cdebec5e40
Even though hw/i386/pc.c tries to compute a valid loading address for the initrd, close to the top of RAM, this does not take into account other data that is malloced into that memory by SeaBIOS. Luckily we can easily look at the memory map to find out how much memory is used up there. This patch places the initrd in the first four gigabytes, below the first hole (as returned by INT 15h, AX=e801h). Without this patch: [ 0.000000] init_memory_mapping: [mem 0x07000000-0x07fdffff] [ 0.000000] RAMDISK: [mem 0x0710a000-0x07fd7fff] With this patch: [ 0.000000] init_memory_mapping: [mem 0x07000000-0x07fdffff] [ 0.000000] RAMDISK: [mem 0x07112000-0x07fdffff] So linuxboot is able to use the 64k that were added as padding for QEMU <= 2.1. Acked-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
179 lines
3.7 KiB
ArmAsm
179 lines
3.7 KiB
ArmAsm
/*
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* Linux Boot Option ROM
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*
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* Copyright Novell Inc, 2009
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* Authors: Alexander Graf <agraf@suse.de>
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*
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* Based on code in hw/pc.c.
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*/
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#include "optionrom.h"
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#define BOOT_ROM_PRODUCT "Linux loader"
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BOOT_ROM_START
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run_linuxboot:
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cli
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cld
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jmp copy_kernel
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boot_kernel:
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read_fw FW_CFG_SETUP_ADDR
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mov %eax, %ebx
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shr $4, %ebx
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/* All segments contain real_addr */
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mov %bx, %ds
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mov %bx, %es
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mov %bx, %fs
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mov %bx, %gs
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mov %bx, %ss
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/* CX = CS we want to jump to */
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add $0x20, %bx
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mov %bx, %cx
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/* SP = cmdline_addr-real_addr-16 */
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read_fw FW_CFG_CMDLINE_ADDR
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mov %eax, %ebx
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read_fw FW_CFG_SETUP_ADDR
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sub %eax, %ebx
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sub $16, %ebx
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mov %ebx, %esp
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/* Build indirect lret descriptor */
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pushw %cx /* CS */
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xor %ax, %ax
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pushw %ax /* IP = 0 */
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/* Clear registers */
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xor %eax, %eax
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xor %ebx, %ebx
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xor %ecx, %ecx
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xor %edx, %edx
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xor %edi, %edi
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xor %ebp, %ebp
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/* Jump to Linux */
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lret
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copy_kernel:
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/* Compute initrd address */
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mov $0xe801, %ax
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xor %cx, %cx
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xor %dx, %dx
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int $0x15
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/* Output could be in AX/BX or CX/DX */
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or %cx, %cx
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jnz 1f
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or %dx, %dx
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jnz 1f
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mov %ax, %cx
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mov %bx, %dx
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1:
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or %dx, %dx
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jnz 2f
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addw $1024, %cx /* add 1 MB */
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movzwl %cx, %edi
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shll $10, %edi /* convert to bytes */
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jmp 3f
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2:
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addw $16777216 >> 16, %dx /* add 16 MB */
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movzwl %dx, %edi
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shll $16, %edi /* convert to bytes */
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3:
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read_fw FW_CFG_INITRD_SIZE
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subl %eax, %edi
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andl $-4096, %edi /* EDI = start of initrd */
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/* We need to load the kernel into memory we can't access in 16 bit
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mode, so let's get into 32 bit mode, write the kernel and jump
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back again. */
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/* Reserve space on the stack for our GDT descriptor. */
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mov %esp, %ebp
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sub $16, %esp
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/* Now create the GDT descriptor */
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movw $((3 * 8) - 1), -16(%bp)
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mov %cs, %eax
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movzwl %ax, %eax
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shl $4, %eax
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addl $gdt, %eax
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movl %eax, -14(%bp)
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/* And load the GDT */
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data32 lgdt -16(%bp)
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mov %ebp, %esp
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/* Get us to protected mode now */
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mov $1, %eax
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mov %eax, %cr0
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/* So we can set ES to a 32-bit segment */
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mov $0x10, %eax
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mov %eax, %es
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/* We're now running in 16-bit CS, but 32-bit ES! */
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/* Load kernel and initrd */
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pushl %edi
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read_fw_blob_addr32_edi(FW_CFG_INITRD)
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read_fw_blob_addr32(FW_CFG_KERNEL)
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read_fw_blob_addr32(FW_CFG_CMDLINE)
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read_fw FW_CFG_SETUP_ADDR
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mov %eax, %edi
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mov %eax, %ebx
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read_fw_blob_addr32_edi(FW_CFG_SETUP)
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/* Update the header with the initrd address we chose above */
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popl %es:0x218(%ebx)
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/* And now jump into Linux! */
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mov $0, %eax
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mov %eax, %cr0
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/* ES = CS */
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mov %cs, %ax
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mov %ax, %es
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jmp boot_kernel
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/* Variables */
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.align 4, 0
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gdt:
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/* 0x00 */
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.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
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/* 0x08: code segment (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k) */
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.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00
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/* 0x10: data segment (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k) */
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.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00
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BOOT_ROM_END
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