/* * QEMU Xen emulation: Shared/overlay pages support * * Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved. * * Authors: David Woodhouse * * This work is licensed under the terms of the GNU GPL, version 2 or later. * See the COPYING file in the top-level directory. */ #include "qemu/osdep.h" #include "qemu/host-utils.h" #include "qemu/module.h" #include "qemu/main-loop.h" #include "qemu/cutils.h" #include "qemu/error-report.h" #include "qapi/error.h" #include "qom/object.h" #include "migration/vmstate.h" #include "hw/sysbus.h" #include "hw/xen/xen.h" #include "hw/xen/xen_backend_ops.h" #include "xen_overlay.h" #include "xen_evtchn.h" #include "xen_xenstore.h" #include "sysemu/kvm.h" #include "sysemu/kvm_xen.h" #include "trace.h" #include "xenstore_impl.h" #include "hw/xen/interface/io/xs_wire.h" #include "hw/xen/interface/event_channel.h" #include "hw/xen/interface/grant_table.h" #define TYPE_XEN_XENSTORE "xen-xenstore" OBJECT_DECLARE_SIMPLE_TYPE(XenXenstoreState, XEN_XENSTORE) #define ENTRIES_PER_FRAME_V1 (XEN_PAGE_SIZE / sizeof(grant_entry_v1_t)) #define ENTRIES_PER_FRAME_V2 (XEN_PAGE_SIZE / sizeof(grant_entry_v2_t)) #define XENSTORE_HEADER_SIZE ((unsigned int)sizeof(struct xsd_sockmsg)) struct XenXenstoreState { /*< private >*/ SysBusDevice busdev; /*< public >*/ XenstoreImplState *impl; GList *watch_events; /* for the guest */ MemoryRegion xenstore_page; struct xenstore_domain_interface *xs; uint8_t req_data[XENSTORE_HEADER_SIZE + XENSTORE_PAYLOAD_MAX]; uint8_t rsp_data[XENSTORE_HEADER_SIZE + XENSTORE_PAYLOAD_MAX]; uint32_t req_offset; uint32_t rsp_offset; bool rsp_pending; bool fatal_error; evtchn_port_t guest_port; evtchn_port_t be_port; struct xenevtchn_handle *eh; uint8_t *impl_state; uint32_t impl_state_size; struct xengntdev_handle *gt; void *granted_xs; }; struct XenXenstoreState *xen_xenstore_singleton; static void xen_xenstore_event(void *opaque); static void fire_watch_cb(void *opaque, const char *path, const char *token); static struct xenstore_backend_ops emu_xenstore_backend_ops; static void G_GNUC_PRINTF (4, 5) relpath_printf(XenXenstoreState *s, GList *perms, const char *relpath, const char *fmt, ...) { gchar *abspath; gchar *value; va_list args; GByteArray *data; int err; abspath = g_strdup_printf("/local/domain/%u/%s", xen_domid, relpath); va_start(args, fmt); value = g_strdup_vprintf(fmt, args); va_end(args); data = g_byte_array_new_take((void *)value, strlen(value)); err = xs_impl_write(s->impl, DOMID_QEMU, XBT_NULL, abspath, data); assert(!err); g_byte_array_unref(data); err = xs_impl_set_perms(s->impl, DOMID_QEMU, XBT_NULL, abspath, perms); assert(!err); g_free(abspath); } static void xen_xenstore_realize(DeviceState *dev, Error **errp) { XenXenstoreState *s = XEN_XENSTORE(dev); GList *perms; if (xen_mode != XEN_EMULATE) { error_setg(errp, "Xen xenstore support is for Xen emulation"); return; } memory_region_init_ram(&s->xenstore_page, OBJECT(dev), "xen:xenstore_page", XEN_PAGE_SIZE, &error_abort); memory_region_set_enabled(&s->xenstore_page, true); s->xs = memory_region_get_ram_ptr(&s->xenstore_page); memset(s->xs, 0, XEN_PAGE_SIZE); /* We can't map it this early as KVM isn't ready */ xen_xenstore_singleton = s; s->eh = xen_be_evtchn_open(); if (!s->eh) { error_setg(errp, "Xenstore evtchn port init failed"); return; } aio_set_fd_handler(qemu_get_aio_context(), xen_be_evtchn_fd(s->eh), xen_xenstore_event, NULL, NULL, NULL, s); s->impl = xs_impl_create(xen_domid); /* Populate the default nodes */ /* Nodes owned by 'dom0' but readable by the guest */ perms = g_list_append(NULL, xs_perm_as_string(XS_PERM_NONE, DOMID_QEMU)); perms = g_list_append(perms, xs_perm_as_string(XS_PERM_READ, xen_domid)); relpath_printf(s, perms, "", "%s", ""); relpath_printf(s, perms, "domid", "%u", xen_domid); relpath_printf(s, perms, "control/platform-feature-xs_reset_watches", "%u", 1); relpath_printf(s, perms, "control/platform-feature-multiprocessor-suspend", "%u", 1); relpath_printf(s, perms, "platform/acpi", "%u", 1); relpath_printf(s, perms, "platform/acpi_s3", "%u", 1); relpath_printf(s, perms, "platform/acpi_s4", "%u", 1); relpath_printf(s, perms, "platform/acpi_laptop_slate", "%u", 0); g_list_free_full(perms, g_free); /* Nodes owned by the guest */ perms = g_list_append(NULL, xs_perm_as_string(XS_PERM_NONE, xen_domid)); relpath_printf(s, perms, "attr", "%s", ""); relpath_printf(s, perms, "control/shutdown", "%s", ""); relpath_printf(s, perms, "control/feature-poweroff", "%u", 1); relpath_printf(s, perms, "control/feature-reboot", "%u", 1); relpath_printf(s, perms, "control/feature-suspend", "%u", 1); relpath_printf(s, perms, "control/feature-s3", "%u", 1); relpath_printf(s, perms, "control/feature-s4", "%u", 1); relpath_printf(s, perms, "data", "%s", ""); relpath_printf(s, perms, "device", "%s", ""); relpath_printf(s, perms, "drivers", "%s", ""); relpath_printf(s, perms, "error", "%s", ""); relpath_printf(s, perms, "feature", "%s", ""); g_list_free_full(perms, g_free); xen_xenstore_ops = &emu_xenstore_backend_ops; } static bool xen_xenstore_is_needed(void *opaque) { return xen_mode == XEN_EMULATE; } static int xen_xenstore_pre_save(void *opaque) { XenXenstoreState *s = opaque; GByteArray *save; if (s->eh) { s->guest_port = xen_be_evtchn_get_guest_port(s->eh); } g_free(s->impl_state); save = xs_impl_serialize(s->impl); s->impl_state = save->data; s->impl_state_size = save->len; g_byte_array_free(save, false); return 0; } static int xen_xenstore_post_load(void *opaque, int ver) { XenXenstoreState *s = opaque; GByteArray *save; int ret; /* * As qemu/dom0, rebind to the guest's port. The Windows drivers may * unbind the XenStore evtchn and rebind to it, having obtained the * "remote" port through EVTCHNOP_status. In the case that migration * occurs while it's unbound, the "remote" port needs to be the same * as before so that the guest can find it, but should remain unbound. */ if (s->guest_port) { int be_port = xen_be_evtchn_bind_interdomain(s->eh, xen_domid, s->guest_port); if (be_port < 0) { return be_port; } s->be_port = be_port; } save = g_byte_array_new_take(s->impl_state, s->impl_state_size); s->impl_state = NULL; s->impl_state_size = 0; ret = xs_impl_deserialize(s->impl, save, xen_domid, fire_watch_cb, s); return ret; } static const VMStateDescription xen_xenstore_vmstate = { .name = "xen_xenstore", .unmigratable = 1, /* The PV back ends don't migrate yet */ .version_id = 1, .minimum_version_id = 1, .needed = xen_xenstore_is_needed, .pre_save = xen_xenstore_pre_save, .post_load = xen_xenstore_post_load, .fields = (VMStateField[]) { VMSTATE_UINT8_ARRAY(req_data, XenXenstoreState, sizeof_field(XenXenstoreState, req_data)), VMSTATE_UINT8_ARRAY(rsp_data, XenXenstoreState, sizeof_field(XenXenstoreState, rsp_data)), VMSTATE_UINT32(req_offset, XenXenstoreState), VMSTATE_UINT32(rsp_offset, XenXenstoreState), VMSTATE_BOOL(rsp_pending, XenXenstoreState), VMSTATE_UINT32(guest_port, XenXenstoreState), VMSTATE_BOOL(fatal_error, XenXenstoreState), VMSTATE_UINT32(impl_state_size, XenXenstoreState), VMSTATE_VARRAY_UINT32_ALLOC(impl_state, XenXenstoreState, impl_state_size, 0, vmstate_info_uint8, uint8_t), VMSTATE_END_OF_LIST() } }; static void xen_xenstore_class_init(ObjectClass *klass, void *data) { DeviceClass *dc = DEVICE_CLASS(klass); dc->realize = xen_xenstore_realize; dc->vmsd = &xen_xenstore_vmstate; } static const TypeInfo xen_xenstore_info = { .name = TYPE_XEN_XENSTORE, .parent = TYPE_SYS_BUS_DEVICE, .instance_size = sizeof(XenXenstoreState), .class_init = xen_xenstore_class_init, }; void xen_xenstore_create(void) { DeviceState *dev = sysbus_create_simple(TYPE_XEN_XENSTORE, -1, NULL); xen_xenstore_singleton = XEN_XENSTORE(dev); /* * Defer the init (xen_xenstore_reset()) until KVM is set up and the * overlay page can be mapped. */ } static void xen_xenstore_register_types(void) { type_register_static(&xen_xenstore_info); } type_init(xen_xenstore_register_types) uint16_t xen_xenstore_get_port(void) { XenXenstoreState *s = xen_xenstore_singleton; if (!s) { return 0; } return s->guest_port; } static bool req_pending(XenXenstoreState *s) { struct xsd_sockmsg *req = (struct xsd_sockmsg *)s->req_data; return s->req_offset == XENSTORE_HEADER_SIZE + req->len; } static void reset_req(XenXenstoreState *s) { memset(s->req_data, 0, sizeof(s->req_data)); s->req_offset = 0; } static void reset_rsp(XenXenstoreState *s) { s->rsp_pending = false; memset(s->rsp_data, 0, sizeof(s->rsp_data)); s->rsp_offset = 0; } static void xs_error(XenXenstoreState *s, unsigned int id, xs_transaction_t tx_id, int errnum) { struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; const char *errstr = NULL; for (unsigned int i = 0; i < ARRAY_SIZE(xsd_errors); i++) { struct xsd_errors *xsd_error = &xsd_errors[i]; if (xsd_error->errnum == errnum) { errstr = xsd_error->errstring; break; } } assert(errstr); trace_xenstore_error(id, tx_id, errstr); rsp->type = XS_ERROR; rsp->req_id = id; rsp->tx_id = tx_id; rsp->len = (uint32_t)strlen(errstr) + 1; memcpy(&rsp[1], errstr, rsp->len); } static void xs_ok(XenXenstoreState *s, unsigned int type, unsigned int req_id, xs_transaction_t tx_id) { struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; const char *okstr = "OK"; rsp->type = type; rsp->req_id = req_id; rsp->tx_id = tx_id; rsp->len = (uint32_t)strlen(okstr) + 1; memcpy(&rsp[1], okstr, rsp->len); } /* * The correct request and response formats are documented in xen.git: * docs/misc/xenstore.txt. A summary is given below for convenience. * The '|' symbol represents a NUL character. * * ---------- Database read, write and permissions operations ---------- * * READ | * WRITE | * Store and read the octet string at . * WRITE creates any missing parent paths, with empty values. * * MKDIR | * Ensures that the exists, by necessary by creating * it and any missing parents with empty values. If * or any parent already exists, its value is left unchanged. * * RM | * Ensures that the does not exist, by deleting * it and all of its children. It is not an error if does * not exist, but it _is_ an error if 's immediate parent * does not exist either. * * DIRECTORY | |* * Gives a list of the immediate children of , as only the * leafnames. The resulting children are each named * /. * * DIRECTORY_PART | ||* * Same as DIRECTORY, but to be used for children lists longer than * XENSTORE_PAYLOAD_MAX. Input are and the byte offset into * the list of children to return. Return values are the generation * count of the node (to be used to ensure the node hasn't * changed between two reads: being the same for multiple * reads guarantees the node hasn't changed) and the list of children * starting at the specified of the complete list. * * GET_PERMS | |+ * SET_PERMS ||+? * is one of the following * w write only * r read only * b both read and write * n no access * See https://wiki.xen.org/wiki/XenBus section * `Permissions' for details of the permissions system. * It is possible to set permissions for the special watch paths * "@introduceDomain" and "@releaseDomain" to enable receiving those * watches in unprivileged domains. * * ---------- Watches ---------- * * WATCH ||? * Adds a watch. * * When a is modified (including path creation, removal, * contents change or permissions change) this generates an event * on the changed . Changes made in transactions cause an * event only if and when committed. Each occurring event is * matched against all the watches currently set up, and each * matching watch results in a WATCH_EVENT message (see below). * * The event's path matches the watch's if it is an child * of . * * can be a to watch or @. In the * latter case may have any syntax but it matches * (according to the rules above) only the following special * events which are invented by xenstored: * @introduceDomain occurs on INTRODUCE * @releaseDomain occurs on any domain crash or * shutdown, and also on RELEASE * and domain destruction * events are sent to privileged callers or explicitly * via SET_PERMS enabled domains only. * * When a watch is first set up it is triggered once straight * away, with equal to . Watches may be triggered * spuriously. The tx_id in a WATCH request is ignored. * * Watches are supposed to be restricted by the permissions * system but in practice the implementation is imperfect. * Applications should not rely on being sent a notification for * paths that they cannot read; however, an application may rely * on being sent a watch when a path which it _is_ able to read * is deleted even if that leaves only a nonexistent unreadable * parent. A notification may omitted if a node's permissions * are changed so as to make it unreadable, in which case future * notifications may be suppressed (and if the node is later made * readable, some notifications may have been lost). * * WATCH_EVENT || * Unsolicited `reply' generated for matching modification events * as described above. req_id and tx_id are both 0. * * is the event's path, ie the actual path that was * modified; however if the event was the recursive removal of an * parent of , is just * (rather than the actual path which was removed). So * is a child of , regardless. * * Iff for the watch was specified as a relative pathname, * the path will also be relative (with the same base, * obviously). * * UNWATCH ||? * * RESET_WATCHES | * Reset all watches and transactions of the caller. * * ---------- Transactions ---------- * * TRANSACTION_START | | * is an opaque uint32_t allocated by xenstored * represented as unsigned decimal. After this, transaction may * be referenced by using (as 32-bit binary) in the * tx_id request header field. When transaction is started whole * db is copied; reads and writes happen on the copy. * It is not legal to send non-0 tx_id in TRANSACTION_START. * * TRANSACTION_END T| * TRANSACTION_END F| * tx_id must refer to existing transaction. After this * request the tx_id is no longer valid and may be reused by * xenstore. If F, the transaction is discarded. If T, * it is committed: if there were any other intervening writes * then our END gets get EAGAIN. * * The plan is that in the future only intervening `conflicting' * writes cause EAGAIN, meaning only writes or other commits * which changed paths which were read or written in the * transaction at hand. * */ static void xs_read(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { const char *path = (const char *)req_data; struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; uint8_t *rsp_data = (uint8_t *)&rsp[1]; g_autoptr(GByteArray) data = g_byte_array_new(); int err; if (len == 0 || req_data[len - 1] != '\0') { xs_error(s, req_id, tx_id, EINVAL); return; } trace_xenstore_read(tx_id, path); err = xs_impl_read(s->impl, xen_domid, tx_id, path, data); if (err) { xs_error(s, req_id, tx_id, err); return; } rsp->type = XS_READ; rsp->req_id = req_id; rsp->tx_id = tx_id; rsp->len = 0; len = data->len; if (len > XENSTORE_PAYLOAD_MAX) { xs_error(s, req_id, tx_id, E2BIG); return; } memcpy(&rsp_data[rsp->len], data->data, len); rsp->len += len; } static void xs_write(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { g_autoptr(GByteArray) data = g_byte_array_new(); const char *path; int err; if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } path = (const char *)req_data; while (len--) { if (*req_data++ == '\0') { break; } if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } } g_byte_array_append(data, req_data, len); trace_xenstore_write(tx_id, path); err = xs_impl_write(s->impl, xen_domid, tx_id, path, data); if (err) { xs_error(s, req_id, tx_id, err); return; } xs_ok(s, XS_WRITE, req_id, tx_id); } static void xs_mkdir(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { g_autoptr(GByteArray) data = g_byte_array_new(); const char *path; int err; if (len == 0 || req_data[len - 1] != '\0') { xs_error(s, req_id, tx_id, EINVAL); return; } path = (const char *)req_data; trace_xenstore_mkdir(tx_id, path); err = xs_impl_read(s->impl, xen_domid, tx_id, path, data); if (err == ENOENT) { err = xs_impl_write(s->impl, xen_domid, tx_id, path, data); } if (!err) { xs_error(s, req_id, tx_id, err); return; } xs_ok(s, XS_MKDIR, req_id, tx_id); } static void xs_append_strings(XenXenstoreState *s, struct xsd_sockmsg *rsp, GList *strings, unsigned int start, bool truncate) { uint8_t *rsp_data = (uint8_t *)&rsp[1]; GList *l; for (l = strings; l; l = l->next) { size_t len = strlen(l->data) + 1; /* Including the NUL termination */ char *str = l->data; if (rsp->len + len > XENSTORE_PAYLOAD_MAX) { if (truncate) { len = XENSTORE_PAYLOAD_MAX - rsp->len; if (!len) { return; } } else { xs_error(s, rsp->req_id, rsp->tx_id, E2BIG); return; } } if (start) { if (start >= len) { start -= len; continue; } str += start; len -= start; start = 0; } memcpy(&rsp_data[rsp->len], str, len); rsp->len += len; } /* XS_DIRECTORY_PART wants an extra NUL to indicate the end */ if (truncate && rsp->len < XENSTORE_PAYLOAD_MAX) { rsp_data[rsp->len++] = '\0'; } } static void xs_directory(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; GList *items = NULL; const char *path; int err; if (len == 0 || req_data[len - 1] != '\0') { xs_error(s, req_id, tx_id, EINVAL); return; } path = (const char *)req_data; trace_xenstore_directory(tx_id, path); err = xs_impl_directory(s->impl, xen_domid, tx_id, path, NULL, &items); if (err != 0) { xs_error(s, req_id, tx_id, err); return; } rsp->type = XS_DIRECTORY; rsp->req_id = req_id; rsp->tx_id = tx_id; rsp->len = 0; xs_append_strings(s, rsp, items, 0, false); g_list_free_full(items, g_free); } static void xs_directory_part(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { const char *offset_str, *path = (const char *)req_data; struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; char *rsp_data = (char *)&rsp[1]; uint64_t gencnt = 0; unsigned int offset; GList *items = NULL; int err; if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } while (len--) { if (*req_data++ == '\0') { break; } if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } } offset_str = (const char *)req_data; while (len--) { if (*req_data++ == '\0') { break; } if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } } if (len) { xs_error(s, req_id, tx_id, EINVAL); return; } if (qemu_strtoui(offset_str, NULL, 10, &offset) < 0) { xs_error(s, req_id, tx_id, EINVAL); return; } trace_xenstore_directory_part(tx_id, path, offset); err = xs_impl_directory(s->impl, xen_domid, tx_id, path, &gencnt, &items); if (err != 0) { xs_error(s, req_id, tx_id, err); return; } rsp->type = XS_DIRECTORY_PART; rsp->req_id = req_id; rsp->tx_id = tx_id; rsp->len = snprintf(rsp_data, XENSTORE_PAYLOAD_MAX, "%" PRIu64, gencnt) + 1; xs_append_strings(s, rsp, items, offset, true); g_list_free_full(items, g_free); } static void xs_transaction_start(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; char *rsp_data = (char *)&rsp[1]; int err; if (len != 1 || req_data[0] != '\0') { xs_error(s, req_id, tx_id, EINVAL); return; } rsp->type = XS_TRANSACTION_START; rsp->req_id = req_id; rsp->tx_id = tx_id; rsp->len = 0; err = xs_impl_transaction_start(s->impl, xen_domid, &tx_id); if (err) { xs_error(s, req_id, tx_id, err); return; } trace_xenstore_transaction_start(tx_id); rsp->len = snprintf(rsp_data, XENSTORE_PAYLOAD_MAX, "%u", tx_id); assert(rsp->len < XENSTORE_PAYLOAD_MAX); rsp->len++; } static void xs_transaction_end(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { bool commit; int err; if (len != 2 || req_data[1] != '\0') { xs_error(s, req_id, tx_id, EINVAL); return; } switch (req_data[0]) { case 'T': commit = true; break; case 'F': commit = false; break; default: xs_error(s, req_id, tx_id, EINVAL); return; } trace_xenstore_transaction_end(tx_id, commit); err = xs_impl_transaction_end(s->impl, xen_domid, tx_id, commit); if (err) { xs_error(s, req_id, tx_id, err); return; } xs_ok(s, XS_TRANSACTION_END, req_id, tx_id); } static void xs_rm(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { const char *path = (const char *)req_data; int err; if (len == 0 || req_data[len - 1] != '\0') { xs_error(s, req_id, tx_id, EINVAL); return; } trace_xenstore_rm(tx_id, path); err = xs_impl_rm(s->impl, xen_domid, tx_id, path); if (err) { xs_error(s, req_id, tx_id, err); return; } xs_ok(s, XS_RM, req_id, tx_id); } static void xs_get_perms(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { const char *path = (const char *)req_data; struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; GList *perms = NULL; int err; if (len == 0 || req_data[len - 1] != '\0') { xs_error(s, req_id, tx_id, EINVAL); return; } trace_xenstore_get_perms(tx_id, path); err = xs_impl_get_perms(s->impl, xen_domid, tx_id, path, &perms); if (err) { xs_error(s, req_id, tx_id, err); return; } rsp->type = XS_GET_PERMS; rsp->req_id = req_id; rsp->tx_id = tx_id; rsp->len = 0; xs_append_strings(s, rsp, perms, 0, false); g_list_free_full(perms, g_free); } static void xs_set_perms(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { const char *path = (const char *)req_data; uint8_t *perm; GList *perms = NULL; int err; if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } while (len--) { if (*req_data++ == '\0') { break; } if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } } perm = req_data; while (len--) { if (*req_data++ == '\0') { perms = g_list_append(perms, perm); perm = req_data; } } /* * Note that there may be trailing garbage at the end of the buffer. * This is explicitly permitted by the '?' at the end of the definition: * * SET_PERMS ||+? */ trace_xenstore_set_perms(tx_id, path); err = xs_impl_set_perms(s->impl, xen_domid, tx_id, path, perms); g_list_free(perms); if (err) { xs_error(s, req_id, tx_id, err); return; } xs_ok(s, XS_SET_PERMS, req_id, tx_id); } static void xs_watch(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { const char *token, *path = (const char *)req_data; int err; if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } while (len--) { if (*req_data++ == '\0') { break; } if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } } token = (const char *)req_data; while (len--) { if (*req_data++ == '\0') { break; } if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } } /* * Note that there may be trailing garbage at the end of the buffer. * This is explicitly permitted by the '?' at the end of the definition: * * WATCH ||? */ trace_xenstore_watch(path, token); err = xs_impl_watch(s->impl, xen_domid, path, token, fire_watch_cb, s); if (err) { xs_error(s, req_id, tx_id, err); return; } xs_ok(s, XS_WATCH, req_id, tx_id); } static void xs_unwatch(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { const char *token, *path = (const char *)req_data; int err; if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } while (len--) { if (*req_data++ == '\0') { break; } if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } } token = (const char *)req_data; while (len--) { if (*req_data++ == '\0') { break; } if (len == 0) { xs_error(s, req_id, tx_id, EINVAL); return; } } trace_xenstore_unwatch(path, token); err = xs_impl_unwatch(s->impl, xen_domid, path, token, fire_watch_cb, s); if (err) { xs_error(s, req_id, tx_id, err); return; } xs_ok(s, XS_UNWATCH, req_id, tx_id); } static void xs_reset_watches(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *req_data, unsigned int len) { if (len == 0 || req_data[len - 1] != '\0') { xs_error(s, req_id, tx_id, EINVAL); return; } trace_xenstore_reset_watches(); xs_impl_reset_watches(s->impl, xen_domid); xs_ok(s, XS_RESET_WATCHES, req_id, tx_id); } static void xs_priv(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *data, unsigned int len) { xs_error(s, req_id, tx_id, EACCES); } static void xs_unimpl(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *data, unsigned int len) { xs_error(s, req_id, tx_id, ENOSYS); } typedef void (*xs_impl)(XenXenstoreState *s, unsigned int req_id, xs_transaction_t tx_id, uint8_t *data, unsigned int len); struct xsd_req { const char *name; xs_impl fn; }; #define XSD_REQ(_type, _fn) \ [_type] = { .name = #_type, .fn = _fn } struct xsd_req xsd_reqs[] = { XSD_REQ(XS_READ, xs_read), XSD_REQ(XS_WRITE, xs_write), XSD_REQ(XS_MKDIR, xs_mkdir), XSD_REQ(XS_DIRECTORY, xs_directory), XSD_REQ(XS_DIRECTORY_PART, xs_directory_part), XSD_REQ(XS_TRANSACTION_START, xs_transaction_start), XSD_REQ(XS_TRANSACTION_END, xs_transaction_end), XSD_REQ(XS_RM, xs_rm), XSD_REQ(XS_GET_PERMS, xs_get_perms), XSD_REQ(XS_SET_PERMS, xs_set_perms), XSD_REQ(XS_WATCH, xs_watch), XSD_REQ(XS_UNWATCH, xs_unwatch), XSD_REQ(XS_CONTROL, xs_priv), XSD_REQ(XS_INTRODUCE, xs_priv), XSD_REQ(XS_RELEASE, xs_priv), XSD_REQ(XS_IS_DOMAIN_INTRODUCED, xs_priv), XSD_REQ(XS_RESUME, xs_priv), XSD_REQ(XS_SET_TARGET, xs_priv), XSD_REQ(XS_RESET_WATCHES, xs_reset_watches), }; static void process_req(XenXenstoreState *s) { struct xsd_sockmsg *req = (struct xsd_sockmsg *)s->req_data; xs_impl handler = NULL; assert(req_pending(s)); assert(!s->rsp_pending); if (req->type < ARRAY_SIZE(xsd_reqs)) { handler = xsd_reqs[req->type].fn; } if (!handler) { handler = &xs_unimpl; } handler(s, req->req_id, req->tx_id, (uint8_t *)&req[1], req->len); s->rsp_pending = true; reset_req(s); } static unsigned int copy_from_ring(XenXenstoreState *s, uint8_t *ptr, unsigned int len) { if (!len) { return 0; } XENSTORE_RING_IDX prod = qatomic_read(&s->xs->req_prod); XENSTORE_RING_IDX cons = qatomic_read(&s->xs->req_cons); unsigned int copied = 0; /* Ensure the ring contents don't cross the req_prod access. */ smp_rmb(); while (len) { unsigned int avail = prod - cons; unsigned int offset = MASK_XENSTORE_IDX(cons); unsigned int copylen = avail; if (avail > XENSTORE_RING_SIZE) { error_report("XenStore ring handling error"); s->fatal_error = true; break; } else if (avail == 0) { break; } if (copylen > len) { copylen = len; } if (copylen > XENSTORE_RING_SIZE - offset) { copylen = XENSTORE_RING_SIZE - offset; } memcpy(ptr, &s->xs->req[offset], copylen); copied += copylen; ptr += copylen; len -= copylen; cons += copylen; } /* * Not sure this ever mattered except on Alpha, but this barrier * is to ensure that the update to req_cons is globally visible * only after we have consumed all the data from the ring, and we * don't end up seeing data written to the ring *after* the other * end sees the update and writes more to the ring. Xen's own * xenstored has the same barrier here (although with no comment * at all, obviously, because it's Xen code). */ smp_mb(); qatomic_set(&s->xs->req_cons, cons); return copied; } static unsigned int copy_to_ring(XenXenstoreState *s, uint8_t *ptr, unsigned int len) { if (!len) { return 0; } XENSTORE_RING_IDX cons = qatomic_read(&s->xs->rsp_cons); XENSTORE_RING_IDX prod = qatomic_read(&s->xs->rsp_prod); unsigned int copied = 0; /* * This matches the barrier in copy_to_ring() (or the guest's * equivalent) betweem writing the data to the ring and updating * rsp_prod. It protects against the pathological case (which * again I think never happened except on Alpha) where our * subsequent writes to the ring could *cross* the read of * rsp_cons and the guest could see the new data when it was * intending to read the old. */ smp_mb(); while (len) { unsigned int avail = cons + XENSTORE_RING_SIZE - prod; unsigned int offset = MASK_XENSTORE_IDX(prod); unsigned int copylen = len; if (avail > XENSTORE_RING_SIZE) { error_report("XenStore ring handling error"); s->fatal_error = true; break; } else if (avail == 0) { break; } if (copylen > avail) { copylen = avail; } if (copylen > XENSTORE_RING_SIZE - offset) { copylen = XENSTORE_RING_SIZE - offset; } memcpy(&s->xs->rsp[offset], ptr, copylen); copied += copylen; ptr += copylen; len -= copylen; prod += copylen; } /* Ensure the ring contents are seen before rsp_prod update. */ smp_wmb(); qatomic_set(&s->xs->rsp_prod, prod); return copied; } static unsigned int get_req(XenXenstoreState *s) { unsigned int copied = 0; if (s->fatal_error) { return 0; } assert(!req_pending(s)); if (s->req_offset < XENSTORE_HEADER_SIZE) { void *ptr = s->req_data + s->req_offset; unsigned int len = XENSTORE_HEADER_SIZE; unsigned int copylen = copy_from_ring(s, ptr, len); copied += copylen; s->req_offset += copylen; } if (s->req_offset >= XENSTORE_HEADER_SIZE) { struct xsd_sockmsg *req = (struct xsd_sockmsg *)s->req_data; if (req->len > (uint32_t)XENSTORE_PAYLOAD_MAX) { error_report("Illegal XenStore request"); s->fatal_error = true; return 0; } void *ptr = s->req_data + s->req_offset; unsigned int len = XENSTORE_HEADER_SIZE + req->len - s->req_offset; unsigned int copylen = copy_from_ring(s, ptr, len); copied += copylen; s->req_offset += copylen; } return copied; } static unsigned int put_rsp(XenXenstoreState *s) { if (s->fatal_error) { return 0; } assert(s->rsp_pending); struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; assert(s->rsp_offset < XENSTORE_HEADER_SIZE + rsp->len); void *ptr = s->rsp_data + s->rsp_offset; unsigned int len = XENSTORE_HEADER_SIZE + rsp->len - s->rsp_offset; unsigned int copylen = copy_to_ring(s, ptr, len); s->rsp_offset += copylen; /* Have we produced a complete response? */ if (s->rsp_offset == XENSTORE_HEADER_SIZE + rsp->len) { reset_rsp(s); } return copylen; } static void deliver_watch(XenXenstoreState *s, const char *path, const char *token) { struct xsd_sockmsg *rsp = (struct xsd_sockmsg *)s->rsp_data; uint8_t *rsp_data = (uint8_t *)&rsp[1]; unsigned int len; assert(!s->rsp_pending); trace_xenstore_watch_event(path, token); rsp->type = XS_WATCH_EVENT; rsp->req_id = 0; rsp->tx_id = 0; rsp->len = 0; len = strlen(path); /* XENSTORE_ABS/REL_PATH_MAX should ensure there can be no overflow */ assert(rsp->len + len < XENSTORE_PAYLOAD_MAX); memcpy(&rsp_data[rsp->len], path, len); rsp->len += len; rsp_data[rsp->len] = '\0'; rsp->len++; len = strlen(token); /* * It is possible for the guest to have chosen a token that will * not fit (along with the patch) into a watch event. We have no * choice but to drop the event if this is the case. */ if (rsp->len + len >= XENSTORE_PAYLOAD_MAX) { return; } memcpy(&rsp_data[rsp->len], token, len); rsp->len += len; rsp_data[rsp->len] = '\0'; rsp->len++; s->rsp_pending = true; } struct watch_event { char *path; char *token; }; static void free_watch_event(struct watch_event *ev) { if (ev) { g_free(ev->path); g_free(ev->token); g_free(ev); } } static void queue_watch(XenXenstoreState *s, const char *path, const char *token) { struct watch_event *ev = g_new0(struct watch_event, 1); ev->path = g_strdup(path); ev->token = g_strdup(token); s->watch_events = g_list_append(s->watch_events, ev); } static void fire_watch_cb(void *opaque, const char *path, const char *token) { XenXenstoreState *s = opaque; assert(qemu_mutex_iothread_locked()); /* * If there's a response pending, we obviously can't scribble over * it. But if there's a request pending, it has dibs on the buffer * too. * * In the common case of a watch firing due to backend activity * when the ring was otherwise idle, we should be able to copy the * strings directly into the rsp_data and thence the actual ring, * without needing to perform any allocations and queue them. */ if (s->rsp_pending || req_pending(s)) { queue_watch(s, path, token); } else { deliver_watch(s, path, token); /* * If the message was queued because there was already ring activity, * no need to wake the guest. But if not, we need to send the evtchn. */ xen_be_evtchn_notify(s->eh, s->be_port); } } static void process_watch_events(XenXenstoreState *s) { struct watch_event *ev = s->watch_events->data; deliver_watch(s, ev->path, ev->token); s->watch_events = g_list_remove(s->watch_events, ev); free_watch_event(ev); } static void xen_xenstore_event(void *opaque) { XenXenstoreState *s = opaque; evtchn_port_t port = xen_be_evtchn_pending(s->eh); unsigned int copied_to, copied_from; bool processed, notify = false; if (port != s->be_port) { return; } /* We know this is a no-op. */ xen_be_evtchn_unmask(s->eh, port); do { copied_to = copied_from = 0; processed = false; if (!s->rsp_pending && s->watch_events) { process_watch_events(s); } if (s->rsp_pending) { copied_to = put_rsp(s); } if (!req_pending(s)) { copied_from = get_req(s); } if (req_pending(s) && !s->rsp_pending && !s->watch_events) { process_req(s); processed = true; } notify |= copied_to || copied_from; } while (copied_to || copied_from || processed); if (notify) { xen_be_evtchn_notify(s->eh, s->be_port); } } static void alloc_guest_port(XenXenstoreState *s) { struct evtchn_alloc_unbound alloc = { .dom = DOMID_SELF, .remote_dom = DOMID_QEMU, }; if (!xen_evtchn_alloc_unbound_op(&alloc)) { s->guest_port = alloc.port; } } int xen_xenstore_reset(void) { XenXenstoreState *s = xen_xenstore_singleton; int err; if (!s) { return -ENOTSUP; } s->req_offset = s->rsp_offset = 0; s->rsp_pending = false; if (!memory_region_is_mapped(&s->xenstore_page)) { uint64_t gpa = XEN_SPECIAL_PFN(XENSTORE) << TARGET_PAGE_BITS; xen_overlay_do_map_page(&s->xenstore_page, gpa); } alloc_guest_port(s); /* * As qemu/dom0, bind to the guest's port. For incoming migration, this * will be unbound as the guest's evtchn table is overwritten. We then * rebind to the correct guest port in xen_xenstore_post_load(). */ err = xen_be_evtchn_bind_interdomain(s->eh, xen_domid, s->guest_port); if (err < 0) { return err; } s->be_port = err; /* * We don't actually access the guest's page through the grant, because * this isn't real Xen, and we can just use the page we gave it in the * first place. Map the grant anyway, mostly for cosmetic purposes so * it *looks* like it's in use in the guest-visible grant table. */ s->gt = qemu_xen_gnttab_open(); uint32_t xs_gntref = GNTTAB_RESERVED_XENSTORE; s->granted_xs = qemu_xen_gnttab_map_refs(s->gt, 1, xen_domid, &xs_gntref, PROT_READ | PROT_WRITE); return 0; } struct qemu_xs_handle { XenstoreImplState *impl; GList *watches; QEMUBH *watch_bh; }; struct qemu_xs_watch { struct qemu_xs_handle *h; char *path; xs_watch_fn fn; void *opaque; GList *events; }; static char *xs_be_get_domain_path(struct qemu_xs_handle *h, unsigned int domid) { return g_strdup_printf("/local/domain/%u", domid); } static char **xs_be_directory(struct qemu_xs_handle *h, xs_transaction_t t, const char *path, unsigned int *num) { GList *items = NULL, *l; unsigned int i = 0; char **items_ret; int err; err = xs_impl_directory(h->impl, DOMID_QEMU, t, path, NULL, &items); if (err) { errno = err; return NULL; } items_ret = g_new0(char *, g_list_length(items) + 1); *num = 0; for (l = items; l; l = l->next) { items_ret[i++] = l->data; (*num)++; } g_list_free(items); return items_ret; } static void *xs_be_read(struct qemu_xs_handle *h, xs_transaction_t t, const char *path, unsigned int *len) { GByteArray *data = g_byte_array_new(); bool free_segment = false; int err; err = xs_impl_read(h->impl, DOMID_QEMU, t, path, data); if (err) { free_segment = true; errno = err; } else { if (len) { *len = data->len; } /* The xen-bus-helper code expects to get NUL terminated string! */ g_byte_array_append(data, (void *)"", 1); } return g_byte_array_free(data, free_segment); } static bool xs_be_write(struct qemu_xs_handle *h, xs_transaction_t t, const char *path, const void *data, unsigned int len) { GByteArray *gdata = g_byte_array_new(); int err; g_byte_array_append(gdata, data, len); err = xs_impl_write(h->impl, DOMID_QEMU, t, path, gdata); g_byte_array_unref(gdata); if (err) { errno = err; return false; } return true; } static bool xs_be_create(struct qemu_xs_handle *h, xs_transaction_t t, unsigned int owner, unsigned int domid, unsigned int perms, const char *path) { g_autoptr(GByteArray) data = g_byte_array_new(); GList *perms_list = NULL; int err; /* mkdir does this */ err = xs_impl_read(h->impl, DOMID_QEMU, t, path, data); if (err == ENOENT) { err = xs_impl_write(h->impl, DOMID_QEMU, t, path, data); } if (err) { errno = err; return false; } perms_list = g_list_append(perms_list, xs_perm_as_string(XS_PERM_NONE, owner)); perms_list = g_list_append(perms_list, xs_perm_as_string(perms, domid)); err = xs_impl_set_perms(h->impl, DOMID_QEMU, t, path, perms_list); g_list_free_full(perms_list, g_free); if (err) { errno = err; return false; } return true; } static bool xs_be_destroy(struct qemu_xs_handle *h, xs_transaction_t t, const char *path) { int err = xs_impl_rm(h->impl, DOMID_QEMU, t, path); if (err) { errno = err; return false; } return true; } static void be_watch_bh(void *_h) { struct qemu_xs_handle *h = _h; GList *l; for (l = h->watches; l; l = l->next) { struct qemu_xs_watch *w = l->data; while (w->events) { struct watch_event *ev = w->events->data; w->fn(w->opaque, ev->path); w->events = g_list_remove(w->events, ev); free_watch_event(ev); } } } static void xs_be_watch_cb(void *opaque, const char *path, const char *token) { struct watch_event *ev = g_new0(struct watch_event, 1); struct qemu_xs_watch *w = opaque; /* We don't care about the token */ ev->path = g_strdup(path); w->events = g_list_append(w->events, ev); qemu_bh_schedule(w->h->watch_bh); } static struct qemu_xs_watch *xs_be_watch(struct qemu_xs_handle *h, const char *path, xs_watch_fn fn, void *opaque) { struct qemu_xs_watch *w = g_new0(struct qemu_xs_watch, 1); int err; w->h = h; w->fn = fn; w->opaque = opaque; err = xs_impl_watch(h->impl, DOMID_QEMU, path, NULL, xs_be_watch_cb, w); if (err) { errno = err; g_free(w); return NULL; } w->path = g_strdup(path); h->watches = g_list_append(h->watches, w); return w; } static void xs_be_unwatch(struct qemu_xs_handle *h, struct qemu_xs_watch *w) { xs_impl_unwatch(h->impl, DOMID_QEMU, w->path, NULL, xs_be_watch_cb, w); h->watches = g_list_remove(h->watches, w); g_list_free_full(w->events, (GDestroyNotify)free_watch_event); g_free(w->path); g_free(w); } static xs_transaction_t xs_be_transaction_start(struct qemu_xs_handle *h) { unsigned int new_tx = XBT_NULL; int err = xs_impl_transaction_start(h->impl, DOMID_QEMU, &new_tx); if (err) { errno = err; return XBT_NULL; } return new_tx; } static bool xs_be_transaction_end(struct qemu_xs_handle *h, xs_transaction_t t, bool abort) { int err = xs_impl_transaction_end(h->impl, DOMID_QEMU, t, !abort); if (err) { errno = err; return false; } return true; } static struct qemu_xs_handle *xs_be_open(void) { XenXenstoreState *s = xen_xenstore_singleton; struct qemu_xs_handle *h; if (!s && !s->impl) { errno = -ENOSYS; return NULL; } h = g_new0(struct qemu_xs_handle, 1); h->impl = s->impl; h->watch_bh = aio_bh_new(qemu_get_aio_context(), be_watch_bh, h); return h; } static void xs_be_close(struct qemu_xs_handle *h) { while (h->watches) { struct qemu_xs_watch *w = h->watches->data; xs_be_unwatch(h, w); } qemu_bh_delete(h->watch_bh); g_free(h); } static struct xenstore_backend_ops emu_xenstore_backend_ops = { .open = xs_be_open, .close = xs_be_close, .get_domain_path = xs_be_get_domain_path, .directory = xs_be_directory, .read = xs_be_read, .write = xs_be_write, .create = xs_be_create, .destroy = xs_be_destroy, .watch = xs_be_watch, .unwatch = xs_be_unwatch, .transaction_start = xs_be_transaction_start, .transaction_end = xs_be_transaction_end, };