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 } 289