diff options
Diffstat (limited to 'pc-bios/optionrom/linuxboot_dma.c')
| -rw-r--r-- | pc-bios/optionrom/linuxboot_dma.c | 212 |
1 files changed, 212 insertions, 0 deletions
diff --git a/pc-bios/optionrom/linuxboot_dma.c b/pc-bios/optionrom/linuxboot_dma.c new file mode 100644 index 000000000..cbcf6679d --- /dev/null +++ b/pc-bios/optionrom/linuxboot_dma.c @@ -0,0 +1,212 @@ +/* + * Linux Boot Option ROM for fw_cfg DMA + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <http://www.gnu.org/licenses/>. + * + * Copyright (c) 2015-2016 Red Hat Inc. + * Authors: + * Marc Marí <marc.mari.barcelo@gmail.com> + * Richard W.M. Jones <rjones@redhat.com> + */ + +asm( +".text\n" +".global _start\n" +"_start:\n" +" .short 0xaa55\n" +" .byte 3\n" /* desired size in 512 units; signrom.py adds padding */ +" .byte 0xcb\n" /* far return without prefix */ +" .org 0x18\n" +" .short 0\n" +" .short _pnph\n" +"_pnph:\n" +" .ascii \"$PnP\"\n" +" .byte 0x01\n" +" .byte (_pnph_len / 16)\n" +" .short 0x0000\n" +" .byte 0x00\n" +" .byte 0x00\n" +" .long 0x00000000\n" +" .short _manufacturer\n" +" .short _product\n" +" .long 0x00000000\n" +" .short 0x0000\n" +" .short 0x0000\n" +" .short _bev\n" +" .short 0x0000\n" +" .short 0x0000\n" +" .equ _pnph_len, . - _pnph\n" +"_manufacturer:\n" +" .asciz \"QEMU\"\n" +"_product:\n" +" .asciz \"Linux loader DMA\"\n" +" .align 4, 0\n" +"_bev:\n" +" cli\n" +" cld\n" +" jmp load_kernel\n" +); + +/* + * The includes of C headers must be after the asm block to avoid compiler + * errors. + */ +#include <stdint.h> +#include "optrom.h" +#include "optrom_fw_cfg.h" + +static inline void set_es(void *addr) +{ + uint32_t seg = (uint32_t)addr >> 4; + asm("movl %0, %%es" : : "r"(seg)); +} + +static inline uint16_t readw_es(uint16_t offset) +{ + uint16_t val; + asm(ADDR32 "movw %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset)); + barrier(); + return val; +} + +static inline uint32_t readl_es(uint16_t offset) +{ + uint32_t val; + asm(ADDR32 "movl %%es:(%1), %0" : "=r"(val) : "r"((uint32_t)offset)); + barrier(); + return val; +} + +static inline void writel_es(uint16_t offset, uint32_t val) +{ + barrier(); + asm(ADDR32 "movl %0, %%es:(%1)" : : "r"(val), "r"((uint32_t)offset)); +} + +/* Return top of memory using BIOS function E801. */ +static uint32_t get_e801_addr(void) +{ + uint16_t ax, bx, cx, dx; + uint32_t ret; + + asm("int $0x15\n" + : "=a"(ax), "=b"(bx), "=c"(cx), "=d"(dx) + : "a"(0xe801), "b"(0), "c"(0), "d"(0)); + + /* Not SeaBIOS, but in theory a BIOS could return CX=DX=0 in which + * case we need to use the result from AX & BX instead. + */ + if (cx == 0 && dx == 0) { + cx = ax; + dx = bx; + } + + if (dx) { + /* DX = extended memory above 16M, in 64K units. + * Convert it to bytes and return. + */ + ret = ((uint32_t)dx + 256 /* 16M in 64K units */) << 16; + } else { + /* This is a fallback path for machines with <= 16MB of RAM, + * which probably would never be the case, but deal with it + * anyway. + * + * CX = extended memory between 1M and 16M, in kilobytes + * Convert it to bytes and return. + */ + ret = ((uint32_t)cx + 1024 /* 1M in K */) << 10; + } + + return ret; +} + +/* Force the asm name without leading underscore, even on Win32. */ +extern void load_kernel(void) asm("load_kernel"); + +void load_kernel(void) +{ + void *setup_addr; + void *initrd_addr; + void *kernel_addr; + void *cmdline_addr; + uint32_t setup_size; + uint32_t initrd_size; + uint32_t kernel_size; + uint32_t cmdline_size; + uint32_t initrd_end_page, max_allowed_page; + uint32_t segment_addr, stack_addr; + + bios_cfg_read_entry_dma(&setup_addr, FW_CFG_SETUP_ADDR, 4); + bios_cfg_read_entry_dma(&setup_size, FW_CFG_SETUP_SIZE, 4); + bios_cfg_read_entry_dma(setup_addr, FW_CFG_SETUP_DATA, setup_size); + + set_es(setup_addr); + + /* For protocol < 0x203 we don't have initrd_max ... */ + if (readw_es(0x206) < 0x203) { + /* ... so we assume initrd_max = 0x37ffffff. */ + writel_es(0x22c, 0x37ffffff); + } + + bios_cfg_read_entry_dma(&initrd_addr, FW_CFG_INITRD_ADDR, 4); + bios_cfg_read_entry_dma(&initrd_size, FW_CFG_INITRD_SIZE, 4); + + initrd_end_page = ((uint32_t)(initrd_addr + initrd_size) & -4096); + max_allowed_page = (readl_es(0x22c) & -4096); + + if (initrd_end_page != 0 && max_allowed_page != 0 && + initrd_end_page != max_allowed_page) { + /* Initrd at the end of memory. Compute better initrd address + * based on e801 data + */ + initrd_addr = (void *)((get_e801_addr() - initrd_size) & -4096); + writel_es(0x218, (uint32_t)initrd_addr); + + } + + bios_cfg_read_entry_dma(initrd_addr, FW_CFG_INITRD_DATA, initrd_size); + + bios_cfg_read_entry_dma(&kernel_addr, FW_CFG_KERNEL_ADDR, 4); + bios_cfg_read_entry_dma(&kernel_size, FW_CFG_KERNEL_SIZE, 4); + bios_cfg_read_entry_dma(kernel_addr, FW_CFG_KERNEL_DATA, kernel_size); + + bios_cfg_read_entry_dma(&cmdline_addr, FW_CFG_CMDLINE_ADDR, 4); + bios_cfg_read_entry_dma(&cmdline_size, FW_CFG_CMDLINE_SIZE, 4); + bios_cfg_read_entry_dma(cmdline_addr, FW_CFG_CMDLINE_DATA, cmdline_size); + + /* Boot linux */ + segment_addr = ((uint32_t)setup_addr >> 4); + stack_addr = (uint32_t)(cmdline_addr - setup_addr - 16); + + /* As we are changing critical registers, we cannot leave freedom to the + * compiler. + */ + asm("movw %%ax, %%ds\n" + "movw %%ax, %%es\n" + "movw %%ax, %%fs\n" + "movw %%ax, %%gs\n" + "movw %%ax, %%ss\n" + "movl %%ebx, %%esp\n" + "addw $0x20, %%ax\n" + "pushw %%ax\n" /* CS */ + "pushw $0\n" /* IP */ + /* Clear registers and jump to Linux */ + "xor %%ebx, %%ebx\n" + "xor %%ecx, %%ecx\n" + "xor %%edx, %%edx\n" + "xor %%edi, %%edi\n" + "xor %%ebp, %%ebp\n" + "lretw\n" + : : "a"(segment_addr), "b"(stack_addr)); +} |