/* Copyright (C) 1993, 1995-2002 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, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA. */ #include <alloca.h> #include <assert.h> #include <errno.h> #include <dirent.h> #include <stddef.h> #include <stdint.h> #include <string.h> #include <unistd.h> #include <sys/param.h> #include <sys/types.h> #include <sys/syscall.h> #ifndef offsetof #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) #endif struct kernel_dirent { long d_ino; __kernel_off_t d_off; unsigned short d_reclen; char d_name[256]; }; #define __NR___syscall_getdents __NR_getdents static inline _syscall3(int, __syscall_getdents, int, fd, unsigned char *, kdirp, size_t, count); ssize_t attribute_hidden __getdents (int fd, char *buf, size_t nbytes) { struct dirent *dp; off_t last_offset = -1; ssize_t retval; size_t red_nbytes; struct kernel_dirent *skdp, *kdp; const size_t size_diff = (offsetof (struct dirent, d_name) - offsetof (struct kernel_dirent, d_name)); red_nbytes = MIN (nbytes - ((nbytes / (offsetof (struct dirent, d_name) + 14)) * size_diff), nbytes - size_diff); dp = (struct dirent *) buf; skdp = kdp = alloca (red_nbytes); retval = __syscall_getdents(fd, (char *)kdp, red_nbytes); if (retval == -1) return -1; while ((char *) kdp < (char *) skdp + retval) { const size_t alignment = __alignof__ (struct dirent); /* Since kdp->d_reclen is already aligned for the kernel structure this may compute a value that is bigger than necessary. */ size_t new_reclen = ((kdp->d_reclen + size_diff + alignment - 1) & ~(alignment - 1)); if ((char *) dp + new_reclen > buf + nbytes) { /* Our heuristic failed. We read too many entries. Reset the stream. */ assert (last_offset != -1); __lseek(fd, last_offset, SEEK_SET); if ((char *) dp == buf) { /* The buffer the user passed in is too small to hold even one entry. */ __set_errno (EINVAL); return -1; } break; } last_offset = kdp->d_off; dp->d_ino = kdp->d_ino; dp->d_off = kdp->d_off; dp->d_reclen = new_reclen; dp->d_type = DT_UNKNOWN; __memcpy (dp->d_name, kdp->d_name, kdp->d_reclen - offsetof (struct kernel_dirent, d_name)); dp = (struct dirent *) ((char *) dp + new_reclen); kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen); } return (char *) dp - buf; }