Re: [LinuxBIOS] [PATCH] pci_rom.c checksum extension rom

[Stefan Reinauer]

* Alex Beregszaszi  [070907 12:54]:
> Hi,
>
> On Wed, 2007-09-05 at 04:29 +0200, Stefan Reinauer wrote:
> > Alex Beregszaszi  [070904 13:17]:
> > > Hi,
> > >
> > > the attached patch adds code to checksum the pci extension rom and stop
> > > if the stored and calculated checksum differ.
> >
> > Is this checksum reliably correct? I am hesitating to add new
> > restrictions that might break otherwise working cards.
>
> You are right, attached is a correct method. There is no fixed checksum
> byte, instead the whole should sum to zero.
>
> Signed-off-by: Alex Beregszaszi

Acked-by: Stefan Reinauer
> Index: device/pci_rom.c
>
> --- device/pci_rom.c	(revision 494)
> +++ device/pci_rom.c	(working copy)
> @@ -33,6 +33,8 @@
>    unsigned long rom_address;
>    struct rom_header *rom_header;
>    struct pci_data *rom_data;
>
> unsigned int i;
>
> unsigned char sum = 0, *rom_bytes;
>
> if (dev->on_mainboard) {
> /* In case some device PCI_ROM_ADDRESS can not be set
>
> @@ -67,7 +69,17 @@
>    	       le32_to_cpu(rom_header->signature));
>    	return NULL;
>    }
>
> /* checksum */
>
> rom_bytes = (unsigned char *)rom_address;
>
> for (i = 0; i < rom_header->size * 512; i++)
>    sum += *(rom_bytes + i);
>
> if (sum != 0) {
> printk(BIOS_ERR, "Incorrent Expansion ROM checksum (%02x != 0)\n", sum);
> return NULL;
>
> }
>
> rom_data = (struct pci_data *)((unsigned char *)rom_header +
>   		       le32_to_cpu(rom_header->data));