/* * Copyright (C) 2006-2009 Red Hat, Inc. * * This file is released under the LGPL. */ #include <linux/kernel.h> #include <linux/module.h> #include <linux/slab.h> #include <net/sock.h> #include <linux/workqueue.h> #include <linux/connector.h> #include <linux/device-mapper.h> #include <linux/dm-log-userspace.h> #include "dm-log-userspace-transfer.h" static uint32_t dm_ulog_seq; /* * Netlink/Connector is an unreliable protocol. How long should * we wait for a response before assuming it was lost and retrying? * (If we do receive a response after this time, it will be discarded * and the response to the resent request will be waited for. */ #define DM_ULOG_RETRY_TIMEOUT (15 * HZ) /* * Pre-allocated space for speed */ #define DM_ULOG_PREALLOCED_SIZE 512 static struct cn_msg *prealloced_cn_msg; static struct dm_ulog_request *prealloced_ulog_tfr; static struct cb_id ulog_cn_id = { .idx = CN_IDX_DM, .val = CN_VAL_DM_USERSPACE_LOG }; static DEFINE_MUTEX(dm_ulog_lock); struct receiving_pkg { struct list_head list; struct completion complete; uint32_t seq; int error; size_t *data_size; char *data; }; static DEFINE_SPINLOCK(receiving_list_lock); static struct list_head receiving_list; static int dm_ulog_sendto_server(struct dm_ulog_request *tfr) { int r; struct cn_msg *msg = prealloced_cn_msg; memset(msg, 0, sizeof(struct cn_msg)); msg->id.idx = ulog_cn_id.idx; msg->id.val = ulog_cn_id.val; msg->ack = 0; msg->seq = tfr->seq; msg->len = sizeof(struct dm_ulog_request) + tfr->data_size; r = cn_netlink_send(msg, 0, 0, gfp_any()); return r; } /* * Parameters for this function can be either msg or tfr, but not * both. This function fills in the reply for a waiting request. * If just msg is given, then the reply is simply an ACK from userspace * that the request was received. * * Returns: 0 on success, -ENOENT on failure */ static int fill_pkg(struct cn_msg *msg, struct dm_ulog_request *tfr) { uint32_t rtn_seq = (msg) ? msg->seq : (tfr) ? tfr->seq : 0; struct receiving_pkg *pkg; /* * The 'receiving_pkg' entries in this list are statically * allocated on the stack in 'dm_consult_userspace'. * Each process that is waiting for a reply from the user * space server will have an entry in this list. * * We are safe to do it this way because the stack space * is unique to each process, but still addressable by * other processes. */ list_for_each_entry(pkg, &receiving_list, list) { if (rtn_seq != pkg->seq) continue; if (msg) { pkg->error = -msg->ack; /* * If we are trying again, we will need to know our * storage capacity. Otherwise, along with the * error code, we make explicit that we have no data. */ if (pkg->error != -EAGAIN) *(pkg->data_size) = 0; } else if (tfr->data_size > *(pkg->data_size)) { DMERR("Insufficient space to receive package [%u] " "(%u vs %zu)", tfr->request_type, tfr->data_size, *(pkg->data_size)); *(pkg->data_size) = 0; pkg->error = -ENOSPC; } else { pkg->error = tfr->error; memcpy(pkg->data, tfr->data, tfr->data_size); *(pkg->data_size) = tfr->data_size; } complete(&pkg->complete); return 0; } return -ENOENT; } /* * This is the connector callback that delivers data * that was sent from userspace. */ static void cn_ulog_callback(struct cn_msg *msg, struct netlink_skb_parms *nsp) { struct dm_ulog_request *tfr = (struct dm_ulog_request *)(msg + 1); if (!capable(CAP_SYS_ADMIN)) return; spin_lock(&receiving_list_lock); if (msg->len == 0) fill_pkg(msg, NULL); else if (msg->len < sizeof(*tfr)) DMERR("Incomplete message received (expected %u, got %u): [%u]", (unsigned)sizeof(*tfr), msg->len, msg->seq); else fill_pkg(NULL, tfr); spin_unlock(&receiving_list_lock); } /** * dm_consult_userspace * @uuid: log's universal unique identifier (must be DM_UUID_LEN in size) * @luid: log's local unique identifier * @request_type: found in include/linux/dm-log-userspace.h * @data: data to tx to the server * @data_size: size of data in bytes * @rdata: place to put return data from server * @rdata_size: value-result (amount of space given/amount of space used) * * rdata_size is undefined on failure. * * Memory used to communicate with userspace is zero'ed * before populating to ensure that no unwanted bits leak * from kernel space to user-space. All userspace log communications * between kernel and user space go through this function. * * Returns: 0 on success, -EXXX on failure **/ int dm_consult_userspace(const char *uuid, uint64_t luid, int request_type, char *data, size_t data_size, char *rdata, size_t *rdata_size) { int r = 0; size_t dummy = 0; int overhead_size = sizeof(struct dm_ulog_request) + sizeof(struct cn_msg); struct dm_ulog_request *tfr = prealloced_ulog_tfr; struct receiving_pkg pkg; /* * Given the space needed to hold the 'struct cn_msg' and * 'struct dm_ulog_request' - do we have enough payload * space remaining? */ if (data_size > (DM_ULOG_PREALLOCED_SIZE - overhead_size)) { DMINFO("Size of tfr exceeds preallocated size"); return -EINVAL; } if (!rdata_size) rdata_size = &dummy; resend: /* * We serialize the sending of requests so we can * use the preallocated space. */ mutex_lock(&dm_ulog_lock); memset(tfr, 0, DM_ULOG_PREALLOCED_SIZE - sizeof(struct cn_msg)); memcpy(tfr->uuid, uuid, DM_UUID_LEN); tfr->version = DM_ULOG_REQUEST_VERSION; tfr->luid = luid; tfr->seq = dm_ulog_seq++; /* * Must be valid request type (all other bits set to * zero). This reserves other bits for possible future * use. */ tfr->request_type = request_type & DM_ULOG_REQUEST_MASK; tfr->data_size = data_size; if (data && data_size) memcpy(tfr->data, data, data_size); memset(&pkg, 0, sizeof(pkg)); init_completion(&pkg.complete); pkg.seq = tfr->seq; pkg.data_size = rdata_size; pkg.data = rdata; spin_lock(&receiving_list_lock); list_add(&(pkg.list), &receiving_list); spin_unlock(&receiving_list_lock); r = dm_ulog_sendto_server(tfr); mutex_unlock(&dm_ulog_lock); if (r) { DMERR("Unable to send log request [%u] to userspace: %d", request_type, r); spin_lock(&receiving_list_lock); list_del_init(&(pkg.list)); spin_unlock(&receiving_list_lock); goto out; } r = wait_for_completion_timeout(&(pkg.complete), DM_ULOG_RETRY_TIMEOUT); spin_lock(&receiving_list_lock); list_del_init(&(pkg.list)); spin_unlock(&receiving_list_lock); if (!r) { DMWARN("[%s] Request timed out: [%u/%u] - retrying", (strlen(uuid) > 8) ? (uuid + (strlen(uuid) - 8)) : (uuid), request_type, pkg.seq); goto resend; } r = pkg.error; if (r == -EAGAIN) goto resend; out: return r; } int dm_ulog_tfr_init(void) { int r; void *prealloced; INIT_LIST_HEAD(&receiving_list); prealloced = kmalloc(DM_ULOG_PREALLOCED_SIZE, GFP_KERNEL); if (!prealloced) return -ENOMEM; prealloced_cn_msg = prealloced; prealloced_ulog_tfr = prealloced + sizeof(struct cn_msg); r = cn_add_callback(&ulog_cn_id, "dmlogusr", cn_ulog_callback); if (r) { cn_del_callback(&ulog_cn_id); return r; } return 0; } void dm_ulog_tfr_exit(void) { cn_del_callback(&ulog_cn_id); kfree(prealloced_cn_msg); }