diff options
| -rw-r--r-- | support/Makefile | 2 | ||||
| -rw-r--r-- | support/support-open-dev-null-range.c | 134 | ||||
| -rw-r--r-- | support/support.h | 8 | ||||
| -rw-r--r-- | support/tst-support-open-dev-null-range.c | 155 |
4 files changed, 299 insertions, 0 deletions
diff --git a/support/Makefile b/support/Makefile index a462781..6332e7b 100644 --- a/support/Makefile +++ b/support/Makefile @@ -66,6 +66,7 @@ libsupport-routines = \ support_path_support_time64 \ support_process_state \ support_ptrace \ + support-open-dev-null-range \ support_openpty \ support_paths \ support_quote_blob \ @@ -264,6 +265,7 @@ tests = \ tst-support_capture_subprocess \ tst-support_descriptors \ tst-support_format_dns_packet \ + tst-support-open-dev-null-range \ tst-support-process_state \ tst-support_quote_blob \ tst-support_quote_string \ diff --git a/support/support-open-dev-null-range.c b/support/support-open-dev-null-range.c new file mode 100644 index 0000000..80d9dba --- /dev/null +++ b/support/support-open-dev-null-range.c @@ -0,0 +1,134 @@ +/* Return a range of open file descriptors. + Copyright (C) 2021 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library 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. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <errno.h> +#include <fcntl.h> +#include <support/support.h> +#include <support/check.h> +#include <support/xunistd.h> +#include <stdlib.h> +#include <sys/resource.h> + +static void +increase_nofile (void) +{ + struct rlimit rl; + if (getrlimit (RLIMIT_NOFILE, &rl) == -1) + FAIL_EXIT1 ("getrlimit (RLIMIT_NOFILE): %m"); + + rl.rlim_cur += 128; + + if (setrlimit (RLIMIT_NOFILE, &rl) == 1) + FAIL_EXIT1 ("setrlimit (RLIMIT_NOFILE): %m"); +} + +static int +open_dev_null (int flags, mode_t mode) +{ + int fd = open64 ("/dev/null", flags, mode); + if (fd > 0) + return fd; + + if (fd < 0 && errno != EMFILE) + FAIL_EXIT1 ("open64 (\"/dev/null\", 0x%x, 0%o): %m", flags, mode); + + increase_nofile (); + + return xopen ("/dev/null", flags, mode); +} + +struct range +{ + int lowfd; + size_t len; +}; + +struct range_list +{ + size_t total; + size_t used; + struct range *ranges; +}; + +static void +range_init (struct range_list *r) +{ + r->total = 8; + r->used = 0; + r->ranges = xmalloc (r->total * sizeof (struct range)); +} + +static void +range_add (struct range_list *r, int lowfd, size_t len) +{ + if (r->used == r->total) + { + r->total *= 2; + r->ranges = xrealloc (r->ranges, r->total * sizeof (struct range)); + } + r->ranges[r->used].lowfd = lowfd; + r->ranges[r->used].len = len; + r->used++; +} + +static void +range_close (struct range_list *r) +{ + for (size_t i = 0; i < r->used; i++) + { + int minfd = r->ranges[i].lowfd; + int maxfd = r->ranges[i].lowfd + r->ranges[i].len; + for (int fd = minfd; fd < maxfd; fd++) + xclose (fd); + } + free (r->ranges); +} + +int +support_open_dev_null_range (int num, int flags, mode_t mode) +{ + /* We keep track of the ranges that hit an already opened descriptor, so + we close them after we get a working range. */ + struct range_list rl; + range_init (&rl); + + int lowfd = open_dev_null (flags, mode); + int prevfd = lowfd; + while (true) + { + int i = 1; + for (; i < num; i++) + { + int fd = open_dev_null (flags, mode); + if (fd != lowfd + i) + { + range_add (&rl, lowfd, prevfd - lowfd + 1); + + prevfd = lowfd = fd; + break; + } + prevfd = fd; + } + if (i == num) + break; + } + + range_close (&rl); + + return lowfd; +} diff --git a/support/support.h b/support/support.h index 834dba9..e6911e1 100644 --- a/support/support.h +++ b/support/support.h @@ -193,6 +193,14 @@ struct support_stack support_stack_alloc (size_t size); /* Deallocate the STACK. */ void support_stack_free (struct support_stack *stack); + +/* Create a range of NUM opened '/dev/null' file descriptors using FLAGS and + MODE. The function takes care of restarting the open range if a file + descriptor is found within the specified range and also increases + RLIMIT_NOFILE if required. + The returned value is the lowest file descriptor number. */ +int support_open_dev_null_range (int num, int flags, mode_t mode); + __END_DECLS #endif /* SUPPORT_H */ diff --git a/support/tst-support-open-dev-null-range.c b/support/tst-support-open-dev-null-range.c new file mode 100644 index 0000000..8e29def --- /dev/null +++ b/support/tst-support-open-dev-null-range.c @@ -0,0 +1,155 @@ +/* Tests for support_open_dev_null_range. + Copyright (C) 2021 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library 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. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + <https://www.gnu.org/licenses/>. */ + +#include <errno.h> +#include <dirent.h> +#include <fcntl.h> +#include <limits.h> +#include <support/check.h> +#include <support/support.h> +#include <support/xunistd.h> +#include <sys/resource.h> +#include <stdlib.h> + +#ifndef PATH_MAX +# define PATH_MAX 1024 +#endif + +#include <stdio.h> + +static void +check_path (int fd) +{ + char *proc_fd_path = xasprintf ("/proc/self/fd/%d", fd); + char file_path[PATH_MAX]; + ssize_t file_path_length + = readlink (proc_fd_path, file_path, sizeof (file_path)); + free (proc_fd_path); + if (file_path_length < 0) + FAIL_EXIT1 ("readlink (%s, %p, %zu)", proc_fd_path, file_path, + sizeof (file_path)); + file_path[file_path_length] = '\0'; + TEST_COMPARE_STRING (file_path, "/dev/null"); +} + +static int +number_of_opened_files (void) +{ + DIR *fds = opendir ("/proc/self/fd"); + if (fds == NULL) + FAIL_EXIT1 ("opendir (\"/proc/self/fd\"): %m"); + + int r = 0; + while (true) + { + errno = 0; + struct dirent64 *e = readdir64 (fds); + if (e == NULL) + { + if (errno != 0) + FAIL_EXIT1 ("readdir: %m"); + break; + } + + if (e->d_name[0] == '.') + continue; + + char *endptr; + long int fd = strtol (e->d_name, &endptr, 10); + if (*endptr != '\0' || fd < 0 || fd > INT_MAX) + FAIL_EXIT1 ("readdir: invalid file descriptor name: /proc/self/fd/%s", + e->d_name); + + /* Skip the descriptor which is used to enumerate the + descriptors. */ + if (fd == dirfd (fds)) + continue; + + r = r + 1; + } + + closedir (fds); + + return r; +} + +static int +do_test (void) +{ + const int nfds1 = 8; + int lowfd = support_open_dev_null_range (nfds1, O_RDONLY, 0600); + for (int i = 0; i < nfds1; i++) + { + TEST_VERIFY (fcntl (lowfd + i, F_GETFL) > -1); + check_path (lowfd + i); + } + + /* create some gaps. */ + xclose (lowfd + 1); + xclose (lowfd + 5); + xclose (lowfd + 6); + + const int nfds2 = 16; + int lowfd2 = support_open_dev_null_range (nfds2, O_RDONLY, 0600); + for (int i = 0; i < nfds2; i++) + { + TEST_VERIFY (fcntl (lowfd2 + i, F_GETFL) > -1); + check_path (lowfd2 + i); + } + + /* Decrease the maximum number of files. */ + { + struct rlimit rl; + if (getrlimit (RLIMIT_NOFILE, &rl) == -1) + FAIL_EXIT1 ("getrlimit (RLIMIT_NOFILE): %m"); + + rl.rlim_cur = number_of_opened_files (); + + if (setrlimit (RLIMIT_NOFILE, &rl) == 1) + FAIL_EXIT1 ("setrlimit (RLIMIT_NOFILE): %m"); + } + + const int nfds3 = 16; + int lowfd3 = support_open_dev_null_range (nfds3, O_RDONLY, 0600); + for (int i = 0; i < nfds3; i++) + { + TEST_VERIFY (fcntl (lowfd3 + i, F_GETFL) > -1); + check_path (lowfd3 + i); + } + + /* create a lot of gaps to trigger the range extension. */ + xclose (lowfd3 + 1); + xclose (lowfd3 + 3); + xclose (lowfd3 + 5); + xclose (lowfd3 + 7); + xclose (lowfd3 + 9); + xclose (lowfd3 + 11); + xclose (lowfd3 + 13); + + const int nfds4 = 16; + int lowfd4 = support_open_dev_null_range (nfds4, O_RDONLY, 0600); + for (int i = 0; i < nfds4; i++) + { + TEST_VERIFY (fcntl (lowfd4 + i, F_GETFL) > -1); + check_path (lowfd4 + i); + } + + return 0; +} + +#include <support/test-driver.c> |