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)
16static 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
21static 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
53struct 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 */
73void df_debug(struct pt_regs *regs, long error_code) {}
74
75#else /* !CONFIG_X86_32 */
76
77void 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