Loading 64-bit segments into all selectors

Makefile

@@ -13,8 +13,11 @@ config.mk: | config.default.mk
 boot.bin: boot.elf
 	objcopy -O binary --only-section=.text boot.elf $@
 
-boot.elf: lboot.o fernlader.ld
-	$(LD) $(LDFLAGS) -o $@ lboot.o
+boot.elf: lboot.o loader.o fernlader.ld
+	$(LD) $(LDFLAGS) -o $@ lboot.o loader.o
 
-.S.o:
+lboot.o: lboot.S
 	$(CC) $(CFLAGS) -c -o $@ $(@:.o=.S)
+
+loader.o: loader.c
+	$(CC) $(CFLAGS) -m64 -Os -c -o $@ $(@:.o=.c)

fernlader.ld

@@ -1,6 +1,7 @@
 SECTIONS {
-    . = 0x7C00;
-    .text : {
-        *(*)
+    .text 0x7C00: {
+        lboot.o(.text*, .data*)
+        loader.o(.text*, .data*, .bss*)
     }
+    memmap = ALIGN(8);
 }

lboot.S

@@ -255,9 +255,15 @@ long:
             or          $0x80000001, %eax
             mov         %eax, %cr0
 
-            lgdt        gdt64_ptr
+            // Linearize stack address
+            mov         %ss, %eax
+            shl         $4, %eax
+            add         %eax, %esp
+            mov         %esp, %ebp
 
-            ret
+            // Load long mode GDT, switch to 64-bit CS
+            lgdt        gdt64_ptr
+            ljmp        $0x8, $trampo64
 
             // hang: sleep indefinitely
 hang:       hlt
@@ -303,7 +309,7 @@ gdt64:      // entry 0: null descriptor
             .word       0
             .word       0
             .byte       0
-            .byte       0x90
+            .byte       0x92
             .byte       0x00
             .byte       0
             .set        gdt64_size, .-gdt64
@@ -328,7 +334,17 @@ pd_ptr:     .long       0
 pdp_ptr:    .long       0
 pml4_ptr:   .long       0
 
-            // Memory map area
+            // Points to the end of the memory map
 memmap_end: .word       0
-            .align      8
-memmap:     // begins at end of binary
+
+            .code64
+            // trampo64: Trampoline function to load long-mode segments
+            // before entering the loader.
+trampo64:   
+            mov         $0x10, %eax
+            mov         %eax, %ds
+            mov         %eax, %es
+            mov         %eax, %fs
+            mov         %eax, %gs
+            mov         %eax, %ss // FIXME why does this crash?
+            jmp         loader_main

loader.c

@@ -0,0 +1,5 @@
+void
+loader_main(void)
+{
+	for (;;) {}
+}