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https://github.com/freebsd/freebsd-src
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Add in a hack to support IBM "El Torito" CD-ROM booting BIOS's which expect
the first sector of the emulated floppy to contain a valid MS-DOS BPB that it can modify. Since boot1 is the first sector of boot.flp, this resulted in the BIOS overwriting part of boot1: specifically the function used to read in sectors from the disk. Submitted by: Mark Peek <mark@whistle.com> Submitted by: Doug Ambrisko <ambrisko@ambrisko.com> PR: i386/26382 Obtained from: NetBSD, OpenBSD (the example BPB) MFC after: 1 month
This commit is contained in:
John Baldwin
parent
a079a625af
commit
b0606ca15f
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=80751
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@ -6,9 +6,11 @@ STRIP=
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BINDIR?= /boot
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BINMODE= 444
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CLEANFILES+= boot1 boot1.out boot1.o \
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boot2.ldr boot2.bin boot2.ld boot2.out boot2.o \
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boot2.ldr boot2.bin boot2.ld boot2.out boot2.o boot2.h \
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sio.o
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NM?= nm
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# A value of 0x80 enables LBA support.
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B1FLAGS= 0x80
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@ -46,6 +48,11 @@ boot1.out: boot1.o
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boot1.o: boot1.s
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${AS} ${AFLAGS} --defsym FLAGS=${B1FLAGS} ${.IMPSRC} -o ${.TARGET}
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boot2.h: boot1.out
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${NM} -t d ${.ALLSRC} | awk '/([0-9])+ T xread/ \
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{ x = $$1 - ORG1; printf("#define XREADORG 0x7%x\n", x) }' \
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ORG1=`printf "%d" ${ORG1}` > boot2.h
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boot2: boot2.ldr boot2.bin ${BTX}/btx/btx
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btxld -v -E ${ORG2} -f bin -b ${BTX}/btx/btx -l boot2.ldr \
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-o boot2.ld -P 1 boot2.bin
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@ -63,6 +70,8 @@ boot2.out: boot2.o sio.o
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${LD} ${LDFLAGS} -Ttext ${ORG2} -o ${.TARGET} \
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${BTX}/lib/crt0.o boot2.o sio.o
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boot2.o: boot2.h
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sio.o: sio.s
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${AS} ${AFLAGS} --defsym SIOPRT=${BOOT_COMCONSOLE_PORT} \
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--defsym SIOFMT=${B2SIOFMT} \
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@ -43,7 +43,40 @@
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start: jmp main # Start recognizably
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.org 0x4,0x90
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# This is the start of a standard BIOS Parameter Block (BPB). Most bootable
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# FAT disks have this at the start of their MBR. While normal BIOS's will
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# work fine without this section, IBM's El Torito emulation "fixes" up the
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# BPB by writing into the memory copy of the MBR. Rather than have data
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# written into our xread routine, we'll define a BPB to work around it.
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# The data marked with (T) indicates a field required for a ThinkPad to
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# recognize the disk and (W) indicates fields written from IBM BIOS code.
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# The use of the BPB is based on what OpenBSD and NetBSD implemented in
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# their boot code but the required fields were determined by trial and error.
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#
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# Note: If additional space is needed in boot1, one solution would be to
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# move the "prompt" message data (below) to replace the OEM ID.
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.org 0x03, 0x00
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oemid: .space 0x08, 0x00 # OEM ID
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.org 0x0b, 0x00
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bpb: .word 512 # sector size (T)
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.byte 0 # sectors/clustor
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.word 0 # reserved sectors
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.byte 0 # number of FATs
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.word 0 # root entries
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.word 0 # small sectors
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.byte 0 # media type (W)
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.word 0 # sectors/fat
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.word 18 # sectors per track (T)
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.word 2 # number of heads (T)
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.long 0 # hidden sectors (W)
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.long 0 # large sectors
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.org 0x24, 0x00
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ebpb: .byte 0 # BIOS physical drive number (W)
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.org 0x25,0x90
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#
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# Trampoline used by boot2 to call read to read data from the disk via
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# the BIOS. Call with:
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@ -43,7 +43,40 @@
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start: jmp main # Start recognizably
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.org 0x4,0x90
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# This is the start of a standard BIOS Parameter Block (BPB). Most bootable
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# FAT disks have this at the start of their MBR. While normal BIOS's will
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# work fine without this section, IBM's El Torito emulation "fixes" up the
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# BPB by writing into the memory copy of the MBR. Rather than have data
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# written into our xread routine, we'll define a BPB to work around it.
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# The data marked with (T) indicates a field required for a ThinkPad to
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# recognize the disk and (W) indicates fields written from IBM BIOS code.
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# The use of the BPB is based on what OpenBSD and NetBSD implemented in
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# their boot code but the required fields were determined by trial and error.
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#
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# Note: If additional space is needed in boot1, one solution would be to
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# move the "prompt" message data (below) to replace the OEM ID.
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.org 0x03, 0x00
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oemid: .space 0x08, 0x00 # OEM ID
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.org 0x0b, 0x00
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bpb: .word 512 # sector size (T)
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.byte 0 # sectors/clustor
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.word 0 # reserved sectors
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.byte 0 # number of FATs
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.word 0 # root entries
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.word 0 # small sectors
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.byte 0 # media type (W)
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.word 0 # sectors/fat
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.word 18 # sectors per track (T)
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.word 2 # number of heads (T)
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.long 0 # hidden sectors (W)
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.long 0 # large sectors
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.org 0x24, 0x00
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ebpb: .byte 0 # BIOS physical drive number (W)
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.org 0x25,0x90
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#
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# Trampoline used by boot2 to call read to read data from the disk via
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# the BIOS. Call with:
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@ -34,6 +34,7 @@
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#include <btxv86.h>
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#include "boot2.h"
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#include "lib.h"
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#define RBX_ASKNAME 0x0 /* -a */
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@ -739,7 +740,7 @@ drvread(void *buf, unsigned lba, unsigned nblk)
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printf("%c\b", c = c << 8 | c >> 24);
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v86.ctl = V86_ADDR | V86_CALLF | V86_FLAGS;
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v86.addr = 0x704; /* call to xread in boot1 */
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v86.addr = XREADORG; /* call to xread in boot1 */
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v86.es = VTOPSEG(buf);
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v86.eax = lba;
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v86.ebx = VTOPOFF(buf);
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@ -6,9 +6,11 @@ STRIP=
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BINDIR?= /boot
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BINMODE= 444
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CLEANFILES+= boot1 boot1.out boot1.o \
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boot2.ldr boot2.bin boot2.ld boot2.out boot2.o \
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boot2.ldr boot2.bin boot2.ld boot2.out boot2.o boot2.h \
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sio.o
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NM?= nm
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# A value of 0x80 enables LBA support.
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B1FLAGS= 0x80
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@ -46,6 +48,11 @@ boot1.out: boot1.o
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boot1.o: boot1.s
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${AS} ${AFLAGS} --defsym FLAGS=${B1FLAGS} ${.IMPSRC} -o ${.TARGET}
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boot2.h: boot1.out
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${NM} -t d ${.ALLSRC} | awk '/([0-9])+ T xread/ \
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{ x = $$1 - ORG1; printf("#define XREADORG 0x7%x\n", x) }' \
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ORG1=`printf "%d" ${ORG1}` > boot2.h
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boot2: boot2.ldr boot2.bin ${BTX}/btx/btx
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btxld -v -E ${ORG2} -f bin -b ${BTX}/btx/btx -l boot2.ldr \
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-o boot2.ld -P 1 boot2.bin
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@ -63,6 +70,8 @@ boot2.out: boot2.o sio.o
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${LD} ${LDFLAGS} -Ttext ${ORG2} -o ${.TARGET} \
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${BTX}/lib/crt0.o boot2.o sio.o
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boot2.o: boot2.h
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sio.o: sio.s
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${AS} ${AFLAGS} --defsym SIOPRT=${BOOT_COMCONSOLE_PORT} \
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--defsym SIOFMT=${B2SIOFMT} \
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@ -34,6 +34,7 @@
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#include <btxv86.h>
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#include "boot2.h"
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#include "lib.h"
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#define RBX_ASKNAME 0x0 /* -a */
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@ -739,7 +740,7 @@ drvread(void *buf, unsigned lba, unsigned nblk)
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printf("%c\b", c = c << 8 | c >> 24);
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v86.ctl = V86_ADDR | V86_CALLF | V86_FLAGS;
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v86.addr = 0x704; /* call to xread in boot1 */
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v86.addr = XREADORG; /* call to xread in boot1 */
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v86.es = VTOPSEG(buf);
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v86.eax = lba;
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v86.ebx = VTOPOFF(buf);
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