Use a linker script for 16bit code.

With a linker script the data sections can be grouped by themselves
   instead of being dispersed throughout the code.

6 files changed, 77 insertions, 44 deletions

diff --git a/Makefile b/Makefile
index c8e68bd..151757a 100644
--- a/Makefile
+++ b/Makefile
@@ -89,13 +89,13 @@ $(OUT)%.offset.auto.h: $(OUT)%.o
 $(OUT)blob.16.s: ; $(call whole-compile, $(CFLAGS16) -S, $(addprefix src/, $(SRC16)),$@)
 
 TABLEASM=$(addprefix $(OUT), $(patsubst %.c,%.proc.16.s,$(TABLESRC)))
-$(OUT)romlayout16.o: romlayout.S $(OUT)blob.proc.16.s $(TABLEASM)
+$(OUT)romlayout16.o: romlayout.S $(OUT)blob.16.s $(TABLEASM)
 	@echo "  Generating 16bit layout of $@"
 	$(Q)$(CC) $(CFLAGS16) -c $< -o $@
 
-$(OUT)rom16.o: $(OUT)romlayout16.o
+$(OUT)rom16.o: $(OUT)romlayout16.o $(OUT)rombios16.lds
 	@echo "  Linking $@"
-	$(Q)ld -melf_i386 -e post16 -Ttext 0 $< -o $@
+	$(Q)ld -T $(OUT)rombios16.lds $< -o $@
 
 $(OUT)romlayout32.o: $(OUT)rom16.offset.auto.h ; $(call whole-compile, $(CFLAGS), $(addprefix src/, $(SRC32)),$@)
 
diff --git a/TODO b/TODO
index 5d6be5c..71f7bb3 100644
--- a/TODO
+++ b/TODO
@@ -18,8 +18,6 @@ Look into ways to reduce stack usage.
 
 Code assumes ebda segment is static - it doesn't read 0x40e.
 
-See if using an ld script for 16bit mode is a good idea.
-
 The __call16 code does a long jump to the interrupt trampolines - this
 is unnecessary.
 
diff --git a/src/config.h b/src/config.h
index 88b54d8..c7ec67e 100644
--- a/src/config.h
+++ b/src/config.h
@@ -43,4 +43,7 @@
 #define CONFIG_SUBMODEL_ID   0x00
 #define CONFIG_BIOS_REVISION 0x01
 
+// Start of fixed addresses in 0xf0000 segment.
+#define CONFIG_START_FIXED 0xe050
+
 #endif // config.h
diff --git a/src/rombios16.lds.S b/src/rombios16.lds.S
new file mode 100644
index 0000000..f699816
--- /dev/null
+++ b/src/rombios16.lds.S
@@ -0,0 +1,31 @@
+// Linker definitions for 16bit code
+//
+// Copyright (C) 2008  Kevin O'Connor <kevin@koconnor.net>
+// Copyright (C) 2002  MandrakeSoft S.A.
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include "config.h"
+
+OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
+OUTPUT_ARCH("i386")
+ENTRY(post16);
+SECTIONS
+{
+        . = 0;
+        .text     : {
+                *(.text)
+                *(.rodata)
+                *(.rodata.*)
+                *(.data)
+                bios16c_end = .;
+                . = CONFIG_START_FIXED;
+                *(.text.fixed.addr)
+                }
+
+        /DISCARD/ : { *(.stab)
+                     *(.stabstr)
+                     *(.comment)
+                     *(.note)
+                  }
+}
diff --git a/src/rombios32.lds.S b/src/rombios32.lds.S
index 94b860e..532317e 100644
--- a/src/rombios32.lds.S
+++ b/src/rombios32.lds.S
@@ -10,14 +10,14 @@
 
 OUTPUT_FORMAT("elf32-i386", "elf32-i386", "elf32-i386")
 OUTPUT_ARCH("i386")
-ENTRY(_start);
+ENTRY(post32);
 SECTIONS
 {
         . = (OFFSET_bios16c_end | 0xf0000);
         . = ALIGN(16);
         _text32_start = . ;
         .text     : { *(.text)    }
-        .rodata    : { *(.rodata) }
+        .rodata   : { *(.rodata)  }
         .data     : { *(.data)    }
         // XXX - should change code so it doesn't require global variables.
         . = 0x00040000;
diff --git a/src/romlayout.S b/src/romlayout.S
index baf68f3..f843d86 100644
--- a/src/romlayout.S
+++ b/src/romlayout.S
@@ -12,18 +12,13 @@
 #define REAL_MODE_CS      (4 << 3) // 0x20
 #define REAL_MODE_DS      (5 << 3) // 0x28
 
-        .code16gcc
-
 
 /****************************************************************
  * Include of 16bit C code
  ****************************************************************/
 
-        .globl bios16c_start, bios16c_end
-bios16c_start:
-.include "out/blob.proc.16.s"
-        .text
-bios16c_end:
+        .code16gcc
+.include "out/blob.16.s"
 
 
 /****************************************************************
@@ -92,12 +87,18 @@ bios16c_end:
         movl $ CONFIG_STACK_OFFSET , %esp
         .endm
 
+        // Specify a location in the fixed part of bios area.
+        .macro ORG addr
+        .section .text.fixed.addr
+        .org \addr - CONFIG_START_FIXED
+        .endm
+
 
 /****************************************************************
  * POST handler
  ****************************************************************/
 
-        .org 0xe05b
+        ORG 0xe05b
         .globl post16
 post16:
         // init the stack pointer
@@ -356,7 +357,7 @@ rombios32_gdt:
         iretw
         .endm
 
-        .org 0xe2c3
+        ORG 0xe2c3
         IRQ_ENTRY nmi
 
         IRQ_ENTRY_ARG 13
@@ -366,23 +367,23 @@ rombios32_gdt:
         IRQ_ENTRY 1c
         IRQ_ENTRY 70
 
-        .org 0xe3fe
+        ORG 0xe3fe
         jmp entry_13
 
-        .org 0xe401
+        ORG 0xe401
         // XXX - Fixed Disk Parameter Table
 
-        .org 0xe6f2
+        ORG 0xe6f2
         jmp entry_19
 
-        .org 0xe6f5
+        ORG 0xe6f5
 .include "out/cbt.proc.16.s"
         .text
 
-        .org 0xe729
+        ORG 0xe729
         // XXX - Baud Rate Generator Table
 
-        .org 0xe739
+        ORG 0xe739
         IRQ_ENTRY_ARG 14
 
         IRQ_ENTRY 74
@@ -417,82 +418,82 @@ entry_18:
         IRQ_TRAMPOLINE 1c
         IRQ_TRAMPOLINE 4a
 
-        .org 0xe82e
+        ORG 0xe82e
         IRQ_ENTRY_ARG 16
 
-        .org 0xe987
+        ORG 0xe987
         IRQ_ENTRY 09
 
-        .org 0xec59
+        ORG 0xec59
         IRQ_ENTRY_ARG 40
 
-        .org 0xef57
+        ORG 0xef57
         IRQ_ENTRY 0e
 
-        .org 0xefc7
+        ORG 0xefc7
 .include "out/floppy_dbt.proc.16.s"
         .text
 
-        .org 0xefd2
+        ORG 0xefd2
         IRQ_ENTRY_ARG 17
 
-        .org 0xf045
+        ORG 0xf045
         // XXX int 10
         iretw
 
-        .org 0xf065
+        ORG 0xf065
         IRQ_ENTRY_ARG 10
 
-        .org 0xf0a4
+        ORG 0xf0a4
         // XXX int 1D
         iretw
 
         .globl freespace2_start, freespace2_end
 freespace2_start:
 
-        .org 0xf841
+        ORG 0xf841
 freespace2_end:
         jmp entry_12
 
-        .org 0xf84d
+        ORG 0xf84d
         jmp entry_11
 
-        .org 0xf859
+        ORG 0xf859
         IRQ_ENTRY_ARG 15
 
-        .org 0xfa6e
+        ORG 0xfa6e
 .include "out/font.proc.16.s"
         .text
 
-        .org 0xfe6e
+        ORG 0xfe6e
         IRQ_ENTRY_ARG 1a
 
-        .org 0xfea5
+        ORG 0xfea5
         IRQ_ENTRY 08
 
-        .org 0xfef3
+        ORG 0xfef3
         // XXX - Initial Interrupt Vector Offsets Loaded by POST
 
-        .org 0xff00
+        ORG 0xff00
         // XXX - BIOS_COPYRIGHT_STRING
         .ascii "(c) 2002 MandrakeSoft S.A. Written by Kevin Lawton & the Bochs team."
 
-        .org 0xff53
+        ORG 0xff53
         .globl dummy_iret_handler
 dummy_iret_handler:
         iretw
 
-        .org 0xff54
+        ORG 0xff54
         IRQ_ENTRY_ARG 05
 
-        .org 0xfff0 // Power-up Entry Point
+        ORG 0xfff0 // Power-up Entry Point
         ljmpw $0xf000, $post16
 
-        .org 0xfff5
+        ORG 0xfff5
         // BIOS build date
         .ascii "06/23/99"
 
-        .org 0xfffe
+        ORG 0xfffe
         .byte CONFIG_MODEL_ID
         .byte 0x00