X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=blobdiff_plain;f=src%2Fcommon%2Fcompat%2Fpoll.c;fp=src%2Fcommon%2Fcompat%2Fpoll.c;h=d9acd901c0382802c136d49d9fa4a32eba22b24e;hp=0000000000000000000000000000000000000000;hb=0060607b4f1947339819316b63f00e42aab2a341;hpb=4fb28dfc10106c4095ca3b1155d4da9a04467fd1

diff --git a/src/common/compat/poll.c b/src/common/compat/poll.c
new file mode 100644
index 000000000..d9acd901c
--- /dev/null
+++ b/src/common/compat/poll.c
@@ -0,0 +1,731 @@
+/*
+ * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
+ * Copyright (C) 2019 Yannick Lamarre <ylamarre@efficios.com>
+ *
+ * SPDX-License-Identifier: GPL-2.0-only
+ *
+ */
+
+#define _LGPL_SOURCE
+#include <assert.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+#include <common/defaults.h>
+#include <common/error.h>
+#include <common/macros.h>
+#include <common/utils.h>
+
+#include "poll.h"
+
+#if HAVE_EPOLL
+
+#include <fcntl.h>
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+
+/*
+ * Maximum number of fd we can monitor.
+ *
+ * For epoll(7), /proc/sys/fs/epoll/max_user_watches (since Linux 2.6.28) will
+ * be used for the maximum size of the poll set. If this interface is not
+ * available, according to the manpage, the max_user_watches value is 1/25 (4%)
+ * of the available low memory divided by the registration cost in bytes which
+ * is 90 bytes on a 32-bit kernel and 160 bytes on a 64-bit kernel.
+ *
+ */
+static unsigned int poll_max_size;
+
+/*
+ * Resize the epoll events structure of the new size.
+ *
+ * Return 0 on success or else -1 with the current events pointer untouched.
+ */
+static int resize_poll_event(struct lttng_poll_event *events,
+		uint32_t new_size)
+{
+	struct epoll_event *ptr;
+
+	assert(events);
+
+	ptr = realloc(events->events, new_size * sizeof(*ptr));
+	if (ptr == NULL) {
+		PERROR("realloc epoll add");
+		goto error;
+	}
+	if (new_size > events->alloc_size) {
+		/* Zero newly allocated memory */
+		memset(ptr + events->alloc_size, 0,
+			(new_size - events->alloc_size) * sizeof(*ptr));
+	}
+	events->events = ptr;
+	events->alloc_size = new_size;
+
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Create epoll set and allocate returned events structure.
+ */
+LTTNG_HIDDEN
+int compat_epoll_create(struct lttng_poll_event *events, int size, int flags)
+{
+	int ret;
+
+	if (events == NULL || size <= 0) {
+		goto error;
+	}
+
+	if (!poll_max_size) {
+		if (lttng_poll_set_max_size()) {
+			goto error;
+		}
+	}
+
+	/* Don't bust the limit here */
+	if (size > poll_max_size) {
+		size = poll_max_size;
+	}
+
+	ret = compat_glibc_epoll_create(size, flags);
+	if (ret < 0) {
+		/* At this point, every error is fatal */
+		PERROR("epoll_create1");
+		goto error;
+	}
+
+	events->epfd = ret;
+
+	/* This *must* be freed by using lttng_poll_free() */
+	events->events = zmalloc(size * sizeof(struct epoll_event));
+	if (events->events == NULL) {
+		PERROR("zmalloc epoll set");
+		goto error_close;
+	}
+
+	events->alloc_size = events->init_size = size;
+	events->nb_fd = 0;
+
+	return 0;
+
+error_close:
+	ret = close(events->epfd);
+	if (ret) {
+		PERROR("close");
+	}
+error:
+	return -1;
+}
+
+/*
+ * Add a fd to the epoll set with requesting events.
+ */
+LTTNG_HIDDEN
+int compat_epoll_add(struct lttng_poll_event *events, int fd, uint32_t req_events)
+{
+	int ret;
+	struct epoll_event ev;
+
+	if (events == NULL || events->events == NULL || fd < 0) {
+		ERR("Bad compat epoll add arguments");
+		goto error;
+	}
+
+	/*
+	 * Zero struct epoll_event to ensure all representations of its
+	 * union are zeroed.
+	 */
+	memset(&ev, 0, sizeof(ev));
+	ev.events = req_events;
+	ev.data.fd = fd;
+
+	ret = epoll_ctl(events->epfd, EPOLL_CTL_ADD, fd, &ev);
+	if (ret < 0) {
+		switch (errno) {
+		case EEXIST:
+			/* If exist, it's OK. */
+			goto end;
+		case ENOSPC:
+		case EPERM:
+			/* Print PERROR and goto end not failing. Show must go on. */
+			PERROR("epoll_ctl ADD");
+			goto end;
+		default:
+			PERROR("epoll_ctl ADD fatal");
+			goto error;
+		}
+	}
+
+	events->nb_fd++;
+
+end:
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Remove a fd from the epoll set.
+ */
+LTTNG_HIDDEN
+int compat_epoll_del(struct lttng_poll_event *events, int fd)
+{
+	int ret;
+
+	if (events == NULL || fd < 0 || events->nb_fd == 0) {
+		goto error;
+	}
+
+	ret = epoll_ctl(events->epfd, EPOLL_CTL_DEL, fd, NULL);
+	if (ret < 0) {
+		switch (errno) {
+		case ENOENT:
+		case EPERM:
+			/* Print PERROR and goto end not failing. Show must go on. */
+			PERROR("epoll_ctl DEL");
+			goto end;
+		default:
+			PERROR("epoll_ctl DEL fatal");
+			goto error;
+		}
+	}
+
+	events->nb_fd--;
+
+end:
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Set an fd's events.
+ */
+LTTNG_HIDDEN
+int compat_epoll_mod(struct lttng_poll_event *events, int fd, uint32_t req_events)
+{
+	int ret;
+	struct epoll_event ev;
+
+	if (events == NULL || fd < 0 || events->nb_fd == 0) {
+		goto error;
+	}
+
+	/*
+	 * Zero struct epoll_event to ensure all representations of its
+	 * union are zeroed.
+	 */
+	memset(&ev, 0, sizeof(ev));
+	ev.events = req_events;
+	ev.data.fd = fd;
+
+	ret = epoll_ctl(events->epfd, EPOLL_CTL_MOD, fd, &ev);
+	if (ret < 0) {
+		switch (errno) {
+		case ENOENT:
+		case EPERM:
+			/* Print PERROR and goto end not failing. Show must go on. */
+			PERROR("epoll_ctl MOD");
+			goto end;
+		default:
+			PERROR("epoll_ctl MOD fatal");
+			goto error;
+		}
+	}
+
+end:
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Wait on epoll set. This is a blocking call of timeout value.
+ */
+LTTNG_HIDDEN
+int compat_epoll_wait(struct lttng_poll_event *events, int timeout,
+		bool interruptible)
+{
+	int ret;
+	uint32_t new_size;
+
+	if (events == NULL || events->events == NULL) {
+		ERR("Wrong arguments in compat_epoll_wait");
+		goto error;
+	}
+
+	if (events->nb_fd == 0) {
+		errno = EINVAL;
+		return -1;
+	}
+
+	/*
+	 * Resize if needed before waiting. We could either expand the array or
+	 * shrink it down. It's important to note that after this step, we are
+	 * ensured that the events argument of the epoll_wait call will be large
+	 * enough to hold every possible returned events.
+	 */
+	new_size = 1U << utils_get_count_order_u32(events->nb_fd);
+	if (new_size != events->alloc_size && new_size >= events->init_size) {
+		ret = resize_poll_event(events, new_size);
+		if (ret < 0) {
+			/* ENOMEM problem at this point. */
+			goto error;
+		}
+	}
+
+	do {
+		ret = epoll_wait(events->epfd, events->events, events->nb_fd, timeout);
+	} while (!interruptible && ret == -1 && errno == EINTR);
+	if (ret < 0) {
+		if (errno != EINTR) {
+			PERROR("epoll_wait");
+		}
+		goto error;
+	}
+
+	/*
+	 * Since the returned events are set sequentially in the "events" structure
+	 * we only need to return the epoll_wait value and iterate over it.
+	 */
+	return ret;
+
+error:
+	return -1;
+}
+
+/*
+ * Setup poll set maximum size.
+ */
+LTTNG_HIDDEN
+int compat_epoll_set_max_size(void)
+{
+	int ret, fd, retval = 0;
+	ssize_t size_ret;
+	char buf[64];
+
+	fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
+	if (fd < 0) {
+		/*
+		 * Failing on opening [1] is not an error per see. [1] was
+		 * introduced in Linux 2.6.28 but epoll is available since
+		 * 2.5.44. Hence, goto end and set a default value without
+		 * setting an error return value.
+		 *
+		 * [1] /proc/sys/fs/epoll/max_user_watches
+		 */
+		retval = 0;
+		goto end;
+	}
+
+	size_ret = lttng_read(fd, buf, sizeof(buf));
+	/*
+	 * Allow reading a file smaller than buf, but keep space for
+	 * final \0.
+	 */
+	if (size_ret < 0 || size_ret >= sizeof(buf)) {
+		PERROR("read set max size");
+		retval = -1;
+		goto end_read;
+	}
+	buf[size_ret] = '\0';
+	poll_max_size = atoi(buf);
+end_read:
+	ret = close(fd);
+	if (ret) {
+		PERROR("close");
+	}
+end:
+	if (!poll_max_size) {
+		poll_max_size = DEFAULT_POLL_SIZE;
+	}
+	DBG("epoll set max size is %d", poll_max_size);
+	return retval;
+}
+
+#else /* HAVE_EPOLL */
+
+#include <sys/resource.h>
+#include <sys/time.h>
+
+/*
+ * Maximum number of fd we can monitor.
+ *
+ * For poll(2), the max fds must not exceed RLIMIT_NOFILE given by
+ * getrlimit(2).
+ */
+static unsigned int poll_max_size;
+
+/*
+ * Resize the epoll events structure of the new size.
+ *
+ * Return 0 on success or else -1 with the current events pointer untouched.
+ */
+static int resize_poll_event(struct compat_poll_event_array *array,
+		uint32_t new_size)
+{
+	struct pollfd *ptr;
+
+	assert(array);
+
+	/* Refuse to resize the array more than the max size. */
+	if (new_size > poll_max_size) {
+		goto error;
+	}
+
+	ptr = realloc(array->events, new_size * sizeof(*ptr));
+	if (ptr == NULL) {
+		PERROR("realloc epoll add");
+		goto error;
+	}
+	if (new_size > array->alloc_size) {
+		/* Zero newly allocated memory */
+		memset(ptr + array->alloc_size, 0,
+			(new_size - array->alloc_size) * sizeof(*ptr));
+	}
+	array->events = ptr;
+	array->alloc_size = new_size;
+
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Update events with the current events object.
+ */
+static int update_current_events(struct lttng_poll_event *events)
+{
+	int ret;
+	struct compat_poll_event_array *current, *wait;
+
+	assert(events);
+
+	current = &events->current;
+	wait = &events->wait;
+
+	wait->nb_fd = current->nb_fd;
+	if (current->alloc_size != wait->alloc_size) {
+		ret = resize_poll_event(wait, current->alloc_size);
+		if (ret < 0) {
+			goto error;
+		}
+	}
+	memcpy(wait->events, current->events,
+			current->nb_fd * sizeof(*current->events));
+
+	/* Update is done. */
+	events->need_update = 0;
+
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Create pollfd data structure.
+ */
+LTTNG_HIDDEN
+int compat_poll_create(struct lttng_poll_event *events, int size)
+{
+	struct compat_poll_event_array *current, *wait;
+
+	if (events == NULL || size <= 0) {
+		ERR("Wrong arguments for poll create");
+		goto error;
+	}
+
+	if (!poll_max_size) {
+		if (lttng_poll_set_max_size()) {
+			goto error;
+		}
+	}
+
+	/* Don't bust the limit here */
+	if (size > poll_max_size) {
+		size = poll_max_size;
+	}
+
+	/* Reset everything before begining the allocation. */
+	memset(events, 0, sizeof(struct lttng_poll_event));
+
+	current = &events->current;
+	wait = &events->wait;
+
+	/* This *must* be freed by using lttng_poll_free() */
+	wait->events = zmalloc(size * sizeof(struct pollfd));
+	if (wait->events == NULL) {
+		PERROR("zmalloc struct pollfd");
+		goto error;
+	}
+
+	wait->alloc_size = wait->init_size = size;
+
+	current->events = zmalloc(size * sizeof(struct pollfd));
+	if (current->events == NULL) {
+		PERROR("zmalloc struct current pollfd");
+		goto error;
+	}
+
+	current->alloc_size = current->init_size = size;
+
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Add fd to pollfd data structure with requested events.
+ */
+LTTNG_HIDDEN
+int compat_poll_add(struct lttng_poll_event *events, int fd,
+		uint32_t req_events)
+{
+	int new_size, ret, i;
+	struct compat_poll_event_array *current;
+
+	if (events == NULL || events->current.events == NULL || fd < 0) {
+		ERR("Bad compat poll add arguments");
+		goto error;
+	}
+
+	current = &events->current;
+
+	/* Check if fd we are trying to add is already there. */
+	for (i = 0; i < current->nb_fd; i++) {
+		if (current->events[i].fd == fd) {
+			errno = EEXIST;
+			goto error;
+		}
+	}
+
+	/* Resize array if needed. */
+	new_size = 1U << utils_get_count_order_u32(current->nb_fd + 1);
+	if (new_size != current->alloc_size && new_size >= current->init_size) {
+		ret = resize_poll_event(current, new_size);
+		if (ret < 0) {
+			goto error;
+		}
+	}
+
+	current->events[current->nb_fd].fd = fd;
+	current->events[current->nb_fd].events = req_events;
+	current->nb_fd++;
+	events->need_update = 1;
+
+	DBG("fd %d of %d added to pollfd", fd, current->nb_fd);
+
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Modify an fd's events..
+ */
+LTTNG_HIDDEN
+int compat_poll_mod(struct lttng_poll_event *events, int fd,
+		uint32_t req_events)
+{
+	int i;
+	struct compat_poll_event_array *current;
+
+	if (events == NULL || events->current.nb_fd == 0 ||
+			events->current.events == NULL || fd < 0) {
+		ERR("Bad compat poll mod arguments");
+		goto error;
+	}
+
+	current = &events->current;
+
+	for (i = 0; i < current->nb_fd; i++) {
+		if (current->events[i].fd == fd) {
+			current->events[i].events = req_events;
+			events->need_update = 1;
+			break;
+		}
+	}
+
+	/*
+	 * The epoll flavor doesn't flag modifying a non-included FD as an
+	 * error.
+	 */
+
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Remove a fd from the pollfd structure.
+ */
+LTTNG_HIDDEN
+int compat_poll_del(struct lttng_poll_event *events, int fd)
+{
+	int i, count = 0, ret;
+	uint32_t new_size;
+	struct compat_poll_event_array *current;
+
+	if (events == NULL || events->current.nb_fd == 0 ||
+			events->current.events == NULL || fd < 0) {
+		goto error;
+	}
+
+	/* Ease our life a bit. */
+	current = &events->current;
+
+	for (i = 0; i < current->nb_fd; i++) {
+		/* Don't put back the fd we want to delete */
+		if (current->events[i].fd != fd) {
+			current->events[count].fd = current->events[i].fd;
+			current->events[count].events = current->events[i].events;
+			count++;
+		}
+	}
+
+	/* The fd was not in our set, return no error as with epoll. */
+	if (current->nb_fd == count) {
+		goto end;
+	}
+
+	/* No fd duplicate should be ever added into array. */
+	assert(current->nb_fd - 1 == count);
+	current->nb_fd = count;
+
+	/* Resize array if needed. */
+	new_size = 1U << utils_get_count_order_u32(current->nb_fd);
+	if (new_size != current->alloc_size && new_size >= current->init_size
+			&& current->nb_fd != 0) {
+		ret = resize_poll_event(current, new_size);
+		if (ret < 0) {
+			goto error;
+		}
+	}
+
+	events->need_update = 1;
+
+end:
+	return 0;
+
+error:
+	return -1;
+}
+
+/*
+ * Wait on poll() with timeout. Blocking call.
+ */
+LTTNG_HIDDEN
+int compat_poll_wait(struct lttng_poll_event *events, int timeout,
+		bool interruptible)
+{
+	int ret, active_fd_count;
+	int idle_pfd_index = 0;
+	size_t i;
+
+	if (events == NULL || events->current.events == NULL) {
+		ERR("poll wait arguments error");
+		goto error;
+	}
+
+	if (events->current.nb_fd == 0) {
+		/* Return an invalid error to be consistent with epoll. */
+		errno = EINVAL;
+		events->wait.nb_fd = 0;
+		goto error;
+	}
+
+	if (events->need_update) {
+		ret = update_current_events(events);
+		if (ret < 0) {
+			errno = ENOMEM;
+			goto error;
+		}
+	}
+
+	do {
+		ret = poll(events->wait.events, events->wait.nb_fd, timeout);
+	} while (!interruptible && ret == -1 && errno == EINTR);
+	if (ret < 0) {
+		if (errno != EINTR) {
+			PERROR("poll wait");
+		}
+		goto error;
+	}
+
+	active_fd_count = ret;
+
+	/*
+	 * Swap all active pollfd structs to the beginning of the
+	 * array to emulate compat-epoll behaviour. This algorithm takes
+	 * advantage of poll's returned value and the burst nature of active
+	 * events on the file descriptors. The while loop guarantees that
+	 * idle_pfd will always point to an idle fd.
+	 */
+	if (active_fd_count == events->wait.nb_fd) {
+		goto end;
+	}
+	while (idle_pfd_index < active_fd_count &&
+			events->wait.events[idle_pfd_index].revents != 0) {
+		idle_pfd_index++;
+	}
+
+	for (i = idle_pfd_index + 1; idle_pfd_index < active_fd_count;
+			i++) {
+		struct pollfd swap_pfd;
+		struct pollfd *idle_pfd = &events->wait.events[idle_pfd_index];
+		struct pollfd *current_pfd = &events->wait.events[i];
+
+		if (idle_pfd->revents != 0) {
+			swap_pfd = *current_pfd;
+			*current_pfd = *idle_pfd;
+			*idle_pfd = swap_pfd;
+			idle_pfd_index++;
+		}
+	}
+
+end:
+	return ret;
+
+error:
+	return -1;
+}
+
+/*
+ * Setup poll set maximum size.
+ */
+LTTNG_HIDDEN
+int compat_poll_set_max_size(void)
+{
+	int ret, retval = 0;
+	struct rlimit lim;
+
+	ret = getrlimit(RLIMIT_NOFILE, &lim);
+	if (ret < 0) {
+		PERROR("getrlimit poll RLIMIT_NOFILE");
+		retval = -1;
+		goto end;
+	}
+
+	poll_max_size = lim.rlim_cur;
+end:
+	if (poll_max_size == 0) {
+		poll_max_size = DEFAULT_POLL_SIZE;
+	}
+	DBG("poll set max size set to %u", poll_max_size);
+	return retval;
+}
+
+#endif /* !HAVE_EPOLL */