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d55e37bb0f
OpenFirmware wasn't quite following 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. OpenFirmware has now been fixed. 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 <dsd@laptop.org> Link: http://lkml.kernel.org/r/20130809221420.618E6FAB03@dev.laptop.org Acked-by: Yinghai Lu <yinghai@kernel.org> Signed-off-by: H. Peter Anvin <hpa@linux.intel.com> Cc: <stable@vger.kernel.org> # v3.9+
55 lines
2.0 KiB
C
55 lines
2.0 KiB
C
#ifndef _ASM_X86_BOOTPARAM_UTILS_H
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#define _ASM_X86_BOOTPARAM_UTILS_H
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#include <asm/bootparam.h>
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/*
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* This file is included from multiple environments. Do not
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* add completing #includes to make it standalone.
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*/
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/*
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* Deal with bootloaders which fail to initialize unknown fields in
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* boot_params to zero. The list fields in this list are taken from
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* analysis of kexec-tools; if other broken bootloaders initialize a
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* different set of fields we will need to figure out how to disambiguate.
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*
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* Note: efi_info is commonly left uninitialized, but that field has a
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* private magic, so it is better to leave it unchanged.
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*/
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static void sanitize_boot_params(struct boot_params *boot_params)
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{
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/*
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* IMPORTANT NOTE TO BOOTLOADER AUTHORS: do not simply clear
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* this field. The purpose of this field is to guarantee
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* compliance with the x86 boot spec located in
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* Documentation/x86/boot.txt . That spec says that the
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* *whole* structure should be cleared, after which only the
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* portion defined by struct setup_header (boot_params->hdr)
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* should be copied in.
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*
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* If you're having an issue because the sentinel is set, you
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* need to change the whole structure to be cleared, not this
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* (or any other) individual field, or you will soon have
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* problems again.
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*/
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if (boot_params->sentinel) {
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/* fields in boot_params are left uninitialized, clear them */
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memset(&boot_params->ext_ramdisk_image, 0,
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(char *)&boot_params->efi_info -
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(char *)&boot_params->ext_ramdisk_image);
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memset(&boot_params->kbd_status, 0,
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(char *)&boot_params->hdr -
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(char *)&boot_params->kbd_status);
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memset(&boot_params->_pad7[0], 0,
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(char *)&boot_params->edd_mbr_sig_buffer[0] -
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(char *)&boot_params->_pad7[0]);
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memset(&boot_params->_pad8[0], 0,
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(char *)&boot_params->eddbuf[0] -
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(char *)&boot_params->_pad8[0]);
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memset(&boot_params->_pad9[0], 0, sizeof(boot_params->_pad9));
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}
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}
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#endif /* _ASM_X86_BOOTPARAM_UTILS_H */
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