diff options
Diffstat (limited to 'sysdeps/unix/sysv/linux/pidfd_getpid.c')
-rw-r--r-- | sysdeps/unix/sysv/linux/pidfd_getpid.c | 126 |
1 files changed, 126 insertions, 0 deletions
diff --git a/sysdeps/unix/sysv/linux/pidfd_getpid.c b/sysdeps/unix/sysv/linux/pidfd_getpid.c new file mode 100644 index 0000000000..d03936e97f --- /dev/null +++ b/sysdeps/unix/sysv/linux/pidfd_getpid.c @@ -0,0 +1,126 @@ +/* pidfd_getpid - Get the associated pid from the pid file descriptor. + Copyright (C) 2023 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 <_itoa.h> +#include <errno.h> +#include <intprops.h> +#include <procutils.h> +#include <stdlib.h> +#include <string.h> +#include <sysdep.h> +#include <unistd.h> + +#define FDINFO_TO_FILENAME_PREFIX "/proc/self/fdinfo/" + +#define FDINFO_FILENAME_LEN \ + (sizeof (FDINFO_TO_FILENAME_PREFIX) + INT_STRLEN_BOUND (int)) + +struct parse_fdinfo_t +{ + bool found; + pid_t pid; +}; + +/* Parse the PID field in the fdinfo entry, if existent. Avoid strtol or + similar to not be locale dependent. */ +static int +parse_fdinfo (const char *l, void *arg) +{ + enum { fieldlen = sizeof ("Pid:") - 1 }; + if (strncmp (l, "Pid:", fieldlen) != 0) + return 0; + + l += fieldlen; + + /* Skip leading spaces. */ + while (*l == ' ' || (unsigned int) (*l) -'\t' < 5) + l++; + + bool neg = false; + switch (*l) + { + case '-': + neg = true; + l++; + break; + case '+': + return -1; + } + + if (*l == '\0') + return 0; + + int n = 0; + while (*l != '\0') + { + /* Check if '*l' is a digit. */ + if ('0' > *l || *l > '9') + return -1; + + /* Ignore invalid large values. */ + if (INT_MULTIPLY_WRAPV (10, n, &n) + || INT_ADD_WRAPV (n, *l++ - '0', &n)) + return -1; + } + + /* -1 indicates that the process is terminated. */ + if (neg && n != 1) + return -1; + + struct parse_fdinfo_t *fdinfo = arg; + fdinfo->pid = neg ? -n : n; + fdinfo->found = true; + + return 1; +} + +pid_t +pidfd_getpid (int fd) +{ + if (__glibc_unlikely (fd < 0)) + { + __set_errno (EBADF); + return -1; + } + + char fdinfoname[FDINFO_FILENAME_LEN]; + + char *p = mempcpy (fdinfoname, FDINFO_TO_FILENAME_PREFIX, + strlen (FDINFO_TO_FILENAME_PREFIX)); + *_fitoa_word (fd, p, 10, 0) = '\0'; + + struct parse_fdinfo_t fdinfo = { .found = false, .pid = -1 }; + if (!procutils_read_file (fdinfoname, parse_fdinfo, &fdinfo)) + /* The fdinfo contains an invalid 'Pid:' value. */ + return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF); + + /* The FD does not have a 'Pid:' entry associated. */ + if (!fdinfo.found) + return INLINE_SYSCALL_ERROR_RETURN_VALUE (EBADF); + + /* The pidfd cannot be resolved because it is in a separate pid + namespace. */ + if (fdinfo.pid == 0) + return INLINE_SYSCALL_ERROR_RETURN_VALUE (EREMOTE); + + /* A negative value means the process is terminated. */ + if (fdinfo.pid < 0) + return INLINE_SYSCALL_ERROR_RETURN_VALUE (ESRCH); + + return fdinfo.pid; +} |