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/* Get directory entries. Linux/MIPSn64 LFS version.
Copyright (C) 2018-2020 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 <string.h>
#include <dirent.h>
#include <errno.h>
#include <assert.h>
#include <sys/param.h>
#include <unistd.h>
#include <limits.h>
#include <include/libc-pointer-arith.h>
ssize_t
__getdents64 (int fd, void *buf, size_t nbytes)
{
/* The system call takes an unsigned int argument, and some length
checks in the kernel use an int type. */
if (nbytes > INT_MAX)
nbytes = INT_MAX;
#ifdef __NR_getdents64
static int getdents64_supported = true;
if (atomic_load_relaxed (&getdents64_supported))
{
ssize_t ret = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
if (ret >= 0 || errno != ENOSYS)
return ret;
atomic_store_relaxed (&getdents64_supported, false);
}
#endif
/* Unfortunately getdents64 was only wire-up for MIPS n64 on Linux 3.10.
If the syscall is not available it need to fallback to the non-LFS one.
Also to avoid an unbounded allocation through VLA/alloca or malloc (which
would make the syscall non async-signal-safe) it uses a limited buffer.
This is sub-optimal for large NBYTES, however this is a fallback
mechanism to emulate a syscall that kernel should provide. */
struct kernel_dirent
{
#if _MIPS_SIM == _ABI64
uint64_t d_ino;
uint64_t d_off;
#else
uint32_t d_ino;
uint32_t d_off;
#endif
unsigned short int d_reclen;
char d_name[1];
};
/* The largest possible practical length of the d_name member are 255
Unicode characters in UTF-8 encoding, so d_name is 766 bytes long, plus
18 (mips64) / 10 (mips64n32) bytes from header, for total of 784 (mips64)
/ 776 (mips64n32) bytes total. Ensure that the minimum size holds at
least one entry. */
enum { KBUF_SIZE = 1024 };
char kbuf[KBUF_SIZE];
size_t kbuf_size = nbytes < KBUF_SIZE ? nbytes : KBUF_SIZE;
const size_t size_diff = (offsetof (struct dirent64, d_name)
- offsetof (struct kernel_dirent, d_name));
struct dirent64 *dp = (struct dirent64 *) buf;
size_t nb = 0;
off64_t last_offset = -1;
ssize_t r = INLINE_SYSCALL_CALL (getdents, fd, kbuf, kbuf_size);
if (r <= 0)
return r;
struct kernel_dirent *skdp, *kdp;
skdp = kdp = (struct kernel_dirent *) kbuf;
while ((char *) kdp < (char *) skdp + r)
{
/* This macro is used to avoid aliasing violation. */
#define KDP_MEMBER(src, member) \
(__typeof__((struct kernel_dirent){0}.member) *) \
memcpy (&((__typeof__((struct kernel_dirent){0}.member)){0}), \
((char *)(src) + offsetof (struct kernel_dirent, member)),\
sizeof ((struct kernel_dirent){0}.member))
/* This is a conservative approximation, since some of size_diff might
fit into the existing padding for alignment. */
unsigned short int k_reclen = *KDP_MEMBER (kdp, d_reclen);
unsigned short int new_reclen = ALIGN_UP (k_reclen + size_diff,
_Alignof (struct dirent64));
if (nb + new_reclen > nbytes)
{
/* Entry is too large for the fixed-size buffer. */
if (last_offset == -1)
{
__set_errno (EINVAL);
return -1;
}
/* The new entry will overflow the input buffer, rewind to last
obtained entry and return. */
__lseek64 (fd, last_offset, SEEK_SET);
return (char *) dp - (char *) buf;
}
nb += new_reclen;
memcpy (((char *) dp + offsetof (struct dirent64, d_ino)),
KDP_MEMBER (kdp, d_ino), sizeof ((struct dirent64){0}.d_ino));
memcpy (((char *) dp + offsetof (struct dirent64, d_off)),
KDP_MEMBER (kdp, d_off), sizeof ((struct dirent64){0}.d_off));
last_offset = *KDP_MEMBER (kdp, d_off);
memcpy (((char *) dp + offsetof (struct dirent64, d_reclen)),
&new_reclen, sizeof (new_reclen));
dp->d_type = *((char *) kdp + k_reclen - 1);
memcpy (dp->d_name, kdp->d_name,
k_reclen - offsetof (struct kernel_dirent, d_name));
dp = (struct dirent64 *) ((char *) dp + new_reclen);
kdp = (struct kernel_dirent *) (((char *) kdp) + k_reclen);
}
return (char *) dp - (char *) buf;
}
libc_hidden_def (__getdents64)
weak_alias (__getdents64, getdents64)
#if _DIRENT_MATCHES_DIRENT64
strong_alias (__getdents64, __getdents)
#endif
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