#include <assert.h>
#include <sys/param.h>
#include <unistd.h>
-#include <scratch_buffer.h>
#include <limits.h>
+#include <include/libc-pointer-arith.h>
+
ssize_t
-__getdents64 (int fd, void *buf0, size_t nbytes)
+__getdents64 (int fd, void *buf, size_t nbytes)
{
- char *buf = buf0;
-
/* 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
- ssize_t ret = INLINE_SYSCALL_CALL (getdents64, fd, buf, nbytes);
- if (ret != -1)
- return ret;
+ 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 syscall is not available it need to fallback to non-LFS one. */
+ 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
- {
- unsigned long d_ino;
- unsigned long d_off;
- unsigned short int d_reclen;
- char d_name[256];
- };
+ {
+#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));
- size_t red_nbytes = MIN (nbytes
- - ((nbytes / (offsetof (struct dirent64, d_name)
- + 14)) * size_diff),
- nbytes - size_diff);
+ struct dirent64 *dp = (struct dirent64 *) buf;
- struct scratch_buffer tmpbuf;
- scratch_buffer_init (&tmpbuf);
- if (!scratch_buffer_set_array_size (&tmpbuf, red_nbytes, sizeof (uint8_t)))
- INLINE_SYSCALL_ERROR_RETURN_VALUE (ENOMEM);
+ size_t nb = 0;
+ off64_t last_offset = -1;
- struct kernel_dirent *skdp, *kdp;
- skdp = kdp = tmpbuf.data;
+ ssize_t r = INLINE_SYSCALL_CALL (getdents, fd, kbuf, kbuf_size);
+ if (r <= 0)
+ return r;
- ssize_t retval = INLINE_SYSCALL_CALL (getdents, fd, kdp, red_nbytes);
- if (retval == -1)
- {
- scratch_buffer_free (&tmpbuf);
- return -1;
- }
+ struct kernel_dirent *skdp, *kdp;
+ skdp = kdp = (struct kernel_dirent *) kbuf;
- off64_t last_offset = -1;
- struct dirent64 *dp = (struct dirent64 *) buf;
- while ((char *) kdp < (char *) skdp + retval)
+ while ((char *) kdp < (char *) skdp + r)
{
- const size_t alignment = _Alignof (struct dirent64);
- /* 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)
+ /* 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)
{
- scratch_buffer_free (&tmpbuf);
- return INLINE_SYSCALL_ERROR_RETURN_VALUE (EINVAL);
+ __set_errno (EINVAL);
+ return -1;
}
- break;
+ /* 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;
}
-
- 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 = *((char *) kdp + kdp->d_reclen - 1);
+ 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,
- kdp->d_reclen - offsetof (struct kernel_dirent, d_name));
+ k_reclen - offsetof (struct kernel_dirent, d_name));
dp = (struct dirent64 *) ((char *) dp + new_reclen);
- kdp = (struct kernel_dirent *) (((char *) kdp) + kdp->d_reclen);
+ kdp = (struct kernel_dirent *) (((char *) kdp) + k_reclen);
}
- scratch_buffer_free (&tmpbuf);
- return (char *) dp - buf;
+ return (char *) dp - (char *) buf;
}
libc_hidden_def (__getdents64)
weak_alias (__getdents64, getdents64)
projects / thirdparty / glibc.git / commitdiff
