Improved Linker script & Makefile

Makefile

@@ -1,21 +1,41 @@
-objects = entry.o kernel.o task.o handler.o interrupt.o v86.o print.o tss.o dosfs/dosfs.o gdt.o usermode.o paging.o fault.o tests.o kbd.o helper.o progs.o disk.o hexedit.o
-CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding -march=i686 -fno-stack-protector -Wno-int-conversion -nostdlib -c
+objects = entry.o kernel.o task.o handler.o interrupt.o v86.o print.o tss.o dosfs/dosfs.o gdt.o\
+		  usermode.o paging.o fault.o tests.o kbd.o helper.o progs.o disk.o hexedit.o
+CFLAGS = -target "i686-elf" -m32 -mgeneral-regs-only -ffreestanding\
+		 -march=i686 -fno-stack-protector -Wno-int-conversion -nostdlib -c
+LFLAGS = -Wl,--gc-sections -Wl,--print-gc-sections -m32 -nostartfiles -nostdlib
+
+ifeq ($(OUTFILE),)
+OUTFILE = virtdisk.bin
+endif
+
+.PHONY: $(OUTFILE)
+
+all: $(OUTFILE)
+
+$(OUTFILE): boot.bin kernel.bin
+	# Copy to boot sector, don't overwrite MBR
+	dd bs=400 count=1 conv=notrunc if=boot.bin of=$@
+	# Write kernel beyond boot sector, maximum 128K (256 sectors)
+	dd bs=512 count=256 seek=1 conv=notrunc if=kernel.bin of=$@
+
+boot.bin: boot.nasm
+	nasm -o $@ $<
+
+kernel.bin: out.o link.ld
+	clang $(LFLAGS) -Wl,-M -Tlink.ld -ffreestanding -o $@ $<
+
+out.o: $(objects)
+	clang $(LFLAGS) -e entry -r -o $@ $^
 
 %.o: %.nasm
 	nasm -f elf32 -o $@ $<
 
 %.o: %.c
-	clang $(CFLAGS) -O2 -o $@ $<
+	clang $(CFLAGS) -ffunction-sections -fdata-sections -Os -o $@ $<
 
-all: $(objects)
-	nasm boot.nasm -o boot.bin
-	gcc -Tlink.ld -Wl,-M -m32 -ffreestanding -nostartfiles -nostdlib -o kernel.bin\
-		$(objects)
-	dd bs=400 count=1 conv=notrunc if=boot.bin of=virtdisk.bin
-	dd bs=512 seek=1 conv=notrunc if=kernel.bin of=virtdisk.bin
 virtdisk:
 	dd bs=1M count=32 if=/dev/zero of=virtdisk.bin
 	echo -n -e '\x55\xaa' | dd bs=1 seek=510 conv=notrunc of=virtdisk.bin
 
 clean:
-	rm $(objects)
+	rm -f $(objects) out.o kernel.bin boot.bin

hexedit.c

@@ -5,12 +5,12 @@
 #define BLOCKSHIFT 16 // blockSize = 1 << blockShift
 #define MAXFILESIZE 0x80000000 // 2GB
 #define TOTALBLOCKS (MAXFILESIZE/BLOCKSIZE)
-uint16_t writtenMap[TOTALBLOCKS];
-uint32_t blockLenMap[TOTALBLOCKS];
+uint16_t writtenMap[TOTALBLOCKS] __attribute__((section(".progbss")));;
+uint32_t blockLenMap[TOTALBLOCKS] __attribute__((section(".progbss")));;
 // NOTE This is linked at the end of program BSS section,
 // so that it can be expanded without telling C how much
 // it actually needs
-uint8_t writeStoreBase[BLOCKSIZE] __attribute__((section(".bss.end")));
+uint8_t writeStoreBase[BLOCKSIZE] __attribute__((section(".proglatebss")));
 void HexEditor(uint8_t *path, VOLINFO *vi) {
     uint32_t err;
     uint16_t *vga_text = (uint16_t *)0xb8000;

link.ld

@@ -10,33 +10,40 @@ SECTIONS {
 
     .data : {
         *(.data);
+        *(.data*);
         *(.rodata);
         *(.rodata*);
         _edata = .;
     }
 
     .realmode 0x4000 :
-        AT ( ADDR(.data) + SIZEOF(.data) )
+        AT ( _edata )
         { _v86code = .; *(.v86); _ev86code = .; }
 
-    . = ADDR(.data) + SIZEOF(.data) + SIZEOF(.realmode);
+    . = _edata + SIZEOF(.realmode);
     .thing : { _loadusercode = .; }
 
-    .usermode 0x400000 :
-        AT ( ADDR(.data) + SIZEOF(.data) + SIZEOF(.realmode) )
-        { _usercode = .; *(.user); _eusercode = .; }
-
-    .bss 0x400000 : {
+    .usermode 0x400000 : AT(_loadusercode) {
+        _usercode = .; *(.user); _eusercode = .;
+    }
+    .bss 0x400000 (NOLOAD) : AT(_loadusercode + SIZEOF(.usermode)) {
         _bprogstart = .;
-        hexedit.o(.bss);
+        *(.progbss);
+        *(.progbss*);
         _bprogend = .;
-        hexedit.o(.bss.end);
+        *(.proglatebss);
+        *(.proglatebss*);
     }
 
     . = ADDR(.data) + SIZEOF(.data) + SIZEOF(.realmode) + SIZEOF(.usermode);
 
     .bss : ALIGN(0x1000)
     {
-        _bstart = .; *(.bss); _bend = .;
+        _bstart = .; *(.bss); *(.bss*) _bend = .;
+    }
+
+    /DISCARD/ : {
+        *(.note*)
+        *(.comment*)
     }
 }

progs.c

@@ -1,6 +1,4 @@
 #include "progs.h"
-#include "helper.h"
-#include "kbd.h"
 
 void TextViewTest(uint8_t *path, VOLINFO *vi) {
     uint16_t *vga_text = (uint16_t *)0xb8000;