X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fthreads%2Floader.S;h=58fb837aec5471c90f57a78354189b3c841bec55;hb=fba4443410241dd95c25a0fd7c5f8c0d8ff30ada;hp=f2563bb149af8b64c46a07473b3ec1d80906cd1c;hpb=750d21936d284127e265d050ccbce76fca1ece1a;p=pintos-anon diff --git a/src/threads/loader.S b/src/threads/loader.S index f2563bb..58fb837 100644 --- a/src/threads/loader.S +++ b/src/threads/loader.S @@ -1,169 +1,217 @@ -#include "mmu.h" +/* This file is derived from source code used in MIT's 6.828 + course. The original copyright notice is reproduced in full + below. */ + +/* + * Copyright (C) 1997 Massachusetts Institute of Technology + * + * This software is being provided by the copyright holders under the + * following license. By obtaining, using and/or copying this software, + * you agree that you have read, understood, and will comply with the + * following terms and conditions: + * + * Permission to use, copy, modify, distribute, and sell this software + * and its documentation for any purpose and without fee or royalty is + * hereby granted, provided that the full text of this NOTICE appears on + * ALL copies of the software and documentation or portions thereof, + * including modifications, that you make. + * + * THIS SOFTWARE IS PROVIDED "AS IS," AND COPYRIGHT HOLDERS MAKE NO + * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED. BY WAY OF EXAMPLE, + * BUT NOT LIMITATION, COPYRIGHT HOLDERS MAKE NO REPRESENTATIONS OR + * WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE OR + * THAT THE USE OF THE SOFTWARE OR DOCUMENTATION WILL NOT INFRINGE ANY + * THIRD PARTY PATENTS, COPYRIGHTS, TRADEMARKS OR OTHER RIGHTS. COPYRIGHT + * HOLDERS WILL BEAR NO LIABILITY FOR ANY USE OF THIS SOFTWARE OR + * DOCUMENTATION. + * + * The name and trademarks of copyright holders may NOT be used in + * advertising or publicity pertaining to the software without specific, + * written prior permission. Title to copyright in this software and any + * associated documentation will at all times remain with copyright + * holders. See the file AUTHORS which should have accompanied this software + * for a list of all copyright holders. + * + * This file may be derived from previously copyrighted software. This + * copyright applies only to those changes made by the copyright + * holders listed in the AUTHORS file. The rest of this file is covered by + * the copyright notices, if any, listed below. + */ + +#include "threads/loader.h" -################################################################################### -# ENTRY POINT -# 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 jumps to the beginning of it, in real-mode (BIOS runs in real mode). -# -# This code switches into protected mode (32-bit mode) so that all of -# memory can accessed, then calls into C. -################################################################################### + .intel_syntax noprefix -.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. + +#### 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. -#### 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. - -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. - - movb $0x88,%ah - int $0x15 - jc panic # Carry flag set on error - 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 at 1 MB by frobbing the IDE controller directly. - - movl $1, %ebx - movl $0x100000, %edi -read_sector: - movl $0x1f7, %edx -1: inb %dx, %al - testb $0x80, %al - jnz 1b - - movl $0x1f2, %edx - movb $1, %al - outb %al, %dx - - movl %ebx, %eax - andl $0x0fffffff, %eax - orl $0xe0000000, %eax - - movl $4, %ecx -2: incl %edx - outb %al, %dx - shrl $8, %eax - loop 2b - - incw %dx - movb $0x20, %al - outb %al, %dx - -1: inb %dx, %al - testb $0x80, %al - jnz 1b - - movl $512 / 4, %ecx - movl $0x1f0, %edx - rep insl - - incl %ebx - cmpl $KERNEL_LOAD_PAGES*8 + 1, %ebx - jnz read_sector - -##### Create temporary PDE and PTE and set page directory pointer -##### FIXME? We could use a single 4 MB page instead of 1024 4 kB pages. - - movl $0x10000, %edi - movl %edi, %cr3 - subl %eax, %eax - movl $0x400, %ecx - rep stosl - movl $0x11000 | PG_U | PG_W | PG_P, %eax - movl %eax, 0x10000 - movl %eax, 0x10c00 - movl $PG_U | PG_W | PG_P, %eax - movl $0x400, %ecx -1: stosl - addl $0x1000, %eax - loop 1b - -##### Enable paging. +/* Flags in control register 0. */ +#define CR0_PE 0x00000001 /* Protection Enable. */ +#define CR0_EM 0x00000004 /* (Floating-point) Emulation. */ +#define CR0_PG 0x80000000 /* Paging. */ +#define CR0_WP 0x00010000 /* Write-Protect enable in kernel mode. */ - movl %cr0, %eax - orl $CR0_PG, %eax - movl %eax, %cr0 - jmp 1f -1: - -##### Jump to kernel entry point. +# Code runs in real mode, which is a 16-bit segment. - movl $0xc0007c00, %esp - movl $0xc0100000, %eax - jmp *%eax +.globl start +start: + .code16 -##### GDT +# Set up segment registers. +# Stack grows downward starting from us. -gdt: - .quad 0x0000000000000000 # null seg - .quad 0x00cf9a000000ffff # code seg - .quad 0x00cf92000000ffff # data seg + sub ax, ax + mov ds, ax + mov ss, ax + mov sp, 0x7c00 -gdtdesc: - .word 0x17 # sizeof (gdt) - 1 - .long gdt # address gdt - -##### Arrive here on error -panic: jmp panic +# 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 scan_partitions + inc dl + jnc 1b + + call panic + .asciz "No boot partition" + +scan_partitions: + # EBX = sector number of partition table + # DL = drive number + # ES:0000 -> buffer for partition table + # Returns CF set if drive exists, CF clear otherwise. + call read_sector + jnc no_such_drive +2: cmp word ptr [es:510], 0xaa55 + jnz no_boot_partition + + 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 -##### Memory size in 4 kB pages. - .org 0x200 - 8 -ram_pages: - .long 0 + ljmp 0x1000, 0 + + # 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 + js read_floppy_sector + +read_harddrv_sector: + sub eax, eax + push eax # LBA sector number [32:63] + push ebx # LBA sector number [0:31] + mov ax, es + shl eax, 4 + push eax # Buffer linear address + 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 +success: + 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 + pusha + int 0x13 + popa + jnc success + + # Reset floppy drive motor, try again. + sub ah, ah + int 0x13 + popa + jmp read_sector + +#### The partition table goes here. + .org 446 +part_tbl: -##### Boot-sector signature for BIOS inspection. - .org 0x200 - 2 +#### Boot-sector signature for BIOS inspection. + .org 510 .word 0xaa55