X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fthreads%2Floader.S;h=aeb58bc9fd55b572d670fe5087fbd5bdbdb96c06;hb=0550d2e705c042d659a7fab480431c62cb26213d;hp=535c442c4f1f39a0d59cf43aa51c0e3cc8beee33;hpb=c9c283cb3e26a5b6d918ee47dcf8efe28522b18d;p=pintos-anon diff --git a/src/threads/loader.S b/src/threads/loader.S index 535c442..aeb58bc 100644 --- a/src/threads/loader.S +++ b/src/threads/loader.S @@ -1,228 +1,207 @@ -#include "loader.h" -#include "mmu.h" -#include "gdt.h" +#include "threads/loader.h" -############################################################################## -# Kernel loader. -# -# This code should be stored in the first sector of the hard disk. When the -# BIOS runs, it loads this code at physical address 0x7c00-0x7e00 (512 bytes). -# Then it jumps to the beginning of it, in real mode. -# This code switches into protected mode (32-bit mode) so that all of -# memory can accessed, loads the kernel into memory, and jumps to the -# first byte of the kernel, where start.S is linked. -############################################################################## + .intel_syntax noprefix -/* Flags in control register 0 */ -#define CR0_PE 0x00000001 /* Protection Enable. */ -#define CR0_EM 0x00000004 /* (Floating-point) Emulation. */ -#define CR0_PG 0x80000000 /* Paging. */ - -.globl start # Entry point -start: .code16 # This runs in real mode - cli # Disable interrupts - cld # String ops inc - xorw %ax,%ax # Zero - movw %ax,%es # Address - movw %ax,%ds # data - movw %ax,%ss # Set up - movw $start,%sp # stack (grows down) +#### Kernel loader. + +# Runs in real mode, which is a 16-bit segment. + .code16 + +# Set up segment registers. +# Stack grows downward starting from us. + +.globl start +start: + sub ax, ax + mov ds, ax + mov ss, ax + mov sp, 0x7c00 + cld + + mov ax, 0x00e3 + sub dx, dx + int 0x14 + +# Scan floppy disks. + + sub dl, dl + sub ebx, ebx + mov eax, 0x7e00 + mov es, ax +1: call scan_partitions + inc dl + jnc 1b + +# Scan hard disks. + mov dl, 0x80 +1: call outw + call scan_partitions + inc dl + jnc 1b + +1: jmp 1b + +scan_partitions: + # EBX = sector number of partition table + # DL = drive number + # ES:0000 -> buffer for partition table + # Returns CF set if drive does not exist, CF clear otherwise. + call read_sector + jc no_such_drive -#### Enable A20: -#### Address line 20 is tied to low when the machine boots, -#### obviously this a bit of a drag, such as when trying to -#### address memory above 1MB. This code undoes this. +2: pusha + mov edx, [es:508] + call outw + popa -1: inb $0x64,%al # Get status - testb $0x2,%al # Busy? - jnz 1b # Yes - movb $0xd1,%al # Command: Write - outb %al,$0x64 # output port -2: inb $0x64,%al # Get status - testb $0x2,%al # Busy? - jnz 2b # Yes - movb $0xdf,%al # Enable - outb %al,$0x60 # A20 - -#### Get memory size, via interrupt 15h function 88h. -#### Returns CF clear if successful, with AX = (kB of physical memory) - 1024. -#### This only works for memory sizes <= 65 MB, which should be fine for our purposes. + cmp word ptr [es:510], 0xaa55 + jnz no_boot_partition - movb $0x88,%ah - int $0x15 - jc panic # Carry flag set on error -2: addl $1024,%eax # Total kB - shrl $2,%eax # Total 4 kB pages - movl %eax, ram_pages - -#### switch from real to protected mode -#### The segments in GDT allow all of physical memory to be accessed. -#### Furthermore, the segments have base addresses of 0, so that the -#### segment translation is a NOP, ie. virtual addresses are identical to -#### their physical addresses. With this setup, it appears to this code -#### that it is running directly on physical memory. - - cli # Mandatory since we dont set up an IDT - lgdt gdtdesc # load GDT -- mandatory in protected mode - movl %cr0, %eax # turn on protected mode - orl $CR0_PE, %eax # - movl %eax, %cr0 # - ### CPU magic: jump to relocation, flush prefetch queue, and - ### reload %cs Has the effect of just jmp to the next - ### instruction, but simultaneous loads CS with - ### $PROT_MODE_CSEG. - ljmp $SEL_KCSEG, $protcseg - -#### We are in protected mode in a 32-bit segment (hence the .code32) -protcseg: - .code32 - movw $SEL_KDSEG, %ax # set up data segment registers - movw %ax, %ds - movw %ax, %es - movw %ax, %fs - movw %ax, %gs - movw %ax, %ss - -#### Load kernel starting at physical address LOADER_KERN_BASE by -#### frobbing the IDE controller directly. - - movl $1, %ebx - movl $LOADER_KERN_BASE, %edi -read_sector: - - ### Poll status register while controller busy. - movl $0x1f7, %edx -1: inb %dx, %al - testb $0x80, %al - jnz 1b - - ### Read a single sector. - movl $0x1f2, %edx - movb $1, %al - outb %al, %dx - - ### Sector number to write in low 28 bits. - ### LBA mode, device 0 in top 4 bits. - movl %ebx, %eax - andl $0x0fffffff, %eax - orl $0xe0000000, %eax - - ### Dump %eax to ports 0x1f3...0x1f6. - movl $4, %ecx -2: incw %dx - outb %al, %dx - shrl $8, %eax - loop 2b - - ### READ command to command register. - incw %dx - movb $0x20, %al - outb %al, %dx - - ### Poll status register while controller busy. -1: inb %dx, %al - testb $0x80, %al - jnz 1b - - ### Poll status register until data ready. -1: inb %dx, %al - testb $0x08, %al - jz 1b - - ### Transfer sector. - movl $512 / 4, %ecx - movl $0x1f0, %edx - rep insl - - ### Next sector. - incl %ebx - cmpl $KERNEL_LOAD_PAGES*8 + 1, %ebx - jnz read_sector - -##### Create temporary page directory and page table, set page -##### directory pointer, and turn on paging. -##### FIXME? We could use a single 4 MB page instead of 1024 4 kB pages. - - # Create page directory at 64 kB. - movl $0x10000, %edi - movl %edi, %cr3 - - # Fill page directory with zeroes. - subl %eax, %eax - movl $0x400, %ecx - rep stosl - - # Set PDEs for 0 and LOADER_PHYS_BASE to point to the - # page table. - movl $0x11000 | PG_U | PG_W | PG_P, %eax - movl %eax, 0x10000 - movl %eax, 0x10000 | (LOADER_PHYS_BASE >> 20) - - # Initialize page table. - movl $PG_U | PG_W | PG_P, %eax - movl $0x400, %ecx -1: stosl - addl $0x1000, %eax + mov si, 446 +1: mov al, [es:si+4] + cmp al, 0x20 + jz found_boot_partition + cmp al, 0x05 + jz found_extended_partition + cmp al, 0x0f + jz found_extended_partition + cmp al, 0x85 + jz found_extended_partition + cmp al, 0xc5 + jz found_extended_partition +next_parttbl_entry: + add si, 16 + cmp si, 510 + jb 1b + +no_boot_partition: + clc + ret +no_such_drive: + stc + ret + +found_extended_partition: + # DL = drive number. + # ES:SI -> partition table entry for extended partition. + # Recursively examine it. + pusha + mov ebx, es:[si+8] + mov ax, es + add ax, 0x20 + mov es, ax + call scan_partitions + popa + jmp next_parttbl_entry + +found_boot_partition: + mov ebx, [es:si+8] # EBX = first sector + mov cx, [es:si+12] # CX = number of sectors + mov ax, 0x1000 # ES:0000 -> load address + mov es, ax +1: call read_sector + add ax, 0x20 + mov es, ax loop 1b - # Turn on paging. - movl %cr0, %eax - orl $CR0_PG, %eax - movl %eax, %cr0 - jmp 1f -1: - -##### Turn on EM bit in CR0, forcing most floating-point instructions -##### to trap. We don't support floating-point or MMX. + ljmp 0x1000, 0 - movl %cr0, %eax - orl $CR0_EM, %eax - movl %eax, %cr0 + # ebx: sector number + # dl: drive number + # es:0000: destination buffer + # returns error flag in CF +read_sector: + pusha + or dl, dl # Floppy drives: DL >= 0 + jns read_floppy_sector + +read_harddrv_sector: + sub eax, eax + push eax # LBA sector number [32:63] + push ebx # LBA sector number [0:31] + push es + push 0 + push 1 # Transfer one sector + push 16 # Packet size + mov ah, 0x42 # Extended read + mov si, sp # DS:SI -> packet + int 0x13 # Error code in CF + lahf + add sp, 16 + sahf +read_sector_done: + popa + ret # Error code in CF + +read_floppy_sector: + #define HEADS 2 + #define SECTORS 36 + + # In: BX = LBA sector number, DL = drive. + # Out: BL = drive, DX = cylinder, AL = head, AH = sector. + sub ax, ax + xchg dx, bx # DX = LBA sector number, BL = drive + mov cx, HEADS * SECTORS + div cx # AX = cyl, DX = hd + (sec-1) * SECTORS + xchg ax, dx # DX = cyl, AX = hd + (sec-1) * SECTORS + mov cl, SECTORS + div cl # AL = head, AH = sector - 1 + inc ah + + # Read sector. + mov ch, dl # CH = cylinder + mov cl, ah # CL = sector + mov dh, al # DH = head + mov dl, bl # DL = drive + mov ax, 0x0201 # AH = function, AL = sectors to read + sub bx, bx # ES:BX -> buffer + mov di, 3 # Number of tries left. -##### Jump to kernel entry point. - - movl $LOADER_PHYS_BASE + LOADER_BASE, %esp - movl $LOADER_PHYS_BASE + LOADER_KERN_BASE, %eax - jmp *%eax +try_read_floppy: + pusha + int 0x13 + popa + jnc read_sector_done + dec di + jnz 1f + stc + jmp read_sector_done + +1: # Reset floppy drive motor, try again. + pusha + sub ah, ah + int 0x13 + popa + jmp try_read_floppy + +outw: pushf + pusha + + mov cx, 8 + mov ebx, edx + mov dx, 0xe9 +1: rol ebx, 4 + mov al, bl + and al, 15 + add al, '0' + cmp al, '9' + jbe 2f + add al, 'a' - '0' - 10 +2: out dx, al + loop 1b -##### GDT + mov al, '\n' + out dx, al -gdt: - .quad 0x0000000000000000 # null seg - .quad 0x00cf9a000000ffff # code seg - .quad 0x00cf92000000ffff # data seg + popa + popf + ret + +#### The partition table goes here. + .org 446 +part_tbl: -gdtdesc: - .word 0x17 # sizeof (gdt) - 1 - .long gdt # address gdt - -##### To panic, we print panicmsg (with help from the BIOS) and spin. -panic: .code16 # We only panic in real mode. - movw $panicmsg, %si - movb $0xe, %ah - xorb %bh, %bh -1: lodsb - test %al, %al -2: jz 2b # Spin. - int $0x10 - jmp 1b - -panicmsg: - .ascii "Loader panic!\r\n" - .byte 0 - -##### Memory size in 4 kB pages. - .org LOADER_RAM_PAGES - LOADER_BASE -ram_pages: - .long 0 - -##### Command-line arguments inserted by another utility. -##### The loader doesn't use these, but we note their -##### location here for easy reference. - .org LOADER_CMD_LINE - LOADER_BASE -cmd_line: - .fill 0x80, 1, 0 - -##### Boot-sector signature for BIOS inspection. - .org LOADER_BIOS_SIG - LOADER_BASE + +#### Boot-sector signature for BIOS inspection. + .org 510 .word 0xaa55