qemu/pc-bios/optionrom/pvh.S
Stefano Garzarella 2785dc7b17 optionrom: add new PVH option rom
The new pvh.bin option rom can be used with SeaBIOS to boot
uncompressed kernel using the x86/HVM direct boot ABI.

pvh.S contains the entry point of the option rom. It runs
in real mode, loads the e820 table querying the BIOS, and
then it switches to 32bit protected mode and jumps to the
pvh_load_kernel() written in pvh_main.c.
pvh_load_kernel() loads the cmdline and kernel entry_point
using fw_cfg, then it looks for RSDP, fills the
hvm_start_info required by x86/HVM ABI, and finally jumps
to the kernel entry_point.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Liam Merwick <liam.merwick@oracle.com>
2019-02-05 16:50:17 +01:00

201 lines
4.2 KiB
ArmAsm

/*
* PVH Option ROM
*
* 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 Novell Inc, 2009
* Authors: Alexander Graf <agraf@suse.de>
*
* Copyright (c) 2019 Red Hat Inc.
* Authors: Stefano Garzarella <sgarzare@redhat.com>
*/
#include "optionrom.h"
#define BOOT_ROM_PRODUCT "PVH loader"
#define GS_PROT_JUMP 0
#define GS_GDT_DESC 6
#ifdef OPTION_ROM_START
#undef OPTION_ROM_START
#endif
#ifdef OPTION_ROM_END
#undef OPTION_ROM_END
#endif
/*
* Redefine OPTION_ROM_START and OPTION_ROM_END, because this rom is produced
* linking multiple objects.
* signrom.py will add padding.
*/
#define OPTION_ROM_START \
.code16; \
.text; \
.global _start; \
_start:; \
.short 0xaa55; \
.byte 3; /* desired size in 512 units */
#define OPTION_ROM_END \
_end:
BOOT_ROM_START
run_pvhboot:
cli
cld
mov %cs, %eax
shl $0x4, %eax
/* set up a long jump descriptor that is PC relative */
/* move stack memory to %gs */
mov %ss, %ecx
shl $0x4, %ecx
mov %esp, %ebx
add %ebx, %ecx
sub $0x20, %ecx
sub $0x30, %esp
shr $0x4, %ecx
mov %cx, %gs
/* now push the indirect jump descriptor there */
mov (prot_jump), %ebx
add %eax, %ebx
movl %ebx, %gs:GS_PROT_JUMP
mov $8, %bx
movw %bx, %gs:GS_PROT_JUMP + 4
/* fix the gdt descriptor to be PC relative */
movw (gdt_desc), %bx
movw %bx, %gs:GS_GDT_DESC
movl (gdt_desc+2), %ebx
add %eax, %ebx
movl %ebx, %gs:GS_GDT_DESC + 2
/* initialize HVM memmap table using int 0x15(e820) */
/* ES = pvh_e820 struct */
mov $pvh_e820, %eax
shr $4, %eax
mov %ax, %es
/* start storing memmap table at %es:8 (pvh_e820.table) */
mov $8,%edi
xor %ebx, %ebx
jmp memmap_loop
memmap_loop_check:
/* pvh_e820 can contains up to 128 entries */
cmp $128, %ebx
je memmap_done
memmap_loop:
/* entry size (hvm_memmap_table_entry) & max buffer size (int15) */
movl $24, %ecx
/* e820 */
movl $0x0000e820, %eax
/* 'SMAP' magic */
movl $0x534d4150, %edx
/* store counter value at %es:0 (pvh_e820.entries) */
movl %ebx, %es:0
int $0x15
/* error or last entry already done? */
jb memmap_err
/* %edi += entry size (hvm_memmap_table_entry) */
add $24, %edi
/* continuation value 0 means last entry */
test %ebx, %ebx
jnz memmap_loop_check
/* increase pvh_e820.entries to save the last entry */
movl %es:0, %ebx
inc %ebx
memmap_done:
movl %ebx, %es:0
memmap_err:
/* load the GDT before going into protected mode */
lgdt:
data32 lgdt %gs:GS_GDT_DESC
/* get us to protected mode now */
movl $1, %eax
movl %eax, %cr0
/* the LJMP sets CS for us and gets us to 32-bit */
ljmp:
data32 ljmp *%gs:GS_PROT_JUMP
prot_mode:
.code32
/* initialize all other segments */
movl $0x10, %eax
movl %eax, %ss
movl %eax, %ds
movl %eax, %es
movl %eax, %fs
movl %eax, %gs
jmp pvh_load_kernel
/* Variables */
.align 4, 0
prot_jump: .long prot_mode
.short 8
.align 4, 0
gdt:
/* 0x00 */
.byte 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00
/*
* 0x08: code segment
* (base=0, limit=0xfffff, type=32bit code exec/read, DPL=0, 4k)
*/
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9a, 0xcf, 0x00
/*
* 0x10: data segment
* (base=0, limit=0xfffff, type=32bit data read/write, DPL=0, 4k)
*/
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0xcf, 0x00
/*
* 0x18: code segment
* (base=0, limit=0x0ffff, type=16bit code exec/read/conf, DPL=0, 1b)
*/
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x9e, 0x00, 0x00
/*
* 0x20: data segment
* (base=0, limit=0x0ffff, type=16bit data read/write, DPL=0, 1b)
*/
.byte 0xff, 0xff, 0x00, 0x00, 0x00, 0x92, 0x00, 0x00
gdt_desc:
.short (5 * 8) - 1
.long gdt
BOOT_ROM_END