1 files changed, 65 insertions, 0 deletions
diff --git a/arch/i386/kernel/doublefault.c b/arch/i386/kernel/doublefault.c
new file mode 100644
index 00000000000..789af3e9fb1
--- /dev/null
+++ b/arch/i386/kernel/doublefault.c
@@ -0,0 +1,65 @@
+#include <linux/mm.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/init_task.h>
+#include <linux/fs.h>
+
+#include <asm/uaccess.h>
+#include <asm/pgtable.h>
+#include <asm/processor.h>
+#include <asm/desc.h>
+
+#define DOUBLEFAULT_STACKSIZE (1024)
+static unsigned long doublefault_stack[DOUBLEFAULT_STACKSIZE];
+#define STACK_START (unsigned long)(doublefault_stack+DOUBLEFAULT_STACKSIZE)
+
+#define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + 0x1000000)
+
+static void doublefault_fn(void)
+{
+	struct Xgt_desc_struct gdt_desc = {0, 0};
+	unsigned long gdt, tss;
+
+	__asm__ __volatile__("sgdt %0": "=m" (gdt_desc): :"memory");
+	gdt = gdt_desc.address;
+
+	printk("double fault, gdt at %08lx [%d bytes]\n", gdt, gdt_desc.size);
+
+	if (ptr_ok(gdt)) {
+		gdt += GDT_ENTRY_TSS << 3;
+		tss = *(u16 *)(gdt+2);
+		tss += *(u8 *)(gdt+4) << 16;
+		tss += *(u8 *)(gdt+7) << 24;
+		printk("double fault, tss at %08lx\n", tss);
+
+		if (ptr_ok(tss)) {
+			struct tss_struct *t = (struct tss_struct *)tss;
+
+			printk("eip = %08lx, esp = %08lx\n", t->eip, t->esp);
+
+			printk("eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n",
+				t->eax, t->ebx, t->ecx, t->edx);
+			printk("esi = %08lx, edi = %08lx\n",
+				t->esi, t->edi);
+		}
+	}
+
+	for (;;) /* nothing */;
+}
+
+struct tss_struct doublefault_tss __cacheline_aligned = {
+	.esp0		= STACK_START,
+	.ss0		= __KERNEL_DS,
+	.ldt		= 0,
+	.io_bitmap_base	= INVALID_IO_BITMAP_OFFSET,
+
+	.eip		= (unsigned long) doublefault_fn,
+	.eflags		= X86_EFLAGS_SF | 0x2,	/* 0x2 bit is always set */
+	.esp		= STACK_START,
+	.es		= __USER_DS,
+	.cs		= __KERNEL_CS,
+	.ss		= __KERNEL_DS,
+	.ds		= __USER_DS,
+
+	.__cr3		= __pa(swapper_pg_dir)
+};