Consolidate Linux getdents{64} implementation

This patch consolidates Linux getdents{64} implementation on just
the default sysdeps/unix/sysv/linux/getdents{64}{_r}.c ones.

Although this symbol is used only internally, the non-LFS version
still need to be build due the non-LFS getdirentries which requires
its semantic.

The non-LFS default implementation now uses the wordsize-32 as base
which uses getdents64 syscall plus adjustment for overflow (it allows
to use the same code for architectures that does not support non-LFS
getdents syscall).  It has two main differences to wordsize-32 one:

  - DIRENT_SET_DP_INO is added to handle alpha requirement to zero
    the padding.

  - alloca is removed by allocating a bounded temporary buffer (it
    increases stack usage by roughly 276 bytes).

The default implementation handle the Linux requirements:

  * getdents is only built for _DIRENT_MATCHES_DIRENT64 being 0.

  * getdents64 is always built and aliased to getdents for ABIs
    that define _DIRENT_MATCHES_DIRENT64 to 1.

  * A compat symbol is added for getdents64 for ABI that used to
    export the old non-LFS version.

Checked on aarch64-linux-gnu, x86_64-linux-gnu, i686-linux-gnu,
sparcv9-linux-gnu, sparc64-linux-gnu, powerpc-linux-gnu, and
powerpc64le-linux-gnu.

	* sysdeps/unix/sysv/linux/alpha/getdents.c: Add comments with alpha
	requirements.
	 (_DIRENT_MATCHES_DIRENT64): Undef
	* sysdeps/unix/sysv/linux/alpha/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/arm/getdents64.c: Remove file.
	* sysdeps/unix/sysv/linux/generic/getdents.c: Likewise.
	* sysdeps/unix/sysv/linux/generic/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/getdents.c: Likewise.
	* sysdeps/unix/sysv/linux/getdents.c: Simplify implementation by
	use getdents64 syscalls as base.
	* sysdeps/unix/sysv/linux/getdents64.c: Likewise and add compatibility
	symbol if required.
	* sysdeps/unix/sysv/linux/hppa/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/i386/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/m68k/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc32/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/wordsize-64/getdents.c: Likewise.
	* sysdeps/unix/sysv/linux/wordsize-64/getdents64.c: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sparc64/get_clockfreq.c
	(__get_clockfreq_via_proc_openprom): Use __getdents64.
	* sysdeps/unix/sysv/linux/mips/mips64/getdents64.c: New file.

1 files changed, 84 insertions, 240 deletions

diff --git a/sysdeps/unix/sysv/linux/getdents.c b/sysdeps/unix/sysv/linux/getdents.c
index 591ce67196..6d09a5be70 100644
--- a/sysdeps/unix/sysv/linux/getdents.c
+++ b/sysdeps/unix/sysv/linux/getdents.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 1993-2018 Free Software Foundation, Inc.
+/* Get directory entries.  Linux non-LFS version.
+   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
@@ -12,260 +13,103 @@
    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
+   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>
+#if !_DIRENT_MATCHES_DIRENT64
 
-#include <linux/posix_types.h>
+# include <unistd.h>
+# include <string.h>
+# include <errno.h>
 
-#include <kernel-features.h>
+# ifndef DIRENT_SET_DP_INO
+#  define DIRENT_SET_DP_INO(dp, value) (dp)->d_ino = (value)
+# endif
 
-/* 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.  */
+/* Pack the dirent64 struct down into 32-bit offset/inode fields, and
+   ensure that no overflow occurs.  */
 ssize_t
-__GETDENTS (int fd, char *buf, size_t nbytes)
+__getdents (int fd, char *buf, size_t nbytes)
 {
+  union
+  {
+    /* For !_DIRENT_MATCHES_DIRENT64 kernel 'linux_dirent64' has the same
+       layout of 'struct dirent64'.  */
+    struct dirent64 k;
+    struct dirent u;
+    char b[1];
+  } *kbuf = (void *) buf, *outp, *inp;
+  size_t kbytes = nbytes;
+  off64_t last_offset = -1;
   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);
+# define size_diff (offsetof (struct dirent64, d_name) \
+		    - offsetof (struct dirent, d_name))
+  char kbuftmp[sizeof (struct dirent) + size_diff];
+  if (nbytes <= sizeof (struct dirent))
+    kbuf = (void*) kbuftmp;
 
-      /* 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;
+  retval = INLINE_SYSCALL_CALL (getdents64, fd, kbuf, kbytes);
+  if (retval == -1)
+    return -1;
 
-	  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;
+  /* 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;
 
-	      kbuf = (void *) ((char *) kbuf + kbuf->k.d_reclen);
-	    }
-	}
-
-      return retval;
-    }
-
-  off64_t last_offset = -1;
-
-#ifdef __NR_getdents64
-  {
-    union
+  while (&inp->b < &kbuf->b + retval)
     {
-      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;
-	  }
+      const size_t alignment = _Alignof (struct dirent);
+      /* 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 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;
+            }
+	  return INLINE_SYSCALL_ERROR_RETURN_VALUE (EOVERFLOW);
+        }
+
+      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;
+    }
 
-	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));
+  return outp->b - buf;
+}
 
-	dp = (DIRENT_TYPE *) ((char *) dp + new_reclen);
-	kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen);
-      }
+# undef DIRENT_SET_DP_INO
 
-    return (char *) dp - buf;
-  }
-}
+#endif /* _DIRENT_MATCHES_DIRENT64  */