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Diffstat (limited to 'samples/kdbus/kdbus-workers.c')
| -rw-r--r-- | samples/kdbus/kdbus-workers.c | 1345 |
1 files changed, 1345 insertions, 0 deletions
diff --git a/samples/kdbus/kdbus-workers.c b/samples/kdbus/kdbus-workers.c new file mode 100644 index 000000000..c3ba95863 --- /dev/null +++ b/samples/kdbus/kdbus-workers.c @@ -0,0 +1,1345 @@ +/* + * Copyright (C) 2013-2015 David Herrmann <dh.herrmann@gmail.com> + * + * kdbus is free software; you can redistribute it and/or modify it under + * the terms of the GNU Lesser General Public License as published by the + * Free Software Foundation; either version 2.1 of the License, or (at + * your option) any later version. + */ + +/* + * Example: Workers + * This program computes prime-numbers based on the sieve of Eratosthenes. The + * master sets up a shared memory region and spawns workers which clear out the + * non-primes. The master reacts to keyboard input and to client-requests to + * control what each worker does. Note that this is in no way meant as efficient + * way to compute primes. It should only serve as example how a master/worker + * concept can be implemented with kdbus used as control messages. + * + * The main process is called the 'master'. It creates a new, private bus which + * will be used between the master and its workers to communicate. The master + * then spawns a fixed number of workers. Whenever a worker dies (detected via + * SIGCHLD), the master spawns a new worker. When done, the master waits for all + * workers to exit, prints a status report and exits itself. + * + * The master process does *not* keep track of its workers. Instead, this + * example implements a PULL model. That is, the master acquires a well-known + * name on the bus which each worker uses to request tasks from the master. If + * there are no more tasks, the master will return an empty task-list, which + * casues a worker to exit immediately. + * + * As tasks can be computationally expensive, we support cancellation. Whenever + * the master process is interrupted, it will drop its well-known name on the + * bus. This causes kdbus to broadcast a name-change notification. The workers + * check for broadcast messages regularly and will exit if they receive one. + * + * This example exists of 4 objects: + * * master: The master object contains the context of the master process. This + * process manages the prime-context, spawns workers and assigns + * prime-ranges to each worker to compute. + * The master itself does not do any prime-computations itself. + * * child: The child object contains the context of a worker. It inherits the + * prime context from its parent (the master) and then creates a new + * bus context to request prime-ranges to compute. + * * prime: The "prime" object is used to abstract how we compute primes. When + * allocated, it prepares a memory region to hold 1 bit for each + * natural number up to a fixed maximum ('MAX_PRIMES'). + * The memory region is backed by a memfd which we share between + * processes. Each worker now gets assigned a range of natural + * numbers which it clears multiples of off the memory region. The + * master process is responsible of distributing all natural numbers + * up to the fixed maximum to its workers. + * * bus: The bus object is an abstraction of the kdbus API. It is pretty + * straightfoward and only manages the connection-fd plus the + * memory-mapped pool in a single object. + * + * This example is in reversed order, which should make it easier to read + * top-down, but requires some forward-declarations. Just ignore those. + */ + +#include <stdio.h> +#include <stdlib.h> + +/* glibc < 2.7 does not ship sys/signalfd.h */ +#if __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 7 + +#include <ctype.h> +#include <errno.h> +#include <fcntl.h> +#include <linux/memfd.h> +#include <signal.h> +#include <stdbool.h> +#include <stddef.h> +#include <stdint.h> +#include <string.h> +#include <sys/mman.h> +#include <sys/poll.h> +#include <sys/signalfd.h> +#include <sys/syscall.h> +#include <sys/time.h> +#include <sys/wait.h> +#include <time.h> +#include <unistd.h> +#include "kdbus-api.h" + +/* FORWARD DECLARATIONS */ + +#define POOL_SIZE (16 * 1024 * 1024) +#define MAX_PRIMES (2UL << 24) +#define WORKER_COUNT (16) +#define PRIME_STEPS (65536 * 4) + +static const char *arg_busname = "example-workers"; +static const char *arg_modname = "kdbus"; +static const char *arg_master = "org.freedesktop.master"; + +static int err_assert(int r_errno, const char *msg, const char *func, int line, + const char *file) +{ + r_errno = (r_errno != 0) ? -abs(r_errno) : -EFAULT; + if (r_errno < 0) { + errno = -r_errno; + fprintf(stderr, "ERR: %s: %m (%s:%d in %s)\n", + msg, func, line, file); + } + return r_errno; +} + +#define err_r(_r, _msg) err_assert((_r), (_msg), __func__, __LINE__, __FILE__) +#define err(_msg) err_r(errno, (_msg)) + +struct prime; +struct bus; +struct master; +struct child; + +struct prime { + int fd; + uint8_t *area; + size_t max; + size_t done; + size_t status; +}; + +static int prime_new(struct prime **out); +static void prime_free(struct prime *p); +static bool prime_done(struct prime *p); +static void prime_consume(struct prime *p, size_t amount); +static int prime_run(struct prime *p, struct bus *cancel, size_t number); +static void prime_print(struct prime *p); + +struct bus { + int fd; + uint8_t *pool; +}; + +static int bus_open_connection(struct bus **out, uid_t uid, const char *name, + uint64_t recv_flags); +static void bus_close_connection(struct bus *b); +static void bus_poool_free_slice(struct bus *b, uint64_t offset); +static int bus_acquire_name(struct bus *b, const char *name); +static int bus_install_name_loss_match(struct bus *b, const char *name); +static int bus_poll(struct bus *b); +static int bus_make(uid_t uid, const char *name); + +struct master { + size_t n_workers; + size_t max_workers; + + int signal_fd; + int control_fd; + + struct prime *prime; + struct bus *bus; +}; + +static int master_new(struct master **out); +static void master_free(struct master *m); +static int master_run(struct master *m); +static int master_poll(struct master *m); +static int master_handle_stdin(struct master *m); +static int master_handle_signal(struct master *m); +static int master_handle_bus(struct master *m); +static int master_reply(struct master *m, const struct kdbus_msg *msg); +static int master_waitpid(struct master *m); +static int master_spawn(struct master *m); + +struct child { + struct bus *bus; + struct prime *prime; +}; + +static int child_new(struct child **out, struct prime *p); +static void child_free(struct child *c); +static int child_run(struct child *c); + +/* END OF FORWARD DECLARATIONS */ + +/* + * This is the main entrypoint of this example. It is pretty straightforward. We + * create a master object, run the computation, print a status report and then + * exit. Nothing particularly interesting here, so lets look into the master + * object... + */ +int main(int argc, char **argv) +{ + struct master *m = NULL; + int r; + + r = master_new(&m); + if (r < 0) + goto out; + + r = master_run(m); + if (r < 0) + goto out; + + if (0) + prime_print(m->prime); + +out: + master_free(m); + if (r < 0 && r != -EINTR) + fprintf(stderr, "failed\n"); + else + fprintf(stderr, "done\n"); + return r < 0 ? EXIT_FAILURE : EXIT_SUCCESS; +} + +/* + * ...this will allocate a new master context. It keeps track of the current + * number of children/workers that are running, manages a signalfd to track + * SIGCHLD, and creates a private kdbus bus. Afterwards, it opens its connection + * to the bus and acquires a well known-name (arg_master). + */ +static int master_new(struct master **out) +{ + struct master *m; + sigset_t smask; + int r; + + m = calloc(1, sizeof(*m)); + if (!m) + return err("cannot allocate master"); + + m->max_workers = WORKER_COUNT; + m->signal_fd = -1; + m->control_fd = -1; + + /* Block SIGINT and SIGCHLD signals */ + sigemptyset(&smask); + sigaddset(&smask, SIGINT); + sigaddset(&smask, SIGCHLD); + sigprocmask(SIG_BLOCK, &smask, NULL); + + m->signal_fd = signalfd(-1, &smask, SFD_CLOEXEC); + if (m->signal_fd < 0) { + r = err("cannot create signalfd"); + goto error; + } + + r = prime_new(&m->prime); + if (r < 0) + goto error; + + m->control_fd = bus_make(getuid(), arg_busname); + if (m->control_fd < 0) { + r = m->control_fd; + goto error; + } + + /* + * Open a bus connection for the master, and require each received + * message to have a metadata item of type KDBUS_ITEM_PIDS attached. + * The current UID is needed to compute the name of the bus node to + * connect to. + */ + r = bus_open_connection(&m->bus, getuid(), + arg_busname, KDBUS_ATTACH_PIDS); + if (r < 0) + goto error; + + /* + * Acquire a well-known name on the bus, so children can address + * messages to the master using KDBUS_DST_ID_NAME as destination-ID + * of messages. + */ + r = bus_acquire_name(m->bus, arg_master); + if (r < 0) + goto error; + + *out = m; + return 0; + +error: + master_free(m); + return r; +} + +/* pretty straightforward destructor of a master object */ +static void master_free(struct master *m) +{ + if (!m) + return; + + bus_close_connection(m->bus); + if (m->control_fd >= 0) + close(m->control_fd); + prime_free(m->prime); + if (m->signal_fd >= 0) + close(m->signal_fd); + free(m); +} + +static int master_run(struct master *m) +{ + int res, r = 0; + + while (!prime_done(m->prime)) { + while (m->n_workers < m->max_workers) { + r = master_spawn(m); + if (r < 0) + break; + } + + r = master_poll(m); + if (r < 0) + break; + } + + if (r < 0) { + bus_close_connection(m->bus); + m->bus = NULL; + } + + while (m->n_workers > 0) { + res = master_poll(m); + if (res < 0) { + if (m->bus) { + bus_close_connection(m->bus); + m->bus = NULL; + } + r = res; + } + } + + return r == -EINTR ? 0 : r; +} + +static int master_poll(struct master *m) +{ + struct pollfd fds[3] = {}; + int r = 0, n = 0; + + /* + * Add stdin, the eventfd and the connection owner file descriptor to + * the pollfd table, and handle incoming traffic on the latter in + * master_handle_bus(). + */ + fds[n].fd = STDIN_FILENO; + fds[n++].events = POLLIN; + fds[n].fd = m->signal_fd; + fds[n++].events = POLLIN; + if (m->bus) { + fds[n].fd = m->bus->fd; + fds[n++].events = POLLIN; + } + + r = poll(fds, n, -1); + if (r < 0) + return err("poll() failed"); + + if (fds[0].revents & POLLIN) + r = master_handle_stdin(m); + else if (fds[0].revents) + r = err("ERR/HUP on stdin"); + if (r < 0) + return r; + + if (fds[1].revents & POLLIN) + r = master_handle_signal(m); + else if (fds[1].revents) + r = err("ERR/HUP on signalfd"); + if (r < 0) + return r; + + if (fds[2].revents & POLLIN) + r = master_handle_bus(m); + else if (fds[2].revents) + r = err("ERR/HUP on bus"); + + return r; +} + +static int master_handle_stdin(struct master *m) +{ + char buf[128]; + ssize_t l; + int r = 0; + + l = read(STDIN_FILENO, buf, sizeof(buf)); + if (l < 0) + return err("cannot read stdin"); + if (l == 0) + return err_r(-EINVAL, "EOF on stdin"); + + while (l-- > 0) { + switch (buf[l]) { + case 'q': + /* quit */ + r = -EINTR; + break; + case '\n': + case ' ': + /* ignore */ + break; + default: + if (isgraph(buf[l])) + fprintf(stderr, "invalid input '%c'\n", buf[l]); + else + fprintf(stderr, "invalid input 0x%x\n", buf[l]); + break; + } + } + + return r; +} + +static int master_handle_signal(struct master *m) +{ + struct signalfd_siginfo val; + ssize_t l; + + l = read(m->signal_fd, &val, sizeof(val)); + if (l < 0) + return err("cannot read signalfd"); + if (l != sizeof(val)) + return err_r(-EINVAL, "invalid data from signalfd"); + + switch (val.ssi_signo) { + case SIGCHLD: + return master_waitpid(m); + case SIGINT: + return err_r(-EINTR, "interrupted"); + default: + return err_r(-EINVAL, "caught invalid signal"); + } +} + +static int master_handle_bus(struct master *m) +{ + struct kdbus_cmd_recv recv = { .size = sizeof(recv) }; + const struct kdbus_msg *msg = NULL; + const struct kdbus_item *item; + const struct kdbus_vec *vec = NULL; + int r = 0; + + /* + * To receive a message, the KDBUS_CMD_RECV ioctl is used. + * It takes an argument of type 'struct kdbus_cmd_recv', which + * will contain information on the received message when the call + * returns. See kdbus.message(7). + */ + r = kdbus_cmd_recv(m->bus->fd, &recv); + /* + * EAGAIN is returned when there is no message waiting on this + * connection. This is not an error - simply bail out. + */ + if (r == -EAGAIN) + return 0; + if (r < 0) + return err_r(r, "cannot receive message"); + + /* + * Messages received by a connection are stored inside the connection's + * pool, at an offset that has been returned in the 'recv' command + * struct above. The value describes the relative offset from the + * start address of the pool. A message is described with + * 'struct kdbus_msg'. See kdbus.message(7). + */ + msg = (void *)(m->bus->pool + recv.msg.offset); + + /* + * A messages describes its actual payload in an array of items. + * KDBUS_FOREACH() is a simple iterator that walks such an array. + * struct kdbus_msg has a field to denote its total size, which is + * needed to determine the number of items in the array. + */ + KDBUS_FOREACH(item, msg->items, + msg->size - offsetof(struct kdbus_msg, items)) { + /* + * An item of type PAYLOAD_OFF describes in-line memory + * stored in the pool at a described offset. That offset is + * relative to the start address of the message header. + * This example program only expects one single item of that + * type, remembers the struct kdbus_vec member of the item + * when it sees it, and bails out if there is more than one + * of them. + */ + if (item->type == KDBUS_ITEM_PAYLOAD_OFF) { + if (vec) { + r = err_r(-EEXIST, + "message with multiple vecs"); + break; + } + vec = &item->vec; + if (vec->size != 1) { + r = err_r(-EINVAL, "invalid message size"); + break; + } + + /* + * MEMFDs are transported as items of type PAYLOAD_MEMFD. + * If such an item is attached, a new file descriptor was + * installed into the task when KDBUS_CMD_RECV was called, and + * its number is stored in item->memfd.fd. + * Implementers *must* handle this item type and close the + * file descriptor when no longer needed in order to prevent + * file descriptor exhaustion. This example program just bails + * out with an error in this case, as memfds are not expected + * in this context. + */ + } else if (item->type == KDBUS_ITEM_PAYLOAD_MEMFD) { + r = err_r(-EINVAL, "message with memfd"); + break; + } + } + if (r < 0) + goto exit; + if (!vec) { + r = err_r(-EINVAL, "empty message"); + goto exit; + } + + switch (*((const uint8_t *)msg + vec->offset)) { + case 'r': { + r = master_reply(m, msg); + break; + } + default: + r = err_r(-EINVAL, "invalid message type"); + break; + } + +exit: + /* + * We are done with the memory slice that was given to us through + * recv.msg.offset. Tell the kernel it can use it for other content + * in the future. See kdbus.pool(7). + */ + bus_poool_free_slice(m->bus, recv.msg.offset); + return r; +} + +static int master_reply(struct master *m, const struct kdbus_msg *msg) +{ + struct kdbus_cmd_send cmd; + struct kdbus_item *item; + struct kdbus_msg *reply; + size_t size, status, p[2]; + int r; + + /* + * This functions sends a message over kdbus. To do this, it uses the + * KDBUS_CMD_SEND ioctl, which takes a command struct argument of type + * 'struct kdbus_cmd_send'. This struct stores a pointer to the actual + * message to send. See kdbus.message(7). + */ + p[0] = m->prime->done; + p[1] = prime_done(m->prime) ? 0 : PRIME_STEPS; + + size = sizeof(*reply); + size += KDBUS_ITEM_SIZE(sizeof(struct kdbus_vec)); + + /* Prepare the message to send */ + reply = alloca(size); + memset(reply, 0, size); + reply->size = size; + + /* Each message has a cookie that can be used to send replies */ + reply->cookie = 1; + + /* The payload_type is arbitrary, but it must be non-zero */ + reply->payload_type = 0xdeadbeef; + + /* + * We are sending a reply. Let the kernel know the cookie of the + * message we are replying to. + */ + reply->cookie_reply = msg->cookie; + + /* + * Messages can either be directed to a well-known name (stored as + * string) or to a unique name (stored as number). This example does + * the latter. If the message would be directed to a well-known name + * instead, the message's dst_id field would be set to + * KDBUS_DST_ID_NAME, and the name would be attaches in an item of type + * KDBUS_ITEM_DST_NAME. See below for an example, and also refer to + * kdbus.message(7). + */ + reply->dst_id = msg->src_id; + + /* Our message has exactly one item to store its payload */ + item = reply->items; + item->type = KDBUS_ITEM_PAYLOAD_VEC; + item->size = KDBUS_ITEM_HEADER_SIZE + sizeof(struct kdbus_vec); + item->vec.address = (uintptr_t)p; + item->vec.size = sizeof(p); + + /* + * Now prepare the command struct, and reference the message we want + * to send. + */ + memset(&cmd, 0, sizeof(cmd)); + cmd.size = sizeof(cmd); + cmd.msg_address = (uintptr_t)reply; + + /* + * Finally, employ the command on the connection owner + * file descriptor. + */ + r = kdbus_cmd_send(m->bus->fd, &cmd); + if (r < 0) + return err_r(r, "cannot send reply"); + + if (p[1]) { + prime_consume(m->prime, p[1]); + status = m->prime->done * 10000 / m->prime->max; + if (status != m->prime->status) { + m->prime->status = status; + fprintf(stderr, "status: %7.3lf%%\n", + (double)status / 100); + } + } + + return 0; +} + +static int master_waitpid(struct master *m) +{ + pid_t pid; + int r; + + while ((pid = waitpid(-1, &r, WNOHANG)) > 0) { + if (m->n_workers > 0) + --m->n_workers; + if (!WIFEXITED(r)) + r = err_r(-EINVAL, "child died unexpectedly"); + else if (WEXITSTATUS(r) != 0) + r = err_r(-WEXITSTATUS(r), "child failed"); + } + + return r; +} + +static int master_spawn(struct master *m) +{ + struct child *c = NULL; + struct prime *p = NULL; + pid_t pid; + int r; + + /* Spawn off one child and call child_run() inside it */ + + pid = fork(); + if (pid < 0) + return err("cannot fork"); + if (pid > 0) { + /* parent */ + ++m->n_workers; + return 0; + } + + /* child */ + + p = m->prime; + m->prime = NULL; + master_free(m); + + r = child_new(&c, p); + if (r < 0) + goto exit; + + r = child_run(c); + +exit: + child_free(c); + exit(abs(r)); +} + +static int child_new(struct child **out, struct prime *p) +{ + struct child *c; + int r; + + c = calloc(1, sizeof(*c)); + if (!c) + return err("cannot allocate child"); + + c->prime = p; + + /* + * Open a connection to the bus and require each received message to + * carry a list of the well-known names the sendind connection currently + * owns. The current UID is needed in order to determine the name of the + * bus node to connect to. + */ + r = bus_open_connection(&c->bus, getuid(), + arg_busname, KDBUS_ATTACH_NAMES); + if (r < 0) + goto error; + + /* + * Install a kdbus match so the child's connection gets notified when + * the master loses its well-known name. + */ + r = bus_install_name_loss_match(c->bus, arg_master); + if (r < 0) + goto error; + + *out = c; + return 0; + +error: + child_free(c); + return r; +} + +static void child_free(struct child *c) +{ + if (!c) + return; + + bus_close_connection(c->bus); + prime_free(c->prime); + free(c); +} + +static int child_run(struct child *c) +{ + struct kdbus_cmd_send cmd; + struct kdbus_item *item; + struct kdbus_vec *vec = NULL; + struct kdbus_msg *msg; + struct timespec spec; + size_t n, steps, size; + int r = 0; + + /* + * Let's send a message to the master and ask for work. To do this, + * we use the KDBUS_CMD_SEND ioctl, which takes an argument of type + * 'struct kdbus_cmd_send'. This struct stores a pointer to the actual + * message to send. See kdbus.message(7). + */ + size = sizeof(*msg); + size += KDBUS_ITEM_SIZE(strlen(arg_master) + 1); + size += KDBUS_ITEM_SIZE(sizeof(struct kdbus_vec)); + + msg = alloca(size); + memset(msg, 0, size); + msg->size = size; + + /* + * Tell the kernel that we expect a reply to this message. This means + * that + * + * a) The remote peer will gain temporary permission to talk to us + * even if it would not be allowed to normally. + * + * b) A timeout value is required. + * + * For asynchronous send commands, if no reply is received, we will + * get a kernel notification with an item of type + * KDBUS_ITEM_REPLY_TIMEOUT attached. + * + * For synchronous send commands (which this example does), the + * ioctl will block until a reply is received or the timeout is + * exceeded. + */ + msg->flags = KDBUS_MSG_EXPECT_REPLY; + + /* Set our cookie. Replies must use this cookie to send their reply. */ + msg->cookie = 1; + + /* The payload_type is arbitrary, but it must be non-zero */ + msg->payload_type = 0xdeadbeef; + + /* + * We are sending our message to the current owner of a well-known + * name. This makes an item of type KDBUS_ITEM_DST_NAME mandatory. + */ + msg->dst_id = KDBUS_DST_ID_NAME; + + /* + * Set the reply timeout to 5 seconds. Timeouts are always set in + * absolute timestamps, based con CLOCK_MONOTONIC. See kdbus.message(7). + */ + clock_gettime(CLOCK_MONOTONIC_COARSE, &spec); + msg->timeout_ns += (5 + spec.tv_sec) * 1000ULL * 1000ULL * 1000ULL; + msg->timeout_ns += spec.tv_nsec; + + /* + * Fill the appended items. First, set the well-known name of the + * destination we want to talk to. + */ + item = msg->items; + item->type = KDBUS_ITEM_DST_NAME; + item->size = KDBUS_ITEM_HEADER_SIZE + strlen(arg_master) + 1; + strcpy(item->str, arg_master); + + /* + * The 2nd item contains a vector to memory we want to send. It + * can be content of any type. In our case, we're sending a one-byte + * string only. The memory referenced by this item will be copied into + * the pool of the receiver connection, and does not need to be valid + * after the command is employed. + */ + item = KDBUS_ITEM_NEXT(item); + item->type = KDBUS_ITEM_PAYLOAD_VEC; + item->size = KDBUS_ITEM_HEADER_SIZE + sizeof(struct kdbus_vec); + item->vec.address = (uintptr_t)"r"; + item->vec.size = 1; + + /* Set up the command struct and reference the message we prepared */ + memset(&cmd, 0, sizeof(cmd)); + cmd.size = sizeof(cmd); + cmd.msg_address = (uintptr_t)msg; + + /* + * The send commands knows a mode in which it will block until a + * reply to a message is received. This example uses that mode. + * The pool offset to the received reply will be stored in the command + * struct after the send command returned. See below. + */ + cmd.flags = KDBUS_SEND_SYNC_REPLY; + + /* + * Finally, employ the command on the connection owner + * file descriptor. + */ + r = kdbus_cmd_send(c->bus->fd, &cmd); + if (r == -ESRCH || r == -EPIPE || r == -ECONNRESET) + return 0; + if (r < 0) + return err_r(r, "cannot send request to master"); + + /* + * The command was sent with the KDBUS_SEND_SYNC_REPLY flag set, + * and returned successfully, which means that cmd.reply.offset now + * points to a message inside our connection's pool where the reply + * is found. This is equivalent to receiving the reply with + * KDBUS_CMD_RECV, but it doesn't require waiting for the reply with + * poll() and also saves the ioctl to receive the message. + */ + msg = (void *)(c->bus->pool + cmd.reply.offset); + + /* + * A messages describes its actual payload in an array of items. + * KDBUS_FOREACH() is a simple iterator that walks such an array. + * struct kdbus_msg has a field to denote its total size, which is + * needed to determine the number of items in the array. + */ + KDBUS_FOREACH(item, msg->items, + msg->size - offsetof(struct kdbus_msg, items)) { + /* + * An item of type PAYLOAD_OFF describes in-line memory + * stored in the pool at a described offset. That offset is + * relative to the start address of the message header. + * This example program only expects one single item of that + * type, remembers the struct kdbus_vec member of the item + * when it sees it, and bails out if there is more than one + * of them. + */ + if (item->type == KDBUS_ITEM_PAYLOAD_OFF) { + if (vec) { + r = err_r(-EEXIST, + "message with multiple vecs"); + break; + } + vec = &item->vec; + if (vec->size != 2 * sizeof(size_t)) { + r = err_r(-EINVAL, "invalid message size"); + break; + } + /* + * MEMFDs are transported as items of type PAYLOAD_MEMFD. + * If such an item is attached, a new file descriptor was + * installed into the task when KDBUS_CMD_RECV was called, and + * its number is stored in item->memfd.fd. + * Implementers *must* handle this item type close the + * file descriptor when no longer needed in order to prevent + * file descriptor exhaustion. This example program just bails + * out with an error in this case, as memfds are not expected + * in this context. + */ + } else if (item->type == KDBUS_ITEM_PAYLOAD_MEMFD) { + r = err_r(-EINVAL, "message with memfd"); + break; + } + } + if (r < 0) + goto exit; + if (!vec) { + r = err_r(-EINVAL, "empty message"); + goto exit; + } + + n = ((size_t *)((const uint8_t *)msg + vec->offset))[0]; + steps = ((size_t *)((const uint8_t *)msg + vec->offset))[1]; + + while (steps-- > 0) { + ++n; + r = prime_run(c->prime, c->bus, n); + if (r < 0) + break; + r = bus_poll(c->bus); + if (r != 0) { + r = r < 0 ? r : -EINTR; + break; + } + } + +exit: + /* + * We are done with the memory slice that was given to us through + * cmd.reply.offset. Tell the kernel it can use it for other content + * in the future. See kdbus.pool(7). + */ + bus_poool_free_slice(c->bus, cmd.reply.offset); + return r; +} + +/* + * Prime Computation + * + */ + +static int prime_new(struct prime **out) +{ + struct prime *p; + int r; + + p = calloc(1, sizeof(*p)); + if (!p) + return err("cannot allocate prime memory"); + + p->fd = -1; + p->area = MAP_FAILED; + p->max = MAX_PRIMES; + + /* + * Prepare and map a memfd to store the bit-fields for the number + * ranges we want to perform the prime detection on. + */ + p->fd = syscall(__NR_memfd_create, "prime-area", MFD_CLOEXEC); + if (p->fd < 0) { + r = err("cannot create memfd"); + goto error; + } + + r = ftruncate(p->fd, p->max / 8 + 1); + if (r < 0) { + r = err("cannot ftruncate area"); + goto error; + } + + p->area = mmap(NULL, p->max / 8 + 1, PROT_READ | PROT_WRITE, + MAP_SHARED, p->fd, 0); + if (p->area == MAP_FAILED) { + r = err("cannot mmap memfd"); + goto error; + } + + *out = p; + return 0; + +error: + prime_free(p); + return r; +} + +static void prime_free(struct prime *p) +{ + if (!p) + return; + + if (p->area != MAP_FAILED) + munmap(p->area, p->max / 8 + 1); + if (p->fd >= 0) + close(p->fd); + free(p); +} + +static bool prime_done(struct prime *p) +{ + return p->done >= p->max; +} + +static void prime_consume(struct prime *p, size_t amount) +{ + p->done += amount; +} + +static int prime_run(struct prime *p, struct bus *cancel, size_t number) +{ + size_t i, n = 0; + int r; + + if (number < 2 || number > 65535) + return 0; + + for (i = number * number; + i < p->max && i > number; + i += number) { + p->area[i / 8] |= 1 << (i % 8); + + if (!(++n % (1 << 20))) { + r = bus_poll(cancel); + if (r != 0) + return r < 0 ? r : -EINTR; + } + } + + return 0; +} + +static void prime_print(struct prime *p) +{ + size_t i, l = 0; + + fprintf(stderr, "PRIMES:"); + for (i = 0; i < p->max; ++i) { + if (!(p->area[i / 8] & (1 << (i % 8)))) + fprintf(stderr, "%c%7zu", !(l++ % 16) ? '\n' : ' ', i); + } + fprintf(stderr, "\nEND\n"); +} + +static int bus_open_connection(struct bus **out, uid_t uid, const char *name, + uint64_t recv_flags) +{ + struct kdbus_cmd_hello hello; + char path[128]; + struct bus *b; + int r; + + /* + * The 'bus' object is our representation of a kdbus connection which + * stores two details: the connection owner file descriptor, and the + * mmap()ed memory of its associated pool. See kdbus.connection(7) and + * kdbus.pool(7). + */ + b = calloc(1, sizeof(*b)); + if (!b) + return err("cannot allocate bus memory"); + + b->fd = -1; + b->pool = MAP_FAILED; + + /* Compute the name of the bus node to connect to. */ + snprintf(path, sizeof(path), "/sys/fs/%s/%lu-%s/bus", + arg_modname, (unsigned long)uid, name); + b->fd = open(path, O_RDWR | O_CLOEXEC); + if (b->fd < 0) { + r = err("cannot open bus"); + goto error; + } + + /* + * To make a connection to the bus, the KDBUS_CMD_HELLO ioctl is used. + * It takes an argument of type 'struct kdbus_cmd_hello'. + */ + memset(&hello, 0, sizeof(hello)); + hello.size = sizeof(hello); + + /* + * Specify a mask of metadata attach flags, describing metadata items + * that this new connection allows to be sent. + */ + hello.attach_flags_send = _KDBUS_ATTACH_ALL; + + /* + * Specify a mask of metadata attach flags, describing metadata items + * that this new connection wants to be receive along with each message. + */ + hello.attach_flags_recv = recv_flags; + + /* + * A connection may choose the size of its pool, but the number has to + * comply with two rules: a) it must be greater than 0, and b) it must + * be a mulitple of PAGE_SIZE. See kdbus.pool(7). + */ + hello.pool_size = POOL_SIZE; + + /* + * Now employ the command on the file descriptor opened above. + * This command will turn the file descriptor into a connection-owner + * file descriptor that controls the life-time of the connection; once + * it's closed, the connection is shut down. + */ + r = kdbus_cmd_hello(b->fd, &hello); + if (r < 0) { + err_r(r, "HELLO failed"); + goto error; + } + + bus_poool_free_slice(b, hello.offset); + + /* + * Map the pool of the connection. Its size has been set in the + * command struct above. See kdbus.pool(7). + */ + b->pool = mmap(NULL, POOL_SIZE, PROT_READ, MAP_SHARED, b->fd, 0); + if (b->pool == MAP_FAILED) { + r = err("cannot mmap pool"); + goto error; + } + + *out = b; + return 0; + +error: + bus_close_connection(b); + return r; +} + +static void bus_close_connection(struct bus *b) +{ + if (!b) + return; + + /* + * A bus connection is closed by simply calling close() on the + * connection owner file descriptor. The unique name and all owned + * well-known names of the conneciton will disappear. + * See kdbus.connection(7). + */ + if (b->pool != MAP_FAILED) + munmap(b->pool, POOL_SIZE); + if (b->fd >= 0) + close(b->fd); + free(b); +} + +static void bus_poool_free_slice(struct bus *b, uint64_t offset) +{ + struct kdbus_cmd_free cmd = { + .size = sizeof(cmd), + .offset = offset, + }; + int r; + + /* + * Once we're done with a piece of pool memory that was returned + * by a command, we have to call the KDBUS_CMD_FREE ioctl on it so it + * can be reused. The command takes an argument of type + * 'struct kdbus_cmd_free', in which the pool offset of the slice to + * free is stored. The ioctl is employed on the connection owner + * file descriptor. See kdbus.pool(7), + */ + r = kdbus_cmd_free(b->fd, &cmd); + if (r < 0) + err_r(r, "cannot free pool slice"); +} + +static int bus_acquire_name(struct bus *b, const char *name) +{ + struct kdbus_item *item; + struct kdbus_cmd *cmd; + size_t size; + int r; + + /* + * This function acquires a well-known name on the bus through the + * KDBUS_CMD_NAME_ACQUIRE ioctl. This ioctl takes an argument of type + * 'struct kdbus_cmd', which is assembled below. See kdbus.name(7). + */ + size = sizeof(*cmd); + size += KDBUS_ITEM_SIZE(strlen(name) + 1); + + cmd = alloca(size); + memset(cmd, 0, size); + cmd->size = size; + + /* + * The command requires an item of type KDBUS_ITEM_NAME, and its + * content must be a valid bus name. + */ + item = cmd->items; + item->type = KDBUS_ITEM_NAME; + item->size = KDBUS_ITEM_HEADER_SIZE + strlen(name) + 1; + strcpy(item->str, name); + + /* + * Employ the command on the connection owner file descriptor. + */ + r = kdbus_cmd_name_acquire(b->fd, cmd); + if (r < 0) + return err_r(r, "cannot acquire name"); + + return 0; +} + +static int bus_install_name_loss_match(struct bus *b, const char *name) +{ + struct kdbus_cmd_match *match; + struct kdbus_item *item; + size_t size; + int r; + + /* + * In order to install a match for signal messages, we have to + * assemble a 'struct kdbus_cmd_match' and use it along with the + * KDBUS_CMD_MATCH_ADD ioctl. See kdbus.match(7). + */ + size = sizeof(*match); + size += KDBUS_ITEM_SIZE(sizeof(item->name_change) + strlen(name) + 1); + + match = alloca(size); + memset(match, 0, size); + match->size = size; + + /* + * A match is comprised of many 'rules', each of which describes a + * mandatory detail of the message. All rules of a match must be + * satified in order to make a message pass. + */ + item = match->items; + + /* + * In this case, we're interested in notifications that inform us + * about a well-known name being removed from the bus. + */ + item->type = KDBUS_ITEM_NAME_REMOVE; + item->size = KDBUS_ITEM_HEADER_SIZE + + sizeof(item->name_change) + strlen(name) + 1; + + /* + * We could limit the match further and require a specific unique-ID + * to be the new or the old owner of the name. In this case, however, + * we don't, and allow 'any' id. + */ + item->name_change.old_id.id = KDBUS_MATCH_ID_ANY; + item->name_change.new_id.id = KDBUS_MATCH_ID_ANY; + + /* Copy in the well-known name we're interested in */ + strcpy(item->name_change.name, name); + + /* + * Add the match through the KDBUS_CMD_MATCH_ADD ioctl, employed on + * the connection owner fd. + */ + r = kdbus_cmd_match_add(b->fd, match); + if (r < 0) + return err_r(r, "cannot add match"); + + return 0; +} + +static int bus_poll(struct bus *b) +{ + struct pollfd fds[1] = {}; + int r; + + /* + * A connection endpoint supports poll() and will wake-up the + * task with POLLIN set once a message has arrived. + */ + fds[0].fd = b->fd; + fds[0].events = POLLIN; + r = poll(fds, sizeof(fds) / sizeof(*fds), 0); + if (r < 0) + return err("cannot poll bus"); + return !!(fds[0].revents & POLLIN); +} + +static int bus_make(uid_t uid, const char *name) +{ + struct kdbus_item *item; + struct kdbus_cmd *make; + char path[128], busname[128]; + size_t size; + int r, fd; + + /* + * Compute the full path to the 'control' node. 'arg_modname' may be + * set to a different value than 'kdbus' for development purposes. + * The 'control' node is the primary entry point to kdbus that must be + * used in order to create a bus. See kdbus(7) and kdbus.bus(7). + */ + snprintf(path, sizeof(path), "/sys/fs/%s/control", arg_modname); + + /* + * Compute the bus name. A valid bus name must always be prefixed with + * the EUID of the currently running process in order to avoid name + * conflicts. See kdbus.bus(7). + */ + snprintf(busname, sizeof(busname), "%lu-%s", (unsigned long)uid, name); + + fd = open(path, O_RDWR | O_CLOEXEC); + if (fd < 0) + return err("cannot open control file"); + + /* + * The KDBUS_CMD_BUS_MAKE ioctl takes an argument of type + * 'struct kdbus_cmd', and expects at least two items attached to + * it: one to decribe the bloom parameters to be propagated to + * connections of the bus, and the name of the bus that was computed + * above. Assemble this struct now, and fill it with values. + */ + size = sizeof(*make); + size += KDBUS_ITEM_SIZE(sizeof(struct kdbus_bloom_parameter)); + size += KDBUS_ITEM_SIZE(strlen(busname) + 1); + + make = alloca(size); + memset(make, 0, size); + make->size = size; + + /* + * Each item has a 'type' and 'size' field, and must be stored at an + * 8-byte aligned address. The KDBUS_ITEM_NEXT macro is used to advance + * the pointer. See kdbus.item(7) for more details. + */ + item = make->items; + item->type = KDBUS_ITEM_BLOOM_PARAMETER; + item->size = KDBUS_ITEM_HEADER_SIZE + sizeof(item->bloom_parameter); + item->bloom_parameter.size = 8; + item->bloom_parameter.n_hash = 1; + + /* The name of the new bus is stored in the next item. */ + item = KDBUS_ITEM_NEXT(item); + item->type = KDBUS_ITEM_MAKE_NAME; + item->size = KDBUS_ITEM_HEADER_SIZE + strlen(busname) + 1; + strcpy(item->str, busname); + + /* + * Now create the bus via the KDBUS_CMD_BUS_MAKE ioctl and return the + * fd that was used back to the caller of this function. This fd is now + * called a 'bus owner file descriptor', and it controls the life-time + * of the newly created bus; once the file descriptor is closed, the + * bus goes away, and all connections are shut down. See kdbus.bus(7). + */ + r = kdbus_cmd_bus_make(fd, make); + if (r < 0) { + err_r(r, "cannot make bus"); + close(fd); + return r; + } + + return fd; +} + +#else + +#warning "Skipping compilation due to unsupported libc version" + +int main(int argc, char **argv) +{ + fprintf(stderr, + "Compilation of %s was skipped due to unsupported libc.\n", + argv[0]); + + return EXIT_FAILURE; +} + +#endif /* libc sanity check */ |