tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
driver: Google Memory Console
This patch introduces the 'memconsole' driver.
Our firmware gives us access to an in-memory log of the firmware's
output. This gives us visibility in a data-center of headless machines
as to what the firmware is doing.
The memory console is found by the driver by finding a header block in
the EBDA. The buffer is then copied out, and is exported to userland in
the file /sys/firmware/log.
Signed-off-by: San Mehat <san@google.com>
Signed-off-by: Mike Waychison <mikew@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
authored by
Mike Waychison
and committed by
Greg Kroah-Hartman
e561bc45
74c5b31c
+182
+7
Documentation/ABI/testing/sysfs-firmware-log
+7
Documentation/ABI/testing/sysfs-firmware-log
+8
drivers/firmware/google/Kconfig
+8
drivers/firmware/google/Kconfig
···
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platforms. This provides an interface for writing to and
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clearing the EFI event log and reading and writing NVRAM
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variables.
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config GOOGLE_MEMCONSOLE
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tristate "Firmware Memory Console"
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depends on DMI
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help
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This option enables the kernel to search for a firmware log in
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the EBDA on Google servers. If found, this log is exported to
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userland in the file /sys/firmware/log.
+1
drivers/firmware/google/Makefile
+1
drivers/firmware/google/Makefile
+166
drivers/firmware/google/memconsole.c
+166
drivers/firmware/google/memconsole.c
···
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/*
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* memconsole.c
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*
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* Infrastructure for importing the BIOS memory based console
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* into the kernel log ringbuffer.
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*
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* Copyright 2010 Google Inc. All rights reserved.
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*/
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#include <linux/ctype.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/sysfs.h>
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#include <linux/kobject.h>
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#include <linux/module.h>
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#include <linux/dmi.h>
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#include <asm/bios_ebda.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(struct file *filp, struct kobject *kobp,
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struct bin_attribute *bin_attr, char *buf,
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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 struct bin_attribute memconsole_bin_attr = {
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.attr = {.name = "log", .mode = 0444},
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.read = memconsole_read,
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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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printk(KERN_INFO "BIOS console v1 EBDA structure found at %p\n", hdr);
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printk(KERN_INFO "BIOS console buffer at 0x%.8x, "
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"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_length = hdr->v1.num_chars;
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memconsole_baseaddr = phys_to_virt(hdr->v1.buffer_addr);
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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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printk(KERN_INFO "BIOS console v2 EBDA structure found at %p\n", hdr);
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printk(KERN_INFO "BIOS console buffer at 0x%.8x, "
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"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_length = hdr->v2.end - hdr->v2.start;
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memconsole_baseaddr = phys_to_virt(hdr->v2.buffer_addr
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+ hdr->v2.start);
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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 found_memconsole(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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printk(KERN_INFO "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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printk(KERN_INFO "BIOS console EBDA structure not found!\n");
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return false;
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}
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static struct dmi_system_id memconsole_dmi_table[] __initdata = {
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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 int __init memconsole_init(void)
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{
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int ret;
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if (!dmi_check_system(memconsole_dmi_table))
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return -ENODEV;
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if (!found_memconsole())
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return -ENODEV;
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memconsole_bin_attr.size = memconsole_length;
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ret = sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
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return ret;
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}
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static void __exit memconsole_exit(void)
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{
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sysfs_remove_bin_file(firmware_kobj, &memconsole_bin_attr);
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}
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module_init(memconsole_init);
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module_exit(memconsole_exit);
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MODULE_AUTHOR("Google, Inc.");
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MODULE_LICENSE("GPL");