Subject: mmap problems
To: None <>
From: Jared D. McNeill <>
List: tech-kern
Date: 05/27/2001 14:02:17
I've been working on updating the emulators/snes9x package to 1.37c, and
in the process I remembered that DGA didn't work in the current package.
So, I've been poking around with things, and it looks like mmap is failing
where it shouldn't be.

From XF86DGA.c:
   /* This requires linux-0.99.pl10 or above */
   *addr = (void *)mmap(NULL, *bank, PROT_READ,
                        MAP_FILE | MAP_SHARED, fd,
                        (off_t)offset + bus_base_addr);
#ifdef DEBUG
   fprintf(stderr, "XF86DGAGetVideo: physaddr: 0x%08x, size: %d\n",
           (long)offset, *bank);
   if (*addr == (char *) -1) {
        fprintf(stderr, "XF86DGAGetVideo: failed to mmap %s (%s)\n",
                           DEV_MEM, strerror(errno));
        exit (-2);

Running snes9x (with DGA support) at securelevel -1 (with or without the
aperture driver loaded) yields the following:

sun:/home/jmcneill/roms# snes9x -y
Rate: 22050, Buffer size: 1024, 16-bit: yes, Stereo: yes, Encoded: yes
Found ROM file header (and ignored it).
"STAR FOX" [checksum ok] LoROM, 8Mbits, Type: ROM+SuperFX, Mode: 20, TV:
NTSC, S-RAM: 64Kb, ROMId: ???? Company: ??
XF86DGAGetVideo: physaddr: 0xca000000, size: 16646144
XF86DGAGetVideo: failed to mmap /dev/mem (Invalid argument)

According to the mmap(2) man page, mmap should only fail with EINVAL and
the flags that XF86DGAGetVideo uses if len (in this case, size (which is
16646144)) is less than zero.

The current xmame package exhibits the same behavior. Is this a bug with
UVM, mmap, or libXxf86dga?