diff options
Diffstat (limited to 'drivers/firmware/google/memconsole-x86-legacy.c')
| -rw-r--r-- | drivers/firmware/google/memconsole-x86-legacy.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/drivers/firmware/google/memconsole-x86-legacy.c b/drivers/firmware/google/memconsole-x86-legacy.c new file mode 100644 index 000000000..19bcbd108 --- /dev/null +++ b/drivers/firmware/google/memconsole-x86-legacy.c @@ -0,0 +1,165 @@ +/* + * memconsole-x86-legacy.c + * + * EBDA specific parts of the memory based BIOS console. + * + * Copyright 2017 Google Inc. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License v2.0 as published by + * the Free Software Foundation. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + */ + +#include <linux/kernel.h> +#include <linux/module.h> +#include <linux/dmi.h> +#include <linux/mm.h> +#include <asm/bios_ebda.h> +#include <linux/acpi.h> + +#include "memconsole.h" + +#define BIOS_MEMCONSOLE_V1_MAGIC 0xDEADBABE +#define BIOS_MEMCONSOLE_V2_MAGIC (('M')|('C'<<8)|('O'<<16)|('N'<<24)) + +struct biosmemcon_ebda { + u32 signature; + union { + struct { + u8 enabled; + u32 buffer_addr; + u16 start; + u16 end; + u16 num_chars; + u8 wrapped; + } __packed v1; + struct { + u32 buffer_addr; + /* Misdocumented as number of pages! */ + u16 num_bytes; + u16 start; + u16 end; + } __packed v2; + }; +} __packed; + +static char *memconsole_baseaddr; +static size_t memconsole_length; + +static ssize_t memconsole_read(char *buf, loff_t pos, size_t count) +{ + return memory_read_from_buffer(buf, count, &pos, memconsole_baseaddr, + memconsole_length); +} + +static void found_v1_header(struct biosmemcon_ebda *hdr) +{ + pr_info("memconsole: BIOS console v1 EBDA structure found at %p\n", + hdr); + pr_info("memconsole: BIOS console buffer at 0x%.8x, start = %d, end = %d, num = %d\n", + hdr->v1.buffer_addr, hdr->v1.start, + hdr->v1.end, hdr->v1.num_chars); + + memconsole_baseaddr = phys_to_virt(hdr->v1.buffer_addr); + memconsole_length = hdr->v1.num_chars; + memconsole_setup(memconsole_read); +} + +static void found_v2_header(struct biosmemcon_ebda *hdr) +{ + pr_info("memconsole: BIOS console v2 EBDA structure found at %p\n", + hdr); + pr_info("memconsole: BIOS console buffer at 0x%.8x, start = %d, end = %d, num_bytes = %d\n", + hdr->v2.buffer_addr, hdr->v2.start, + hdr->v2.end, hdr->v2.num_bytes); + + memconsole_baseaddr = phys_to_virt(hdr->v2.buffer_addr + hdr->v2.start); + memconsole_length = hdr->v2.end - hdr->v2.start; + memconsole_setup(memconsole_read); +} + +/* + * Search through the EBDA for the BIOS Memory Console, and + * set the global variables to point to it. Return true if found. + */ +static bool memconsole_ebda_init(void) +{ + unsigned int address; + size_t length, cur; + + address = get_bios_ebda(); + if (!address) { + pr_info("memconsole: BIOS EBDA non-existent.\n"); + return false; + } + + /* EBDA length is byte 0 of EBDA (in KB) */ + length = *(u8 *)phys_to_virt(address); + length <<= 10; /* convert to bytes */ + + /* + * Search through EBDA for BIOS memory console structure + * note: signature is not necessarily dword-aligned + */ + for (cur = 0; cur < length; cur++) { + struct biosmemcon_ebda *hdr = phys_to_virt(address + cur); + + /* memconsole v1 */ + if (hdr->signature == BIOS_MEMCONSOLE_V1_MAGIC) { + found_v1_header(hdr); + return true; + } + + /* memconsole v2 */ + if (hdr->signature == BIOS_MEMCONSOLE_V2_MAGIC) { + found_v2_header(hdr); + return true; + } + } + + pr_info("memconsole: BIOS console EBDA structure not found!\n"); + return false; +} + +static const struct dmi_system_id memconsole_dmi_table[] __initconst = { + { + .ident = "Google Board", + .matches = { + DMI_MATCH(DMI_BOARD_VENDOR, "Google, Inc."), + }, + }, + {} +}; +MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table); + +static bool __init memconsole_find(void) +{ + if (!dmi_check_system(memconsole_dmi_table)) + return false; + + return memconsole_ebda_init(); +} + +static int __init memconsole_x86_init(void) +{ + if (!memconsole_find()) + return -ENODEV; + + return memconsole_sysfs_init(); +} + +static void __exit memconsole_x86_exit(void) +{ + memconsole_exit(); +} + +module_init(memconsole_x86_init); +module_exit(memconsole_x86_exit); + +MODULE_AUTHOR("Google, Inc."); +MODULE_LICENSE("GPL"); |