Fix numerous problems in the new MBR code.syslinux-3.36-pre5

3 files changed, 97 insertions, 15 deletions

diff --git a/mbr/Makefile b/mbr/Makefile
index 1772d14e..75da4484 100644
--- a/mbr/Makefile
+++ b/mbr/Makefile
@@ -33,8 +33,8 @@ all:	mbr.bin
 %.o: %.S
 	$(CC) $(SFLAGS) -Wa,-a=$*.lst -c -o $@ $<
 
-mbr.elf: mbr.o
-	$(LD) -Ttext 0x600 -e _start -o $@ $^
+mbr.elf: mbr.o mbr.ld
+	$(LD) -T mbr.ld -e _start -o $@ $<
 
 mbr.bin: mbr.elf checksize.pl
 	$(OBJCOPY) -O binary $< $@
diff --git a/mbr/mbr.S b/mbr/mbr.S
index 82dc5a6e..81e5dd00 100644
--- a/mbr/mbr.S
+++ b/mbr/mbr.S
@@ -28,14 +28,21 @@
 	.code16
 	.text
 
-bootsec = 0x7c00
-stack	= bootsec
-driveno	= (stack-4)
-heads	= (stack-6)
-sectors	= (stack-8)
+	.globl	bootsec
+stack   = 0x7c00
+driveno	= (stack-6)
+heads	= (stack-8)
+sectors	= (stack-10)
 
 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
@@ -74,7 +81,7 @@ next:
 	jz	1f
 
 	/* We have EBIOS; patch in a jump to read_sector_ebios */
-	movw	$0xeb+((read_sector_ebios-read_sector_cbios+2)<< 8), (read_sector_cbios)
+	movw	$0xeb+((read_sector_ebios-read_sector_cbios-2)<< 8), (read_sector_cbios)
 
 1:
 	popw	%dx
@@ -93,7 +100,6 @@ next:
 	pushl	%eax		/* Base */
 	pushl	%eax		/* Root */
 	call	scan_partition_table
-
 	
 	/* If we get here, we have no OS */
 	jmp	missing_os
@@ -126,6 +132,7 @@ read_sector_ebios:
 	movl	%eax, 8(%si)
 	movb	$0x42, %ah
 read_common:
+	movb	(driveno), %dl
 	int	$0x13
 	ret
 
@@ -232,11 +239,13 @@ boot:
 	movl	8(%si), %eax
 	addl	22(%bp), %eax
 	movl	%eax, 8(%si)
+	pushw	%si
 	call	read_sector
+	popw	%si
 	jc	disk_error
-	cmpw	$0xaa55, (bootsec+0x510)
-	je	missing_os		/* Not a valid boot sector */
-	movw	$stack-6, %sp
+	cmpw	$0xaa55, (bootsec+510)
+	jne	missing_os		/* Not a valid boot sector */
+	movw	$driveno, %sp
 	popw	%dx		/* dl -> drive number */
 	popw	%di		/* es:di -> $PnP vector */
 	popw	%es
@@ -274,10 +283,10 @@ missing_os_msg:
 	.ascii	"Missing operating system."
 	.byte	0
 disk_error_msg:
-	.ascii	"Failed to load operating system."
+	.ascii	"Operating system load error."
 	.byte	0
 too_many_active_msg:
-	.ascii	"Multiple active partititons."
+	.ascii	"Multiple active partitions."
 	.byte	0
 
 	.balign	4
diff --git a/mbr/mbr.ld b/mbr/mbr.ld
new file mode 100644
index 00000000..d14ba802
--- /dev/null
+++ b/mbr/mbr.ld
@@ -0,0 +1,73 @@
+/*
+ * Linker script for MBR
+ */
+
+/* Script for -z combreloc: combine and sort reloc sections */
+OUTPUT_FORMAT("elf32-i386", "elf32-i386",
+	      "elf32-i386")
+OUTPUT_ARCH(i386)
+EXTERN(_start)
+ENTRY(_start)
+SECTIONS
+{
+  /* Read-only sections, merged into text segment: */
+  . = 0x600;
+  .text           :
+  {
+    *(.text*)
+    *(.rodata*)
+  } =0x90909090
+
+  . = ALIGN(4);
+  .data		  :
+  {
+    *(.data*)
+  }
+
+  . = ALIGN(128);
+  .bss		  :
+  {
+    *(.bss*)
+  }
+
+  . = 0x7c00;
+  .bootsec	  :
+  {
+    *(.bootsec)
+  }
+
+  /* Stabs debugging sections.  */
+  .stab          0 : { *(.stab) }
+  .stabstr       0 : { *(.stabstr) }
+  .stab.excl     0 : { *(.stab.excl) }
+  .stab.exclstr  0 : { *(.stab.exclstr) }
+  .stab.index    0 : { *(.stab.index) }
+  .stab.indexstr 0 : { *(.stab.indexstr) }
+  .comment       0 : { *(.comment) }
+  /* DWARF debug sections.
+     Symbols in the DWARF debugging sections are relative to the beginning
+     of the section so we begin them at 0.  */
+  /* DWARF 1 */
+  .debug          0 : { *(.debug) }
+  .line           0 : { *(.line) }
+  /* GNU DWARF 1 extensions */
+  .debug_srcinfo  0 : { *(.debug_srcinfo) }
+  .debug_sfnames  0 : { *(.debug_sfnames) }
+  /* DWARF 1.1 and DWARF 2 */
+  .debug_aranges  0 : { *(.debug_aranges) }
+  .debug_pubnames 0 : { *(.debug_pubnames) }
+  /* DWARF 2 */
+  .debug_info     0 : { *(.debug_info .gnu.linkonce.wi.*) }
+  .debug_abbrev   0 : { *(.debug_abbrev) }
+  .debug_line     0 : { *(.debug_line) }
+  .debug_frame    0 : { *(.debug_frame) }
+  .debug_str      0 : { *(.debug_str) }
+  .debug_loc      0 : { *(.debug_loc) }
+  .debug_macinfo  0 : { *(.debug_macinfo) }
+  /* SGI/MIPS DWARF 2 extensions */
+  .debug_weaknames 0 : { *(.debug_weaknames) }
+  .debug_funcnames 0 : { *(.debug_funcnames) }
+  .debug_typenames 0 : { *(.debug_typenames) }
+  .debug_varnames  0 : { *(.debug_varnames) }
+  /DISCARD/ : { *(.note.GNU-stack) }
+}