changes to kernel build process

- use a linker script while building kernel
- dump debug symbols in its own file
- strip kernel of debug symbols to reduce size
- add gdbinit to autoload commands

.gdbinit

@@ -0,0 +1,3 @@
+file kernel/kernel.sym
+target remote localhost:1234
+

.gitignore

@@ -41,3 +41,4 @@ bochs.out
 # builds
 *.img
 *.bin
+*.sym

Makefile

@@ -1,6 +1,6 @@
 export CCFLAGS = -fno-builtin -m32 -Wall -nostartfiles -nostdlib -nostdinc -std=gnu99 -g -c -O0
 export ASFLAGS = -f elf32
-export LDFLAGS = -melf_i386 -Ttext 0x1000 --oformat binary # -T linker.ld
+export LDFLAGS = -melf_i386 -Ttext 0x1000 --oformat elf32-i386 -T link.ld
 
 export KERNEL_INCDIR = $(shell pwd)/kernel/include
 export LIBC_INCDIR = $(shell pwd)/libc/include

kernel/Makefile

@@ -13,6 +13,8 @@ entry.o: entry.asm
 	gcc $(CCFLAGS) -o $@ $< -I$(KERNEL_INCDIR) -I$(LIBC_INCDIR)
 
 kernel.bin: entry.o kernel.o ${OBJ}
-	ld $(LDFLAGS) -o $@ $^ -L../build -lc
+	ld $(LDFLAGS) -o kernel.elf $^ -L../build -lc
+	objcopy --only-keep-debug kernel.elf kernel.sym
+	objcopy -O binary kernel.elf $@
 	cp $@ ../build
 

kernel/entry.asm

@@ -1,5 +1,6 @@
 [bits 32]
 [extern kmain]
+_start:
     call kmain
     jmp $               ; this should happen when returning from kernel main
                         ; shutdown?

kernel/link.ld

@@ -1,32 +1,5 @@
-/* Link.ld -- Linker script for the kernel - ensure everything goes in the */
-/*            Correct place.  */
-/*            Original file taken from Bran's Kernel Development */
-/*            tutorials: http://www.osdever.net/bkerndev/index.php. */
-
-ENTRY(start)
-SECTIONS
-{
-  .text 0x100000 :
-  {
-    code = .; _code = .; __code = .;
-    *(.text)
-    . = ALIGN(4096);
-  }
-
-  .data :
-  {
-     data = .; _data = .; __data = .;
-     *(.data)
-     *(.rodata)
-     . = ALIGN(4096);
-  }
-
-  .bss :
-  {
-    bss = .; _bss = .; __bss = .;
-    *(.bss)
-    . = ALIGN(4096);
-  }
-
-  end = .; _end = .; __end = .;
+SECTIONS {
+    . = 0x1000;
+    .text : { * (.text); }
 }
+