drivers/firmware/google/memconsole.c

   1 /*
   2  * memconsole.c
   3  *
   4  * Infrastructure for importing the BIOS memory based console
   5  * into the kernel log ringbuffer.
   6  *
   7  * Copyright 2010 Google Inc. All rights reserved.
   8  */
   9
  10 #include <linux/ctype.h>
  11 #include <linux/init.h>
  12 #include <linux/kernel.h>
  13 #include <linux/string.h>
  14 #include <linux/sysfs.h>
  15 #include <linux/kobject.h>
  16 #include <linux/module.h>
  17 #include <linux/dmi.h>
  18 #include <linux/mm.h>
  19 #include <asm/bios_ebda.h>
  20 #include <asm/e820.h>
  21 #include <acpi/acpi_bus.h>
  22
  23 #define BIOS_MEMCONSOLE_V1_MAGIC        0xDEADBABE
  24 #define BIOS_MEMCONSOLE_V2_MAGIC        (('M')|('C'<<8)|('O'<<16)|('N'<<24))
  25
  26 struct biosmemcon_ebda {
  27         u32 signature;
  28         union {
  29                 struct {
  30                         u8  enabled;
  31                         u32 buffer_addr;
  32                         u16 start;
  33                         u16 end;
  34                         u16 num_chars;
  35                         u8  wrapped;
  36                 } __packed v1;
  37                 struct {
  38                         u32 buffer_addr;
  39                         /* Misdocumented as number of pages! */
  40                         u16 num_bytes;
  41                         u16 start;
  42                         u16 end;
  43                 } __packed v2;
  44         };
  45 } __packed;
  46
  47 static char *memconsole_baseaddr;
  48 static size_t memconsole_length;
  49 static bool coreboot_system;
  50
  51 static int set_coreboot_system_flag(const struct dmi_system_id *unused)
  52 {
  53         coreboot_system = true;
  54         return true;
  55 }
  56
  57 static ssize_t memconsole_read(struct file *filp, struct kobject *kobp,
  58                                struct bin_attribute *bin_attr, char *buf,
  59                                loff_t pos, size_t count)
  60 {
  61         return memory_read_from_buffer(buf, count, &pos, memconsole_baseaddr,
  62                                        memconsole_length);
  63 }
  64
  65 static struct bin_attribute memconsole_bin_attr = {
  66         .attr = {.name = "log", .mode = 0444},
  67         .read = memconsole_read,
  68 };
  69
  70
  71 static void found_v1_header(struct biosmemcon_ebda *hdr)
  72 {
  73         printk(KERN_INFO "BIOS console v1 EBDA structure found at %p\n", hdr);
  74         printk(KERN_INFO "BIOS console buffer at 0x%.8x, "
  75                "start = %d, end = %d, num = %d\n",
  76                hdr->v1.buffer_addr, hdr->v1.start,
  77                hdr->v1.end, hdr->v1.num_chars);
  78
  79         memconsole_length = hdr->v1.num_chars;
  80         memconsole_baseaddr = phys_to_virt(hdr->v1.buffer_addr);
  81 }
  82
  83 static void found_v2_header(struct biosmemcon_ebda *hdr)
  84 {
  85         printk(KERN_INFO "BIOS console v2 EBDA structure found at %p\n", hdr);
  86         printk(KERN_INFO "BIOS console buffer at 0x%.8x, "
  87                "start = %d, end = %d, num_bytes = %d\n",
  88                hdr->v2.buffer_addr, hdr->v2.start,
  89                hdr->v2.end, hdr->v2.num_bytes);
  90
  91         memconsole_length = hdr->v2.end - hdr->v2.start;
  92         memconsole_baseaddr = phys_to_virt(hdr->v2.buffer_addr
  93                                            + hdr->v2.start);
  94 }
  95
  96 /*
  97  * The function below tries to find the firmware console log saved in the
  98  * appropriate coreboot CBMEM section, using the structures and constants from
  99  * coreboot code.
 100  *
 101  * Coreboot's CBMEM is a structure allocated by coreboot above usable memory
 102  * at a 128K aligned address. One of the CBMEM sections could contain the
 103  * firmare console log.
 104  */
 105
 106 /* Coreboot CBMEM section descriptor. */
 107 struct cbmem_entry {
 108         u32 magic;
 109         u32 id;
 110         u64 base;
 111         u64 size;
 112 } __packed;
 113
 114 /* CBMEM firmware console log descriptor. */
 115 struct cbmem_cons {
 116         u32 buffer_size;
 117         u32 buffer_cursor;
 118         u8  buffer_body[0];
 119 } __packed;
 120
 121 struct cbmem_cons __iomem *cbmem_console;
 122
 123 /* coreboot CBMEM constants */
 124 #define CBMEM_ALIGNMENT   (128 * 1024)
 125 #define MEMORY_BOUNDARY   (1024 * 1024 * 1024)
 126 #define MAX_CBMEM_ENTRIES 16
 127 #define CBMEM_ENTRY_MAGIC 0x434f5245
 128 #define CBMEM_CONSOLE_ID  0x434f4e53
 129 #define CBMEM_ACPI_NAME   "\\CMEM"
 130
 131 static bool check_cbmem(void)
 132 {
 133         struct sysinfo sysi;
 134         phys_addr_t top_of_ram, scan_addr = 0;
 135         acpi_handle handle;
 136         acpi_status status;
 137         unsigned long long value;
 138
 139         /*
 140          * Attempt to use defined ACPI name to locate CBMEM TOC.
 141          */
 142         status = acpi_get_handle(NULL, CBMEM_ACPI_NAME, &handle);
 143         if (ACPI_SUCCESS(status)) {
 144                 status = acpi_evaluate_integer(handle, CBMEM_ACPI_NAME,
 145                                                NULL, &value);
 146                 /* Start scan at this address */
 147                 if (ACPI_SUCCESS(status) && value > 0)
 148                         scan_addr = (phys_addr_t) value;
 149         }
 150
 151         /*
 152          * Otherwise determine where to start looking for CBMEM signature:
 153          * take the top of usable memory and align it up to 128K boundary.
 154          */
 155         if (!scan_addr) {
 156                 si_meminfo(&sysi);
 157                 top_of_ram = (phys_addr_t) sysi.totalram << PAGE_SHIFT;
 158                 scan_addr = ALIGN(top_of_ram, CBMEM_ALIGNMENT) +
 159                         CBMEM_ALIGNMENT;
 160         }
 161
 162         while (scan_addr % MEMORY_BOUNDARY) {
 163                 struct cbmem_entry __iomem *pcbm;
 164                 int i, remap_size = sizeof(struct cbmem_entry) * 16;
 165
 166                 /*
 167                  * See if we reached reserved memory. Bail out if so, as it is
 168                  * not mappable and is above the region where the CBMEM could
 169                  * be.
 170                  */
 171                 if (e820_any_mapped(scan_addr,
 172                                     scan_addr + remap_size,
 173                                     E820_RESERVED))
 174                         break;
 175
 176                 pcbm = ioremap_cache(scan_addr, remap_size);
 177                 if (!pcbm) {
 178                         scan_addr += CBMEM_ALIGNMENT;
 179                         continue;
 180                 }
 181
 182                 if (pcbm->magic != CBMEM_ENTRY_MAGIC) {
 183                         iounmap(pcbm);
 184                         scan_addr += CBMEM_ALIGNMENT;
 185                         continue;
 186                 }
 187
 188                 /* CBMEM found. Is the console log there? */
 189                 for (i = 1; i < MAX_CBMEM_ENTRIES; i++) {
 190                         if ((pcbm[i].magic == CBMEM_ENTRY_MAGIC) &&
 191                             (pcbm[i].id == CBMEM_CONSOLE_ID)) {
 192                                 /* Yes, map the log. */
 193                                 cbmem_console = ioremap_cache(pcbm[i].base,
 194                                                         pcbm[i].size);
 195                                 break;
 196                         }
 197                 }
 198                 iounmap(pcbm);
 199                 break;
 200         }
 201
 202         if (cbmem_console) {
 203                 memconsole_baseaddr = cbmem_console->buffer_body;
 204                 memconsole_length = min(cbmem_console->buffer_cursor,
 205                                         cbmem_console->buffer_size);
 206                 return true;
 207         }
 208
 209         printk(KERN_INFO "CBMEM console structure not found!\n");
 210         return false;
 211 }
 212
 213 /*
 214  * Search through the EBDA for the BIOS Memory Console, and
 215  * set the global variables to point to it.  Return true if found.
 216  */
 217 static bool found_memconsole(void)
 218 {
 219         unsigned int address;
 220         size_t length, cur;
 221
 222         /* Is it communicated through CBMEM? */
 223         if (coreboot_system && check_cbmem())
 224                 return true;
 225
 226         address = get_bios_ebda();
 227         if (!address) {
 228                 printk(KERN_INFO "BIOS EBDA non-existent.\n");
 229                 return false;
 230         }
 231
 232         /* EBDA length is byte 0 of EBDA (in KB) */
 233         length = *(u8 *)phys_to_virt(address);
 234         length <<= 10; /* convert to bytes */
 235
 236         /*
 237          * Search through EBDA for BIOS memory console structure
 238          * note: signature is not necessarily dword-aligned
 239          */
 240         for (cur = 0; cur < length; cur++) {
 241                 struct biosmemcon_ebda *hdr = phys_to_virt(address + cur);
 242
 243                 /* memconsole v1 */
 244                 if (hdr->signature == BIOS_MEMCONSOLE_V1_MAGIC) {
 245                         found_v1_header(hdr);
 246                         return true;
 247                 }
 248
 249                 /* memconsole v2 */
 250                 if (hdr->signature == BIOS_MEMCONSOLE_V2_MAGIC) {
 251                         found_v2_header(hdr);
 252                         return true;
 253                 }
 254         }
 255
 256         printk(KERN_INFO "BIOS console EBDA structure not found!\n");
 257         return false;
 258 }
 259
 260 static struct dmi_system_id memconsole_dmi_table[] __initdata = {
 261         {
 262                 .ident = "Google Board",
 263                 .matches = {
 264                         DMI_MATCH(DMI_BOARD_VENDOR, "Google, Inc."),
 265                 },
 266         },
 267         {
 268                 .ident = "Google Board",
 269                 .callback = set_coreboot_system_flag,
 270                 .matches = {
 271                         DMI_MATCH(DMI_BIOS_VENDOR, "coreboot"),
 272                 },
 273         },
 274         {}
 275 };
 276 MODULE_DEVICE_TABLE(dmi, memconsole_dmi_table);
 277
 278 static int __init memconsole_init(void)
 279 {
 280         int ret;
 281
 282         if (!dmi_check_system(memconsole_dmi_table))
 283                 return -ENODEV;
 284
 285         if (!found_memconsole())
 286                 return -ENODEV;
 287
 288         memconsole_bin_attr.size = memconsole_length;
 289
 290         ret = sysfs_create_bin_file(firmware_kobj, &memconsole_bin_attr);
 291
 292         return ret;
 293 }
 294
 295 static void __exit memconsole_exit(void)
 296 {
 297         if (cbmem_console)
 298                 iounmap(cbmem_console);
 299
 300         sysfs_remove_bin_file(firmware_kobj, &memconsole_bin_attr);
 301 }
 302
 303 module_init(memconsole_init);
 304 module_exit(memconsole_exit);
 305
 306 MODULE_AUTHOR("Google, Inc.");
 307 MODULE_LICENSE("GPL");