[thirdparty/glibc.git] / sysdeps / unix / sysv / linux / getdents.c

/* Copyright (C) 1993-2018 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
__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;
  }
}
Commit	Line	Data
688903eb	1	/* Copyright (C) 1993-2018 Free Software Foundation, Inc.
df4ef2ab UD	2	This file is part of the GNU C Library.
	3
	4	The GNU C Library is free software; you can redistribute it and/or
41bdb6e2 AJ	5	modify it under the terms of the GNU Lesser General Public
	6	License as published by the Free Software Foundation; either
	7	version 2.1 of the License, or (at your option) any later version.
df4ef2ab UD	8
	9	The GNU C Library is distributed in the hope that it will be useful,
	10	but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
41bdb6e2	12	Lesser General Public License for more details.
df4ef2ab	13
41bdb6e2	14	You should have received a copy of the GNU Lesser General Public
59ba27a6 PE	15	License along with the GNU C Library; if not, see
59ba27a6 PE	16	<http://www.gnu.org/licenses/>. */
df4ef2ab	17
8d57beea	18	#include <alloca.h>
4186c9f4	19	#include <assert.h>
0dee6738	20	#include <errno.h>
df4ef2ab UD	21	#include <dirent.h>
df4ef2ab UD	22	#include <stddef.h>
da0fdef0	23	#include <stdint.h>
df4ef2ab UD	24	#include <string.h>
df4ef2ab UD	25	#include <unistd.h>
8d57beea	26	#include <sys/param.h>
df4ef2ab UD	27	#include <sys/types.h>
df4ef2ab UD	28
0dee6738 UD	29	#include <sysdep.h>
	30	#include <sys/syscall.h>
	31
df4ef2ab UD	32	#include <linux/posix_types.h>
df4ef2ab UD	33
6ddd37a4	34	#include <kernel-features.h>
14860991	35
df4ef2ab UD	36	/* For Linux we need a special version of this file since the
	37	definition of `struct dirent' is not the same for the kernel and
	38	the libc. There is one additional field which might be introduced
	39	in the kernel structure in the future.
	40
0dee6738	41	Here is the kernel definition of `struct dirent' as of 2.1.20: */
df4ef2ab UD	42
	43	struct kernel_dirent
	44	{
	45	long int d_ino;
	46	__kernel_off_t d_off;
	47	unsigned short int d_reclen;
	48	char d_name[256];
	49	};
	50
14860991 UD	51	struct kernel_dirent64
14860991 UD	52	{
da0fdef0	53	uint64_t d_ino;
14860991 UD	54	int64_t d_off;
	55	unsigned short int d_reclen;
	56	unsigned char d_type;
	57	char d_name[256];
	58	};
	59
56ddf355 UD	60	#ifndef __GETDENTS
56ddf355 UD	61	# define __GETDENTS __getdents
14860991 UD	62	#endif
14860991 UD	63	#ifndef DIRENT_TYPE
56ddf355 UD	64	# define DIRENT_TYPE struct dirent
	65	#endif
	66	#ifndef DIRENT_SET_DP_INO
	67	# define DIRENT_SET_DP_INO(dp, value) (dp)->d_ino = (value)
9756dfe1	68	#endif
df4ef2ab UD	69
	70	/* The problem here is that we cannot simply read the next NBYTES
	71	bytes. We need to take the additional field into account. We use
831372e7	72	some heuristic. Assuming the directory contains names with 14
980e5832	73	characters on average we can compute an estimated number of entries
831372e7	74	which fit in the buffer. Taking this number allows us to specify a
980e5832 UD	75	reasonable number of bytes to read. If we should be wrong, we can
	76	reset the file descriptor. In practice the kernel is limiting the
	77	amount of data returned much more then the reduced buffer size. */
8d57beea	78	ssize_t
56ddf355	79	__GETDENTS (int fd, char *buf, size_t nbytes)
df4ef2ab	80	{
14860991	81	ssize_t retval;
980e5832	82
7cd195df L	83	/* The d_ino and d_off fields in kernel_dirent and dirent must have
	84	the same sizes and alignments. */
	85	if (sizeof (DIRENT_TYPE) == sizeof (struct dirent)
	86	&& (sizeof (((struct kernel_dirent *) 0)->d_ino)
	87	== sizeof (((struct dirent *) 0)->d_ino))
	88	&& (sizeof (((struct kernel_dirent *) 0)->d_off)
	89	== sizeof (((struct dirent *) 0)->d_off))
	90	&& (offsetof (struct kernel_dirent, d_off)
	91	== offsetof (struct dirent, d_off))
	92	&& (offsetof (struct kernel_dirent, d_reclen)
	93	== offsetof (struct dirent, d_reclen)))
afedc4af	94	{
a2da1673	95	retval = INLINE_SYSCALL (getdents, 3, fd, buf, nbytes);
afedc4af UD	96
	97	/* The kernel added the d_type value after the name. Change
	98	this now. */
	99	if (retval != -1)
	100	{
	101	union
	102	{
	103	struct kernel_dirent k;
	104	struct dirent u;
	105	} kbuf = (void ) buf;
	106
	107	while ((char *) kbuf < buf + retval)
	108	{
	109	char d_type = ((char ) kbuf + kbuf->k.d_reclen - 1);
	110	memmove (kbuf->u.d_name, kbuf->k.d_name,
	111	strlen (kbuf->k.d_name) + 1);
	112	kbuf->u.d_type = d_type;
	113
	114	kbuf = (void ) ((char ) kbuf + kbuf->k.d_reclen);
	115	}
	116	}
	117
	118	return retval;
	119	}
afedc4af UD	120
	121	off64_t last_offset = -1;
	122
14860991	123	#ifdef __NR_getdents64
37ad3473 JM	124	{
37ad3473 JM	125	union
df4ef2ab	126	{
37ad3473 JM	127	struct kernel_dirent64 k;
	128	DIRENT_TYPE u;
	129	char b[1];
	130	} kbuf = (void ) buf, outp, inp;
	131	size_t kbytes = nbytes;
	132	if (offsetof (DIRENT_TYPE, d_name)
	133	< offsetof (struct kernel_dirent64, d_name)
	134	&& nbytes <= sizeof (DIRENT_TYPE))
c213fe9c	135	{
37ad3473 JM	136	kbytes = (nbytes + offsetof (struct kernel_dirent64, d_name)
	137	- offsetof (DIRENT_TYPE, d_name));
	138	kbuf = __alloca(kbytes);
	139	}
	140	retval = INLINE_SYSCALL (getdents64, 3, fd, kbuf, kbytes);
	141	const size_t size_diff = (offsetof (struct kernel_dirent64, d_name)
	142	- offsetof (DIRENT_TYPE, d_name));
	143
	144	/* Return the error if encountered. */
	145	if (retval == -1)
	146	return -1;
14860991	147
37ad3473 JM	148	/* If the structure returned by the kernel is identical to what we
	149	need, don't do any conversions. */
	150	if (offsetof (DIRENT_TYPE, d_name)
	151	== offsetof (struct kernel_dirent64, d_name)
	152	&& sizeof (outp->u.d_ino) == sizeof (inp->k.d_ino)
	153	&& sizeof (outp->u.d_off) == sizeof (inp->k.d_off))
	154	return retval;
	155
	156	/* These two pointers might alias the same memory buffer.
	157	Standard C requires that we always use the same type for them,
	158	so we must use the union type. */
	159	inp = kbuf;
	160	outp = (void *) buf;
	161
	162	while (&inp->b < &kbuf->b + retval)
	163	{
	164	const size_t alignment = __alignof__ (DIRENT_TYPE);
	165	/* Since inp->k.d_reclen is already aligned for the kernel
	166	structure this may compute a value that is bigger
	167	than necessary. */
	168	size_t old_reclen = inp->k.d_reclen;
	169	size_t new_reclen = ((old_reclen - size_diff + alignment - 1)
	170	& ~(alignment - 1));
	171
	172	/* Copy the data out of the old structure into temporary space.
	173	Then copy the name, which may overlap if BUF == KBUF. */
	174	const uint64_t d_ino = inp->k.d_ino;
	175	const int64_t d_off = inp->k.d_off;
	176	const uint8_t d_type = inp->k.d_type;
	177
	178	memmove (outp->u.d_name, inp->k.d_name,
	179	old_reclen - offsetof (struct kernel_dirent64, d_name));
	180
	181	/* Now we have copied the data from INP and access only OUTP. */
	182
	183	DIRENT_SET_DP_INO (&outp->u, d_ino);
	184	outp->u.d_off = d_off;
	185	if ((sizeof (outp->u.d_ino) != sizeof (inp->k.d_ino)
	186	&& outp->u.d_ino != d_ino)
	187	\|\| (sizeof (outp->u.d_off) != sizeof (inp->k.d_off)
	188	&& outp->u.d_off != d_off))
	189	{
	190	/* Overflow. If there was at least one entry
	191	before this one, return them without error,
	192	otherwise signal overflow. */
	193	if (last_offset != -1)
	194	{
	195	__lseek64 (fd, last_offset, SEEK_SET);
	196	return outp->b - buf;
	197	}
	198	__set_errno (EOVERFLOW);
05ae4d6a	199	return -1;
37ad3473	200	}
05ae4d6a	201
37ad3473 JM	202	last_offset = d_off;
	203	outp->u.d_reclen = new_reclen;
	204	outp->u.d_type = d_type;
f11b9da6	205
37ad3473 JM	206	inp = (void *) inp + old_reclen;
	207	outp = (void *) outp + new_reclen;
	208	}
831372e7	209
37ad3473 JM	210	return outp->b - buf;
37ad3473 JM	211	}
14860991 UD	212	#endif
	213	{
	214	size_t red_nbytes;
	215	struct kernel_dirent skdp, kdp;
	216	const size_t size_diff = (offsetof (DIRENT_TYPE, d_name)
	217	- offsetof (struct kernel_dirent, d_name));
	218
	219	red_nbytes = MIN (nbytes
	220	- ((nbytes / (offsetof (DIRENT_TYPE, d_name) + 14))
	221	* size_diff),
	222	nbytes - size_diff);
	223
14860991 UD	224	skdp = kdp = __alloca (red_nbytes);
14860991 UD	225
a2da1673	226	retval = INLINE_SYSCALL (getdents, 3, fd, (char *) kdp, red_nbytes);
14860991 UD	227
	228	if (retval == -1)
	229	return -1;
	230
c213fe9c	231	DIRENT_TYPE dp = (DIRENT_TYPE ) buf;
14860991 UD	232	while ((char ) kdp < (char ) skdp + retval)
	233	{
	234	const size_t alignment = __alignof__ (DIRENT_TYPE);
	235	/* Since kdp->d_reclen is already aligned for the kernel structure
	236	this may compute a value that is bigger than necessary. */
	237	size_t new_reclen = ((kdp->d_reclen + size_diff + alignment - 1)
	238	& ~(alignment - 1));
	239	if ((char *) dp + new_reclen > buf + nbytes)
	240	{
	241	/* Our heuristic failed. We read too many entries. Reset
	242	the stream. */
	243	assert (last_offset != -1);
f9ef3e72	244	__lseek64 (fd, last_offset, SEEK_SET);
14860991 UD	245
	246	if ((char *) dp == buf)
	247	{
	248	/* The buffer the user passed in is too small to hold even
	249	one entry. */
	250	__set_errno (EINVAL);
	251	return -1;
	252	}
	253
	254	break;
	255	}
	256
	257	last_offset = kdp->d_off;
	258	DIRENT_SET_DP_INO(dp, kdp->d_ino);
	259	dp->d_off = kdp->d_off;
	260	dp->d_reclen = new_reclen;
1ac7a2c7	261	dp->d_type = ((char ) kdp + kdp->d_reclen - 1);
14860991 UD	262	memcpy (dp->d_name, kdp->d_name,
	263	kdp->d_reclen - offsetof (struct kernel_dirent, d_name));
	264
	265	dp = (DIRENT_TYPE ) ((char ) dp + new_reclen);
	266	kdp = (struct kernel_dirent ) (((char ) kdp) + kdp->d_reclen);
	267	}
df4ef2ab	268
c213fe9c RM	269	return (char *) dp - buf;
c213fe9c RM	270	}
df4ef2ab	271	}