# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1297833963 -7200
# Node ID 611b2d66420bd94f9f0c7c45101dfd1e18200501
# Parent  7e40f14617ed8c0ff7821942bb7ed800b0871650
segment descriptors

diff -r 7e40f14617ed -r 611b2d66420b .gdbinit
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/.gdbinit	Wed Feb 16 07:26:03 2011 +0200
@@ -0,0 +1,2 @@
+file kernel.elf
+target remote localhost:1234
diff -r 7e40f14617ed -r 611b2d66420b Makefile
--- a/Makefile	Thu Jan 13 20:24:10 2011 +0200
+++ b/Makefile	Wed Feb 16 07:26:03 2011 +0200
@@ -1,6 +1,7 @@
 # collect all of our C and assembly source files
 csrc = $(wildcard src/*.c) $(wildcard src/klibc/*.c)
 asmsrc = $(wildcard src/*.S) $(wildcard src/klibc/*.S)
+dep = $(asmsrc:.S=.d) $(csrc:.c=.d)
 
 # each source file will generate one object file
 obj = $(asmsrc:.S=.o) $(csrc:.c=.o)
@@ -20,6 +21,18 @@
 $(bin): $(obj)
 	ld -melf_i386 -o $@ -Ttext 0x100000 -e kentry $(obj)
 
+-include $(dep)
+
+%.d: %.c
+	@$(CPP) $(CFLAGS) -MM -MT $(@:.d=.o) $< >$@
+
+%.d: %.S
+	@$(CPP) $(ASFLAGS) -MM -MT $(@:.d=.o) $< >$@
+
 .PHONY: clean
 clean:
 	rm -f $(obj) $(bin)
+
+.PHONY: cleandep
+cleandep:
+	rm -f $(dep)
diff -r 7e40f14617ed -r 611b2d66420b src/main.c
--- a/src/main.c	Thu Jan 13 20:24:10 2011 +0200
+++ b/src/main.c	Wed Feb 16 07:26:03 2011 +0200
@@ -2,6 +2,7 @@
 #include "vid.h"
 #include "term.h"
 #include <asmops.h>
+#include "segm.h"
 
 /* special keys */
 enum {
@@ -31,12 +32,13 @@
 	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0									/* 70 - 7f */
 };
 
-
 void kmain(void)
 {
 	clear_scr();
 	puts("kernel starting up");
 
+	init_segm();
+
 	set_text_color(YELLOW);
 	puts("<initialization code goes here>");
 	set_text_color(LTGRAY);
@@ -49,7 +51,7 @@
 		} while(!(keypress & 1));
 		inb(c, 0x60);
 		if(!(c & 0x80)) {
-			putchar(keycodes[c]);
+			putchar(keycodes[(int)c]);
 		}
 	}
 }
diff -r 7e40f14617ed -r 611b2d66420b src/segm-asm.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/segm-asm.S	Wed Feb 16 07:26:03 2011 +0200
@@ -0,0 +1,41 @@
+	.data
+off:.long 0
+seg:.short 0
+
+	.align
+	.short 0
+gdt_lim:
+	.short 0
+gdt_addr:
+	.long 0
+
+	.text
+/* setup_selectors(uint16_t code, uint16_t data)
+ * loads the requested selectors to all the selector registers */
+	.globl setup_selectors
+setup_selectors:
+	/* setup data selectors */
+	movl 8(%esp), %eax
+	movw %ax, %ss
+	movw %ax, %es
+	movw %ax, %ds
+	movw %ax, %gs
+	movw %ax, %fs
+	/* setup code selector */
+	movl 4(%esp), %eax
+	movw %ax, (seg)
+	movl $ldcs, (off)
+	ljmp *off
+ldcs:
+	ret
+
+/* set_gdt(uint32_t addr, uint16_t limit)
+ * loads the GDTR with the new address and limit for the GDT */
+	.globl set_gdt
+set_gdt:
+	movl 4(%esp), %eax
+	movl %eax, (gdt_addr)
+	movw 8(%esp), %ax
+	movw %ax, (gdt_lim)
+	lgdt (gdt_lim)	
+	ret
diff -r 7e40f14617ed -r 611b2d66420b src/segm.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/segm.c	Wed Feb 16 07:26:03 2011 +0200
@@ -0,0 +1,57 @@
+#include <string.h>
+#include "segm.h"
+
+#define BIT_ACCESSED	(1 << 8)
+#define BIT_WR			(1 << 9)
+#define BIT_RD			(1 << 9)
+#define BIT_EXP_DOWN	(1 << 10)
+#define BIT_CONFORMING	(1 << 10)
+#define BIT_CODE		(1 << 11)
+#define BIT_NOSYS		(1 << 12)
+#define BIT_PRESENT		(1 << 15)
+
+#define BIT_BIG			(1 << 6)
+#define BIT_DEFAULT		(1 << 6)
+#define BIT_GRAN		(1 << 7)
+
+enum {TYPE_DATA, TYPE_CODE};
+
+static void segm_desc(desc_t *desc, uint32_t base, uint32_t limit, int dpl, int type);
+
+
+static desc_t gdt[4];
+
+
+void init_segm(void)
+{
+	memset(gdt, 0, sizeof gdt);
+	segm_desc(gdt + SEGM_KCODE, 0, 0xffffffff, 0, TYPE_CODE);
+	segm_desc(gdt + SEGM_KDATA, 0, 0xffffffff, 0, TYPE_DATA);
+
+	set_gdt((uint32_t)gdt, sizeof gdt - 1);
+
+	setup_selectors(selector(SEGM_KCODE, 0), selector(SEGM_KDATA, 0));
+}
+
+uint16_t selector(int idx, int rpl)
+{
+	return (idx << 3) | (rpl & 3);
+}
+
+static void segm_desc(desc_t *desc, uint32_t base, uint32_t limit, int dpl, int type)
+{
+	desc->d[0] = limit & 0xffff; /* low order 16bits of limit */
+	desc->d[1] = base & 0xffff;  /* low order 16bits of base */
+
+	/* third 16bit part contains the last 8 bits of base, the 2 priviledge
+	 * level bits starting on bit 13, present flag on bit 15, and type bits
+	 * starting from bit 8
+	 */
+	desc->d[2] = ((base >> 16) & 0xff) | ((dpl & 3) << 13) | BIT_PRESENT |
+		BIT_NOSYS | (type == TYPE_DATA ? BIT_WR : (BIT_RD | BIT_CODE));
+
+	/* last 16bit part contains the last nibble of limit, the last byte of
+	 * base, and the granularity and deafult/big flags in bits 23 and 22 resp.
+	 */
+	desc->d[3] = ((limit >> 16) & 0xf) | ((base >> 16) & 0xff00) | BIT_GRAN | BIT_BIG;
+}
diff -r 7e40f14617ed -r 611b2d66420b src/segm.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/segm.h	Wed Feb 16 07:26:03 2011 +0200
@@ -0,0 +1,21 @@
+#ifndef SEGM_H_
+#define SEGM_H_
+
+#define SEGM_KCODE	1
+#define SEGM_KDATA	2
+
+typedef struct {
+	uint16_t d[4];
+} desc_t;
+
+void init_segm(void);
+
+uint16_t selector(int idx, int rpl);
+
+/* these functions are implemented in segm-asm.S */
+void setup_selectors(uint16_t code, uint16_t data);
+void set_gdt(uint32_t addr, uint16_t limit);
+
+
+
+#endif	/* SEGM_H_ */