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 000000000000..789af3e9fb1f
--- /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)
+};