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Convert multiboot to fw_cfg backed data storage 

Right now we load the guest kernel to RAM, fire off the BIOS, hope it
doesn't clobber memory and run an option rom that jumps into the kernel.

That breaks with SeaBIOS, as that clears memory. So let's read all
kernel, module etc. data using the fw_cfg interface when in the int19
handler.

This patch implements said mechanism for multiboot.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
This commit is contained in:
Alexander Graf 2009-11-12 21:53:12 +01:00 committed by Anthony Liguori
parent 235f86ef01
commit 77873196f3
3 changed files with 95 additions and 32 deletions
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5
hw/fw_cfg.h
View File

@ -17,7 +17,10 @@
#define FW_CFG_NUMA 0x0d
#define FW_CFG_BOOT_MENU 0x0e
#define FW_CFG_MAX_CPUS 0x0f
#define FW_CFG_MAX_ENTRY 0x10
#define FW_CFG_KERNEL_ENTRY 0x10
#define FW_CFG_KERNEL_DATA 0x11
#define FW_CFG_INITRD_DATA 0x12
#define FW_CFG_MAX_ENTRY 0x13
#define FW_CFG_WRITE_CHANNEL 0x4000
#define FW_CFG_ARCH_LOCAL 0x8000

45
hw/pc.c
View File

@ -603,6 +603,8 @@ static int load_multiboot(void *fw_cfg,
uint32_t mb_mod_end;
uint8_t bootinfo[0x500];
uint32_t cmdline = 0x200;
uint8_t *mb_kernel_data;
uint8_t *mb_bootinfo_data;
/* Ok, let's see if it is a multiboot image.
The header is 12x32bit long, so the latest entry may be 8192 - 48. */
@ -643,6 +645,12 @@ static int load_multiboot(void *fw_cfg,
mh_load_addr = mh_entry_addr = elf_entry;
mb_kernel_size = kernel_size;
mb_kernel_data = qemu_malloc(mb_kernel_size);
if (rom_copy(mb_kernel_data, elf_entry, kernel_size) != kernel_size) {
fprintf(stderr, "Error while fetching elf kernel from rom\n");
exit(1);
}
#ifdef DEBUG_MULTIBOOT
fprintf(stderr, "qemu: loading multiboot-elf kernel (%#x bytes) with entry %#zx\n",
mb_kernel_size, (size_t)mh_entry_addr);
@ -656,7 +664,6 @@ static int load_multiboot(void *fw_cfg,
uint32_t mh_bss_end_addr = ldl_p(header+i+24);
#endif
uint32_t mb_kernel_text_offset = i - (mh_header_addr - mh_load_addr);
uint8_t *kernel;
mh_entry_addr = ldl_p(header+i+28);
mb_kernel_size = get_file_size(f) - mb_kernel_text_offset;
@ -676,12 +683,9 @@ static int load_multiboot(void *fw_cfg,
mb_kernel_size, mh_load_addr);
#endif
kernel = qemu_malloc(mb_kernel_size);
mb_kernel_data = qemu_malloc(mb_kernel_size);
fseek(f, mb_kernel_text_offset, SEEK_SET);
fread(kernel, 1, mb_kernel_size, f);
rom_add_blob_fixed(kernel_filename, kernel, mb_kernel_size,
mh_load_addr);
qemu_free(kernel);
fread(mb_kernel_data, 1, mb_kernel_size, f);
fclose(f);
}
@ -732,9 +736,14 @@ static int load_multiboot(void *fw_cfg,
exit(1);
}
mb_mod_end = mb_mod_start + mb_mod_length;
rom_add_file_fixed(initrd_filename, mb_mod_start);
mb_mod_count++;
/* append module data at the end of last module */
mb_kernel_data = qemu_realloc(mb_kernel_data,
mh_load_addr - mb_mod_end);
load_image(initrd_filename,
mb_kernel_data + mb_mod_start - mh_load_addr);
stl_p(bootinfo + mb_mod_info + 0, mb_mod_start);
stl_p(bootinfo + mb_mod_info + 4, mb_mod_start + mb_mod_length);
stl_p(bootinfo + mb_mod_info + 12, 0x0); /* reserved */
@ -774,13 +783,21 @@ static int load_multiboot(void *fw_cfg,
fprintf(stderr, "multiboot: mh_entry_addr = %#x\n", mh_entry_addr);
#endif
/* Pass variables to option rom */
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, mh_entry_addr);
fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_ADDR, mb_bootinfo);
fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_SIZE, mmap_addr);
/* save bootinfo off the stack */
mb_bootinfo_data = qemu_malloc(sizeof(bootinfo));
memcpy(mb_bootinfo_data, bootinfo, sizeof(bootinfo));
rom_add_blob_fixed("multiboot-info", bootinfo, sizeof(bootinfo),
mb_bootinfo);
/* Pass variables to option rom */
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ENTRY, mh_entry_addr);
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_ADDR, mh_load_addr);
fw_cfg_add_i32(fw_cfg, FW_CFG_KERNEL_SIZE, mb_mod_end - mh_load_addr);
fw_cfg_add_bytes(fw_cfg, FW_CFG_KERNEL_DATA, mb_kernel_data,
mb_mod_end - mh_load_addr);
fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_ADDR, mb_bootinfo);
fw_cfg_add_i32(fw_cfg, FW_CFG_INITRD_SIZE, sizeof(bootinfo));
fw_cfg_add_bytes(fw_cfg, FW_CFG_INITRD_DATA, mb_bootinfo_data,
sizeof(bootinfo));
option_rom[nb_option_roms] = "multiboot.bin";
nb_option_roms++;

77
pc-bios/optionrom/multiboot.S
View File

@ -26,6 +26,14 @@
#define MULTIBOOT_MAGIC 0x2badb002
#define GS_PROT_JUMP 0
#define GS_GDT_DESC 6
/* Break the translation block flow so -d cpu shows us values */
#define DEBUG_HERE \
jmp 1f; \
1:
/* Read a variable from the fw_cfg device.
Clobbers: %edx
Out: %eax */
@ -44,12 +52,31 @@
bswap %eax
.endm
/*
* Read a blob from the fw_cfg device.
* Requires _ADDR, _SIZE and _DATA values for the parameter.
*
* Clobbers: %eax, %edx, %es, %ecx, %edi
*/
#define read_fw_blob(var) \
read_fw var ## _ADDR; \
mov %eax, %edi; \
read_fw var ## _SIZE; \
mov %eax, %ecx; \
mov $var ## _DATA, %ax; \
mov $BIOS_CFG_IOPORT_CFG, %edx; \
outw %ax, (%dx); \
mov $BIOS_CFG_IOPORT_DATA, %dx; \
cld; \
DEBUG_HERE \
rep insb (%dx), %es:(%edi);
.code16
.text
.global _start
_start:
.short 0xaa55
.byte 1 /* (_end - _start) / 512 */
.byte (_end - _start) / 512
push %eax
push %ds
@ -57,10 +84,6 @@ _start:
xor %ax, %ax
mov %ax, %ds
/* save old int 19 */
mov (0x19*4), %eax
mov %eax, %cs:old_int19
/* install our int 19 handler */
movw $int19_handler, (0x19*4)
mov %cs, (0x19*4+2)
@ -84,15 +107,34 @@ run_multiboot:
mov %cs, %eax
shl $0x4, %eax
/* fix the gdt descriptor to be PC relative */
mov (gdt_desc+2), %ebx
add %eax, %ebx
mov %ebx, (gdt_desc+2)
/* set up a long jump descriptor that is PC relative */
/* fix the prot mode indirect jump to be 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 decriptor there */
mov (prot_jump), %ebx
add %eax, %ebx
mov %ebx, (prot_jump)
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
/* Read the bootinfo struct into RAM */
read_fw_blob(FW_CFG_INITRD)
/* FS = bootinfo_struct */
read_fw FW_CFG_INITRD_ADDR
@ -100,7 +142,7 @@ run_multiboot:
mov %ax, %fs
/* ES = mmap_addr */
read_fw FW_CFG_INITRD_SIZE
mov %eax, %fs:0x48
shr $4, %eax
mov %ax, %es
@ -144,7 +186,7 @@ mmap_done:
real_to_prot:
/* Load the GDT before going into protected mode */
lgdt:
data32 lgdt %cs:gdt_desc
data32 lgdt %gs:GS_GDT_DESC
/* get us to protected mode now */
movl $1, %eax
@ -152,7 +194,7 @@ lgdt:
/* the LJMP sets CS for us and gets us to 32-bit */
ljmp:
data32 ljmp *%cs:prot_jump
data32 ljmp *%gs:GS_PROT_JUMP
prot_mode:
.code32
@ -165,8 +207,11 @@ prot_mode:
movl %eax, %fs
movl %eax, %gs
/* Read the kernel and modules into RAM */
read_fw_blob(FW_CFG_KERNEL)
/* Jump off to the kernel */
read_fw FW_CFG_KERNEL_ADDR
read_fw FW_CFG_KERNEL_ENTRY
mov %eax, %ecx
/* EBX contains a pointer to the bootinfo struct */
@ -180,8 +225,6 @@ ljmp2:
/* Variables */
.align 4, 0
old_int19: .long 0
prot_jump: .long prot_mode
.short 8