efi-bgrt.c 2.1 KB
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/*
 * Copyright 2012 Intel Corporation
 * Author: Josh Triplett <josh@joshtriplett.org>
 *
 * Based on the bgrt driver:
 * Copyright 2012 Red Hat, Inc <mjg@redhat.com>
 * Author: Matthew Garrett
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/acpi.h>
#include <linux/efi.h>
#include <linux/efi-bgrt.h>

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struct acpi_table_bgrt bgrt_tab;
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size_t __initdata bgrt_image_size;
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struct bmp_header {
	u16 id;
	u32 size;
} __packed;

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void __init efi_bgrt_init(struct acpi_table_header *table)
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{
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	void *image;
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	struct bmp_header bmp_header;
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	struct acpi_table_bgrt *bgrt = &bgrt_tab;
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	if (acpi_disabled)
		return;

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	if (table->length < sizeof(bgrt_tab)) {
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		pr_notice("Ignoring BGRT: invalid length %u (expected %zu)\n",
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		       table->length, sizeof(bgrt_tab));
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		return;
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	}
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	*bgrt = *(struct acpi_table_bgrt *)table;
	if (bgrt->version != 1) {
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		pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",
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		       bgrt->version);
		goto out;
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	}
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	if (bgrt->status & 0xfe) {
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		pr_notice("Ignoring BGRT: reserved status bits are non-zero %u\n",
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		       bgrt->status);
		goto out;
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	}
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	if (bgrt->image_type != 0) {
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		pr_notice("Ignoring BGRT: invalid image type %u (expected 0)\n",
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		       bgrt->image_type);
		goto out;
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	}
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	if (!bgrt->image_address) {
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		pr_notice("Ignoring BGRT: null image address\n");
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		goto out;
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	}
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	image = early_memremap(bgrt->image_address, sizeof(bmp_header));
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	if (!image) {
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		pr_notice("Ignoring BGRT: failed to map image header memory\n");
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		goto out;
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	}

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	memcpy(&bmp_header, image, sizeof(bmp_header));
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	early_memunmap(image, sizeof(bmp_header));
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	if (bmp_header.id != 0x4d42) {
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		pr_notice("Ignoring BGRT: Incorrect BMP magic number 0x%x (expected 0x4d42)\n",
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			bmp_header.id);
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		goto out;
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	}
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	bgrt_image_size = bmp_header.size;
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	efi_mem_reserve(bgrt->image_address, bgrt_image_size);
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	return;
out:
	memset(bgrt, 0, sizeof(bgrt_tab));
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}