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authorH. Peter Anvin <hpa@zytor.com>2008-09-05 14:49:42 -0700
committerH. Peter Anvin <hpa@zytor.com>2008-09-05 14:49:42 -0700
commit058dd028ac7d8ae217d1b3b00213751d63034195 (patch)
tree53bd1e95555370d939258873062db00c7d74bf7d /mbr
parent1eb0d6f7cfa7547470580d821ca815e20df4e93e (diff)
downloadsyslinux.git-058dd028ac7d8ae217d1b3b00213751d63034195.tar.gz
syslinux.git-058dd028ac7d8ae217d1b3b00213751d63034195.tar.xz
syslinux.git-058dd028ac7d8ae217d1b3b00213751d63034195.zip
ISOLINUX: support for hybrid mode (CD-ROM/USB key)
Still a work in progress. Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Diffstat (limited to 'mbr')
-rw-r--r--mbr/Makefile12
-rw-r--r--mbr/isohdpfx.S212
2 files changed, 219 insertions, 5 deletions
diff --git a/mbr/Makefile b/mbr/Makefile
index 7952e60b..a57b3946 100644
--- a/mbr/Makefile
+++ b/mbr/Makefile
@@ -17,23 +17,25 @@
topdir = ..
include $(topdir)/MCONFIG.embedded
-all: mbr.bin gptmbr.bin
+all: mbr.bin gptmbr.bin isohdpfx.bin
.PRECIOUS: %.o
%.o: %.S
$(CC) $(SFLAGS) -Wa,-a=$*.lst -c -o $@ $<
-mbr.elf: mbr.o mbr.ld
+.PRECIOUS: %.elf
+%.elf: %.o mbr.ld
$(LD) $(LDFLAGS) -T mbr.ld -e _start -o $@ $<
mbr.bin: mbr.elf checksize.pl
$(OBJCOPY) -O binary $< $@
$(PERL) checksize.pl mbr.bin 440
-mbr_bin.c: mbr.bin
+isohdpfx.bin: isohdpfx.elf checksize.pl
+ $(OBJCOPY) -O binary $< $@
+ $(PERL) checksize.pl mbr.bin 432
-gptmbr.elf: gptmbr.o mbr.ld
- $(LD) $(LDFLAGS) -T mbr.ld -e _start -o $@ $<
+mbr_bin.c: mbr.bin
gptmbr.bin: gptmbr.elf checksize.pl
$(OBJCOPY) -O binary $< $@
diff --git a/mbr/isohdpfx.S b/mbr/isohdpfx.S
new file mode 100644
index 00000000..f2bc7dc6
--- /dev/null
+++ b/mbr/isohdpfx.S
@@ -0,0 +1,212 @@
+/* -----------------------------------------------------------------------
+ *
+ * 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.
+ *
+ * ----------------------------------------------------------------------- */
+
+/*
+ * Modified MBR code used on an ISO image in hybrid mode.
+ *
+ * This doesn't follow the El Torito spec at all -- it is just a stub
+ * loader of a hard-coded offset, but that's good enough to load
+ * ISOLINUX.
+ */
+
+ .code16
+ .text
+
+HYBRID_MAGIC = 0x7078c0fb
+isolinux_hybrid_signature = 0x7c00+64
+isolinux_start_hybrid = 0x7c00+64+4
+
+ .globl bootsec
+/* Important: the top 6 words on the stack are passed to isolinux.bin */
+stack = 0x7c00
+driveno = (stack-6)
+sectors = (stack-8)
+heads = (stack-10)
+secpercyl = (stack-14)
+
+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 */
+ pushw %ax /* Save heads on the stack */
+ mulw %cx /* Heads*sectors -> sectors per cylinder */
+
+ /* Save sectors/cylinder on the stack */
+ pushw %dx /* High word */
+ pushw %ax /* Low word */
+
+ /*
+ * Load sectors. We do this one at a time mostly to avoid
+ * pitfalls and to share code with the stock MBR code.
+ */
+ movw $0x7c00, %bx
+ movw $4, %cx /* Sector count */
+ movl (lba_offset), %eax
+
+2:
+ call read_sector
+ jc disk_error
+ incl %eax
+ addw $512, %bx
+ loopw 2b
+
+ /*
+ * Okay, that actually worked... update the stack pointer
+ * and jump into isolinux.bin...
+ */
+ cmpl $HYBRID_MAGIC,(isolinux_hybrid_signature)
+ jne bad_signature
+
+ cli
+ movw $heads, %sp
+ jmp isolinux_start_hybrid
+
+bad_signature:
+ call error
+ .ascii "isolinux.bin missing or corrupt.\r\n"
+
+/*
+ * read_sector: read a single sector pointed to by %eax to %es:%bx.
+ * CF is set on error. All registers saved.
+ */
+read_sector:
+ pushal
+ xorl %edx, %edx
+ 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 %eax before this chunk! */
+ /* This also relies on %bx and %edx as set up above. */
+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
+ ret
+
+disk_error:
+ call error
+ .ascii "Operating system load error.\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
+
+ /* Address of pointer to isolinux.bin */
+lba_offset = _start+432