klibc/mmap.c

/*
 * mmap.c
 */

#include <stdint.h>
#include <errno.h>
#include <sys/syscall.h>
#include <sys/mman.h>
#include <unistd.h>
#include <bitsize.h>

/*
 * MMAP2_SHIFT is definitely *NOT* equal to getpageshift() for
 * at least some architectures...
 */
#if defined(__i386__) || defined( __sparc__) || defined(__arm__)
# define MMAP2_SHIFT	12	/* Fixed by syscall definition */
#endif

/*
 * Set in SYSCALLS whether or not we should use an unadorned mmap() system
 * call (typical on 64-bit architectures).
 */
#if (_BITSIZE == 32 && defined(__NR_mmap2)) || (_BITSIZE == 64 && !defined(__NR_mmap))

/* This architecture uses mmap2(). The Linux mmap2() system call takes
   a page offset as the offset argument.  We need to make sure we have
   the proper conversion in place. */

extern void *__mmap2(void *, size_t, int, int, int, size_t);

void *mmap(void *start, size_t length, int prot, int flags, int fd, off_t offset)
{
#ifdef MMAP2_SHIFT
  const int mmap2_shift = MMAP2_SHIFT;
  const unsigned long mmap2_mask = (1UL << mmap2_shift) - 1;
#else
  extern unsigned int __page_size, __page_shift;
  const int mmap2_shift = __page_shift;
  const unsigned long mmap2_mask = (unsigned long)__page_size - 1;
#endif

  if ( offset & mmap2_mask ) {
    errno = EINVAL;
    return MAP_FAILED;
  }

  return __mmap2(start, length, prot, flags, fd, (size_t)offset >> mmap2_shift);
}

#endif