diff options
Diffstat (limited to 'sys/boot/i386/zfsboot/zfsldr.S')
| -rw-r--r-- | sys/boot/i386/zfsboot/zfsldr.S | 220 |
1 files changed, 85 insertions, 135 deletions
diff --git a/sys/boot/i386/zfsboot/zfsldr.S b/sys/boot/i386/zfsboot/zfsldr.S index 182d88e..b8be282 100644 --- a/sys/boot/i386/zfsboot/zfsldr.S +++ b/sys/boot/i386/zfsboot/zfsldr.S @@ -16,7 +16,6 @@ */ /* Memory Locations */ - .set MEM_REL,0x700 # Relocation address .set MEM_ARG,0x900 # Arguments .set MEM_ORG,0x7c00 # Origin .set MEM_BUF,0x8000 # Load area @@ -38,43 +37,6 @@ .globl start .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 code, 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 /* * Load the rest of zfsboot2 and BTX up, copy the parts to the right locations, * and start it all up. @@ -84,33 +46,24 @@ ebpb: .byte 0 # BIOS physical drive number (W) * Setup the segment registers to flat addressing (segment 0) and setup the * stack to end just below the start of our code. */ -main: cld # String ops inc +start: 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 MEM_REL. Since %cx == 0, the inc %ch sets - * %cx == 0x100. - */ - mov %sp,%si # Source - mov $MEM_REL,%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. We use the fake partition entry below that points to - * the MBR when we call nread. The first pass looks for the first active - * FreeBSD slice. The second pass looks for the first non-active FreeBSD - * slice if the first one fails. + * Load the MBR and look for the first FreeBSD slice. We use the fake + * partition entry below that points to the MBR when we call read. + * The first pass looks for the first active FreeBSD slice. The + * second pass looks for the first non-active FreeBSD slice if the + * first one fails. */ - mov $part4,%si # Partition - cmpb $0x80,%dl # Hard drive? - jb main.4 # No - movb $0x1,%dh # Block count - callw nread # Read MBR + call check_edd # Make sure EDD works + mov $part4,%si # Dummy partition + xor %eax,%eax # Read MBR + movl $MEM_BUF,%ebx # from first + call read # sector mov $0x1,%cx # Two passes main.1: mov $MEM_BUF+PRT_OFF,%si # Partition table movb $0x1,%dh # Partition @@ -131,60 +84,55 @@ main.3: add $0x10,%si # Next entry */ mov $msg_part,%si # Message 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 64 sectors starting at sector 1024 + * for, so go ahead and load up the 128 sectors starting at sector 1024 * (i.e. after the two vdev labels). We don't have do anything fancy * here to allow for an extra copy of boot1 and a partition table * (compare to this section of the UFS bootstrap) so we just load it - * all at 0x8000. The first part of boot2 is BTX, which wants to run + * all at 0x9000. The first part of boot2 is BTX, which wants to run * at 0x9000. 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. After we have moved the client, we relocate BTX - * itself to 0x9000 - doing it in this order means that none of the - * memcpy regions overlap which would corrupt the copy. Normally, BTX - * clients start at MEM_USR, or 0xa000, but when we use btxld to - * create zfsboot2, we use an entry point of 0x2000. That entry point is - * relative to MEM_USR; thus boot2.bin starts at 0xc000. + * binary to 0xc000. Normally, BTX clients start at MEM_USR, or 0xa000, + * but when we use btxld to create zfsboot2, we use an entry point of + * 0x2000. That entry point is relative to MEM_USR; thus boot2.bin + * starts at 0xc000. * * The load area and the target area for the client overlap so we have * to use a decrementing string move. We also play segment register * games with the destination address for the move so that the client * can be larger than 16k (which would overflow the zero segment since - * the client starts at 0xc000). Relocating BTX is easy since the load - * area and target area do not overlap. + * the client starts at 0xc000). */ main.5: mov %dx,MEM_ARG # Save args - movb $NSECT,%dh # Sector count + mov $NSECT,%cx # Sector count movl $1024,%eax # Offset to boot2 - callw nread.1 # Read disk -main.6: mov $MEM_BUF,%si # BTX (before reloc) - mov 0xa(%si),%bx # Get BTX length and set + mov $MEM_BTX,%ebx # Destination buffer +main.6: pushal # Save params + call read # Read disk + popal # Restore + incl %eax # Advance to + add $SIZ_SEC,%ebx # next sector + loop main.6 # If not last, read another + mov MEM_BTX+0xa,%bx # Get BTX length mov $NSECT*SIZ_SEC-1,%di # Size of load area (less one) - mov %di,%si # End of load - add $MEM_BUF,%si # area + mov %di,%si # End of load area, 0x9000 rel sub %bx,%di # End of client, 0xc000 rel mov %di,%cx # Size of inc %cx # client + mov $(MEM_BTX)>>4,%dx # Segment + mov %dx,%ds # addressing 0x9000 mov $(MEM_USR+2*SIZ_PAG)>>4,%dx # Segment mov %dx,%es # addressing 0xc000 std # Move with decrement rep # Relocate movsb # client - mov %ds,%dx # Back to - mov %dx,%es # zero segment - mov $MEM_BUF,%si # BTX (before reloc) - mov $MEM_BTX,%di # BTX - mov %bx,%cx # Get BTX length - cld # Increment this time - rep # Relocate - movsb # BTX + cld # Back to increment + xor %dx,%dx # Back + mov %ds,%dx # to zero + mov %dx,%es # segment /* * Enable A20 so we can access memory above 1 meg. @@ -210,33 +158,37 @@ seta20.3: sti # Enable interrupts /* - * Trampoline used to call read from within zfsldr. Sets up an EDD - * packet on the stack and passes it to read. + * Read a sector from the disk. Sets up an EDD packet on the stack + * and passes it to read. We assume that the destination address is + * always segment-aligned. * * %eax - int - LBA to read in relative to partition start + * %ebx - ptr - destination address * %dl - byte - drive to read from - * %dh - byte - num sectors to read * %si - ptr - MBR partition entry */ -nread: xor %eax,%eax # Sector offset in partition -nread.1: xor %ecx,%ecx # Get +read: xor %ecx,%ecx # Get addl 0x8(%si),%eax # LBA adc $0,%ecx pushl %ecx # Starting absolute block pushl %eax # block number - push %es # Address of - push $MEM_BUF # transfer buffer - xor %ax,%ax # Number of - movb %dh,%al # blocks to - push %ax # transfer + shr $4,%ebx # Convert to segment + push %bx # Address of + push $0 # transfer buffer + push $0x1 # Read 1 sector push $0x10 # Size of packet - mov %sp,%bp # Packet pointer - callw read # Read from disk - lea 0x10(%bp),%sp # Clear stack - jnc return # If success, return - mov $msg_read,%si # Otherwise, set the error - # message and fall through to - # the error routine + mov %sp,%si # Packet pointer + mov $0x42,%ah # BIOS: Extended + int $0x13 # read + jc read.1 # If error, fail + lea 0x10(%si),%sp # Clear stack + ret # If success, return +read.1: mov %ah,%al # Format + mov $read_err,%di # error + call hex8 # code + mov $msg_read,%si # Set the error message and + # fall through to the error + # routine /* * Print out the error message pointed to by %ds:(%si) followed * by a prompt, wait for a keypress, and then reboot the machine. @@ -257,51 +209,49 @@ putstr.0: mov $0x7,%bx # Page:attribute putstr: lodsb # Get char testb %al,%al # End of string? jne putstr.0 # No - + ret # To caller /* - * 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 + * Check to see if the disk supports EDD. zfsboot requires EDD and does not + * support older C/H/S disk I/O. */ -read: cmpb $0x80,%dl # Hard drive? - jb read.1 # No, use CHS +check_edd: cmpb $0x80,%dl # Hard drive? + jb check_edd.1 # No, fail to boot mov $0x55aa,%bx # Magic push %dx # Save movb $0x41,%ah # BIOS: Check int $0x13 # extensions present pop %dx # Restore - jc read.1 # If error, use CHS + jc check_edd.1 # If error, fail cmp $0xaa55,%bx # Magic? - jne read.1 # No, so use CHS + jne check_edd.1 # No, so fail testb $0x1,%cl # Packet interface? - jz read.1 # No, so use CHS - mov %bp,%si # Disk packet - movb $0x42,%ah # BIOS: Extended - int $0x13 # read - retw # To caller -read.1: mov $msg_chs,%si - jmp error -msg_chs: .asciz "CHS not supported" + jz check_edd.1 # No, so fail + ret # EDD ok, keep booting +check_edd.1: mov $msg_chs,%si # Warn that CHS is + jmp error # unsupported and fail +/* + * AL to hex, saving the result to [EDI]. + */ +hex8: push %ax # Save + shrb $0x4,%al # Do upper + call hex8.1 # 4 + pop %ax # Restore +hex8.1: andb $0xf,%al # Get lower 4 + cmpb $0xa,%al # Convert + sbbb $0x69,%al # to hex + das # digit + orb $0x20,%al # To lower case + stosb # Save char + ret # (Recursive) /* Messages */ -msg_read: .asciz "Read" -msg_part: .asciz "Boot" +msg_chs: .asciz "CHS not supported" +msg_read: .ascii "Read error: " +read_err: .asciz "XX" +msg_part: .asciz "Boot error" -prompt: .asciz " error\r\n" +prompt: .asciz "\r\n" .org PRT_OFF,0x90 |
