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157 lines
3.5 KiB
157 lines
3.5 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* memconsole-x86-legacy.c |
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* |
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* EBDA specific parts of the memory based BIOS console. |
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* |
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* Copyright 2017 Google Inc. |
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*/ |
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#include <linux/kernel.h> |
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#include <linux/module.h> |
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#include <linux/dmi.h> |
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#include <linux/mm.h> |
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#include <asm/bios_ebda.h> |
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#include <linux/acpi.h> |
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#include "memconsole.h" |
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#define BIOS_MEMCONSOLE_V1_MAGIC 0xDEADBABE |
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#define BIOS_MEMCONSOLE_V2_MAGIC (('M')|('C'<<8)|('O'<<16)|('N'<<24)) |
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struct biosmemcon_ebda { |
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u32 signature; |
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union { |
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struct { |
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u8 enabled; |
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u32 buffer_addr; |
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u16 start; |
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u16 end; |
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u16 num_chars; |
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u8 wrapped; |
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} __packed v1; |
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struct { |
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u32 buffer_addr; |
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/* Misdocumented as number of pages! */ |
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u16 num_bytes; |
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u16 start; |
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u16 end; |
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} __packed v2; |
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}; |
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} __packed; |
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static char *memconsole_baseaddr; |
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static size_t memconsole_length; |
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static ssize_t memconsole_read(char *buf, loff_t pos, size_t count) |
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{ |
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return memory_read_from_buffer(buf, count, &pos, memconsole_baseaddr, |
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memconsole_length); |
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} |
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static void found_v1_header(struct biosmemcon_ebda *hdr) |
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{ |
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pr_info("memconsole: BIOS console v1 EBDA structure found at %p\n", |
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hdr); |
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pr_info("memconsole: BIOS console buffer at 0x%.8x, start = %d, end = %d, num = %d\n", |
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hdr->v1.buffer_addr, hdr->v1.start, |
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hdr->v1.end, hdr->v1.num_chars); |
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memconsole_baseaddr = phys_to_virt(hdr->v1.buffer_addr); |
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memconsole_length = hdr->v1.num_chars; |
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memconsole_setup(memconsole_read); |
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} |
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static void found_v2_header(struct biosmemcon_ebda *hdr) |
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{ |
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pr_info("memconsole: BIOS console v2 EBDA structure found at %p\n", |
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hdr); |
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pr_info("memconsole: BIOS console buffer at 0x%.8x, start = %d, end = %d, num_bytes = %d\n", |
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hdr->v2.buffer_addr, hdr->v2.start, |
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hdr->v2.end, hdr->v2.num_bytes); |
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memconsole_baseaddr = phys_to_virt(hdr->v2.buffer_addr + hdr->v2.start); |
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memconsole_length = hdr->v2.end - hdr->v2.start; |
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memconsole_setup(memconsole_read); |
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} |
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/* |
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* Search through the EBDA for the BIOS Memory Console, and |
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* set the global variables to point to it. Return true if found. |
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*/ |
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static bool memconsole_ebda_init(void) |
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{ |
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unsigned int address; |
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size_t length, cur; |
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address = get_bios_ebda(); |
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if (!address) { |
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pr_info("memconsole: BIOS EBDA non-existent.\n"); |
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return false; |
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} |
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/* EBDA length is byte 0 of EBDA (in KB) */ |
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length = *(u8 *)phys_to_virt(address); |
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length <<= 10; /* convert to bytes */ |
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/* |
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* Search through EBDA for BIOS memory console structure |
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* note: signature is not necessarily dword-aligned |
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*/ |
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for (cur = 0; cur < length; cur++) { |
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struct biosmemcon_ebda *hdr = phys_to_virt(address + cur); |
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/* memconsole v1 */ |
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if (hdr->signature == BIOS_MEMCONSOLE_V1_MAGIC) { |
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found_v1_header(hdr); |
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return true; |
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} |
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/* memconsole v2 */ |
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if (hdr->signature == BIOS_MEMCONSOLE_V2_MAGIC) { |
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found_v2_header(hdr); |
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return true; |
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} |
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} |
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pr_info("memconsole: BIOS console EBDA structure not found!\n"); |
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return false; |
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} |
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static const struct dmi_system_id memconsole_dmi_table[] __initconst = { |
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{ |
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.ident = "Google Board", |
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.matches = { |
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DMI_MATCH(DMI_BOARD_VENDOR, "Google, Inc."), |
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}, |
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}, |
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{} |
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}; |
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MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table); |
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static bool __init memconsole_find(void) |
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{ |
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if (!dmi_check_system(memconsole_dmi_table)) |
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return false; |
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return memconsole_ebda_init(); |
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} |
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static int __init memconsole_x86_init(void) |
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{ |
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if (!memconsole_find()) |
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return -ENODEV; |
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return memconsole_sysfs_init(); |
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} |
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static void __exit memconsole_x86_exit(void) |
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{ |
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memconsole_exit(); |
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} |
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module_init(memconsole_x86_init); |
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module_exit(memconsole_x86_exit); |
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MODULE_AUTHOR("Google, Inc."); |
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MODULE_LICENSE("GPL");
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