📄 bootlace.inc
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movl 0x14(iSI), %eax /* s_first_data_block */ incw %ax stosl /* Machine code begins at offset 0x30, 462 bytes plus * 2 bytes of boot signature */ movl $ABS(_start1 + 0x830), %esi lodsl movb ABS(floppy), %cl /* partition number(0xFF for floppy) */ cmpb $0xff, %cl jne 10f /* real floppy */ cmpl $0x90C031FC, %eax /* FC=cld; 31 C0=xor ax,ax; 90=nop */ jne 10f movl $0x99C031FC, %eax /* FC=cld; 31 C0=xor ax,ax; 99=cwd */10: stosl movl $((464 / 4) - 1), %ecx repz movsl movl $1, ABS(sectors_to_write) movl $ABS(msg_fstype_ext2_allow), %ecx call 8f /* linux_print */ clc popal ret1: /* Secondly, try FAT12/16/32/NTFS */ cld cmpw $0xAA55, 0x1fe(iSI) /* boot signature */ jne 1f /* not a normal BPB */ cmpw $0x200, 0x0b(iSI) /* bytes per sector */ jne 1f /* not a normal BPB */ movb 0x0d(iSI), %al /* sectors per cluster */ testb %al, %al jz 1f /* invalid if = 0 */ movb %al, %cl movw $128, %ax divb %cl /* quo=AL, rem=AH */ testb %ah, %ah jnz 1f /* invalid if not 2^n */ movw 0x18(iSI), %ax /* sectors per track */ testw %ax, %ax jz 1f /* invalid if = 0 */ cmpw $63, %ax ja 1f /* invalid if > 63 */ movw 0x1a(iSI), %ax /* number of heads */ decw %ax /* Max head number, should be a byte */ testb %ah, %ah /* should be 0 */ jnz 1f /* invalid if number of heads > 256 */ cmpb $0xf0, 0x15(iSI) /* media descriptor */ jb 1f// movw $0x0600, %bx /* FAT12/FAT16 */// movw $0x003c, %cx /* FAT12/FAT16 */ movb 0x10(iSI), %al /* number of FATs(NTFS:0, FAT:1,2) */ cmpb $2, %al ja 1f /* abnormal FAT */ movw 0x11(iSI), %ax /* max root entries */ testw %ax, %ax jnz 2f /* FAT12/FAT16 */ /* FAT32 or NTFS */ movw 0x13(iSI), %ax /* total sectors(small) */ testw %ax, %ax jnz 1f /* invalid FAT32 BPB */ movw 0x16(iSI), %ax /* sectors per FAT(small) */ testw %ax, %ax jnz 1f /* invalid FAT32 BPB */ movb 0x10(iSI), %al /* number of FATs(NTFS:0, FAT:1,2) */ testb %al, %al jz 4f /* NTFS */ /* FAT32 */ movl 0x20(iSI), %eax /* FAT32 total sectors */ testl %eax, %eax jz 1f movl 0x24(iSI), %eax /* FAT32 sectors per FAT */ testl %eax, %eax jz 1f /* sure it is FAT32 */ /* is FAT32 allowed write? */ testl $0x04, ABS(fstypes) jnz 3f /* FAT32 write not allowed */ movl $0, ABS(sectors_to_write) movl $ABS(msg_fstype_fat32_deny), %ecx call 8f /* linux_print */ stc popal ret3: /* write to FAT32 boot area */ cld movl $ABS(_start1 + 0x400), %esi /* points to the 3rd sector */ movl $ABS(mbr_63_sectors), %edi lodsw /* The first 2 byte: short jmp */ //leal 0x400(%edi), %esi /* ESI points to super block */ stosw /* check lba-chs-mode specified, 1 byte */ cmpl $-1, ABS(lba) /* lba-chs-mode not specified? */ je 3f /* yes, do nothing. */ movb $0x0e, %al /* initialize to lba mode. */ cmpl $0, ABS(lba) /* chs ? */ jnz 10f /* no, it is not chs.*/ movb $0x90, %al /* yes, it is chs. */10: stosb decl %edi3: addl $(1+8+2+1+2+1+2+2+1+2), %edi addl $(1+8+2+1+2+1+2+2+1+2), %esi /* skip 8-byte OEM name and Bytes per sector */ /* and Sectors per cluster, byte */ /* and Reserved sectors, word */ /* and Number of FATs, byte */ /* (Max root dir entries)Must be 0, word */ /* (Total sectors small)Must be 0, word */ /* Media descriptor, byte */ /* (Sectors per FAT)Must be 0, word */ /* sectors per track, word */ lodsw addl $2, %edi cmpl $0xffffff3f, ABS(sectors_per_track) je 3f movb ABS(sectors_per_track), %al cbw subl $2, %edi stosw3: /* number of heads, word */ lodsw addl $2, %edi cmpl $0xffff00ff, ABS(heads) je 3f movw ABS(heads), %ax subl $2, %edi stosw3: /* hidden sectors(i.e., partition start), dword */ lodsl addl $4, %edi cmpl $0xffffffff, ABS(start_sector) je 3f movl ABS(start_sector), %eax subl $4, %edi stosl3: /* total sectors, dword */ lodsl addl $4, %edi cmpl $0, ABS(total_sectors) je 3f movl ABS(total_sectors), %eax subl $4, %edi stosl3: /* FAT32 sectors per FAT, dword, etc... */ addl $(4+2+2+4+2+2+12+1+1+1+4+11+8), %esi addl $(4+2+2+4+2+2+12+1+1+1+4+11+8), %edi //movl $0xFFB6FCFA, %eax /* CLI, CLD, MOV DH,FF */ lodsw stosw lodsb stosb lodsb //decl %edi /* partition number, byte */ movb ABS(floppy), %al stosb /* Machine code begins at offset 0x5e, 416 bytes without * the ending 2 bytes of boot signature */ //movl $ABS(_start1 + 0x45e), %esi movl $(416 / 4), %ecx repz movsl movl $1, ABS(sectors_to_write) movl $ABS(msg_fstype_fat32_allow), %ecx call 8f /* linux_print */ clc popal ret4: /* NTFS */ movl 0x20(iSI), %eax /* FAT32 total sectors */ testl %eax, %eax jnz 1f //movw 0x11(%si), %ax /* max root entries */ //testw %ax, %ax //jnz 1f movw 0x0e(iSI), %ax /* reserved sectors */ testw %ax, %ax jnz 1f /* sure it is NTFS */ /* is NTFS allowed write? */ testl $0x08, ABS(fstypes) jnz 3f /* NTFS write not allowed */ movl $0, ABS(sectors_to_write) movl $ABS(msg_fstype_ntfs_deny), %ecx call 8f /* linux_print */ stc popal ret3:#if 1 /* write to NTFS boot area */ cld movl $ABS(_start1 + 0xA00), %esi /* points to the 6th sector */ movl $ABS(mbr_63_sectors), %edi lodsw /* The first 2 byte: short jmp */ stosw /* check lba-chs-mode specified, 1 byte */ cmpl $-1, ABS(lba) /* lba-chs-mode not specified? */ je 3f /* yes, do nothing. */ movb $0x0e, %al /* initialize to lba mode. */ cmpl $0, ABS(lba) /* chs ? */ jnz 10f /* no, it is not chs.*/ movb $0x90, %al /* yes, it is chs. */10: stosb decl %edi3: addl $(1+8+2+1+2+1+2+2+1+2), %edi addl $(1+8+2+1+2+1+2+2+1+2), %esi /* skip 8-byte OEM name and Bytes per sector */ /* and Sectors per cluster, byte */ /* and Reserved sectors, word */ /* and Number of FATs, byte */ /* (Max root dir entries)Must be 0, word */ /* (Total sectors small)Must be 0, word */ /* Media descriptor, byte */ /* (Sectors per FAT)Must be 0, word */ /* sectors per track, word */ lodsw addl $2, %edi cmpl $0xffffff3f, ABS(sectors_per_track) je 3f movb ABS(sectors_per_track), %al cbw subl $2, %edi stosw3: /* number of heads, word */ lodsw addl $2, %edi cmpl $0xffff00ff, ABS(heads) je 3f movw ABS(heads), %ax subl $2, %edi stosw3: /* hidden sectors(i.e., partition start), dword */ lodsl addl $4, %edi cmpl $0xffffffff, ABS(start_sector) je 3f movl ABS(start_sector), %eax subl $4, %edi stosl3: addl $(4+1+1+1+1+8), %esi addl $(4+1+1+1+1+8), %edi /* total sectors, unused, dword */ /* drive number, byte, and another 3 bytes; Usually 80 00 80 00 */ /* Number of sectors in the volume, qword */ //lodsl //lodsl //addl $8, %edi cmpl $0, ABS(total_sectors) je 3f movl ABS(total_sectors), %eax subl $8, %edi stosl xorl %eax, %eax /* high 32 bits */ stosl3: addl $(8+8+4+4+8+4), %esi addl $(8+8+4+4+8+4), %edi /* 30 - LCN of VCN 0 of the $MFT, qword */ /* 38 - LCN of VCN 0 of the $MFTMirr, qword */ /* 40 - Clusters per MFT Record, dword */ /* 44 - Clusters per Index Record, dword */ /* 48 - Volume serial number, qword */ /* 50 - Checksum, usually 0, dword */ //movl $0xFFB6FCFA, %eax /* CLI, CLD, MOV DH,FF */ lodsw stosw lodsb stosb lodsb //decl %edi /* partition number, byte */ movb ABS(floppy), %al stosb /* Machine code begins at offset 0x58, ending at 0x7FF, where * we assume that NTFS boot record takes up 4 sectors. */ movl $((0x800 - 0x58)/ 4), %ecx repz movsl movl $4, ABS(sectors_to_write) movl $ABS(msg_fstype_ntfs_allow), %ecx call 8f /* linux_print */ clc popal ret#else /* write to NTFS boot area */ movl $ABS(mbr_63_sectors), %edi LEAL 0x400(%edi), %esi /* ESI points to super block */ /* hidden sectors(i.e., partition start), dword */ cmpl $0xffffffff, ABS(start_sector) je 3f movl ABS(start_sector), %eax movl %eax, 0x1c(iDI)3: /* drive number needn't touch */ /* partition number */ call 4f jc 5f movl 0x06(iSI), %eax /* NT 4 */ cmpl $0x03E8B800, %eax /* MOV ES,AX */ jnz 3f cmpl $0x680007E8, 0x84(iDI) /* call 008e; push (0D00) */ jnz 3f movb $0xB6, %al /* 0xB6="MOV DH,imm8" */ movb ABS(floppy), %ah /* partition number */ movw %ax, 0x0a(iSI) movl $4, ABS(sectors_to_write) movl $ABS(msg_fstype_ntfs_allow), %ecx call 8f /* linux_print */ clc popal ret3: /* NT 5.0 */ cmpl $0x680053E8, 0x71(iDI) /* call 00C7; push (0D00) */ jnz 5f movl $0x4b, %ebx movl (iBX, iSI), %eax /* NT 5 */ cmpl $0x03E8B800, %eax /* MOV ES,AX */ jz 3f movl $0x79, %ebx movl (iBX, iSI), %eax /* NT 5p */ cmpl $0x03E8B800, %eax /* MOV ES,AX */ jnz 5f3: movb $0xB6, %al /* 0xB6="MOV DH,imm8" */ movb ABS(floppy), %ah /* partition number */ movw %ax, 4(iBX, iSI) movl $4, ABS(sectors_to_write) movl $ABS(msg_fstype_ntfs_allow), %ecx call 8f /* linux_print */ clc popal ret5: /* No NTFS boot record present */ movl $0, ABS(sectors_to_write) movl $ABS(msg_no_ntfs_boot_record), %ecx call 8f /* linux_print */ stc popal ret4: /* change NT to GR */ pushal cld movl $0x00520047, 0x202(iDI) /* G R L D R */ addl $0x0100, %edi movl $0x00fa, %ecx movw $0x014e, %ax /* AL="N", AH=Carry for SAHF below */ movl $0x52444c54, %ebx /* "TLDR" */3: repnz scasb /* find "N" */ jcxz 4f /* gets the end, exit */ cmpl %ebx, (iDI) /* is it "NTLDR"? */ jnz 3b /* no, continue to find */ /* "NTLDR" is found, so we believe it is NT boot sector. */ movw $0x5247, -1(iDI) /* change "NT" to "GR" */ /* CF=0 for now */ lahf /* Load Flags into AH */ /* AH = SF:ZF:xx:AF:xx:PF:xx:CF */ /* AH = binary xxxxxxx0 */ jmp 3b4: sahf /* Store AH into flags SF ZF xx AF xx PF xx CF */ /* CF=0 means "NTLDR" is found, CF=1 means "NTLDR" is not found. */ popal ret#endif2: /* FAT12/FAT16 */ movb 0x10(iSI), %al /* number of FATs(NTFS:0, FAT:1,2) */ testb %al, %al jz 1f movw 0x16(iSI), %ax /* sectors per FAT(small) */ testw %ax, %ax jz 1f// movw $(FAT16_message - _start1), %si cmpw $12, %ax ja 4f /* FAT16 */ /* sure it is FAT12 */ /* is FAT12 allowed write? */ testl $0x01, ABS(fstypes) jnz 2f /* FAT12 write not allowed */ movl $0, ABS(sectors_to_write) movl $ABS(msg_fstype_fat12_deny), %ecx call 8f /* linux_print */ stc popal ret2: /* write to FAT12 boot area */ cld movl $ABS(_start1 + 0x600), %esi /* points to the 4th sector */ movl $ABS(mbr_63_sectors), %edi lodsw /* The first 2 byte: short jmp */ //leal 0x400(%edi), %esi /* ESI points to super block */ stosw /* check lba-chs-mode specified, 1 byte */ cmpl $-1, ABS(lba) /* lba-chs-mode not specified? */ je 2f /* yes, do nothing. */ movb $0x0e, %al /* initialize to lba mode. */ cmpl $0, ABS(lba) /* chs ? */ jnz 10f /* no, it is not chs.*/ movb $0x90, %al /* yes, it is chs. */10: stosb decl %edi2: addl $(1+8+2+1+2+1+2+2+1+2), %edi addl $(1+8+2+1+2+1+2+2+1+2), %esi /* skip 8-byte OEM name and Bytes per sector */ /* and Sectors per cluster, byte */ /* and Reserved sectors, word */ /* and Number of FATs, byte */ /* (Max root dir entries)Must be 0, word */ /* (Total sectors small)Must be 0, word */ /* Media descriptor, byte */ /* (Sectors per FAT)Must be 0, word */ /* sectors per track, word */ lodsw addl $2, %edi cmpl $0xffffff3f, ABS(sectors_per_track) je 2f movb ABS(sectors_per_track), %al cbw subl $2, %edi stosw2: /* number of heads, word */ lodsw addl $2, %edi cmpl $0xffff00ff, ABS(heads) je 2f movw ABS(heads), %ax subl $2, %edi stosw2: /* hidden sectors(i.e., partition start), dword */ lodsl addl $4, %edi cmpl $0xffffffff, ABS(start_sector) je 2f movl ABS(start_sector), %eax subl $4, %edi stosl2: /* total sectors, dword */ lodsl addl $4, %edi cmpl $0, ABS(total_sectors) je 2f movl ABS(total_sectors), %eax subl $4, %edi stosl2: /* drive number, byte, etc... */ addl $(1+1+1+4+11+8), %esi addl $(1+1+1+4+11+8), %edi //movl $0xFFB6FCFA, %eax /* CLI, CLD, MOV DH,FF */ lodsw stosw lodsb stosb lodsb //decl %edi /* partition number, byte */ movb ABS(floppy), %al stosb /* Machine code begins at offset 0x42, 444 bytes without * the ending 2 bytes of boot signature */ //movl $ABS(_start1 + 0x642), %esi movl $(444 / 4), %ecx repz movsl movl $1, ABS(sectors_to_write) movl $ABS(msg_fstype_fat12_allow), %ecx call 8f /* linux_print */ clc popal ret4: /* sure it is FAT16 */ /* is FAT16 allowed write? */ testl $0x02, ABS(fstypes) jnz 2f /* FAT16 write not allowed */ movl $0, ABS(sectors_to_write) movl $ABS(msg_fstype_fat16_deny), %ecx call 8f /* linux_print */ stc popal ret2: /* write to FAT16 boot area */ cld movl $ABS(_start1 + 0x600), %esi /* points to the 4th sector */ movl $ABS(mbr_63_sectors), %edi lodsw /* The first 2 byte: short jmp */ //leal 0x400(%edi), %esi /* ESI points to super block */ stosw /* check lba-chs-mode specified, 1 byte */ cmpl $-1, ABS(lba) /* lba-chs-mode not specified? */ je 2f /* yes, do nothing. */ movb $0x0e, %al /* initialize to lba mode. */ cmpl $0, ABS(lba) /* chs ? */ jnz 10f /* no, it is not chs.*/ movb $0x90, %al /* yes, it is chs. */10: stosb decl %edi2: addl $(1+8+2+1+2+1+2+2+1+2), %edi addl $(1+8+2+1+2+1+2+2+1+2), %esi /* skip 8-byte OEM name and Bytes per sector */ /* and Sectors per cluster, byte */ /* and Reserved sectors, word */ /* and Number of FATs, byte */ /* (Max root dir entries)Must be 0, word */ /* (Total sectors small)Must be 0, word */ /* Media descriptor, byte */ /* (Sectors per FAT)Must be 0, word */ /* sectors per track, word */ lodsw addl $2, %edi cmpl $0xffffff3f, ABS(sectors_per_track) je 2f movb ABS(sectors_per_track), %al cbw subl $2, %edi stosw2: /* number of heads, word */ lodsw addl $2, %edi cmpl $0xffff00ff, ABS(heads) je 2f movw ABS(heads), %ax subl $2, %edi stosw2: /* hidden sectors(i.e., partition start), dword */ lodsl addl $4, %edi cmpl $0xffffffff, ABS(start_sector) je 2f movl ABS(start_sector), %eax subl $4, %edi stosl2: /* total sectors, dword */ lodsl addl $4, %edi cmpl $0, ABS(total_sectors) je 2f⌨️ 快捷键说明
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