diff options
Diffstat (limited to 'REORG.TODO/sysdeps/unix/sysv/linux/getdents.c')
| -rw-r--r-- | REORG.TODO/sysdeps/unix/sysv/linux/getdents.c | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/REORG.TODO/sysdeps/unix/sysv/linux/getdents.c b/REORG.TODO/sysdeps/unix/sysv/linux/getdents.c new file mode 100644 index 0000000000..4794eb737d --- /dev/null +++ b/REORG.TODO/sysdeps/unix/sysv/linux/getdents.c @@ -0,0 +1,272 @@ +/* Copyright (C) 1993-2017 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 + <http://www.gnu.org/licenses/>. */ + +#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 <sysdep.h> +#include <sys/syscall.h> + +#include <linux/posix_types.h> + +#include <kernel-features.h> + +/* For Linux we need a special version of this file since the + definition of `struct dirent' is not the same for the kernel and + the libc. There is one additional field which might be introduced + in the kernel structure in the future. + + Here is the kernel definition of `struct dirent' as of 2.1.20: */ + +struct kernel_dirent + { + long int d_ino; + __kernel_off_t d_off; + unsigned short int d_reclen; + char d_name[256]; + }; + +struct kernel_dirent64 + { + uint64_t d_ino; + int64_t d_off; + unsigned short int d_reclen; + unsigned char d_type; + char d_name[256]; + }; + +#ifndef __GETDENTS +# define __GETDENTS __getdents +#endif +#ifndef DIRENT_TYPE +# define DIRENT_TYPE struct dirent +#endif +#ifndef DIRENT_SET_DP_INO +# define DIRENT_SET_DP_INO(dp, value) (dp)->d_ino = (value) +#endif + +/* The problem here is that we cannot simply read the next NBYTES + bytes. We need to take the additional field into account. We use + some heuristic. Assuming the directory contains names with 14 + characters on average we can compute an estimated number of entries + which fit in the buffer. Taking this number allows us to specify a + reasonable number of bytes to read. If we should be wrong, we can + reset the file descriptor. In practice the kernel is limiting the + amount of data returned much more then the reduced buffer size. */ +ssize_t +internal_function +__GETDENTS (int fd, char *buf, size_t nbytes) +{ + ssize_t retval; + + /* The d_ino and d_off fields in kernel_dirent and dirent must have + the same sizes and alignments. */ + if (sizeof (DIRENT_TYPE) == sizeof (struct dirent) + && (sizeof (((struct kernel_dirent *) 0)->d_ino) + == sizeof (((struct dirent *) 0)->d_ino)) + && (sizeof (((struct kernel_dirent *) 0)->d_off) + == sizeof (((struct dirent *) 0)->d_off)) + && (offsetof (struct kernel_dirent, d_off) + == offsetof (struct dirent, d_off)) + && (offsetof (struct kernel_dirent, d_reclen) + == offsetof (struct dirent, d_reclen))) + { + retval = INLINE_SYSCALL (getdents, 3, fd, buf, nbytes); + + /* The kernel added the d_type value after the name. Change + this now. */ + if (retval != -1) + { + union + { + struct kernel_dirent k; + struct dirent u; + } *kbuf = (void *) buf; + + while ((char *) kbuf < buf + retval) + { + char d_type = *((char *) kbuf + kbuf->k.d_reclen - 1); + memmove (kbuf->u.d_name, kbuf->k.d_name, + strlen (kbuf->k.d_name) + 1); + kbuf->u.d_type = d_type; + + kbuf = (void *) ((char *) kbuf + kbuf->k.d_reclen); + } + } + + return retval; + } + + off64_t last_offset = -1; + +#ifdef __NR_getdents64 + { + union + { + struct kernel_dirent64 k; + DIRENT_TYPE u; + char b[1]; + } *kbuf = (void *) buf, *outp, *inp; + size_t kbytes = nbytes; + if (offsetof (DIRENT_TYPE, d_name) + < offsetof (struct kernel_dirent64, d_name) + && nbytes <= sizeof (DIRENT_TYPE)) + { + kbytes = (nbytes + offsetof (struct kernel_dirent64, d_name) + - offsetof (DIRENT_TYPE, d_name)); + kbuf = __alloca(kbytes); + } + retval = INLINE_SYSCALL (getdents64, 3, fd, kbuf, kbytes); + const size_t size_diff = (offsetof (struct kernel_dirent64, d_name) + - offsetof (DIRENT_TYPE, d_name)); + + /* Return the error if encountered. */ + if (retval == -1) + return -1; + + /* If the structure returned by the kernel is identical to what we + need, don't do any conversions. */ + if (offsetof (DIRENT_TYPE, d_name) + == offsetof (struct kernel_dirent64, d_name) + && sizeof (outp->u.d_ino) == sizeof (inp->k.d_ino) + && sizeof (outp->u.d_off) == sizeof (inp->k.d_off)) + return retval; + + /* These two pointers might alias the same memory buffer. + Standard C requires that we always use the same type for them, + so we must use the union type. */ + inp = kbuf; + outp = (void *) buf; + + while (&inp->b < &kbuf->b + retval) + { + const size_t alignment = __alignof__ (DIRENT_TYPE); + /* Since inp->k.d_reclen is already aligned for the kernel + structure this may compute a value that is bigger + than necessary. */ + size_t old_reclen = inp->k.d_reclen; + size_t new_reclen = ((old_reclen - size_diff + alignment - 1) + & ~(alignment - 1)); + + /* Copy the data out of the old structure into temporary space. + Then copy the name, which may overlap if BUF == KBUF. */ + const uint64_t d_ino = inp->k.d_ino; + const int64_t d_off = inp->k.d_off; + const uint8_t d_type = inp->k.d_type; + + memmove (outp->u.d_name, inp->k.d_name, + old_reclen - offsetof (struct kernel_dirent64, d_name)); + + /* Now we have copied the data from INP and access only OUTP. */ + + DIRENT_SET_DP_INO (&outp->u, d_ino); + outp->u.d_off = d_off; + if ((sizeof (outp->u.d_ino) != sizeof (inp->k.d_ino) + && outp->u.d_ino != d_ino) + || (sizeof (outp->u.d_off) != sizeof (inp->k.d_off) + && outp->u.d_off != d_off)) + { + /* Overflow. If there was at least one entry + before this one, return them without error, + otherwise signal overflow. */ + if (last_offset != -1) + { + __lseek64 (fd, last_offset, SEEK_SET); + return outp->b - buf; + } + __set_errno (EOVERFLOW); + return -1; + } + + last_offset = d_off; + outp->u.d_reclen = new_reclen; + outp->u.d_type = d_type; + + inp = (void *) inp + old_reclen; + outp = (void *) outp + new_reclen; + } + + return outp->b - buf; + } +#endif + { + size_t red_nbytes; + struct kernel_dirent *skdp, *kdp; + const size_t size_diff = (offsetof (DIRENT_TYPE, d_name) + - offsetof (struct kernel_dirent, d_name)); + + red_nbytes = MIN (nbytes + - ((nbytes / (offsetof (DIRENT_TYPE, d_name) + 14)) + * size_diff), + nbytes - size_diff); + + skdp = kdp = __alloca (red_nbytes); + + retval = INLINE_SYSCALL (getdents, 3, fd, (char *) kdp, red_nbytes); + + if (retval == -1) + return -1; + + DIRENT_TYPE *dp = (DIRENT_TYPE *) buf; + while ((char *) kdp < (char *) skdp + retval) + { + const size_t alignment = __alignof__ (DIRENT_TYPE); + /* 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); + __lseek64 (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; + DIRENT_SET_DP_INO(dp, kdp->d_ino); + dp->d_off = kdp->d_off; + dp->d_reclen = new_reclen; + dp->d_type = *((char *) kdp + kdp->d_reclen - 1); + memcpy (dp->d_name, kdp->d_name, + kdp->d_reclen - offsetof (struct kernel_dirent, d_name)); + + dp = (DIRENT_TYPE *) ((char *) dp + new_reclen); + kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen); + } + + return (char *) dp - buf; + } +} |