38,470 @@ struct dev_9pfs {
evtchn_port_t evtchn;
unsigned int ring_order;
xenbus_event_queue events;
+
+ unsigned int free_reqs;
+ struct req {
+ unsigned int id;
+ unsigned int next_free; /* N_REQS == end of list. */
+ unsigned int cmd;
+ int result;
+ bool inflight;
+ unsigned char *data; /* Returned data. */
+ } req[N_REQS];
+
+ struct wait_queue_head waitq;
+ struct semaphore ring_out_sem;
+ struct semaphore ring_in_sem;
};
#define DEFAULT_9PFS_RING_ORDER 4
+#define P9_CMD_VERSION 100
+#define P9_CMD_ATTACH 104
+#define P9_CMD_ERROR 107
+
+#define P9_QID_SIZE 13
+
+struct p9_header {
+ uint32_t size;
+ uint8_t cmd;
+ uint16_t tag;
+} __attribute__((packed));
+
+#define P9_VERSION "9P2000.u"
+#define P9_ROOT_FID ~0
+
static unsigned int ftype_9pfs;
+static struct req *get_free_req(struct dev_9pfs *dev)
+{
+ struct req *req;
+
+ if ( dev->free_reqs == N_REQS )
+ return NULL;
+
+ req = dev->req + dev->free_reqs;
+ dev->free_reqs = req->next_free;
+
+ return req;
+}
+
+static void put_free_req(struct dev_9pfs *dev, struct req *req)
+{
+ req->next_free = dev->free_reqs;
+ req->inflight = false;
+ req->data = NULL;
+ dev->free_reqs = req->id;
+}
+
+static unsigned int ring_out_free(struct dev_9pfs *dev)
+{
+ RING_IDX ring_size = XEN_FLEX_RING_SIZE(dev->ring_order);
+ unsigned int queued;
+
+ queued = xen_9pfs_queued(dev->prod_pvt_out, dev->intf->out_cons,
ring_size);
+ rmb();
+
+ return ring_size - queued;
+}
+
+static unsigned int ring_in_data(struct dev_9pfs *dev)
+{
+ RING_IDX ring_size = XEN_FLEX_RING_SIZE(dev->ring_order);
+ unsigned int queued;
+
+ queued = xen_9pfs_queued(dev->intf->in_prod, dev->cons_pvt_in, ring_size);
+ rmb();
+
+ return queued;
+}
+
+static void copy_to_ring(struct dev_9pfs *dev, void *data, unsigned int len)
+{
+ RING_IDX ring_size = XEN_FLEX_RING_SIZE(dev->ring_order);
+ RING_IDX prod = xen_9pfs_mask(dev->prod_pvt_out, ring_size);
+ RING_IDX cons = xen_9pfs_mask(dev->intf->out_cons, ring_size);
+
+ xen_9pfs_write_packet(dev->data.out, data, len, &prod, cons, ring_size);
+ dev->prod_pvt_out += len;
+}
+
+static void copy_from_ring(struct dev_9pfs *dev, void *data, unsigned int len)
+{
+ RING_IDX ring_size = XEN_FLEX_RING_SIZE(dev->ring_order);
+ RING_IDX prod = xen_9pfs_mask(dev->intf->in_prod, ring_size);
+ RING_IDX cons = xen_9pfs_mask(dev->cons_pvt_in, ring_size);
+
+ xen_9pfs_read_packet(data, dev->data.in, len, prod, &cons, ring_size);
+ dev->cons_pvt_in += len;
+}
+
+/*
+ * send_9p() and rcv_9p() are using a special format string for specifying
+ * the kind of data sent/expected. Each data item is represented by a single
+ * character:
+ * U: 4 byte unsigned integer (uint32_t)
+ * S: String (2 byte length + <length> characters)
+ * in the rcv_9p() case the data for string is allocated (length omitted,
+ * string terminated by a NUL character)
+ * Q: A 13 byte "qid", consisting of 1 byte file type, 4 byte file version
+ * and 8 bytes unique file id. Only valid for receiving.
+ */
+static void send_9p(struct dev_9pfs *dev, struct req *req, const char *fmt,
...)
+{
+ struct p9_header hdr;
+ va_list ap, aq;
+ const char *f;
+ uint32_t intval;
+ uint16_t len;
+ char *strval;
+
+ hdr.size = sizeof(hdr);
+ hdr.cmd = req->cmd;
+ hdr.tag = req->id;
+
+ va_start(ap, fmt);
+
+ va_copy(aq, ap);
+ for ( f = fmt; *f; f++ )
+ {
+ switch ( *f )
+ {
+ case 'U':
+ hdr.size += 4;
+ intval = va_arg(aq, unsigned int);
+ break;
+ case 'S':
+ hdr.size += 2;
+ strval = va_arg(aq, char *);
+ hdr.size += strlen(strval);
+ break;
+ default:
+ printk("send_9p: unknown format character %c\n", *f);
+ break;
+ }
+ }
+ va_end(aq);
+
+ /*
+ * Waiting for free space must be done in the critical section!
+ * Otherwise we might get overtaken by other short requests.
+ */
+ down(&dev->ring_out_sem);
+
+ wait_event(dev->waitq, ring_out_free(dev) >= hdr.size);
+
+ copy_to_ring(dev, &hdr, sizeof(hdr));
+ for ( f = fmt; *f; f++ )
+ {
+ switch ( *f )
+ {
+ case 'U':
+ intval = va_arg(ap, unsigned int);
+ copy_to_ring(dev, &intval, sizeof(intval));
+ break;
+ case 'S':
+ strval = va_arg(ap, char *);
+ len = strlen(strval);
+ copy_to_ring(dev, &len, sizeof(len));
+ copy_to_ring(dev, strval, len);
+ break;
+ }
+ }
+
+ wmb(); /* Data on ring must be seen before updating index. */
+ dev->intf->out_prod = dev->prod_pvt_out;
+ req->inflight = true;
+
+ up(&dev->ring_out_sem);
+
+ va_end(ap);
+
+ notify_remote_via_evtchn(dev->evtchn);
+}
+
+/*
+ * Using an opportunistic approach for receiving data: in case multiple
+ * requests are outstanding (which is very unlikely), we nevertheless need
+ * to consume all data available until we reach the desired request.
+ * For requests other than the one we are waiting for, we link the complete
+ * data to the request via an intermediate buffer. For our own request we can
+ * omit that buffer and directly fill the caller provided variables.
+ *
+ * Helper functions:
+ *
+ * copy_bufs(): copy raw data into a target buffer. There can be 2 source
+ * buffers involved (in case the copy is done from the ring and it is across
+ * the ring end). The buffer pointers and lengths are updated according to
+ * the number of bytes copied.
+ *
+ * rcv_9p_copy(): copy the data (without the generic header) of a 9p response
+ * to the specified variables using the specified format string for
+ * deciphering the single item types. The decision whether to copy from the
+ * ring or an allocated buffer is done via the "hdr" parameter, which is
+ * NULL in the buffer case (in that case the header is located at the start
+ * of the buffer).
+ *
+ * rcv_9p_one(): Checks for an already filled buffer with the correct tag in
+ * it. If none is found, consumes one response. It checks the tag of the
+ * response in order to decide whether to allocate a buffer for putting the
+ * data into, or to fill the user supplied variables. Return true, if the
+ * tag did match. Waits if no data is ready to be consumed.
+ */
+static void copy_bufs(unsigned char **buf1, unsigned char **buf2,
+ unsigned int *len1, unsigned int *len2,
+ void *target, unsigned int len)
+{
+ if ( len <= *len1 )
+ {
+ memcpy(target, *buf1, len);
+ *buf1 += len;
+ *len1 -= len;
+ }
+ else
+ {
+ memcpy(target, *buf1, *len1);
+ target = (char *)target + *len1;
+ len -= *len1;
+ *buf1 = *buf2;
+ *len1 = *len2;
+ *buf2 = NULL;
+ *len2 = 0;
+ if ( len > *len1 )
+ {
+ printk("9pfs: short copy (dropping %u bytes)\n", len - *len1);
+ len = *len1;
+ }
+ memcpy(target, *buf1, *len1);
+ }
+}
+
+static void rcv_9p_copy(struct dev_9pfs *dev, struct req *req,
+ struct p9_header *hdr, const char *fmt, va_list ap)
+{
+ struct p9_header *h = hdr ? hdr : (void *)req->data;
+ RING_IDX cons = dev->cons_pvt_in + h->size - sizeof(*h);
+ RING_IDX ring_size = XEN_FLEX_RING_SIZE(dev->ring_order);
+ unsigned char *buf1, *buf2;
+ unsigned int len1, len2;
+ const char *f;
+ char *str;
+ uint16_t len;
+ uint32_t err;
+ uint32_t *val;
+ char **strval;
+ uint8_t *qval;
+
+ if ( hdr )
+ {
+ buf1 = xen_9pfs_get_ring_ptr(dev->data.in, dev->cons_pvt_in,
ring_size);
+ buf2 = xen_9pfs_get_ring_ptr(dev->data.in, 0, ring_size);
+ len1 = ring_size - xen_9pfs_mask(dev->cons_pvt_in, ring_size);
+ if ( len1 > h->size - sizeof(*h) )
+ len1 = h->size - sizeof(*h);
+ len2 = h->size - sizeof(*h) - len1;
+ }
+ else
+ {
+ buf1 = req->data + sizeof(*h);
+ buf2 = NULL;
+ len1 = h->size - sizeof(*h);
+ len2 = 0;
+ }
+
+ if ( h->cmd == P9_CMD_ERROR )
+ {
+ copy_bufs(&buf1, &buf2, &len1, &len2, &len, sizeof(len));
+ str = malloc(len + 1);
+ copy_bufs(&buf1, &buf2, &len1, &len2, str, len);
+ str[len] = 0;
+ printk("9pfs: request %u resulted in \"%s\"\n", req->cmd, str);
+ free(str);
+ err = EIO;
+ copy_bufs(&buf1, &buf2, &len1, &len2, &err, sizeof(err));
+ req->result = err;
+
+ if ( hdr )
+ dev->cons_pvt_in = cons;
+
+ return;
+ }
+
+ if ( h->cmd != req->cmd + 1 )
+ {
+ req->result = EDOM;
+ printk("9pfs: illegal response: wrong return type (%u instead of
%u)\n",
+ h->cmd, req->cmd + 1);
+
+ if ( hdr )
+ dev->cons_pvt_in = cons;
+
+ return;
+ }
+
+ req->result = 0;
+
+ for ( f = fmt; *f; f++ )
+ {
+ switch ( *f )
+ {
+ case 'U':
+ val = va_arg(ap, uint32_t *);
+ copy_bufs(&buf1, &buf2, &len1, &len2, val, sizeof(*val));
+ break;
+ case 'S':
+ strval = va_arg(ap, char **);
+ copy_bufs(&buf1, &buf2, &len1, &len2, &len, sizeof(len));
+ *strval = malloc(len + 1);
+ copy_bufs(&buf1, &buf2, &len1, &len2, *strval, len);
+ (*strval)[len] = 0;
+ break;
+ case 'Q':
+ qval = va_arg(ap, uint8_t *);
+ copy_bufs(&buf1, &buf2, &len1, &len2, qval, P9_QID_SIZE);
+ break;
+ default:
+ printk("rcv_9p: unknown format character %c\n", *f);
+ break;
+ }
+ }
+
+ if ( hdr )
+ dev->cons_pvt_in = cons;
+}
+
+static bool rcv_9p_one(struct dev_9pfs *dev, struct req *req, const char *fmt,
+ va_list ap)
+{
+ struct p9_header hdr;
+ struct req *tmp;
+
+ if ( req->data )
+ {
+ rcv_9p_copy(dev, req, NULL, fmt, ap);
+ free(req->data);
+ req->data = NULL;
+
+ return true;
+ }
+
+ wait_event(dev->waitq, ring_in_data(dev) >= sizeof(hdr));
+
+ copy_from_ring(dev, &hdr, sizeof(hdr));
+
+ wait_event(dev->waitq, ring_in_data(dev) >= hdr.size - sizeof(hdr));
+
+ tmp = dev->req + hdr.tag;
+ if ( hdr.tag >= N_REQS || !tmp->inflight )
+ {
+ printk("9pfs: illegal response: %s\n",
+ hdr.tag >= N_REQS ? "tag out of bounds" : "request not
pending");
+ dev->cons_pvt_in += hdr.size - sizeof(hdr);
+
+ return false;
+ }
+
+ tmp->inflight = false;
+
+ if ( tmp != req )
+ {
+ tmp->data = malloc(hdr.size);
+ memcpy(tmp->data, &hdr, sizeof(hdr));
+ copy_from_ring(dev, tmp->data + sizeof(hdr), hdr.size - sizeof(hdr));
+
+ return false;
+ }
+
+ rcv_9p_copy(dev, req, &hdr, fmt, ap);
+
+ return true;
+}
+
+static void rcv_9p(struct dev_9pfs *dev, struct req *req, const char *fmt, ...)
+{
+ va_list ap;
+
+ va_start(ap, fmt);
+
+ down(&dev->ring_in_sem);
+
+ while ( !rcv_9p_one(dev, req, fmt, ap) );
+
+ rmb(); /* Read all data before updating ring index. */
+ dev->intf->in_cons = dev->cons_pvt_in;
+
+ notify_remote_via_evtchn(dev->evtchn);
+
+ up(&dev->ring_in_sem);
+
+ va_end(ap);
+}
+
+static int p9_version(struct dev_9pfs *dev)
+{
+ unsigned int msize = XEN_FLEX_RING_SIZE(dev->ring_order) / 2;
+ struct req *req = get_free_req(dev);
+ char *verret;
+ int ret;
+
+ if ( !req )
+ return EAGAIN;
+
+ req->cmd = P9_CMD_VERSION;
+ send_9p(dev, req, "US", msize, P9_VERSION);
+ rcv_9p(dev, req, "US", &dev->msize_max, &verret);
+ ret = req->result;
+
+ put_free_req(dev, req);
+
+ if ( ret )
+ return ret;
+
+ if ( strcmp(verret, P9_VERSION) )
+ ret = ENOMSG;
+ free(verret);
+
+ return ret;
+}
+
+static int p9_attach(struct dev_9pfs *dev)
+{
+ uint32_t fid = P9_ROOT_FID;
+ uint32_t afid = 0;
+ uint32_t uid = 0;
+ uint8_t qid[P9_QID_SIZE];
+ struct req *req = get_free_req(dev);
+ int ret;
+
+ if ( !req )
+ return EAGAIN;
+
+ req->cmd = P9_CMD_ATTACH;
+ send_9p(dev, req, "UUSSU", fid, afid, "root", "root", uid);
+ rcv_9p(dev, req, "Q", qid);
+ ret = req->result;
+
+ put_free_req(dev, req);
+
+ return ret;
+}
+
+static int connect_9pfs(struct dev_9pfs *dev)
+{
+ int ret;
+
+ ret = p9_version(dev);
+ if ( ret )
+ return ret;
+
+ return p9_attach(dev);
+}
+
static void intr_9pfs(evtchn_port_t port, struct pt_regs *regs, void *data)
{
+ struct dev_9pfs *dev = data;
+
+ wake_up(&dev->waitq);
}
static int open_9pfs(struct mount_point *mnt, const char *pathname, int flags,
@@ -87,6 +549,16 @@ void *init_9pfront(unsigned int id, const char *mnt)
memset(dev, 0, sizeof(*dev));
snprintf(dev->nodename, sizeof(dev->nodename), "device/9pfs/%u", id);
dev->id = id;
+ init_waitqueue_head(&dev->waitq);
+ init_SEMAPHORE(&dev->ring_out_sem, 1);
+ init_SEMAPHORE(&dev->ring_in_sem, 1);
+
+ for ( i = 0; i < N_REQS; i++ )
+ {
+ dev->req[i].id = i;
+ dev->req[i].next_free = i + 1;
+ }
+ dev->free_reqs = 0;
msg = xenbus_read_unsigned(XBT_NIL, dev->nodename, "backend-id",
&dev->dom);
if ( msg )
@@ -205,6 +677,12 @@ void *init_9pfront(unsigned int id, const char *mnt)
unmask_evtchn(dev->evtchn);
+ if ( connect_9pfs(dev) )
+ {
+ reason = "9pfs connect failed";
+ goto err;
+ }
+
dev->mnt = mnt;
if ( mount(dev->mnt, dev, open_9pfs) )
{
--
2.35.3
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