/* ----------------------------------------------------------------------- * * Copyright 2007-2009 H. Peter Anvin - All Rights Reserved * Copyright 2009-2010 Intel Corporation; author: H. Peter Anvin * * Permission is hereby granted, free of charge, to any person * obtaining a copy of this software and associated documentation * files (the "Software"), to deal in the Software without * restriction, including without limitation the rights to use, * copy, modify, merge, publish, distribute, sublicense, and/or * sell copies of the Software, and to permit persons to whom * the Software is furnished to do so, subject to the following * conditions: * * The above copyright notice and this permission notice shall * be included in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. * * ----------------------------------------------------------------------- */ #include "adjust.h" .code16 .text .globl bootsec stack = 0x7c00 /* Partition table header here */ phdr = stack /* Above the stack, overwritten by bootsect */ /* Partition table sector here */ /* To handle > 32K we need to play segment tricks... */ psec = _phdr + 512 /* Where we put DS:SI */ dssi_out = _start + 0x1be BIOS_kbdflags = 0x417 BIOS_page = 0x462 /* gas/ld has issues with doing this as absolute addresses... */ .section ".bootsec", "a", @nobits .globl bootsec bootsec: .space 512 .text .globl _start _start: .byte 0x33, 0xc0 /* xorw %ax, %ax */ cli movw %ax, %ds movw %ax, %ss movw $stack, %sp movw %sp, %si pushw %es /* 4(%bp) es:di -> $PnP header */ pushw %di /* 2(%bp) */ movw %ax, %es sti cld /* Copy down to 0:0x600 */ movw $_start, %di movw $(512/2), %cx rep; movsw ljmpw $0, $next next: ADJUST_DRIVE pushw %dx /* 0(%bp) = %dl -> drive number */ movw %sp, %bp /* %bp -> frame pointer: LEAVE UNCHANGED */ /* prepare to read sector size */ sub $0x1c, %sp /* -28(%bp) == %sp */ pushw $0x1e /* -30(%bp) == %sp */ movw $0x200, -6(%bp) /* -6(%bp) sector size */ /* Check to see if we have EBIOS */ pushw %dx /* drive number */ movb $0x41, %ah /* %al == 0 already */ movw $0x55aa, %bx xorw %cx, %cx xorb %dh, %dh stc int $0x13 popw %dx /* restore drive */ movb $0x08, %ah /* get CHS geometry */ jc 1f cmpw $0xaa55, %bx jne 1f shrw %cx /* Bit 0 = fixed disk subset */ jnc 1f /* We have EBIOS; patch in the following code at read_sector_cbios: movb $0x42, %ah ; jmp read_common */ movl $0xeb42b4+((read_common-read_sector_cbios-4) << 24), \ (read_sector_cbios) /* * read sector size. * Should not fail but if it does I assume that at least * previous 512 value is not overridden */ movb $0x48, %ah movw %sp, %si 1: /* Get (C)HS geometry */ int $0x13 /* here we computer CHS values or just do some dummy computation for EBIOS */ andw $0x3f, %cx /* Sector count */ pushw %cx /* -32(%bp) Save sectors on the stack */ movzbw %dh, %ax /* dh = max head */ incw %ax /* From 0-based max to count */ mulw %cx /* Heads*sectors -> sectors per cylinder */ /* Save sectors/cylinder on the stack */ pushw %dx /* -34(%bp) High word */ pushw %ax /* -36(%bp) Low word */ /* Load partition table header */ xorl %eax,%eax cltd incw %ax /* %edx:%eax = 1 */ call read_sector_phdr /* Number of partition sectors */ /* We assume the partition table is 32K or less */ movw (80+6)(%bp),%cx /* NumberOfPartitionEntries */ movw (84+6)(%bp),%ax /* SizeOfPartitionEntry */ pushw %ax pushw %cx mulw %cx divw -6(%bp) /* %dx == 0 here */ xchgw %ax,%cx incw %cx /* Starting LBA of partition array */ movl (72+6)(%bp),%eax movl (76+6)(%bp),%edx pushw %bx get_ptab: call read_sector loopw get_ptab /* Find the boot partition */ xorw %si,%si /* Nothing found yet */ popw %di /* Partition table in memory */ popw %cx /* NumberOfPartitionEntries */ popw %ax /* SizeOfPartitionEntry */ find_part: /* If the PartitionTypeGUID is all zero, it's an empty slot */ movl (%di),%edx orl 4(%di),%edx orl 8(%di),%edx orl 12(%di),%edx jz not_this testb $0x04,48(%di) jz not_this andw %si,%si jnz found_multiple movw %di,%si not_this: addw %ax,%di loopw find_part andw %si,%si jnz found_part missing_os: call error .ascii "Missing OS\r\n" found_multiple: call error .ascii "Multiple active partitions\r\n" found_part: xchgw %ax,%cx /* Set up %cx for rep movsb further down */ movw $dssi_out,%di pushw %di /* 80 00 00 00 ee 00 00 00 - bootable partition, type EFI (EE), no CHS information */ xorl %eax,%eax movb $0x80,%al stosl movb $0xed,%al stosl movl 32(%si),%eax movl 36(%si),%edx call saturate_stosl /* Partition start */ movl 40(%si),%eax movl 44(%si),%edx subl 32(%si),%eax sbbl 36(%si),%edx call inc64 call saturate_stosl /* Partition length */ movzwl %cx,%eax /* Length of GPT entry */ stosl rep; movsb /* GPT entry follows MBR entry */ popw %si /* * boot: invoke the actual bootstrap. %ds:%si points to the * partition information in memory. The top word on the stack * is phdr == 0x7c00 == the address of the boot sector. */ boot: movl (32+20)(%si),%eax movl (36+20)(%si),%edx call read_sector_phdr cmpw $0xaa55, (0x7c00+0x1fe) jne missing_os /* Not a valid boot sector */ movw %bp, %sp /* driveno == bootsec-6 */ popw %dx /* dl -> drive number */ popw %di /* es:di -> $PnP vector */ popw %es movl $0x54504721,%eax /* !GPT magic number */ cli jmpw *%sp /* %sp == bootsec */ /* * Store the value in %eax to %di iff %edx == 0, otherwise store -1. * Returns the value that was actually written in %eax. */ saturate_stosl: andl %edx,%edx jz 1f orl $-1,%eax 1: stosl ret read_sector_phdr: movw $phdr, %bx /* fall through and read sector */ /* * read_sector: read a single sector pointed to by %edx:%eax to * %es:%bx. CF is set on error. All registers saved. * %edx:%eax and %es:%bx are incremented to read next sector */ read_sector: pushal pushl %edx /* MSW of LBA */ pushl %eax /* LSW of LBA */ pushw %es /* Buffer segment */ pushw %bx /* Buffer offset */ pushw $1 /* Sector count */ pushw $16 /* Size of packet */ movw %sp, %si /* This chunk is skipped if we have ebios */ /* Do not clobber %es:%bx or %edx:%eax before this chunk! */ read_sector_cbios: divl -36(%bp) /* secpercyl */ shlb $6, %ah movb %ah, %cl movb %al, %ch xchgw %dx, %ax divb -32(%bp) /* sectors */ movb %al, %dh orb %ah, %cl incw %cx /* Sectors are 1-based */ movw $0x0201, %ax read_common: movb (%bp), %dl /* driveno */ int $0x13 leaw 16(%si), %sp /* Drop DAPA */ popal jc disk_error addb -5(%bp), %bh /* bx += sector size: point to the next buffer */ /* fall through and increment sector number */ /* * Increment %edx:%eax */ inc64: addl $1,%eax adcl $0,%edx ret disk_error: call error .ascii "Disk error\r\n" /* * Print error messages. This is invoked with "call", with the * error message at the return address. */ error: popw %si 2: lodsb movb $0x0e, %ah movb (BIOS_page), %bh movb $0x07, %bl int $0x10 /* May destroy %bp */ cmpb $10, %al /* Newline? */ jne 2b int $0x18 /* Boot failure */ die: hlt jmp die