root/arch/x86/kernel/doublefault_32.c

DEFINITIONS

1. doublefault_fn

#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 + MAXMEM)

static void doublefault_fn(void)
{
        struct desc_ptr gdt_desc = {0, 0};
        unsigned long gdt, tss;

        store_gdt(&gdt_desc);
        gdt = gdt_desc.address;

        printk(KERN_EMERG "PANIC: 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(KERN_EMERG "double fault, tss at %08lx\n", tss);

                if (ptr_ok(tss)) {
                        struct x86_hw_tss *t = (struct x86_hw_tss *)tss;

                        printk(KERN_EMERG "eip = %08lx, esp = %08lx\n",
                               t->ip, t->sp);

                        printk(KERN_EMERG "eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n",
                                t->ax, t->bx, t->cx, t->dx);
                        printk(KERN_EMERG "esi = %08lx, edi = %08lx\n",
                                t->si, t->di);
                }
        }

        for (;;)
                cpu_relax();
}

struct tss_struct doublefault_tss __cacheline_aligned = {
        .x86_tss = {
                .sp0            = STACK_START,
                .ss0            = __KERNEL_DS,
                .ldt            = 0,
                .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,

                .ip             = (unsigned long) doublefault_fn,
                /* 0x2 bit is always set */
                .flags          = X86_EFLAGS_SF | 0x2,
                .sp             = STACK_START,
                .es             = __USER_DS,
                .cs             = __KERNEL_CS,
                .ss             = __KERNEL_DS,
                .ds             = __USER_DS,
                .fs             = __KERNEL_PERCPU,

                .__cr3          = __pa_nodebug(swapper_pg_dir),
        }
};