pc-bios/optionrom/linuxboot_dma.c

   1 /*
   2  * Linux Boot Option ROM for fw_cfg DMA
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License as published by
   6  * the Free Software Foundation; either version 2 of the License, or
   7  * (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see <http://www.gnu.org/licenses/>.
  16  *
  17  * Copyright (c) 2015-2016 Red Hat Inc.
  18  *   Authors:
  19  *     Marc Marí <marc.mari.barcelo@gmail.com>
  20  *     Richard W.M. Jones <rjones@redhat.com>
  21  */
  22
  23 asm(
  24 ".text\n"
  25 ".global _start\n"
  26 "_start:\n"
  27 "   .short 0xaa55\n"
  28 "   .byte 3\n" /* desired size in 512 units; signrom.py adds padding */
  29 "   .byte 0xcb\n" /* far return without prefix */
  30 "   .org 0x18\n"
  31 "   .short 0\n"
  32 "   .short _pnph\n"
  33 "_pnph:\n"
  34 "   .ascii \"$PnP\"\n"
  35 "   .byte 0x01\n"
  36 "   .byte (_pnph_len / 16)\n"
  37 "   .short 0x0000\n"
  38 "   .byte 0x00\n"
  39 "   .byte 0x00\n"
  40 "   .long 0x00000000\n"
  41 "   .short _manufacturer\n"
  42 "   .short _product\n"
  43 "   .long 0x00000000\n"
  44 "   .short 0x0000\n"
  45 "   .short 0x0000\n"
  46 "   .short _bev\n"
  47 "   .short 0x0000\n"
  48 "   .short 0x0000\n"
  49 "   .equ _pnph_len, . - _pnph\n"
  50 "_manufacturer:\n"
  51 "   .asciz \"QEMU\"\n"
  52 "_product:\n"
  53 "   .asciz \"Linux loader DMA\"\n"
  54 "   .align 4, 0\n"
  55 "_bev:\n"
  56 "   cli\n"
  57 "   cld\n"
  58 "   jmp load_kernel\n"
  59 );
  60
  61 #include "../../include/hw/nvram/fw_cfg_keys.h"
  62
  63 /* QEMU_CFG_DMA_CONTROL bits */
  64 #define BIOS_CFG_DMA_CTL_ERROR   0x01
  65 #define BIOS_CFG_DMA_CTL_READ    0x02
  66 #define BIOS_CFG_DMA_CTL_SKIP    0x04
  67 #define BIOS_CFG_DMA_CTL_SELECT  0x08
  68
  69 #define BIOS_CFG_DMA_ADDR_HIGH 0x514
  70 #define BIOS_CFG_DMA_ADDR_LOW  0x518
  71
  72 #define uint64_t unsigned long long
  73 #define uint32_t unsigned int
  74 #define uint16_t unsigned short
  75
  76 #define barrier() asm("" : : : "memory")
  77
  78 typedef struct FWCfgDmaAccess {
  79     uint32_t control;
  80     uint32_t length;
  81     uint64_t address;
  82 } __attribute__((packed)) FWCfgDmaAccess;
  83
  84 static inline void outl(uint32_t value, uint16_t port)
  85 {
  86     asm("outl %0, %w1" : : "a"(value), "Nd"(port));
  87 }
  88
  89 static inline void set_es(void *addr)
  90 {
  91     uint32_t seg = (uint32_t)addr >> 4;
  92     asm("movl %0, %%es" : : "r"(seg));
  93 }
  94
  95 #ifdef __clang__
  96 #define ADDR32
  97 #else
  98 #define ADDR32 "addr32 "
  99 #endif
 100
 101 static inline uint16_t readw_es(uint16_t offset)
 102 {
 103     uint16_t val;
 104     asm(ADDR32 "movw %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset));
 105     barrier();
 106     return val;
 107 }
 108
 109 static inline uint32_t readl_es(uint16_t offset)
 110 {
 111     uint32_t val;
 112     asm(ADDR32 "movl %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset));
 113     barrier();
 114     return val;
 115 }
 116
 117 static inline void writel_es(uint16_t offset, uint32_t val)
 118 {
 119     barrier();
 120     asm(ADDR32 "movl %0, %%es:(%1)" : : "r"(val), "r"((uint32_t)offset));
 121 }
 122
 123 static inline uint32_t bswap32(uint32_t x)
 124 {
 125     asm("bswapl %0" : "=r" (x) : "0" (x));
 126     return x;
 127 }
 128
 129 static inline uint64_t bswap64(uint64_t x)
 130 {
 131     asm("bswapl %%eax; bswapl %%edx; xchg %%eax, %%edx" : "=A" (x) : "0" (x));
 132     return x;
 133 }
 134
 135 static inline uint64_t cpu_to_be64(uint64_t x)
 136 {
 137     return bswap64(x);
 138 }
 139
 140 static inline uint32_t cpu_to_be32(uint32_t x)
 141 {
 142     return bswap32(x);
 143 }
 144
 145 static inline uint32_t be32_to_cpu(uint32_t x)
 146 {
 147     return bswap32(x);
 148 }
 149
 150 /* clang is happy to inline this function, and bloats the
 151  * ROM.
 152  */
 153 static __attribute__((__noinline__))
 154 void bios_cfg_read_entry(void *buf, uint16_t entry, uint32_t len)
 155 {
 156     FWCfgDmaAccess access;
 157     uint32_t control = (entry << 16) | BIOS_CFG_DMA_CTL_SELECT
 158                         | BIOS_CFG_DMA_CTL_READ;
 159
 160     access.address = cpu_to_be64((uint64_t)(uint32_t)buf);
 161     access.length = cpu_to_be32(len);
 162     access.control = cpu_to_be32(control);
 163
 164     barrier();
 165
 166     outl(cpu_to_be32((uint32_t)&access), BIOS_CFG_DMA_ADDR_LOW);
 167
 168     while (be32_to_cpu(access.control) & ~BIOS_CFG_DMA_CTL_ERROR) {
 169         barrier();
 170     }
 171 }
 172
 173 /* Return top of memory using BIOS function E801. */
 174 static uint32_t get_e801_addr(void)
 175 {
 176     uint16_t ax, bx, cx, dx;
 177     uint32_t ret;
 178
 179     asm("int $0x15\n"
 180         : "=a"(ax), "=b"(bx), "=c"(cx), "=d"(dx)
 181         : "a"(0xe801), "b"(0), "c"(0), "d"(0));
 182
 183     /* Not SeaBIOS, but in theory a BIOS could return CX=DX=0 in which
 184      * case we need to use the result from AX & BX instead.
 185      */
 186     if (cx == 0 && dx == 0) {
 187         cx = ax;
 188         dx = bx;
 189     }
 190
 191     if (dx) {
 192         /* DX = extended memory above 16M, in 64K units.
 193          * Convert it to bytes and return.
 194          */
 195         ret = ((uint32_t)dx + 256 /* 16M in 64K units */) << 16;
 196     } else {
 197         /* This is a fallback path for machines with <= 16MB of RAM,
 198          * which probably would never be the case, but deal with it
 199          * anyway.
 200          *
 201          * CX = extended memory between 1M and 16M, in kilobytes
 202          * Convert it to bytes and return.
 203          */
 204         ret = ((uint32_t)cx + 1024 /* 1M in K */) << 10;
 205     }
 206
 207     return ret;
 208 }
 209
 210 /* Force the asm name without leading underscore, even on Win32. */
 211 extern void load_kernel(void) asm("load_kernel");
 212
 213 void load_kernel(void)
 214 {
 215     void *setup_addr;
 216     void *initrd_addr;
 217     void *kernel_addr;
 218     void *cmdline_addr;
 219     uint32_t setup_size;
 220     uint32_t initrd_size;
 221     uint32_t kernel_size;
 222     uint32_t cmdline_size;
 223     uint32_t initrd_end_page, max_allowed_page;
 224     uint32_t segment_addr, stack_addr;
 225
 226     bios_cfg_read_entry(&setup_addr, FW_CFG_SETUP_ADDR, 4);
 227     bios_cfg_read_entry(&setup_size, FW_CFG_SETUP_SIZE, 4);
 228     bios_cfg_read_entry(setup_addr, FW_CFG_SETUP_DATA, setup_size);
 229
 230     set_es(setup_addr);
 231
 232     /* For protocol < 0x203 we don't have initrd_max ... */
 233     if (readw_es(0x206) < 0x203) {
 234         /* ... so we assume initrd_max = 0x37ffffff. */
 235         writel_es(0x22c, 0x37ffffff);
 236     }
 237
 238     bios_cfg_read_entry(&initrd_addr, FW_CFG_INITRD_ADDR, 4);
 239     bios_cfg_read_entry(&initrd_size, FW_CFG_INITRD_SIZE, 4);
 240
 241     initrd_end_page = ((uint32_t)(initrd_addr + initrd_size) & -4096);
 242     max_allowed_page = (readl_es(0x22c) & -4096);
 243
 244     if (initrd_end_page != 0 && max_allowed_page != 0 &&
 245         initrd_end_page != max_allowed_page) {
 246         /* Initrd at the end of memory. Compute better initrd address
 247          * based on e801 data
 248          */
 249         initrd_addr = (void *)((get_e801_addr() - initrd_size) & -4096);
 250         writel_es(0x218, (uint32_t)initrd_addr);
 251
 252     }
 253
 254     bios_cfg_read_entry(initrd_addr, FW_CFG_INITRD_DATA, initrd_size);
 255
 256     bios_cfg_read_entry(&kernel_addr, FW_CFG_KERNEL_ADDR, 4);
 257     bios_cfg_read_entry(&kernel_size, FW_CFG_KERNEL_SIZE, 4);
 258     bios_cfg_read_entry(kernel_addr, FW_CFG_KERNEL_DATA, kernel_size);
 259
 260     bios_cfg_read_entry(&cmdline_addr, FW_CFG_CMDLINE_ADDR, 4);
 261     bios_cfg_read_entry(&cmdline_size, FW_CFG_CMDLINE_SIZE, 4);
 262     bios_cfg_read_entry(cmdline_addr, FW_CFG_CMDLINE_DATA, cmdline_size);
 263
 264     /* Boot linux */
 265     segment_addr = ((uint32_t)setup_addr >> 4);
 266     stack_addr = (uint32_t)(cmdline_addr - setup_addr - 16);
 267
 268     /* As we are changing critical registers, we cannot leave freedom to the
 269      * compiler.
 270      */
 271     asm("movw %%ax, %%ds\n"
 272         "movw %%ax, %%es\n"
 273         "movw %%ax, %%fs\n"
 274         "movw %%ax, %%gs\n"
 275         "movw %%ax, %%ss\n"
 276         "movl %%ebx, %%esp\n"
 277         "addw $0x20, %%ax\n"
 278         "pushw %%ax\n" /* CS */
 279         "pushw $0\n" /* IP */
 280         /* Clear registers and jump to Linux */
 281         "xor %%ebx, %%ebx\n"
 282         "xor %%ecx, %%ecx\n"
 283         "xor %%edx, %%edx\n"
 284         "xor %%edi, %%edi\n"
 285         "xor %%ebp, %%ebp\n"
 286         "lretw\n"
 287         : : "a"(segment_addr), "b"(stack_addr));
 288 }