x86: don't clear olpc_ofw_header when sentinel is detected

OpenFirmware doesn't quite follow the protocol described in boot.txt and the kernel has detected this through use of the sentinel value in boot_params. OFW does zero out almost all of the stuff that it should do, but not the sentinel.

This causes the kernel to clear olpc_ofw_header, which breaks x86 OLPC support.

We will fix OpenFirmware. However, it would be nice if we could maintain Linux compatibility with old firmware versions. To do that, we just have to avoid zeroing out olpc_ofw_header.

OFW does not write to any other parts of the header that are being zapped by the sentinel-detection code, and all users of olpc_ofw_header are somewhat protected through checking for the OLPC_OFW_SIG magic value before using it. So this should not cause any problems for anyone.

Signed-off-by Daniel Drake <[email protected]>

---
 arch/x86/include/asm/bootparam_utils.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

arch/x86/include/asm/bootparam_utils.h +2 -3

index 653668d..4a8cb8d 100644
@@ -35,9 +35,9 @@ static void sanitize_boot_params(struct boot_params *boot_params)
         */
        if (boot_params->sentinel) {
                /* fields in boot_params are left uninitialized, clear them */
-               memset(&boot_params->olpc_ofw_header, 0,
+               memset(&boot_params->ext_ramdisk_image, 0,
                       (char *)&boot_params->efi_info -
-                       (char *)&boot_params->olpc_ofw_header);
+                       (char *)&boot_params->ext_ramdisk_image);
                memset(&boot_params->kbd_status, 0,
                       (char *)&boot_params->hdr -
                       (char *)&boot_params->kbd_status);
--

1.8.1.4