diff options
Diffstat (limited to 'pc-bios')
| -rw-r--r-- | pc-bios/optionrom/multiboot.S | 77 |
1 files changed, 60 insertions, 17 deletions
diff --git a/pc-bios/optionrom/multiboot.S b/pc-bios/optionrom/multiboot.S index e6cbefd..dafac73 100644 --- a/pc-bios/optionrom/multiboot.S +++ b/pc-bios/optionrom/multiboot.S @@ -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 |