| 1 | /* |
| 2 | * SPDX-License-Identifier: LGPL-2.1-only |
| 3 | * |
| 4 | * Copyright (C) 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> |
| 5 | */ |
| 6 | |
| 7 | #define _LGPL_SOURCE |
| 8 | #include <limits.h> |
| 9 | #include <stdio.h> |
| 10 | #include <sys/types.h> |
| 11 | #include <unistd.h> |
| 12 | #include <dlfcn.h> |
| 13 | #include <errno.h> |
| 14 | |
| 15 | #include <lttng/ust-common.h> |
| 16 | |
| 17 | #include "common/macros.h" |
| 18 | #include "common/ust-fd.h" |
| 19 | |
| 20 | #define LTTNG_UST_DLSYM_FAILED_PTR 0x1 |
| 21 | |
| 22 | static int (*__lttng_ust_fd_plibc_close)(int fd) = NULL; |
| 23 | static int (*__lttng_ust_fd_plibc_fclose)(FILE *stream) = NULL; |
| 24 | |
| 25 | /* |
| 26 | * Use dlsym to find the original libc close() symbol and store it in |
| 27 | * __lttng_ust_fd_plibc_close. |
| 28 | */ |
| 29 | static |
| 30 | void *_lttng_ust_fd_init_plibc_close(void) |
| 31 | { |
| 32 | if (__lttng_ust_fd_plibc_close == NULL) { |
| 33 | __lttng_ust_fd_plibc_close = dlsym(RTLD_NEXT, "close"); |
| 34 | |
| 35 | if (__lttng_ust_fd_plibc_close == NULL) { |
| 36 | __lttng_ust_fd_plibc_close = (void *) LTTNG_UST_DLSYM_FAILED_PTR; |
| 37 | fprintf(stderr, "%s\n", dlerror()); |
| 38 | } |
| 39 | } |
| 40 | |
| 41 | return __lttng_ust_fd_plibc_close; |
| 42 | } |
| 43 | |
| 44 | /* |
| 45 | * Use dlsym to find the original libc fclose() symbol and store it in |
| 46 | * __lttng_ust_fd_plibc_fclose. |
| 47 | */ |
| 48 | static |
| 49 | void *_lttng_ust_fd_init_plibc_fclose(void) |
| 50 | { |
| 51 | if (__lttng_ust_fd_plibc_fclose == NULL) { |
| 52 | __lttng_ust_fd_plibc_fclose = dlsym(RTLD_NEXT, "fclose"); |
| 53 | |
| 54 | if (__lttng_ust_fd_plibc_fclose == NULL) { |
| 55 | __lttng_ust_fd_plibc_fclose = (void *) LTTNG_UST_DLSYM_FAILED_PTR; |
| 56 | fprintf(stderr, "%s\n", dlerror()); |
| 57 | } |
| 58 | } |
| 59 | |
| 60 | return __lttng_ust_fd_plibc_fclose; |
| 61 | } |
| 62 | |
| 63 | static |
| 64 | void _lttng_ust_fd_ctor(void) |
| 65 | __attribute__((constructor)); |
| 66 | static |
| 67 | void _lttng_ust_fd_ctor(void) |
| 68 | { |
| 69 | lttng_ust_common_ctor(); |
| 70 | |
| 71 | /* |
| 72 | * Initialize the function pointers to the original libc symbols in the |
| 73 | * constructor since close() has to stay async-signal-safe and as such, |
| 74 | * we can't call dlsym() in the override functions. |
| 75 | */ |
| 76 | (void) _lttng_ust_fd_init_plibc_close(); |
| 77 | (void) _lttng_ust_fd_init_plibc_fclose(); |
| 78 | } |
| 79 | |
| 80 | /* |
| 81 | * Override the libc close() symbol with our own, allowing applications to |
| 82 | * close arbitrary file descriptors. If the fd is owned by lttng-ust, return |
| 83 | * -1, errno=EBADF instead of closing it. |
| 84 | * |
| 85 | * If dlsym failed to find the original libc close() symbol, return -1, |
| 86 | * errno=ENOSYS. |
| 87 | * |
| 88 | * There is a short window before the library constructor has executed where |
| 89 | * this wrapper could call dlsym() and thus not be async-signal-safe. |
| 90 | */ |
| 91 | int close(int fd) |
| 92 | { |
| 93 | /* |
| 94 | * We can't retry dlsym here since close is async-signal-safe. |
| 95 | */ |
| 96 | if (_lttng_ust_fd_init_plibc_close() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) { |
| 97 | errno = ENOSYS; |
| 98 | return -1; |
| 99 | } |
| 100 | |
| 101 | return lttng_ust_safe_close_fd(fd, __lttng_ust_fd_plibc_close); |
| 102 | } |
| 103 | |
| 104 | /* |
| 105 | * Override the libc fclose() symbol with our own, allowing applications to |
| 106 | * close arbitrary streams. If the fd is owned by lttng-ust, return -1, |
| 107 | * errno=EBADF instead of closing it. |
| 108 | * |
| 109 | * If dlsym failed to find the original libc close() symbol, return -1, |
| 110 | * errno=ENOSYS. |
| 111 | * |
| 112 | * There is a short window before the library constructor has executed where |
| 113 | * this wrapper could call dlsym() and thus not be async-signal-safe. |
| 114 | * |
| 115 | * Note: fcloseall() is not an issue because it closes only the streams it |
| 116 | * knows about, which differs from the problems caused by gnulib |
| 117 | * close_stdout(), which does an explicit fclose(stdout). |
| 118 | */ |
| 119 | int fclose(FILE *stream) |
| 120 | { |
| 121 | if (_lttng_ust_fd_init_plibc_fclose() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) { |
| 122 | errno = ENOSYS; |
| 123 | return -1; |
| 124 | } |
| 125 | |
| 126 | return lttng_ust_safe_fclose_stream(stream, |
| 127 | __lttng_ust_fd_plibc_fclose); |
| 128 | } |
| 129 | |
| 130 | #if defined(__sun__) || defined(__FreeBSD__) |
| 131 | /* Solaris and FreeBSD. */ |
| 132 | void closefrom(int lowfd) |
| 133 | { |
| 134 | if (_lttng_ust_fd_init_plibc_close() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) { |
| 135 | return; |
| 136 | } |
| 137 | |
| 138 | (void) lttng_ust_safe_closefrom_fd(lowfd, __lttng_ust_fd_plibc_close); |
| 139 | } |
| 140 | #elif defined(__NetBSD__) || defined(__OpenBSD__) |
| 141 | /* NetBSD and OpenBSD. */ |
| 142 | int closefrom(int lowfd) |
| 143 | { |
| 144 | if (_lttng_ust_fd_init_plibc_close() == (void *) LTTNG_UST_DLSYM_FAILED_PTR) { |
| 145 | errno = ENOSYS; |
| 146 | return -1; |
| 147 | } |
| 148 | |
| 149 | return lttng_ust_safe_closefrom_fd(lowfd, __lttng_ust_fd_plibc_close); |
| 150 | } |
| 151 | #else |
| 152 | /* As far as we know, this OS does not implement closefrom. */ |
| 153 | #endif |