--- /dev/null
+/*
+ * xenbus.c: static, synchronous, read-only xenbus client for hvmloader.
+ *
+ * Copyright (c) 2009 Tim Deegan, Citrix Systems (R&D) Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59 Temple
+ * Place - Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include "util.h"
+#include "hypercall.h"
+#include <errno.h>
+#include <xen/sched.h>
+#include <xen/event_channel.h>
+#include <xen/hvm/params.h>
+#include <xen/io/xs_wire.h>
+
+struct xenstore_domain_interface *rings; /* Shared ring with dom0 */
+evtchn_port_t event; /* Event-channel to dom0 */
+char payload[XENSTORE_PAYLOAD_MAX + 1]; /* Unmarshalling area */
+
+/* Connect our xenbus client to the backend.
+ * Call once, before any other xenbus actions. */
+void xenbus_setup(void)
+{
+ xen_hvm_param_t param;
+
+ /* Ask Xen where the xenbus shared page is. */
+ param.domid = DOMID_SELF;
+ param.index = HVM_PARAM_STORE_PFN;
+ if ( hypercall_hvm_op(HVMOP_get_param, ¶m) )
+ BUG();
+ rings = (void *) (unsigned long) (param.value << PAGE_SHIFT);
+
+ /* Ask Xen where the xenbus event channel is. */
+ param.domid = DOMID_SELF;
+ param.index = HVM_PARAM_STORE_EVTCHN;
+ if ( hypercall_hvm_op(HVMOP_get_param, ¶m) )
+ BUG();
+ event = param.value;
+
+ printf("Xenbus rings @0x%lx, event channel %lu\n",
+ (unsigned long) rings, (unsigned long) event);
+}
+
+/* Reset the xenbus connection so the next kernel can start again.
+ * We zero out the whole ring -- the backend can handle this, and it's
+ * not going to surprise any frontends since it's equivalent to never
+ * having used the rings. */
+void xenbus_shutdown(void)
+{
+ ASSERT(rings != NULL);
+ memset(rings, 0, sizeof *rings);
+ rings = NULL;
+}
+
+/* Helper functions: copy data in and out of the ring */
+static void ring_write(char *data, uint32_t len)
+{
+ uint32_t part;
+
+ ASSERT(len <= XENSTORE_PAYLOAD_MAX);
+
+ while ( len )
+ {
+ /* Don't overrun the consumer pointer */
+ part = (XENSTORE_RING_SIZE - 1) -
+ MASK_XENSTORE_IDX(rings->req_prod - rings->req_cons);
+ /* Don't overrun the end of the ring */
+ if ( part > (XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(rings->req_prod)) )
+ part = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(rings->req_prod);
+ /* Don't write more than we were asked for */
+ if ( part > len )
+ part = len;
+
+ memcpy(rings->req + MASK_XENSTORE_IDX(rings->req_prod), data, part);
+ barrier(); /* = wmb before prod write, rmb before next cons read */
+ rings->req_prod += part;
+ len -= part;
+
+ if ( len )
+ hypercall_sched_op(SCHEDOP_yield, NULL);
+ }
+}
+
+static void ring_read(char *data, uint32_t len)
+{
+ uint32_t part;
+
+ ASSERT(len <= XENSTORE_PAYLOAD_MAX);
+
+ while ( len )
+ {
+ /* Don't overrun the producer pointer */
+ part = MASK_XENSTORE_IDX(rings->rsp_prod - rings->rsp_cons);
+ /* Don't overrun the end of the ring */
+ if ( part > (XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(rings->rsp_cons)) )
+ part = XENSTORE_RING_SIZE - MASK_XENSTORE_IDX(rings->rsp_cons);
+ /* Don't read more than we were asked for */
+ if ( part > len )
+ part = len;
+
+ memcpy(data, rings->rsp + MASK_XENSTORE_IDX(rings->rsp_cons), part);
+ barrier(); /* = wmb before cons write, rmb before next prod read */
+ rings->rsp_cons += part;
+ len -= part;
+
+ if ( len )
+ hypercall_sched_op(SCHEDOP_yield, NULL);
+ }
+}
+
+
+/* Send a request and wait for the answer.
+ * Returns 0 for success, or an errno for error.
+ * The answer is returned in a static buffer which is only
+ * valid until the next call of xenbus_send(). */
+static int xenbus_send(uint32_t type, uint32_t len, char *data,
+ uint32_t *reply_len, char **reply_data)
+{
+ struct xsd_sockmsg hdr;
+ evtchn_send_t send;
+ int i;
+
+ /* Not acceptable to use xenbus before setting it up */
+ ASSERT(rings != NULL);
+
+ /* Put the request on the ring */
+ hdr.type = type;
+ hdr.req_id = 0; /* We only ever issue one request at a time */
+ hdr.tx_id = 0; /* We never use transactions */
+ hdr.len = len;
+ ring_write((char *) &hdr, sizeof hdr);
+ ring_write(data, len);
+
+ /* Tell the other end about the request */
+ send.port = event;
+ hypercall_event_channel_op(EVTCHNOP_send, &send);
+
+ /* Properly we should poll the event channel now but that involves
+ * mapping the shared-info page and handling the bitmaps. */
+
+ /* Pull the reply off the ring */
+ ring_read((char *) &hdr, sizeof(hdr));
+ ring_read(payload, hdr.len);
+ /* For sanity's sake, nul-terminate the answer */
+ payload[hdr.len] = '\0';
+
+ /* Handle errors */
+ if ( hdr.type == XS_ERROR )
+ {
+ *reply_len = 0;
+ for ( i = 0; i < ((sizeof xsd_errors) / (sizeof xsd_errors[0])); i++ )
+ if ( !strcmp(xsd_errors[i].errstring, payload) )
+ return xsd_errors[i].errnum;
+ /* Default error value if we couldn't decode the ASCII error */
+ return EIO;
+ }
+
+ *reply_data = payload;
+ *reply_len = hdr.len;
+ return 0;
+}
+
+
+/* Read a xenstore key. Returns a nul-terminated string (even if the XS
+ * data wasn't nul-terminated) or NULL. The returned string is in a
+ * static buffer, so only valid until the next xenstore/xenbus operation. */
+char *xenstore_read(char *path)
+{
+ uint32_t len = 0;
+ char *answer = NULL;
+
+ /* Include the nul in the request */
+ if ( xenbus_send(XS_READ, strlen(path) + 1, path, &len, &answer) )
+ return NULL;
+ /* We know xenbus_send() nul-terminates its answer, so just pass it on. */
+ return answer;
+}
+
+
+/*
+ * Local variables:
+ * mode: C
+ * c-set-style: "BSD"
+ * c-basic-offset: 4
+ * tab-width: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
projects / xen.git / commitdiff