| 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 | /* |
| 62 | * The includes of C headers must be after the asm block to avoid compiler |
| 63 | * errors. |
| 64 | */ |
| 65 | #include <stdint.h> |
| 66 | #include "optrom.h" |
| 67 | #include "optrom_fw_cfg.h" |
| 68 | |
| 69 | static inline void set_es(void *addr) |
| 70 | { |
| 71 | uint32_t seg = (uint32_t)addr >> 4; |
| 72 | asm("movl %0, %%es" : : "r"(seg)); |
| 73 | } |
| 74 | |
| 75 | static inline uint16_t readw_es(uint16_t offset) |
| 76 | { |
| 77 | uint16_t val; |
| 78 | asm(ADDR32 "movw %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset)); |
| 79 | barrier(); |
| 80 | return val; |
| 81 | } |
| 82 | |
| 83 | static inline uint32_t readl_es(uint16_t offset) |
| 84 | { |
| 85 | uint32_t val; |
| 86 | asm(ADDR32 "movl %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset)); |
| 87 | barrier(); |
| 88 | return val; |
| 89 | } |
| 90 | |
| 91 | static inline void writel_es(uint16_t offset, uint32_t val) |
| 92 | { |
| 93 | barrier(); |
| 94 | asm(ADDR32 "movl %0, %%es:(%1)" : : "r"(val), "r"((uint32_t)offset)); |
| 95 | } |
| 96 | |
| 97 | /* Return top of memory using BIOS function E801. */ |
| 98 | static uint32_t get_e801_addr(void) |
| 99 | { |
| 100 | uint16_t ax, bx, cx, dx; |
| 101 | uint32_t ret; |
| 102 | |
| 103 | asm("int $0x15\n" |
| 104 | : "=a"(ax), "=b"(bx), "=c"(cx), "=d"(dx) |
| 105 | : "a"(0xe801), "b"(0), "c"(0), "d"(0)); |
| 106 | |
| 107 | /* Not SeaBIOS, but in theory a BIOS could return CX=DX=0 in which |
| 108 | * case we need to use the result from AX & BX instead. |
| 109 | */ |
| 110 | if (cx == 0 && dx == 0) { |
| 111 | cx = ax; |
| 112 | dx = bx; |
| 113 | } |
| 114 | |
| 115 | if (dx) { |
| 116 | /* DX = extended memory above 16M, in 64K units. |
| 117 | * Convert it to bytes and return. |
| 118 | */ |
| 119 | ret = ((uint32_t)dx + 256 /* 16M in 64K units */) << 16; |
| 120 | } else { |
| 121 | /* This is a fallback path for machines with <= 16MB of RAM, |
| 122 | * which probably would never be the case, but deal with it |
| 123 | * anyway. |
| 124 | * |
| 125 | * CX = extended memory between 1M and 16M, in kilobytes |
| 126 | * Convert it to bytes and return. |
| 127 | */ |
| 128 | ret = ((uint32_t)cx + 1024 /* 1M in K */) << 10; |
| 129 | } |
| 130 | |
| 131 | return ret; |
| 132 | } |
| 133 | |
| 134 | /* Force the asm name without leading underscore, even on Win32. */ |
| 135 | extern void load_kernel(void) asm("load_kernel"); |
| 136 | |
| 137 | void load_kernel(void) |
| 138 | { |
| 139 | void *setup_addr; |
| 140 | void *initrd_addr; |
| 141 | void *kernel_addr; |
| 142 | void *cmdline_addr; |
| 143 | uint32_t setup_size; |
| 144 | uint32_t initrd_size; |
| 145 | uint32_t kernel_size; |
| 146 | uint32_t cmdline_size; |
| 147 | uint32_t initrd_end_page, max_allowed_page; |
| 148 | uint32_t segment_addr, stack_addr; |
| 149 | |
| 150 | bios_cfg_read_entry_dma(&setup_addr, FW_CFG_SETUP_ADDR, 4); |
| 151 | bios_cfg_read_entry_dma(&setup_size, FW_CFG_SETUP_SIZE, 4); |
| 152 | bios_cfg_read_entry_dma(setup_addr, FW_CFG_SETUP_DATA, setup_size); |
| 153 | |
| 154 | set_es(setup_addr); |
| 155 | |
| 156 | /* For protocol < 0x203 we don't have initrd_max ... */ |
| 157 | if (readw_es(0x206) < 0x203) { |
| 158 | /* ... so we assume initrd_max = 0x37ffffff. */ |
| 159 | writel_es(0x22c, 0x37ffffff); |
| 160 | } |
| 161 | |
| 162 | bios_cfg_read_entry_dma(&initrd_addr, FW_CFG_INITRD_ADDR, 4); |
| 163 | bios_cfg_read_entry_dma(&initrd_size, FW_CFG_INITRD_SIZE, 4); |
| 164 | |
| 165 | initrd_end_page = ((uint32_t)(initrd_addr + initrd_size) & -4096); |
| 166 | max_allowed_page = (readl_es(0x22c) & -4096); |
| 167 | |
| 168 | if (initrd_end_page != 0 && max_allowed_page != 0 && |
| 169 | initrd_end_page != max_allowed_page) { |
| 170 | /* Initrd at the end of memory. Compute better initrd address |
| 171 | * based on e801 data |
| 172 | */ |
| 173 | initrd_addr = (void *)((get_e801_addr() - initrd_size) & -4096); |
| 174 | writel_es(0x218, (uint32_t)initrd_addr); |
| 175 | |
| 176 | } |
| 177 | |
| 178 | bios_cfg_read_entry_dma(initrd_addr, FW_CFG_INITRD_DATA, initrd_size); |
| 179 | |
| 180 | bios_cfg_read_entry_dma(&kernel_addr, FW_CFG_KERNEL_ADDR, 4); |
| 181 | bios_cfg_read_entry_dma(&kernel_size, FW_CFG_KERNEL_SIZE, 4); |
| 182 | bios_cfg_read_entry_dma(kernel_addr, FW_CFG_KERNEL_DATA, kernel_size); |
| 183 | |
| 184 | bios_cfg_read_entry_dma(&cmdline_addr, FW_CFG_CMDLINE_ADDR, 4); |
| 185 | bios_cfg_read_entry_dma(&cmdline_size, FW_CFG_CMDLINE_SIZE, 4); |
| 186 | bios_cfg_read_entry_dma(cmdline_addr, FW_CFG_CMDLINE_DATA, cmdline_size); |
| 187 | |
| 188 | /* Boot linux */ |
| 189 | segment_addr = ((uint32_t)setup_addr >> 4); |
| 190 | stack_addr = (uint32_t)(cmdline_addr - setup_addr - 16); |
| 191 | |
| 192 | /* As we are changing critical registers, we cannot leave freedom to the |
| 193 | * compiler. |
| 194 | */ |
| 195 | asm("movw %%ax, %%ds\n" |
| 196 | "movw %%ax, %%es\n" |
| 197 | "movw %%ax, %%fs\n" |
| 198 | "movw %%ax, %%gs\n" |
| 199 | "movw %%ax, %%ss\n" |
| 200 | "movl %%ebx, %%esp\n" |
| 201 | "addw $0x20, %%ax\n" |
| 202 | "pushw %%ax\n" /* CS */ |
| 203 | "pushw $0\n" /* IP */ |
| 204 | /* Clear registers and jump to Linux */ |
| 205 | "xor %%ebx, %%ebx\n" |
| 206 | "xor %%ecx, %%ecx\n" |
| 207 | "xor %%edx, %%edx\n" |
| 208 | "xor %%edi, %%edi\n" |
| 209 | "xor %%ebp, %%ebp\n" |
| 210 | "lretw\n" |
| 211 | : : "a"(segment_addr), "b"(stack_addr)); |
| 212 | } |