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269e235849
Old kernels that used high memory only allowed the initrd to be in the
first 896MB of memory. If you load the initrd above, they complain
that "initrd extends beyond end of memory".
In order to fix this, while not breaking machines with small amounts
of memory fixed by cdebec5 (linuxboot: compute initrd loading address,
2014-10-06), we need to distinguish two cases. If pc.c placed the
initrd at end of memory, use the new algorithm based on the e801
memory map. If instead pc.c placed the initrd at the maximum address
specified by the bzImage, leave it there.
The only interesting part is that the low-memory info block is now
loaded very early, in real mode, and thus the 32-bit address has
to be converted into a real mode segment. The initrd address is
also patched in the info block before entering real mode, it is
simpler that way.
This fixes booting the RHEL4.8 32-bit installation image with 1GB
of RAM.
Cc: qemu-stable@nongnu.org
Cc: mst@redhat.com
Cc: jsnow@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
196 lines
4.4 KiB
ArmAsm
196 lines
4.4 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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/* Read info block in low memory (0x10000 or 0x90000) */
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read_fw FW_CFG_SETUP_ADDR
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shr $4, %eax
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mov %eax, %es
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xor %edi, %edi
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read_fw_blob_addr32_edi(FW_CFG_SETUP)
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cmpw $0x203, %es:0x206 // if protocol >= 0x203
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jae 1f // have initrd_max
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movl $0x37ffffff, %es:0x22c // else assume 0x37ffffff
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1:
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/* Check if using kernel-specified initrd address */
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read_fw FW_CFG_INITRD_ADDR
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mov %eax, %edi // (load_kernel wants it in %edi)
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read_fw FW_CFG_INITRD_SIZE // find end of initrd
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add %edi, %eax
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xor %es:0x22c, %eax // if it matches es:0x22c
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and $-4096, %eax // (apart from padding for page)
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jz load_kernel // then initrd is not at top
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// of memory
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/* pc.c placed the initrd at end of memory. Compute a better
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* initrd address based on e801 data.
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*/
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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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movl %edi, %es:0x218 /* put it in the header */
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load_kernel:
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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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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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/* 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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