arch/x86/kernel/doublefault.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/mm.h>
   3 #include <linux/sched.h>
   4 #include <linux/sched/debug.h>
   5 #include <linux/init_task.h>
   6 #include <linux/fs.h>
   7
   8 #include <linux/uaccess.h>
   9 #include <asm/pgtable.h>
  10 #include <asm/processor.h>
  11 #include <asm/desc.h>
  12
  13 #ifdef CONFIG_X86_32
  14
  15 #define DOUBLEFAULT_STACKSIZE (1024)
  16 static unsigned long doublefault_stack[DOUBLEFAULT_STACKSIZE];
  17 #define STACK_START (unsigned long)(doublefault_stack+DOUBLEFAULT_STACKSIZE)
  18
  19 #define ptr_ok(x) ((x) > PAGE_OFFSET && (x) < PAGE_OFFSET + MAXMEM)
  20
  21 static void doublefault_fn(void)
  22 {
  23         struct desc_ptr gdt_desc = {0, 0};
  24         unsigned long gdt, tss;
  25
  26         native_store_gdt(&gdt_desc);
  27         gdt = gdt_desc.address;
  28
  29         printk(KERN_EMERG "PANIC: double fault, gdt at %08lx [%d bytes]\n", gdt, gdt_desc.size);
  30
  31         if (ptr_ok(gdt)) {
  32                 gdt += GDT_ENTRY_TSS << 3;
  33                 tss = get_desc_base((struct desc_struct *)gdt);
  34                 printk(KERN_EMERG "double fault, tss at %08lx\n", tss);
  35
  36                 if (ptr_ok(tss)) {
  37                         struct x86_hw_tss *t = (struct x86_hw_tss *)tss;
  38
  39                         printk(KERN_EMERG "eip = %08lx, esp = %08lx\n",
  40                                t->ip, t->sp);
  41
  42                         printk(KERN_EMERG "eax = %08lx, ebx = %08lx, ecx = %08lx, edx = %08lx\n",
  43                                 t->ax, t->bx, t->cx, t->dx);
  44                         printk(KERN_EMERG "esi = %08lx, edi = %08lx\n",
  45                                 t->si, t->di);
  46                 }
  47         }
  48
  49         for (;;)
  50                 cpu_relax();
  51 }
  52
  53 struct x86_hw_tss doublefault_tss __cacheline_aligned = {
  54         .sp0            = STACK_START,
  55         .ss0            = __KERNEL_DS,
  56         .ldt            = 0,
  57         .io_bitmap_base = INVALID_IO_BITMAP_OFFSET,
  58
  59         .ip             = (unsigned long) doublefault_fn,
  60         /* 0x2 bit is always set */
  61         .flags          = X86_EFLAGS_SF | 0x2,
  62         .sp             = STACK_START,
  63         .es             = __USER_DS,
  64         .cs             = __KERNEL_CS,
  65         .ss             = __KERNEL_DS,
  66         .ds             = __USER_DS,
  67         .fs             = __KERNEL_PERCPU,
  68
  69         .__cr3          = __pa_nodebug(swapper_pg_dir),
  70 };
  71
  72 /* dummy for do_double_fault() call */
  73 void df_debug(struct pt_regs *regs, long error_code) {}
  74
  75 #else /* !CONFIG_X86_32 */
  76
  77 void df_debug(struct pt_regs *regs, long error_code)
  78 {
  79         pr_emerg("PANIC: double fault, error_code: 0x%lx\n", error_code);
  80         show_regs(regs);
  81         panic("Machine halted.");
  82 }
  83 #endif