Commit 77873196 authored by Alexander Graf's avatar Alexander Graf Committed by Anthony Liguori
Browse files

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: default avatarAlexander Graf <agraf@suse.de>
Signed-off-by: default avatarAnthony Liguori <aliguori@us.ibm.com>
parent 235f86ef

hw/fw_cfg.h

+4 −1
Original line number Diff line number Diff line
@@ -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

hw/pc.c

+30 −13
Original line number Diff line number Diff line
@@ -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



    /* save bootinfo off the stack */

    mb_bootinfo_data = qemu_malloc(sizeof(bootinfo));

    memcpy(mb_bootinfo_data, bootinfo, sizeof(bootinfo));



    /* 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);

    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);



    rom_add_blob_fixed("multiboot-info", bootinfo, sizeof(bootinfo),

                       mb_bootinfo);

    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++;

pc-bios/optionrom/multiboot.S

+60 −17
Original line number Diff line number Diff line
@@ -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 */



	/* 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



	/* fix the prot mode indirect jump to be PC relative */

	/* 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