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Diffstat (limited to 'arch/i386/cpu/cpu.c')
-rw-r--r--arch/i386/cpu/cpu.c57
1 files changed, 57 insertions, 0 deletions
diff --git a/arch/i386/cpu/cpu.c b/arch/i386/cpu/cpu.c
index bd6aced87..ae40384f0 100644
--- a/arch/i386/cpu/cpu.c
+++ b/arch/i386/cpu/cpu.c
@@ -37,6 +37,61 @@
#include <command.h>
#include <asm/interrupt.h>
+/* Constructor for a conventional segment GDT (or LDT) entry */
+/* This is a macro so it can be used in initializers */
+#define GDT_ENTRY(flags, base, limit) \
+ ((((base) & 0xff000000ULL) << (56-24)) | \
+ (((flags) & 0x0000f0ffULL) << 40) | \
+ (((limit) & 0x000f0000ULL) << (48-16)) | \
+ (((base) & 0x00ffffffULL) << 16) | \
+ (((limit) & 0x0000ffffULL)))
+
+/* Simple and small GDT entries for booting only */
+
+#define GDT_ENTRY_32BIT_CS 2
+#define GDT_ENTRY_32BIT_DS (GDT_ENTRY_32BIT_CS + 1)
+#define GDT_ENTRY_16BIT_CS (GDT_ENTRY_32BIT_DS + 1)
+#define GDT_ENTRY_16BIT_DS (GDT_ENTRY_16BIT_CS + 1)
+
+/*
+ * Set up the GDT
+ */
+
+struct gdt_ptr {
+ u16 len;
+ u32 ptr;
+} __attribute__((packed));
+
+static void reload_gdt(void)
+{
+ /* There are machines which are known to not boot with the GDT
+ being 8-byte unaligned. Intel recommends 16 byte alignment. */
+ static const u64 boot_gdt[] __attribute__((aligned(16))) = {
+ /* CS: code, read/execute, 4 GB, base 0 */
+ [GDT_ENTRY_32BIT_CS] = GDT_ENTRY(0xc09b, 0, 0xfffff),
+ /* DS: data, read/write, 4 GB, base 0 */
+ [GDT_ENTRY_32BIT_DS] = GDT_ENTRY(0xc093, 0, 0xfffff),
+ /* 16-bit CS: code, read/execute, 64 kB, base 0 */
+ [GDT_ENTRY_16BIT_CS] = GDT_ENTRY(0x109b, 0, 0x0ffff),
+ /* 16-bit DS: data, read/write, 64 kB, base 0 */
+ [GDT_ENTRY_16BIT_DS] = GDT_ENTRY(0x1093, 0, 0x0ffff),
+ };
+ static struct gdt_ptr gdt;
+
+ gdt.len = sizeof(boot_gdt)-1;
+ gdt.ptr = (u32)&boot_gdt;
+
+ asm volatile("lgdtl %0\n" \
+ "movl $((2+1)*8), %%ecx\n" \
+ "movl %%ecx, %%ds\n" \
+ "movl %%ecx, %%es\n" \
+ "movl %%ecx, %%fs\n" \
+ "movl %%ecx, %%gs\n" \
+ "movl %%ecx, %%ss" \
+ : : "m" (gdt) : "ecx");
+}
+
+
int cpu_init_f(void)
{
/* initialize FPU, reset EM, set MP and NE */
@@ -51,6 +106,8 @@ int cpu_init_f(void)
int cpu_init_r(void)
{
+ reload_gdt();
+
/* Initialize core interrupt and exception functionality of CPU */
cpu_init_interrupts ();
return 0;