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