SystemTap: relay-app.h Source File

00001 /*
-00002  *  relay-app.h - kernel 'library' functions for typical relayfs applications
-00003  *
-00004  * This program is free software; you can redistribute it and/or modify
-00005  * it under the terms of the GNU General Public License as published by
-00006  * the Free Software Foundation; either version 2 of the License, or
-00007  * (at your option) any later version.
-00008  *
-00009  * This program is distributed in the hope that it will be useful,
-00010  * but WITHOUT ANY WARRANTY; without even the implied warranty of
-00011  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-00012  * GNU General Public License for more details.
-00013  *
-00014  * You should have received a copy of the GNU General Public License
-00015  * along with this program; if not, write to the Free Software
-00016  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
-00017  *
-00018  * Copyright (C) IBM Corporation, 2005
-00019  *
-00020  * 2005-Feb     Created by Tom Zanussi <zanussi@us.ibm.com>
-00021  *
-00022  * This header file encapsulates the details of channel setup and
-00023  * teardown and communication between the kernel and user parts of a
-00024  * typical and common type of relayfs application, which is that
-00025  * kernel logging is kicked off when a userspace data collection
-00026  * application starts and stopped when the collection app exits, and
-00027  * data is automatically logged to disk in-between.  Channels are
-00028  * created when the collection app is started and destroyed when it
-00029  * exits, not when the kernel module is inserted, so different channel
-00030  * buffer sizes can be specified for each separate run via
-00031  * command-line options for instance.
-00032  *
-00033  * Writing to the channel is done using 2 macros, relayapp_write() and
-00034  * _relayapp_write(), which are just wrappers around relay_write() and
-00035  * _relay_write() but without the channel param.  You can safely call
-00036  * these at any time - if there's no channel yet, they'll just be
-00037  * ignored.
-00038  *
-00039  * To create a relay-app application, do the following:
-00040  *
-00041  * In your kernel module:
-00042  *
-00043  * - #include "relay-app.h"
-00044  *
-00045  * - Call init_relay_app() in your module_init function, with the
-00046  *   names of the directory to create relayfs files in and the base name
-00047  *   of the per-cpu relayfs files e.g. to have /mnt/relay/myapp/cpuXXX
-00048  *   created call init_relay_app("myapp", "cpu", callbacks).
-00049  *
-00050  *   NOTE: The callbacks are entirely optional - pass NULL if you
-00051  *   don't want to define any.  If you want to define some but not
-00052  *   others, just set the ones you want, and ignore or NULL out the
-00053  *   others.
-00054  *
-00055  *   NOTE: This won't actually create the relayfs files - that will
-00056  *   happen when the userspace application starts (i.e. you can supply
-00057  *   the buffer sizes on the application command-line for each new run
-00058  *   of your program).
-00059  *
-00060  *   NOTE: If you pass in NULL for the directory name, the relay files
-00061  *   will be created in the root directory of the relayfs filesystem.
-00062  *
-00063  * - Call close_relay_app() in your module_exit function - this cleans
-00064  *   up the control channel and the relay files from the previous run,
-00065  *   if any.
-00066  *
-00067  * - relay-apps use a control channel to communicate initialization
-00068  *   and status information between the kernel module and user space
-00069  *   program.  This is hidden beneath the API so you normally don't need
-00070  *   to know anything about it, but if you want you can also use it to
-00071  *   send user-defined commands from your user space application.  To do
-00072  *   this, you need to define a definition for the user_command()
-00073  *   callback and in the callback sort out and handle handle the
-00074  *   commands you send from user space (via send_request()).  The
-00075  *   callback must return 1 if the command was handled, or 0 if not
-00076  *   (which will result in a send_error in the user space program,
-00077  *   alerting you to the fact that you're sending something bogus).
-00078  *
-00079  *   NOTE: Currently commands can only be sent before the user space
-00080  *   application enters relay_app_main_loop() i.e. for initialization
-00081  *   purposes only.
-00082  *
-00083  * - the app_started() and app_stopped() callbacks provide an
-00084  *   opportunity for your kernel module to perform app-specific
-00085  *   initialization and cleanup, if desired.  They are purely
-00086  *   informational.  app_started() is called when the user space
-00087  *   application has started and app_stopped() is called when the user
-00088  *   space application has stopped.
-00089  *
-00090  * In your user space application do the following:
-00091  *
-00092  * - Call init_relay_app() with the names of the relayfs file base
-00093  *   name and the base filename of the output files that will be
-00094  *   created, as well as the sub-buffer size and count for the current
-00095  *   run (which can be passed in on the command-line if you want).  This
-00096  *   will create the channel and set up the ouptut files and buffer
-00097  *   mappings.  e.g. to set up reading from the relayfs files specified in the
-00098  *   above example and write them to a set of per-cpu output files named
-00099  *   myoutputXXX:
-00100  * 
-00101  *   init_relay_app("/mnt/relay/myapp/cpu", "myoutput",
-00102  *                  subbuf_size_opt, n_subbufs_opt, 1);
-00103  *
-00104  *   (the last parameter just specifies whether or not to print out a
-00105  *   summary of the number of buffers processed, and the maximum backlog
-00106  *   of sub-buffers encountered e.g. if you have 4 sub-buffers, a
-00107  *   maximum backlog of 3 would mean that you came close to having a
-00108  *   full buffer, so you might want to use more or bigger sub-buffers
-00109  *   next time.  Of course, if the buffers actually filled up, the
-00110  *   maximum backlog would be 4 and you'd have lost data).
-00111  *
-00112  * - Call relay_app_main_loop().  This will set up an infinite loop
-00113  *   (press Control-C to break out and finalize the data) which
-00114  *   automatically reads the data from the relayfs buffers as it becomes
-00115  *   available and and writes it out to per-cpu output files.
-00116  *
-00117  *   NOTE: The control channel is implemented as a netlink socket.
-00118  *   relay-app defaults to using NETLINK_USERSOCK for all
-00119  *   applications, which means that you can't have more than 1
-00120  *   relay-app in use at a time, unless you use different netlink
-00121  *   'units' for each one.  If you want to have more than one
-00122  *   relay-app in use at a time, you can specify a different netlink
-00123  *   'unit' by using the _init_relay_app() versions of the
-00124  *   init_relay_app() functions, on both the kernel and user sides,
-00125  *   which are the same as the init_relay_app() functions but add a
-00126  *   netlink unit param.  See netlink.h for the currently unused
-00127  *   numbers.
-00128  */
-00129 
-00130 #include <linux/inet.h>
-00131 #include <linux/ip.h>
-00132 #include <linux/netlink.h>
-00133 #include <linux/relayfs_fs.h>
-00134 
-00135 /* relay-app pseudo-API */
-00136 
-00137 /*
-00138  * relay-app callbacks
-00139  */
-00140 struct relay_app_callbacks
-00141 {
-00142         /*
-00143          *      user_command - app-specific command callback
-00144          *      @command: user-defined command id
-00145          *      @data: user-defined data associated with the command
-00146          *
-00147          *      Return value: 1 if this callback handled it, 0 if not
-00148          *
-00149          *      define this callback to handle user-defined commands sent
-00150          *      from the user space application via send_request()
-00151          *
-00152          *      NOTE: user commands must be >= RELAY_APP_USERCMD_START
-00153          */
-00154         int (*user_command) (int command, void *data);
-00155 
-00156         /*
-00157          *      app_started - the user-space application has started
-00158          *
-00159          *      Do app-specific initializations now, if desired
-00160          */
-00161         void (*app_started) (void);
-00162 
-00163         /*
-00164          *      app_stopped - the user-space application has stopped
-00165          *
-00166          *      Do app-specific cleanup now, if desired
-00167          */
-00168         void (*app_stopped) (void);
-00169 };
-00170 
-00171 /*
-00172  * relay-app API functions
-00173  */
-00174 static int init_relay_app(const char *dirname,
-00175                           const char *file_basename,
-00176                           struct relay_app_callbacks *callbacks);
-00177 static void close_relay_app(void);
-00178 
-00179 /*
-00180  * relay-app write wrapper macros - use these instead of directly
-00181  * using relay_write() and _relay_write() relayfs functions.
-00182  */
-00183 #define relayapp_write(data, len) \
-00184         if (app.logging) relay_write(app.chan, data, len)
-00185 
-00186 #define _relayapp_write(data, len) \
-00187         if (app.logging) _relay_write(app.chan, data, len)
-00188 
-00189 /* relay-app control channel command values */
-00190 enum
-00191 {
-00192         RELAY_APP_BUF_INFO = 1,
-00193         RELAY_APP_SUBBUFS_CONSUMED,
-00194         RELAY_APP_START,
-00195         RELAY_APP_STOP,
-00196         RELAY_APP_CHAN_CREATE,
-00197         RELAY_APP_CHAN_DESTROY,
-00198         RELAY_APP_USERCMD_START = 32
-00199 };
-00200 
-00201 /* SystemTap extensions */
-00202 enum
-00203 {
-00204         STP_REALTIME_DATA = RELAY_APP_USERCMD_START,
-00205         STP_EXIT,
-00206         STP_DONE
-00207 };
-00208 
-00209 /* internal stuff below here */
-00210 
-00211 /* netlink control channel */
-00212 static struct sock *control;
-00213 static int seq;
-00214 static int stpd_pid = 0;
-00215 
-00216 /* info for this application */
-00217 static struct relay_app
-00218 {
-00219         char dirname[1024];
-00220         char file_basename[1024];
-00221         struct relay_app_callbacks *cb;
-00222         struct rchan *chan;
-00223         struct dentry *dir;
-00224         int logging;
-00225         int mappings;
-00226 } app;
-00227 
-00228 /*
-00229  * subbuf_start() relayfs callback.
-00230  */
-00231 static int relay_app_subbuf_start(struct rchan_buf *buf,
-00232                                   void *subbuf,
-00233                                   unsigned prev_subbuf_idx,
-00234                                   void *prev_subbuf)
-00235 {
-00236         unsigned padding = buf->padding[prev_subbuf_idx];
-00237         if (prev_subbuf)
-00238                 *((unsigned *)prev_subbuf) = padding;
-00239 
-00240         return sizeof(padding); /* reserve space for padding */
-00241 }
-00242 
-00243 /*
-00244  * buf_full() relayfs callback.
-00245  */
-00246 static void relay_app_buf_full(struct rchan_buf *buf,
-00247                                unsigned subbuf_idx,
-00248                                void *subbuf)
-00249 {
-00250         unsigned padding = buf->padding[subbuf_idx];
-00251         *((unsigned *)subbuf) = padding;
-00252 }
-00253 
-00254 static void relay_app_buf_mapped(struct rchan_buf *buf, struct file *filp)
-00255 {
-00256         if (app.cb && app.cb->app_started && !app.mappings++)
-00257                 app.cb->app_started();
-00258 }
-00259 
-00260 static void relay_app_buf_unmapped(struct rchan_buf *buf, struct file *filp)
-00261 {
-00262         if (app.cb && app.cb->app_started && !--app.mappings)
-00263                 app.cb->app_stopped();
-00264 }
-00265 
-00266 static struct rchan_callbacks app_rchan_callbacks =
-00267 {
-00268         .subbuf_start = relay_app_subbuf_start,
-00269         .buf_full = relay_app_buf_full,
-00270         .buf_mapped = relay_app_buf_mapped,
-00271         .buf_unmapped = relay_app_buf_unmapped
-00272 };
-00273 
-00274 /**
-00275  *      create_app_chan - creates channel /mnt/relay/dirname/filebaseXXX
-00276  *
-00277  *      Returns channel on success, NULL otherwise.
-00278  */
-00279 static struct rchan *create_app_chan(unsigned subbuf_size,
-00280                                      unsigned n_subbufs)
-00281 {
-00282         struct rchan *chan;
-00283 
-00284         if (strlen(app.dirname)) {
-00285                 app.dir = relayfs_create_dir(app.dirname, NULL);
-00286                 if (!app.dir) {
-00287                         printk("Couldn't create relayfs app directory %s.\n", app.dirname);
-00288                         return NULL;
-00289                 }
-00290         }
-00291 
-00292         chan = relay_open(app.file_basename, app.dir, subbuf_size,
-00293                               n_subbufs, 0, &app_rchan_callbacks);
-00294         
-00295         if (!chan) {
-00296                 printk("relay app channel creation failed\n");
-00297                 if (app.dir)
-00298                         relayfs_remove_dir(app.dir);
-00299                 return NULL;
-00300         }
-00301 
-00302         return chan;
-00303 }
-00304 
-00305 /**
-00306  *      destroy_app_chan - destroys channel /mnt/relay/dirname/filebaseXXX
-00307  */
-00308 static void destroy_app_chan(struct rchan *chan)
-00309 {
-00310         if (chan)
-00311                 relay_close(chan);
-00312         if (app.dir)
-00313                 relayfs_remove_dir(app.dir);
-00314 
-00315         app.chan = NULL;
-00316         app.dir = NULL;
-00317 }
-00318 
-00319 /* netlink control channel communication with userspace */
-00320 
-00321 struct buf_info
-00322 {
-00323         int cpu;
-00324         unsigned produced;
-00325         unsigned consumed;
-00326 };
-00327 
-00328 struct consumed_info
-00329 {
-00330         int cpu;
-00331         unsigned consumed;
-00332 };
-00333 
-00334 struct channel_create_info
-00335 {
-00336         unsigned subbuf_size;
-00337         unsigned n_subbufs;
-00338 };
-00339 
-00340 /*
-00341  * send_reply - send reply to userspace over netlink control channel
-00342  */
-00343 static int send_reply(int type, void *reply, int len, int pid)
-00344 {
-00345         struct sk_buff *skb;
-00346         struct nlmsghdr *nlh;
-00347         void *data;
-00348         int size;
-00349         int err;
-00350                 
-00351         size = NLMSG_SPACE(len);
-00352         skb = alloc_skb(size, GFP_ATOMIC);
-00353         if (!skb)
-00354                 return -1;
-00355         nlh = NLMSG_PUT(skb, pid, seq++, type, size - sizeof(*nlh));
-00356         nlh->nlmsg_flags = 0;
-00357         data = NLMSG_DATA(nlh);
-00358         memcpy(data, reply, len);
-00359         err = netlink_unicast(control, skb, pid, MSG_DONTWAIT);
-00360 
-00361         return 0;
-00362 
-00363 nlmsg_failure:
-00364         if (skb)
-00365                 kfree_skb(skb);
-00366         
-00367         return -1;
-00368 }
-00369 
-00370 static void handle_buf_info(struct buf_info *in, int pid)
-00371 {
-00372         struct buf_info out;
-00373 
-00374         if (!app.chan)
-00375                 return;
-00376 
-00377         out.cpu = in->cpu;
-00378         out.produced = atomic_read(&app.chan->buf[in->cpu]->subbufs_produced);
-00379         out.consumed = atomic_read(&app.chan->buf[in->cpu]->subbufs_consumed);
-00380 
-00381         send_reply(RELAY_APP_BUF_INFO, &out, sizeof(out), pid);
-00382 }
-00383 
-00384 static inline void handle_subbufs_consumed(struct consumed_info *info)
-00385 {
-00386         if (!app.chan)
-00387                 return;
-00388 
-00389         relay_subbufs_consumed(app.chan, info->cpu, info->consumed);
-00390 }
-00391 
-00392 static inline void handle_create(struct channel_create_info *info)
-00393 {
-00394         destroy_app_chan(app.chan);
-00395         app.chan = create_app_chan(info->subbuf_size, info->n_subbufs);
-00396         if(!app.chan)
-00397                 return;
-00398         app.mappings = 0;
-00399 }
-00400 
-00401 /*
-00402  * msg_rcv_skb - dispatch userspace requests from netlink control channel
-00403  */
-00404 static void msg_rcv_skb(struct sk_buff *skb)
-00405 {
-00406         struct nlmsghdr *nlh = NULL;
-00407         int pid, flags;
-00408         int nlmsglen, skblen;
-00409         void *data;
-00410         
-00411         skblen = skb->len;
-00412         
-00413         if (skblen < sizeof (*nlh))
-00414                 return; 
-00415 
-00416         nlh = (struct nlmsghdr *)skb->data;
-00417         nlmsglen = nlh->nlmsg_len;
-00418         
-00419         if (nlmsglen < sizeof(*nlh) || skblen < nlmsglen)
-00420                 return;
-00421 
-00422         stpd_pid = pid = nlh->nlmsg_pid;
-00423         flags = nlh->nlmsg_flags;
-00424 
-00425         if (pid <= 0 || !(flags & NLM_F_REQUEST)) {
-00426                 netlink_ack(skb, nlh, -EINVAL);
-00427                 return;
-00428         }
-00429 
-00430         if (flags & MSG_TRUNC) {
-00431                 netlink_ack(skb, nlh, -ECOMM);
-00432                 return;
-00433         }
-00434         
-00435         data = NLMSG_DATA(nlh);
-00436 
-00437         switch (nlh->nlmsg_type) {
-00438         case RELAY_APP_CHAN_CREATE:
-00439                 handle_create(data);
-00440                 break;
-00441         case RELAY_APP_CHAN_DESTROY:
-00442                 destroy_app_chan(app.chan);
-00443                 break;
-00444         case RELAY_APP_START:
-00445                 app.logging = 1;
-00446                 break;
-00447         case RELAY_APP_STOP:
-00448                 app.logging = 0;
-00449                 relay_flush(app.chan);
-00450                 break;
-00451         case RELAY_APP_BUF_INFO:
-00452                 handle_buf_info(data, pid);
-00453                 break;
-00454         case RELAY_APP_SUBBUFS_CONSUMED:
-00455                 handle_subbufs_consumed(data);
-00456                 break;
-00457         default:
-00458                 if (!app.cb || !app.cb->user_command ||
-00459                     !app.cb->user_command(nlh->nlmsg_type, data))
-00460                         netlink_ack(skb, nlh, -EINVAL);
-00461                 return;
-00462         }
-00463         
-00464         if (flags & NLM_F_ACK)
-00465                 netlink_ack(skb, nlh, 0);
-00466 }
-00467 
-00468 /*
-00469  * msg_rcv - handle netlink control channel requests
-00470  */
-00471 static void msg_rcv(struct sock *sk, int len)
-00472 {
-00473         struct sk_buff *skb;
-00474         
-00475         while ((skb = skb_dequeue(&sk->sk_receive_queue))) {
-00476                 msg_rcv_skb(skb);
-00477                 kfree_skb(skb);
-00478         }
-00479 }
-00480 
-00481 /*
-00482  * _init_relay_app - adds netlink 'unit' if other than NETLINK_USERSOCK wanted
-00483  */
-00484 static int _init_relay_app(const char *dirname,
-00485                            const char *file_basename,
-00486                            struct relay_app_callbacks *callbacks,
-00487                            int unit)
-00488 {
-00489         if (!file_basename)
-00490                 return -1;
-00491 
-00492         if (dirname)
-00493                 strncpy(app.dirname, dirname, 1024);
-00494         strncpy(app.file_basename, file_basename, 1024);
-00495         app.cb = callbacks;
-00496 
-00497         control = netlink_kernel_create(unit, msg_rcv);
-00498         if (!control) {
-00499                 printk("Couldn't create control channel\n");
-00500                 return -1;
-00501         }
-00502 
-00503         return 0;
-00504 }
-00505 
-00506 /**
-00507  *      init_relay_app - initialize /mnt/relay/dirname/file_basenameXXX
-00508  *      @dirname: the directory to contain relayfs files for this app
-00509  *      @file_basename: the base filename of the relayfs files for this app
-00510  *      @callbacks: the relay_app_callbacks implemented for this app
-00511  *
-00512  *      Returns 0 on success, -1 otherwise.
-00513  *
-00514  *      NOTE: this doesn't create the relayfs files.  That happens via the
-00515  *      control channel protocol.
-00516  */
-00517 static int init_relay_app(const char *dirname,
-00518                           const char *file_basename,
-00519                           struct relay_app_callbacks *callbacks)
-00520 {
-00521         return _init_relay_app(dirname, file_basename, callbacks, NETLINK_USERSOCK);
-00522 }
-00523 
-00524 /**
-00525  *      close_relay_app - close netlink socket and destroy channel if it exists
-00526  *
-00527  *      Returns 0 on success, -1 otherwise.
-00528  */
-00529 static void close_relay_app(void)
-00530 {
-00531         if (control)
-00532                 sock_release(control->sk_socket);
-00533         destroy_app_chan(app.chan);
-00534 }
-