| 1 | /* |
| 2 | * Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 3 | * |
| 4 | * This library is free software; you can redistribute it and/or |
| 5 | * modify it under the terms of the GNU Lesser General Public |
| 6 | * License as published by the Free Software Foundation; version 2.1 of |
| 7 | * the License. |
| 8 | * |
| 9 | * This library is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 12 | * Lesser General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU Lesser General Public |
| 15 | * License along with this library; if not, write to the Free Software |
| 16 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 17 | */ |
| 18 | |
| 19 | #define _GNU_SOURCE |
| 20 | #define _LGPL_SOURCE |
| 21 | #include <limits.h> |
| 22 | #include <stdio.h> |
| 23 | #include <sys/types.h> |
| 24 | #include <unistd.h> |
| 25 | #include <ust-fd.h> |
| 26 | #include <dlfcn.h> |
| 27 | #include <errno.h> |
| 28 | |
| 29 | #include <helper.h> |
| 30 | #include "usterr-signal-safe.h" |
| 31 | |
| 32 | #define LTTNG_UST_DLSYM_FAILED_PTR 0x1 |
| 33 | |
| 34 | static int (*__lttng_ust_fd_plibc_close)(int fd) = NULL; |
| 35 | static int (*__lttng_ust_fd_plibc_fclose)(FILE *stream) = NULL; |
| 36 | |
| 37 | /* |
| 38 | * Use dlsym to find the original libc close() symbol and store it in |
| 39 | * __lttng_ust_fd_plibc_close. |
| 40 | */ |
| 41 | static |
| 42 | void *_lttng_ust_fd_init_plibc_close(void) |
| 43 | { |
| 44 | if (__lttng_ust_fd_plibc_close == NULL) { |
| 45 | __lttng_ust_fd_plibc_close = dlsym(RTLD_NEXT, "close"); |
| 46 | |
| 47 | if (__lttng_ust_fd_plibc_close == NULL) { |
| 48 | __lttng_ust_fd_plibc_close = (void *) LTTNG_UST_DLSYM_FAILED_PTR; |
| 49 | fprintf(stderr, "%s\n", dlerror()); |
| 50 | } |
| 51 | } |
| 52 | |
| 53 | return __lttng_ust_fd_plibc_close; |
| 54 | } |
| 55 | |
| 56 | /* |
| 57 | * Use dlsym to find the original libc fclose() symbol and store it in |
| 58 | * __lttng_ust_fd_plibc_fclose. |
| 59 | */ |
| 60 | static |
| 61 | void *_lttng_ust_fd_init_plibc_fclose(void) |
| 62 | { |
| 63 | if (__lttng_ust_fd_plibc_fclose == NULL) { |
| 64 | __lttng_ust_fd_plibc_fclose = dlsym(RTLD_NEXT, "fclose"); |
| 65 | |
| 66 | if (__lttng_ust_fd_plibc_fclose == NULL) { |
| 67 | __lttng_ust_fd_plibc_fclose = (void *) LTTNG_UST_DLSYM_FAILED_PTR; |
| 68 | fprintf(stderr, "%s\n", dlerror()); |
| 69 | } |
| 70 | } |
| 71 | |
| 72 | return __lttng_ust_fd_plibc_fclose; |
| 73 | } |
| 74 | |
| 75 | static |
| 76 | void _lttng_ust_fd_ctor(void) |
| 77 | __attribute__((constructor)); |
| 78 | static |
| 79 | void _lttng_ust_fd_ctor(void) |
| 80 | { |
| 81 | /* |
| 82 | * Initialize the function pointers to the original libc symbols in the |
| 83 | * constructor since close() has to stay async-signal-safe and as such, |
| 84 | * we can't call dlsym() in the override functions. |
| 85 | */ |
| 86 | (void) _lttng_ust_fd_init_plibc_close(); |
| 87 | (void) _lttng_ust_fd_init_plibc_fclose(); |
| 88 | } |
| 89 | |
| 90 | /* |
| 91 | * Override the libc close() symbol with our own, allowing applications to |
| 92 | * close arbitrary file descriptors. If the fd is owned by lttng-ust, return |
| 93 | * -1, errno=EBADF instead of closing it. |
| 94 | * |
| 95 | * If dlsym failed to find the original libc close() symbol, return -1, |
| 96 | * errno=ENOSYS. |
| 97 | * |
| 98 | * There is a short window before the library constructor has executed where |
| 99 | * this wrapper could call dlsym() and thus not be async-signal-safe. |
| 100 | */ |
| 101 | int close(int fd) |
| 102 | { |
| 103 | /* |
| 104 | * We can't retry dlsym here since close is async-signal-safe. |
| 105 | */ |
| 106 | if (_lttng_ust_fd_init_plibc_close() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) { |
| 107 | errno = ENOSYS; |
| 108 | return -1; |
| 109 | } |
| 110 | |
| 111 | return lttng_ust_safe_close_fd(fd, __lttng_ust_fd_plibc_close); |
| 112 | } |
| 113 | |
| 114 | /* |
| 115 | * Override the libc fclose() symbol with our own, allowing applications to |
| 116 | * close arbitrary streams. If the fd is owned by lttng-ust, return -1, |
| 117 | * errno=EBADF instead of closing it. |
| 118 | * |
| 119 | * If dlsym failed to find the original libc close() symbol, return -1, |
| 120 | * errno=ENOSYS. |
| 121 | * |
| 122 | * There is a short window before the library constructor has executed where |
| 123 | * this wrapper could call dlsym() and thus not be async-signal-safe. |
| 124 | * |
| 125 | * Note: fcloseall() is not an issue because it closes only the streams it |
| 126 | * knows about, which differs from the problems caused by gnulib |
| 127 | * close_stdout(), which does an explicit fclose(stdout). |
| 128 | */ |
| 129 | int fclose(FILE *stream) |
| 130 | { |
| 131 | if (_lttng_ust_fd_init_plibc_fclose() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) { |
| 132 | errno = ENOSYS; |
| 133 | return -1; |
| 134 | } |
| 135 | |
| 136 | return lttng_ust_safe_fclose_stream(stream, |
| 137 | __lttng_ust_fd_plibc_fclose); |
| 138 | } |
| 139 | |
| 140 | #if defined(__sun__) || defined(__FreeBSD__) |
| 141 | /* Solaris and FreeBSD. */ |
| 142 | void closefrom(int lowfd) |
| 143 | { |
| 144 | if (_lttng_ust_fd_init_plibc_close() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) { |
| 145 | return; |
| 146 | } |
| 147 | |
| 148 | (void) lttng_ust_safe_closefrom_fd(lowfd, __lttng_ust_fd_plibc_close); |
| 149 | } |
| 150 | #elif defined(__NetBSD__) || defined(__OpenBSD__) |
| 151 | /* NetBSD and OpenBSD. */ |
| 152 | int closefrom(int lowfd) |
| 153 | { |
| 154 | if (_lttng_ust_fd_init_plibc_close() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) { |
| 155 | errno = ENOSYS; |
| 156 | return -1; |
| 157 | } |
| 158 | |
| 159 | return lttng_ust_safe_closefrom_fd(lowfd, __lttng_ust_fd_plibc_close); |
| 160 | } |
| 161 | #else |
| 162 | /* As far as we know, this OS does not implement closefrom. */ |
| 163 | #endif |