/*
- * Copyright (C) 2011 David Goulet <david.goulet@polymtl.ca>
+ * Copyright (C) 2011 EfficiOS Inc.
* Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*
* SPDX-License-Identifier: GPL-2.0-only
#include "shm.h"
/*
- * Using fork to set umask in the child process (not multi-thread safe). We
- * deal with the shm_open vs ftruncate race (happening when the sessiond owns
+ * We deal with the shm_open vs ftruncate race (happening when the sessiond owns
* the shm and does not let everybody modify it, to ensure safety against
* shm_unlink) by simply letting the mmap fail and retrying after a few
* seconds. For global shm, everybody has rw access to it until the sessiond
static int get_wait_shm(char *shm_path, size_t mmap_size, int global)
{
int wait_shm_fd, ret;
- mode_t mode;
+ mode_t mode, old_mode;
assert(shm_path);
mode |= S_IROTH | S_IWOTH;
}
- /*
- * We're alone in a child process, so we can modify the process-wide
- * umask.
- */
- umask(~mode);
+ old_mode = umask(~mode);
/*
* Try creating shm (or get rw access). We don't do an exclusive open,
wait_shm_fd = shm_open(shm_path, O_RDWR, mode);
}
if (wait_shm_fd < 0) {
- PERROR("Failed to open wait shm at %s", shm_path);
+ PERROR("Failed to open \"wait\" shared memory object: path = '%s'", shm_path);
goto error;
}
}
ret = ftruncate(wait_shm_fd, mmap_size);
if (ret < 0) {
- PERROR("ftruncate wait shm");
- exit(EXIT_FAILURE);
+ PERROR("Failed to truncate \"wait\" shared memory object: fd = %d, size = %zu",
+ wait_shm_fd, mmap_size);
+ goto error;
}
if (global) {
ret = fchown(wait_shm_fd, 0, 0);
if (ret < 0) {
- PERROR("fchown");
- exit(EXIT_FAILURE);
+ PERROR("Failed to set ownership of \"wait\" shared memory object: fd = %d, owner = 0, group = 0",
+ wait_shm_fd);
+ goto error;
}
/*
* If global session daemon, any application can
mode &= ~S_IWOTH;
ret = fchmod(wait_shm_fd, mode);
if (ret < 0) {
- PERROR("fchmod");
- exit(EXIT_FAILURE);
+ PERROR("Failed to set the mode of the \"wait\" shared memory object: fd = %d, mode = %d",
+ wait_shm_fd, mode);
+ goto error;
}
} else {
ret = fchown(wait_shm_fd, getuid(), getgid());
if (ret < 0) {
- PERROR("fchown");
- exit(EXIT_FAILURE);
+ PERROR("Failed to set ownership of \"wait\" shared memory object: fd = %d, owner = %d, group = %d",
+ wait_shm_fd, getuid(), getgid());
+ goto error;
}
}
- DBG("Got the wait shm fd %d", wait_shm_fd);
+ DBG("Wait shared memory file descriptor created successfully: path = '%s', mmap_size = %zu, global = %s, fd = %d",
+ shm_path, mmap_size, global ? "true" : "false",
+ wait_shm_fd);
+end:
+ (void) umask(old_mode);
return wait_shm_fd;
error:
DBG("Failing to get the wait shm fd");
+ if (wait_shm_fd >= 0) {
+ if (close(wait_shm_fd)) {
+ PERROR("Failed to close wait shm file descriptor during error handling");
+ }
+ }
- return -1;
+ wait_shm_fd = -1;
+ goto end;
}
/*
* This returned value is used by futex_wait_update() in futex.c to WAKE all
* waiters which are UST application waiting for a session daemon.
*/
+LTTNG_HIDDEN
char *shm_ust_get_mmap(char *shm_path, int global)
{
size_t mmap_size;
sys_page_size = sysconf(_SC_PAGE_SIZE);
if (sys_page_size < 0) {
- PERROR("sysconf PAGE_SIZE");
+ PERROR("Failed to get PAGE_SIZE of system");
goto error;
}
mmap_size = sys_page_size;
/* close shm fd immediately after taking the mmap reference */
ret = close(wait_shm_fd);
if (ret) {
- PERROR("Error closing fd");
+ PERROR("Failed to close \"wait\" shared memory object file descriptor: fd = %d",
+ wait_shm_fd);
}
if (wait_shm_mmap == MAP_FAILED) {
- DBG("mmap error (can be caused by race with ust).");
+ DBG("Failed to mmap the \"wait\" shareed memory object (can be caused by race with ust): path = '%s', global = %s",
+ shm_path, global ? "true" : "false");
goto error;
}
/*
* shm_create_anonymous is never called concurrently within a process.
*/
+LTTNG_HIDDEN
int shm_create_anonymous(const char *owner_name)
{
char tmp_name[NAME_MAX];
ret = snprintf(tmp_name, NAME_MAX, "/shm-%s-%d", owner_name, getpid());
if (ret < 0) {
- PERROR("snprintf");
+ PERROR("Failed to format shm path: owner_name = '%s', pid = %d",
+ owner_name, getpid());
return -1;
}
+
/*
* Allocate shm, and immediately unlink its shm oject, keeping only the
* file descriptor as a reference to the object.
*/
shmfd = shm_open(tmp_name, O_CREAT | O_EXCL | O_RDWR, 0700);
if (shmfd < 0) {
- PERROR("shm_open");
+ PERROR("Failed to open shared memory object: path = '%s'", tmp_name);
goto error_shm_open;
}
+
ret = shm_unlink(tmp_name);
if (ret < 0 && errno != ENOENT) {
- PERROR("shm_unlink");
+ PERROR("Failed to unlink shared memory object: path = '%s'",
+ tmp_name);
goto error_shm_release;
}
+
return shmfd;
error_shm_release:
ret = close(shmfd);
if (ret) {
- PERROR("close");
+ PERROR("Failed to close shared memory object file descriptor: fd = %d, path = '%s'",
+ shmfd, tmp_name);
}
error_shm_open:
return -1;
projects / lttng-tools.git / blobdiff