1// SPDX-License-Identifier: GPL-2.0
2#include <linux/bug.h>
3#include <linux/io.h>
4#include <linux/types.h>
5#include <linux/kdebug.h>
6#include <linux/signal.h>
7#include <linux/sched.h>
8#include <linux/sched/debug.h>
9#include <linux/sched/task_stack.h>
10#include <linux/uaccess.h>
11#include <linux/hardirq.h>
12#include <linux/kernel.h>
13#include <linux/kexec.h>
14#include <linux/sched/signal.h>
15
16#include <linux/extable.h>
17#include <linux/module.h>	/* print_modules */
18#include <asm/unwinder.h>
19#include <asm/traps.h>
20
21static DEFINE_SPINLOCK(die_lock);
22
23void __noreturn die(const char *str, struct pt_regs *regs, long err)
24{
25	static int die_counter;
26
27	oops_enter();
28
29	spin_lock_irq(&die_lock);
30	console_verbose();
31	bust_spinlocks(1);
32
33	printk("%s: %04lx [#%d]\n", str, err & 0xffff, ++die_counter);
34	print_modules();
35	show_regs(regs);
36
37	printk("Process: %s (pid: %d, stack limit = %p)\n", current->comm,
38			task_pid_nr(current), task_stack_page(current) + 1);
39
40	if (!user_mode(regs) || in_interrupt())
41		dump_mem("Stack: ", KERN_DEFAULT, regs->regs[15],
42			THREAD_SIZE + (unsigned long)task_stack_page(current));
43
44	notify_die(DIE_OOPS, str, regs, err, 255, SIGSEGV);
45
46	bust_spinlocks(0);
47	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
48	spin_unlock_irq(&die_lock);
49	oops_exit();
50
51	if (kexec_should_crash(current))
52		crash_kexec(regs);
53
54	if (in_interrupt())
55		panic("Fatal exception in interrupt");
56
57	if (panic_on_oops)
58		panic("Fatal exception");
59
60	make_task_dead(SIGSEGV);
61}
62
63void die_if_kernel(const char *str, struct pt_regs *regs, long err)
64{
65	if (!user_mode(regs))
66		die(str, regs, err);
67}
68
69/*
70 * try and fix up kernelspace address errors
71 * - userspace errors just cause EFAULT to be returned, resulting in SEGV
72 * - kernel/userspace interfaces cause a jump to an appropriate handler
73 * - other kernel errors are bad
74 */
75void die_if_no_fixup(const char *str, struct pt_regs *regs, long err)
76{
77	if (!user_mode(regs)) {
78		const struct exception_table_entry *fixup;
79		fixup = search_exception_tables(regs->pc);
80		if (fixup) {
81			regs->pc = fixup->fixup;
82			return;
83		}
84
85		die(str, regs, err);
86	}
87}
88
89#ifdef CONFIG_GENERIC_BUG
90static void handle_BUG(struct pt_regs *regs)
91{
92	const struct bug_entry *bug;
93	unsigned long bugaddr = regs->pc;
94	enum bug_trap_type tt;
95
96	if (!is_valid_bugaddr(bugaddr))
97		goto invalid;
98
99	bug = find_bug(bugaddr);
100
101	/* Switch unwinders when unwind_stack() is called */
102	if (bug->flags & BUGFLAG_UNWINDER)
103		unwinder_faulted = 1;
104
105	tt = report_bug(bugaddr, regs);
106	if (tt == BUG_TRAP_TYPE_WARN) {
107		regs->pc += instruction_size(bugaddr);
108		return;
109	}
110
111invalid:
112	die("Kernel BUG", regs, TRAPA_BUG_OPCODE & 0xff);
113}
114
115int is_valid_bugaddr(unsigned long addr)
116{
117	insn_size_t opcode;
118
119	if (addr < PAGE_OFFSET)
120		return 0;
121	if (get_kernel_nofault(opcode, (insn_size_t *)addr))
122		return 0;
123	if (opcode == TRAPA_BUG_OPCODE)
124		return 1;
125
126	return 0;
127}
128#endif
129
130/*
131 * Generic trap handler.
132 */
133BUILD_TRAP_HANDLER(debug)
134{
135	TRAP_HANDLER_DECL;
136
137	/* Rewind */
138	regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
139
140	if (notify_die(DIE_TRAP, "debug trap", regs, 0, vec & 0xff,
141		       SIGTRAP) == NOTIFY_STOP)
142		return;
143
144	force_sig(SIGTRAP);
145}
146
147/*
148 * Special handler for BUG() traps.
149 */
150BUILD_TRAP_HANDLER(bug)
151{
152	TRAP_HANDLER_DECL;
153
154	/* Rewind */
155	regs->pc -= instruction_size(__raw_readw(regs->pc - 4));
156
157	if (notify_die(DIE_TRAP, "bug trap", regs, 0, TRAPA_BUG_OPCODE & 0xff,
158		       SIGTRAP) == NOTIFY_STOP)
159		return;
160
161#ifdef CONFIG_GENERIC_BUG
162	if (__kernel_text_address(instruction_pointer(regs))) {
163		insn_size_t insn = *(insn_size_t *)instruction_pointer(regs);
164		if (insn == TRAPA_BUG_OPCODE)
165			handle_BUG(regs);
166		return;
167	}
168#endif
169
170	force_sig(SIGTRAP);
171}
172
173#ifdef CONFIG_DYNAMIC_FTRACE
174extern void arch_ftrace_nmi_enter(void);
175extern void arch_ftrace_nmi_exit(void);
176#else
177static inline void arch_ftrace_nmi_enter(void) { }
178static inline void arch_ftrace_nmi_exit(void) { }
179#endif
180
181BUILD_TRAP_HANDLER(nmi)
182{
183	TRAP_HANDLER_DECL;
184
185	arch_ftrace_nmi_enter();
186
187	nmi_enter();
188	this_cpu_inc(irq_stat.__nmi_count);
189
190	switch (notify_die(DIE_NMI, "NMI", regs, 0, vec & 0xff, SIGINT)) {
191	case NOTIFY_OK:
192	case NOTIFY_STOP:
193		break;
194	case NOTIFY_BAD:
195		die("Fatal Non-Maskable Interrupt", regs, SIGINT);
196	default:
197		printk(KERN_ALERT "Got NMI, but nobody cared. Ignoring...\n");
198		break;
199	}
200
201	nmi_exit();
202
203	arch_ftrace_nmi_exit();
204}
205