From e0298c88e927849e7f10d4dd0318907886cd50a1 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Mon, 25 Feb 2008 14:22:54 -0800 Subject: Master boot record for GPT partition tables Beginnings of a master boot record for GPT partition tables. --- mbr/Makefile | 9 +- mbr/gptmbr.S | 284 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 292 insertions(+), 1 deletion(-) create mode 100644 mbr/gptmbr.S diff --git a/mbr/Makefile b/mbr/Makefile index a64869b1..ed33aedf 100644 --- a/mbr/Makefile +++ b/mbr/Makefile @@ -29,7 +29,7 @@ PERL = perl .SUFFIXES: .S .s .o .elf -all: mbr.bin +all: mbr.bin gptmbr.bin .PRECIOUS: %.o %.o: %.S @@ -42,6 +42,13 @@ mbr.bin: mbr.elf checksize.pl $(OBJCOPY) -O binary $< $@ $(PERL) checksize.pl mbr.bin 440 +gptmbr.elf: gptmbr.o mbr.ld + $(LD) -T mbr.ld -e _start -o $@ $< + +gptmbr.bin: gptmbr.elf checksize.pl + $(OBJCOPY) -O binary $< $@ + $(PERL) checksize.pl gptmbr.bin 424 + tidy: rm -f *.o *.elf *.lst diff --git a/mbr/gptmbr.S b/mbr/gptmbr.S new file mode 100644 index 00000000..a6b2607e --- /dev/null +++ b/mbr/gptmbr.S @@ -0,0 +1,284 @@ +/* ----------------------------------------------------------------------- + * + * Copyright 2007-2008 H. Peter Anvin - All Rights Reserved + * + * 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. + * + * ----------------------------------------------------------------------- */ + + .code16 + .text + + .globl bootsec +stack = 0x7c00 +driveno = (stack-6) +sectors = (stack-8) +secpercyl = (stack-12) + +/* Partition table header here */ +phdr = _start + 512 +/* Partition table sector here */ +/* To handle > 32K we need to play segment tricks... */ +psec = 0x8000 /* Above the boot sector and stack */ + +/* BootGUID */ +bootguid = _start + 0x1a8 +/* Where we put DS:SI */ +dssi_out = _start + 0x1be + +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 /* es:di -> $PnP header */ + pushw %di + pushw %dx /* dl -> drive number */ + movw %ax, %es + sti + cld + + /* Copy down to 0:0x600 */ + movw $_start, %di + movw $(512/2), %cx + rep; movsw + + ljmpw $0, $next + +next: + /* 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 */ + pushw %cx /* 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 /* High word */ + pushw %ax /* Low word */ + + /* Load partition table header */ + xorl %eax,%eax + xorl %edx,%edx + incl %eax + movw $phdr,%bx + call read_sector + + /* Number of partition sectors */ + /* We assume the partition table is 32K or less, and that + the sector size is 512. */ + movw (phdr+0x80),%cx /* NumberOfPartitionEntries */ + movw (phdr+0x84),%ax /* SizeOfPartitionEntry */ + pushw %ax + pushw %cx + mulw %cx + shrw $9,%ax + xchgw %ax,%cx + incw %cx + + /* Starting LBA of partition array */ + movl (phdr+0x72),%eax + movl (phdr+0x76),%edx + + movw $psec,%bx + pushw %bx +get_ptab: + call read_sector + addw $512,%bx + 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 + rep; 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: + movw $dssi_out+16,%di + movw %ax,%cx + rep; movsb + movw $dssi_out,%si + movw %si,%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 (40+16)(%si),%eax + movl (48+16)(%si),%edx + pushl %eax + pushl %edx + call saturate_stosl /* Partition start */ + + subl (32+16)(%si),%eax + sbbl (36+16)(%si),%edx + call inc64 + call saturate_stosl /* Partition length */ + +/* + * boot: invoke the actual bootstrap. (%si) points to the + * partition information in memory, and the block offset is + * on the stack. + */ +boot: + popl %edx + popl %eax + call read_sector + cmpw $0xaa55, (bootsec+510) + jne missing_os /* Not a valid boot sector */ + movw $driveno, %sp /* driveno == bootsec-6 */ + popw %dx /* dl -> drive number */ + popw %di /* es:di -> $PnP vector */ + popw %es + cli + jmpw *%sp /* %sp == bootsec */ + +missing_os: + call error + .ascii "Operating system 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 (secpercyl) + shlb $6, %ah + movb %ah, %cl + movb %al, %ch + xchgw %dx, %ax + divb (sectors) + movb %al, %dh + orb %ah, %cl + incw %cx /* Sectors are 1-based */ + movw $0x0201, %ax + +read_common: + movb (driveno), %dl + int $0x13 + addw $16, %sp /* Drop DAPA */ + popal + jc disk_error + 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 -- cgit v1.2.1