Archipelago » qemu

#include <sys/types.h>

#include <sys/stat.h>

    /* When mapping files into a memory area larger than the file, accesses

       to pages beyond the file size will cause a SIGBUS. 

       For example, if mmaping a file of 100 bytes on a host with 4K pages

       emulating a target with 8K pages, the target expects to be able to

       access the first 8K. But the host will trap us on any access beyond

       4K.  

       When emulating a target with a larger page-size than the hosts, we

       may need to truncate file maps at EOF and add extra anonymous pages

       up to the targets page boundary.  */

    if ((qemu_real_host_page_size < TARGET_PAGE_SIZE)

        && !(flags & MAP_ANONYMOUS)) {

       struct stat sb;

       if (fstat (fd, &sb) == -1)

           goto fail;

       /* Are we trying to create a map beyond EOF?.  */

       if (offset + len > sb.st_size) {

           /* If so, truncate the file map at eof aligned with 

              the hosts real pagesize. Additional anonymous maps

              will be created beyond EOF.  */

           len = (sb.st_size - offset);

           len += qemu_real_host_page_size - 1;

           len &= ~(qemu_real_host_page_size - 1);

       }

    }

                 host_len, prot, flags | MAP_FIXED | MAP_ANONYMOUS, -1, 0);

        if (!(flags & MAP_ANONYMOUS)) {

            p = mmap(g2h(mmap_start), len, prot, 

                     flags | MAP_FIXED, fd, host_offset);

        }