diff options
Diffstat (limited to 'lib/openat-proc.c')
| -rw-r--r-- | lib/openat-proc.c | 154 |
1 files changed, 154 insertions, 0 deletions
diff --git a/lib/openat-proc.c b/lib/openat-proc.c new file mode 100644 index 0000000..88f70be --- /dev/null +++ b/lib/openat-proc.c @@ -0,0 +1,154 @@ +/* Create /proc/self/fd-related names for subfiles of open directories. + + Copyright (C) 2006, 2009-2023 Free Software Foundation, Inc. + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program 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 General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see <https://www.gnu.org/licenses/>. */ + +/* Written by Paul Eggert. */ + +#include <config.h> + +#include "openat-priv.h" + +#include <sys/types.h> +#include <sys/stat.h> +#include <fcntl.h> + +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> + +#ifdef __KLIBC__ /* OS/2 */ +# include <InnoTekLIBC/backend.h> +#endif +#ifdef __MVS__ /* z/OS */ +# include <termios.h> +#endif + +#include "intprops.h" + +/* Set BUF to the name of the subfile of the directory identified by + FD, where the subfile is named FILE. If successful, return BUF if + the result fits in BUF, dynamically allocated memory otherwise. + Return NULL (setting errno) on error. */ +char * +openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file) +{ + char *result = buf; + int dirlen; + + /* Make sure the caller gets ENOENT when appropriate. */ + if (!*file) + { + buf[0] = '\0'; + return buf; + } + +#if !(defined __KLIBC__ || defined __MVS__) + /* Generic code for Linux, Solaris, and similar platforms. */ +# define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/" + { + enum { + PROC_SELF_FD_DIR_SIZE_BOUND + = (sizeof PROC_SELF_FD_FORMAT - (sizeof "%d" - 1) + + INT_STRLEN_BOUND (int)) + }; + + static int proc_status = 0; + if (! proc_status) + { + /* Set PROC_STATUS to a positive value if /proc/self/fd is + reliable, and a negative value otherwise. Solaris 10 + /proc/self/fd mishandles "..", and any file name might expand + to ".." after symbolic link expansion, so avoid /proc/self/fd + if it mishandles "..". Solaris 10 has openat, but this + problem is exhibited on code that built on Solaris 8 and + running on Solaris 10. */ + + int proc_self_fd = + open ("/proc/self/fd", + O_SEARCH | O_DIRECTORY | O_NOCTTY | O_NONBLOCK | O_CLOEXEC); + if (proc_self_fd < 0) + proc_status = -1; + else + { + /* Detect whether /proc/self/fd/%i/../fd exists, where %i is the + number of a file descriptor open on /proc/self/fd. On Linux, + that name resolves to /proc/self/fd, which was opened above. + However, on Solaris, it may resolve to /proc/self/fd/fd, which + cannot exist, since all names in /proc/self/fd are numeric. */ + char dotdot_buf[PROC_SELF_FD_DIR_SIZE_BOUND + sizeof "../fd" - 1]; + sprintf (dotdot_buf, PROC_SELF_FD_FORMAT "../fd", proc_self_fd); + proc_status = access (dotdot_buf, F_OK) ? -1 : 1; + close (proc_self_fd); + } + } + + if (proc_status < 0) + return NULL; + else + { + size_t bufsize = PROC_SELF_FD_DIR_SIZE_BOUND + strlen (file); + if (OPENAT_BUFFER_SIZE < bufsize) + { + result = malloc (bufsize); + if (! result) + return NULL; + } + + dirlen = sprintf (result, PROC_SELF_FD_FORMAT, fd); + } + } +#else /* (defined __KLIBC__ || defined __MVS__), i.e. OS/2 or z/OS */ + /* OS/2 kLIBC provides a function to retrieve a path from a fd. */ + { + size_t bufsize; + +# ifdef __KLIBC__ + char dir[_MAX_PATH]; + if (__libc_Back_ioFHToPath (fd, dir, sizeof dir)) + return NULL; +# endif +# ifdef __MVS__ + char dir[_XOPEN_PATH_MAX]; + /* Documentation: + https://www.ibm.com/docs/en/zos/2.2.0?topic=functions-w-ioctl-w-pioctl-control-devices */ + if (w_ioctl (fd, _IOCC_GPN, sizeof dir, dir) < 0) + return NULL; + /* Documentation: + https://www.ibm.com/docs/en/zos/2.2.0?topic=functions-e2a-l-convert-characters-from-ebcdic-ascii */ + dirlen = __e2a_l (dir, strlen (dir)); + if (dirlen < 0 || dirlen >= sizeof dir) + return NULL; + dir[dirlen] = '\0'; +# endif + + dirlen = strlen (dir); + bufsize = dirlen + 1 + strlen (file) + 1; /* 1 for '/', 1 for null */ + if (OPENAT_BUFFER_SIZE < bufsize) + { + result = malloc (bufsize); + if (! result) + return NULL; + } + + strcpy (result, dir); + result[dirlen++] = '/'; + } +#endif + + strcpy (result + dirlen, file); + return result; +} |