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torvalds
GitHub Repository: torvalds/linux
 Path: blob/master/drivers/firmware/efi/efi-bgrt.c
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// SPDX-License-Identifier: GPL-2.0

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/*

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 * Copyright 2012 Intel Corporation

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 * Author: Josh Triplett <[email protected]>

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 *

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 * Based on the bgrt driver:

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 * Copyright 2012 Red Hat, Inc <[email protected]>

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 * Author: Matthew Garrett

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 */

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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>

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#include <linux/efi.h>

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#include <linux/efi-bgrt.h>

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struct acpi_table_bgrt bgrt_tab;

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size_t bgrt_image_size;

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struct bmp_header {

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	u16 id;

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	u32 size;

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} __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)

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		return;

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	if (!efi_enabled(EFI_MEMMAP))

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		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;

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	/*

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	 * Only version 1 is defined but some older laptops (seen on Lenovo

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	 * Ivy Bridge models) have a correct version 1 BGRT table with the

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	 * version set to 0, so we accept version 0 and 1.

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	 */

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	if (bgrt->version > 1) {

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		pr_notice("Ignoring BGRT: invalid version %u (expected 1)\n",

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		       bgrt->version);

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		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);

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		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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	if (efi_mem_type(bgrt->image_address) != EFI_BOOT_SERVICES_DATA) {

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		pr_notice("Ignoring BGRT: invalid 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;

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out:

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	memset(bgrt, 0, sizeof(bgrt_tab));

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}

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