From a9c4b5ddc0a4e3fc363471295395984715bfb841 Mon Sep 17 00:00:00 2001
From: Jacek Galowicz <galowicz@lfbs.rwth-aachen.de>
Date: Tue, 19 Apr 2011 18:51:59 +0200
Subject: [PATCH] Encapsulated IDT-/GDT-descriptor configuring code into helper
 functions.

---
 arch/x86/include/asm/gdt.h | 10 ++++++++++
 arch/x86/include/asm/idt.h | 10 ++++++++++
 arch/x86/kernel/gdt.c      | 22 +++++++++++++++-------
 arch/x86/kernel/idt.c      | 19 ++++++++++++++-----
 4 files changed, 49 insertions(+), 12 deletions(-)

diff --git a/arch/x86/include/asm/gdt.h b/arch/x86/include/asm/gdt.h
index cdb65d46..fb4bd4c1 100644
--- a/arch/x86/include/asm/gdt.h
+++ b/arch/x86/include/asm/gdt.h
@@ -115,6 +115,16 @@ typedef struct {
  */
 void gdt_install(void);
 
+/** @brief Configures and returns a GDT descriptor with chosen attributes
+ *
+ * Just feed this function with address, limit and the flags 
+ * you have seen in idt.h
+ *
+ * @return a preconfigured gdt descriptor
+ */
+gdt_entry_t configure_gdt_entry(unsigned long base, unsigned long limit,
+		unsigned char access, unsigned char gran);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/arch/x86/include/asm/idt.h b/arch/x86/include/asm/idt.h
index a43d4383..28fde65a 100644
--- a/arch/x86/include/asm/idt.h
+++ b/arch/x86/include/asm/idt.h
@@ -116,6 +116,16 @@ void idt_install(void);
 void idt_set_gate(unsigned char num, unsigned long base, unsigned short sel,
 		  unsigned char flags);
 
+/** @brief Configures and returns a IDT entry with chosen attributes
+ *
+ * Just feed this function with base, selector and the flags
+ * you have seen in idt.h
+ *
+ * @return a preconfigured idt descriptor
+ */
+idt_entry_t configure_idt_entry(unsigned long base, unsigned short sel,
+		  unsigned char flags);
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/arch/x86/kernel/gdt.c b/arch/x86/kernel/gdt.c
index 33b136ee..5be409c6 100644
--- a/arch/x86/kernel/gdt.c
+++ b/arch/x86/kernel/gdt.c
@@ -157,19 +157,27 @@ int create_default_frame(task_t* task, entry_point_t ep, void* arg)
 static void gdt_set_gate(int num, unsigned long base, unsigned long limit,
 			  unsigned char access, unsigned char gran)
 {
+	gdt[num] = configure_gdt_entry(base, limit, access, gran);
+}
 
+gdt_entry_t configure_gdt_entry(unsigned long base, unsigned long limit,
+		unsigned char access, unsigned char gran)
+{
+	gdt_entry_t desc;
 	/* Setup the descriptor base address */
-	gdt[num].base_low = (base & 0xFFFF);
-	gdt[num].base_middle = (base >> 16) & 0xFF;
-	gdt[num].base_high = (base >> 24) & 0xFF;
+	desc.base_low = (base & 0xFFFF);
+	desc.base_middle = (base >> 16) & 0xFF;
+	desc.base_high = (base >> 24) & 0xFF;
 
 	/* Setup the descriptor limits */
-	gdt[num].limit_low = (limit & 0xFFFF);
-	gdt[num].granularity = ((limit >> 16) & 0x0F);
+	desc.limit_low = (limit & 0xFFFF);
+	desc.granularity = ((limit >> 16) & 0x0F);
 
 	/* Finally, set up the granularity and access flags */
-	gdt[num].granularity |= (gran & 0xF0);
-	gdt[num].access = access;
+	desc.granularity |= (gran & 0xF0);
+	desc.access = access;
+
+	return desc;
 }
 
 /* 
diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c
index fd8156c4..fe3b2bf4 100644
--- a/arch/x86/kernel/idt.c
+++ b/arch/x86/kernel/idt.c
@@ -48,16 +48,25 @@ static idt_ptr_t idtp;
 void idt_set_gate(unsigned char num, unsigned long base, unsigned short sel,
 		  unsigned char flags)
 {
+	idt[num] = configure_idt_entry(base, sel, flags);
+}
+
+idt_entry_t configure_idt_entry(unsigned long base, unsigned short sel,
+		  unsigned char flags)
+{
+	idt_entry_t desc;
 
 	/* The interrupt routine's base address */
-	idt[num].base_lo = (base & 0xFFFF);
-	idt[num].base_hi = (base >> 16) & 0xFFFF;
+	desc.base_lo = (base & 0xFFFF);
+	desc.base_hi = (base >> 16) & 0xFFFF;
 
 	/* The segment or 'selector' that this IDT entry will use
 	 *  is set here, along with any access flags */
-	idt[num].sel = sel;
-	idt[num].always0 = 0;
-	idt[num].flags = flags;
+	desc.sel = sel;
+	desc.always0 = 0;
+	desc.flags = flags;
+
+	return desc;
 }
 
 extern void isrsyscall(void);