/* * Copyright (c) 2003,2004 The DragonFly Project. All rights reserved. * * This code is derived from software contributed to The DragonFly Project * by Matthew Dillon <dillon@backplane.com> * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * 3. Neither the name of The DragonFly Project nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific, prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * Copyright (c) 1998 Robert Nordier * All rights reserved. * * Redistribution and use in source and binary forms are freely * permitted provided that the above copyright notice and this * paragraph and the following disclaimer are duplicated in all * such forms. * * This software is provided "AS IS" and without any express or * implied warranties, including, without limitation, the implied * warranties of merchantability and fitness for a particular * purpose. * * $FreeBSD: src/sys/boot/i386/boot2/boot1.s,v 1.23 2003/08/22 01:59:28 imp Exp $ */ #include "../bootasm.h" // Partition Constants .set PRT_OFF,0x1be // Partition offset .set PRT_NUM,0x4 // Partitions .set PRT_BSD,0xa5 // Partition type .set PRT_DFLY,0x6c // Partition type // Flag Bits .set FL_PACKET,0x80 // Packet mode // Misc. Constants .set SIZ_PAG,0x1000 // Page size .set SIZ_SEC,0x200 // Sector size #ifndef NSECT .set NSECT,0x10 #endif .globl start .globl xread .code16 start: jmp main // Start recognizably // This is the start of a standard BIOS Parameter Block (BPB). Most bootable // FAT disks have this at the start of their MBR. While normal BIOS's will // work fine without this section, IBM's El Torito emulation "fixes" up the // BPB by writing into the memory copy of the MBR. Rather than have data // written into our xread routine, we'll define a BPB to work around it. // The data marked with (T) indicates a field required for a ThinkPad to // recognize the disk and (W) indicates fields written from IBM BIOS code. // The use of the BPB is based on what OpenBSD and NetBSD implemented in // their boot code but the required fields were determined by trial and error. // // Note: If additional space is needed in boot1, one solution would be to // move the "prompt" message data (below) to replace the OEM ID. .org 0x03, 0x00 oemid: .space 0x08, 0x00 // OEM ID .org 0x0b, 0x00 bpb: .word 512 // sector size (T) .byte 0 // sectors/clustor .word 0 // reserved sectors .byte 0 // number of FATs .word 0 // root entries .word 0 // small sectors .byte 0 // media type (W) .word 0 // sectors/fat .word 18 // sectors per track (T) .word 2 // number of heads (T) .long 0 // hidden sectors (W) .long 0 // large sectors .org 0x24, 0x00 ebpb: .byte 0 // BIOS physical drive number (W) .org 0x25,0x90 // // Trampoline used by boot2 to call read to read data from the disk via // the BIOS. Call with: // // %cx:%ax - long - LBA to read in // %es:(%bx) - caddr_t - buffer to read data into // %dl - byte - drive to read from // %dh - byte - num sectors to read // xread: push %ss // Address pop %ds // data // // Setup an EDD disk packet and pass it to read // xread.1: // Starting pushl $0x0 // absolute push %cx // block push %ax // number push %es // Address of push %bx // transfer buffer xor %ax,%ax // Number of movb %dh,%al // blocks to push %ax // transfer push $0x10 // Size of packet mov %sp,%bp // Packet pointer callw read // Read from disk lea 0x10(%bp),%sp // Clear stack lret // To far caller // // Load the rest of boot2 and BTX up, copy the parts to the right locations, // and start it all up. // // // Setup the segment registers to flat addressing (segment 0) and setup the // stack to end just below the start of our code. // // XXX note - our origin (start) points to the MEM_BIOS_LADDR. We run // from there but boot2 later on calls xread at BOOT1_ORIGIN. // main: cld // String ops inc xor %cx,%cx // Zero mov %cx,%es // Address mov %cx,%ds // data mov %cx,%ss // Set up mov $start,%sp // stack // // Relocate ourself to BOOT1_ORIGIN. Since %cx == 0, the inc %ch sets // %cx == 0x100 (256 words == 512 bytes). // mov %sp,%si // Source mov $BOOT1_ORIGIN,%di // Destination incb %ch // Word count rep // Copy movsw // code // // If we are on a hard drive, then load the MBR and look for the first // FreeBSD slice. // // Note, we can't use the fake partition entry (part4), as it may contain // garbage if this is a normal boot1 on a slice, verses a dangerously // dedicated disk. Hardwire sector 0 to acquire the MBR // xor %ax,%ax xor %cx,%cx cmpb $0x80,%dl // Hard drive? jb main.4 // No movb $0x1,%dh // Block count callw nread_alt // Read MBR mov $0x1,%cx // Two passes main.1: mov $BOOT2_LOAD_BUF+PRT_OFF,%si // Partition table movb $0x1,%dh // Partition main.2: cmpb $PRT_BSD,0x4(%si) // FreeBSD / old DFly je main.2a cmpb $PRT_DFLY,0x4(%si) // New DFly jne main.3 // No main.2a: jcxz main.5 // If second pass testb $0x80,(%si) // Active? jnz main.5 // Yes main.3: add $0x10,%si // Next entry incb %dh // Partition cmpb $0x1+PRT_NUM,%dh // In table? jb main.2 // Yes dec %cx // Do two jcxz main.1 // passes // // If we get here, we didn't find any FreeBSD slices at all, so print an // error message and die. // jmp error // Error // // Floppies use partition 0 of drive 0. // main.4: xor %dx,%dx // Partition:drive // // Ok, we have a slice and drive in %dx now, so use that to locate and load // boot2. %si references the start of the slice we are looking for, so go // ahead and load up the first N sectors (boot1 + boot2) from that. // // N is 16 for boot1 in a disklabel32 and up to 32 in a disklabel64. The // disklabel64 can hold up to 64 sectors but MEM_BTX_USR+BOOT2_VORIGIN // will overflow the segment if we use more then 32 sectors. // // When we read it in, we conveniently use BOOT2_LOAD_BUF (0x8c00) as our // transfer buffer. Thus, boot1 ends up at 0x8c00, and boot2 starts at // 0x8c00 + 0x200 = 0x8e00. // // The first part of boot2 is the disklabel, which is 0x200 bytes long. // The second part is BTX, which is thus loaded into 0x9000, which is where // it also runs from. The boot2.bin binary starts right after the end of // BTX, so we have to figure out where the start of it is and then move the // binary to 0xc000. Normally, BTX clients start at MEM_BTX_USR, or 0xa000, // but when we use btxld to create boot2, we use an entry point of 0x2000. // That entry point is relative to MEM_BTX_USR; thus boot2.bin starts // at 0xc000. // // MEM_BTX_USR_ARG will be overwritten by the disk read and the relocation // loop, so we must store the argument after completing said loops. // main.5: pushw %dx // Save args movb $NSECT,%dh // Sector count #ifdef DISKLABEL64 // In disklabel64 boot2 starts addl $7,0x8(%si) // offset 0x1000. #endif callw nread // Read disk mov $MEM_BTX_ORG,%bx // Base of BTX header mov 0xa(%bx),%si // Get BTX text length (btx.S) add %bx,%si // %si = start of boot2.bin // %di = relocation target mov $MEM_BTX_USR+BOOT2_VORIGIN,%di mov $MEM_BTX_ORG+(NSECT-1)*SIZ_SEC,%cx sub %si,%cx // %cx = Size of boot2 client rep // Relocate boot2 movsb popw MEM_BTX_USR_ARG // save (disk,slice) for boot2 #if 0 // XXX DISABLED. This makes incorrect assumptions about // where BSS begins, potentially leaving garbage in the BSS // space. The BSS zeroing code has been moved to // btx/lib/btxcsu.S (BTX client startup code) where we have // more definitive knowledge about where BSS resides. // // %cx now contains 0. Calculate 0x[1]0000 - %di to get a // count of assumed BSS bytes from the end of boot2.bin up // to 0x10000, then zero it out. // sub %di,%cx xorb %al,%al rep stosb #endif callw seta20 // Enable A20 // YYY pushw $MEM_BTX_ENTRY // Start BTX retw /* * Enable A20. Put upper limit on amount of time we wait for the * keyboard controller to get ready (65K x ISA access time). If * we wait more than that amount it's likely that the hardware * is legacy-free and simply doesn't have keyboard controller * and don't need enabling A20 at all. */ seta20: cli # Disable interrupts xor %cx,%cx # Clear seta20.1: inc %cx # Increment, overflow? jz seta20.3 # Yes inb $0x64,%al # Get status testb $0x2,%al # Busy? jnz seta20.1 # Yes movb $0xd1,%al # Command: Write outb %al,$0x64 # output port seta20.2: inb $0x64,%al # Get status testb $0x2,%al # Busy? jnz seta20.2 # Yes movb $0xdf,%al # Enable outb %al,$0x60 # A20 seta20.3: sti # Enable interrupts retw # To caller // // Trampoline used to call read from within boot1. // nread: mov 0x8(%si),%ax // Get mov 0xa(%si),%cx // LBA nread_alt: mov $BOOT2_LOAD_BUF,%bx // Transfer buffer push %cs // Read from callw xread.1 // disk jnc return // If success, return // Print that an error occurred (no room to determine which error // occurred) and the prompt. Then wait for a keypress, then reboot the // machine. // error: mov $prompt,%si // Display callw putstr // prompt xorb %ah,%ah // BIOS: Get int $0x16 // keypress movw $0x1234, BDA_BOOT // Do a warm boot ljmp $0xf000,$0xfff0 // reboot the machine // // Display a null-terminated string using the BIOS output. // putstr.0: mov $0x7,%bx // Page:attribute movb $0xe,%ah // BIOS: Display int $0x10 // character putstr: lodsb // Get char testb %al,%al // End of string? jne putstr.0 // No // // Overused return code. ereturn is used to return an error from the // read function. Since we assume putstr succeeds, we (ab)use the // same code when we return from putstr. // ereturn: movb $0x1,%ah // Invalid stc // argument return: retw // To caller // // Reads sectors from the disk. If EDD is enabled, then check if it is // installed and use it if it is. If it is not installed or not enabled, then // fall back to using CHS. Since we use a LBA, if we are using CHS, we have to // fetch the drive parameters from the BIOS and divide it out ourselves. // Call with: // // %dl - byte - drive number // stack - 10 bytes - EDD Packet read: /* * Try EDD mode first. If not enabled or no BIOS support * exists, fall back to CHS mode. */ testb $FL_PACKET,%cs:BOOT1_ORIGIN+flags-start jz read.1 /* * BIOS: check extensions present */ mov $0x55aa,%bx push %dx movb $0x41,%ah int $0x13 pop %dx jc read.1 /* BIOS error return */ cmp $0xaa55,%bx /* check for proper magic */ jne read.1 testb $0x1,%cl /* packet interface support? */ jz read.1 /* * Issue packet command. * BIOS: Extended read command */ mov %bp,%si movb $0x42,%ah int $0x13 retw /* * Fallback to CHS mode */ read.1: push %dx // Save movb $0x8,%ah // BIOS: Get drive int $0x13 // parameters movb %dh,%ch // Max head number pop %dx // Restore jc return // If error andb $0x3f,%cl // Sectors per track jz ereturn // If zero cli // Disable interrupts mov 0x8(%bp),%eax // Get LBA push %dx // Save movzbl %cl,%ebx // Divide by xor %edx,%edx // sectors div %ebx // per track movb %ch,%bl // Max head number movb %dl,%ch // Sector number inc %bx // Divide by xorb %dl,%dl // number div %ebx // of heads movb %dl,%bh // Head number pop %dx // Restore cmpl $0x3ff,%eax // Cylinder number supportable? sti // Enable interrupts ja ereturn // No, failed xchgb %al,%ah // Set up cylinder rorb $0x2,%al // number orb %ch,%al // Merge inc %ax // sector xchg %ax,%cx // number movb %bh,%dh // Head number subb %ah,%al // Sectors this track mov 0x2(%bp),%ah // Blocks to read cmpb %ah,%al // To read jb read.2 // this #ifdef TRACK_AT_A_TIME movb %ah,%al // track #else movb $1,%al // one sector #endif read.2: mov $0x5,%di // Try count read.3: les 0x4(%bp),%bx // Transfer buffer push %ax // Save movb $0x2,%ah // BIOS: Read int $0x13 // from disk pop %bx // Restore jnc read.4 // If success dec %di // Retry? jz read.6 // No xorb %ah,%ah // BIOS: Reset int $0x13 // disk system xchg %bx,%ax // Block count jmp read.3 // Continue read.4: movzbw %bl,%ax // Sectors read add %ax,0x8(%bp) // Adjust jnc read.5 // LBA, incw 0xa(%bp) // transfer read.5: shlb %bl // buffer add %bl,0x5(%bp) // pointer, sub %al,0x2(%bp) // block count ja read.1 // If not done read.6: retw // To caller // Messages prompt: .asciz " error\r\n" flags: .byte FLAGS // Flags .org PRT_OFF,0x90 // Partition table // // THIS MAY NOT BE WRITTEN OUT TO THE BOOT1 AREA OF THE DISKLABEL. This // section is only written out when the disklabel is placed on the raw // disk instead of in a slice, when creating a dangerously dedicated disk. .fill 0x30,0x1,0x0 part4: .byte 0x80, 0x00, 0x01, 0x00 .byte 0xa5, 0xfe, 0xff, 0xff .byte 0x00, 0x00, 0x00, 0x00 .byte 0x50, 0xc3, 0x00, 0x00 // 50000 sectors long, bleh .word 0xaa55 // Magic number
