| /* ----------------------------------------------------------------------- |
| * |
| * Copyright 2007-2009 H. Peter Anvin - All Rights Reserved |
| * Copyright 2009 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 |
| |
| /* BootGUID */ |
| bootguid = _start + 0x1a8 |
| /* 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: |
| cli |
| xorw %ax, %ax |
| 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 */ |
| |
| /* 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 |
| 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) |
| |
| 1: |
| popw %dx |
| |
| /* Get (C)HS geometry */ |
| movb $0x08, %ah |
| int $0x13 |
| andw $0x3f, %cx /* Sector count */ |
| movw %sp, %bp /* %bp -> frame pointer: LEAVE UNCHANGED */ |
| pushw %cx /* -2(%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 /* -4(%bp) High word */ |
| pushw %ax /* -6(%bp) Low word */ |
| |
| /* Load partition table header */ |
| xorl %eax,%eax |
| cltd |
| incw %ax /* %edx:%eax = 1 */ |
| movw $phdr, %bx |
| pushw %bx /* -8(%bp) phdr == bootsect */ |
| call read_sector |
| |
| /* Number of partition sectors */ |
| /* We assume the partition table is 32K or less, and that |
| the sector size is 512. */ |
| /* Note: phdr == 6(%bp) */ |
| movw (80+6)(%bp),%cx /* NumberOfPartitionEntries */ |
| movw (84+6)(%bp),%ax /* SizeOfPartitionEntry */ |
| pushw %ax |
| pushw %cx |
| mulw %cx |
| shrw $9,%ax |
| 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 |
| call inc64 |
| loopw get_ptab |
| |
| /* Find the boot partition */ |
| popw %si /* Partition table in memory */ |
| popw %cx /* NumberOfPartitionEntries */ |
| popw %ax /* SizeOfPartitionEntry */ |
| find_part: |
| pushw %cx |
| pushw %si |
| addw $16,%si |
| movw $bootguid,%di |
| movw $8,%cx |
| repe; cmpsw |
| popw %si |
| popw %cx |
| je found_part |
| addw %ax,%si |
| loopw find_part |
| |
| call error |
| .ascii "Boot partition not found\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 $0xee,%al |
| stosl |
| movl 32(%si),%eax |
| movl 36(%si),%edx |
| call saturate_stosl /* Partition start */ |
| |
| movl 40(%si),%eax |
| movl 48(%si),%edx |
| subl 32(%si),%eax |
| sbbl 36(%si),%edx |
| call inc64 |
| call saturate_stosl /* Partition length */ |
| |
| 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+16)(%si),%eax |
| movl (36+16)(%si),%edx |
| popw %bx |
| call read_sector |
| cmpw $0xaa55, -2(%bx) |
| 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 */ |
| |
| missing_os: |
| call error |
| .ascii "OS not bootable\r\n" |
| |
| saturate_stosl: |
| pushl %eax |
| andl %edx,%edx |
| jz 1f |
| orl $-1,%eax |
| 1: stosl |
| popl %eax |
| ret |
| |
| inc64: |
| addl $1,%eax |
| adcl $0,%edx |
| ret |
| |
| /* |
| * read_sector: read a single sector pointed to by %edx:%eax to |
| * %es:%bx. CF is set on error. All registers saved. |
| */ |
| 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 -6(%bp) /* secpercyl */ |
| shlb $6, %ah |
| movb %ah, %cl |
| movb %al, %ch |
| xchgw %dx, %ax |
| divb -2(%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 $2, %bh /* bx += 512: point to the next buffer */ |
| ret |
| |
| disk_error: |
| call error |
| .ascii "Disk error on boot\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 |
