xref: /linux/arch/riscv/kernel/traps.c (revision 8e07e0e3964ca4e23ce7b68e2096fe660a888942) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Copyright (C) 2012 Regents of the University of California
4  */
5 
6 #include <linux/cpu.h>
7 #include <linux/kernel.h>
8 #include <linux/init.h>
9 #include <linux/sched.h>
10 #include <linux/sched/debug.h>
11 #include <linux/sched/signal.h>
12 #include <linux/signal.h>
13 #include <linux/kdebug.h>
14 #include <linux/uaccess.h>
15 #include <linux/kprobes.h>
16 #include <linux/uprobes.h>
17 #include <asm/uprobes.h>
18 #include <linux/mm.h>
19 #include <linux/module.h>
20 #include <linux/irq.h>
21 #include <linux/kexec.h>
22 #include <linux/entry-common.h>
23 
24 #include <asm/asm-prototypes.h>
25 #include <asm/bug.h>
26 #include <asm/cfi.h>
27 #include <asm/csr.h>
28 #include <asm/processor.h>
29 #include <asm/ptrace.h>
30 #include <asm/syscall.h>
31 #include <asm/thread_info.h>
32 #include <asm/vector.h>
33 #include <asm/irq_stack.h>
34 
35 int show_unhandled_signals = 1;
36 
37 static DEFINE_SPINLOCK(die_lock);
38 
39 static int copy_code(struct pt_regs *regs, u16 *val, const u16 *insns)
40 {
41 	const void __user *uaddr = (__force const void __user *)insns;
42 
43 	if (!user_mode(regs))
44 		return get_kernel_nofault(*val, insns);
45 
46 	/* The user space code from other tasks cannot be accessed. */
47 	if (regs != task_pt_regs(current))
48 		return -EPERM;
49 
50 	return copy_from_user_nofault(val, uaddr, sizeof(*val));
51 }
52 
53 static void dump_instr(const char *loglvl, struct pt_regs *regs)
54 {
55 	char str[sizeof("0000 ") * 12 + 2 + 1], *p = str;
56 	const u16 *insns = (u16 *)instruction_pointer(regs);
57 	long bad;
58 	u16 val;
59 	int i;
60 
61 	for (i = -10; i < 2; i++) {
62 		bad = copy_code(regs, &val, &insns[i]);
63 		if (!bad) {
64 			p += sprintf(p, i == 0 ? "(%04hx) " : "%04hx ", val);
65 		} else {
66 			printk("%sCode: Unable to access instruction at 0x%px.\n",
67 			       loglvl, &insns[i]);
68 			return;
69 		}
70 	}
71 	printk("%sCode: %s\n", loglvl, str);
72 }
73 
74 void die(struct pt_regs *regs, const char *str)
75 {
76 	static int die_counter;
77 	int ret;
78 	long cause;
79 	unsigned long flags;
80 
81 	oops_enter();
82 
83 	spin_lock_irqsave(&die_lock, flags);
84 	console_verbose();
85 	bust_spinlocks(1);
86 
87 	pr_emerg("%s [#%d]\n", str, ++die_counter);
88 	print_modules();
89 	if (regs) {
90 		show_regs(regs);
91 		dump_instr(KERN_EMERG, regs);
92 	}
93 
94 	cause = regs ? regs->cause : -1;
95 	ret = notify_die(DIE_OOPS, str, regs, 0, cause, SIGSEGV);
96 
97 	if (kexec_should_crash(current))
98 		crash_kexec(regs);
99 
100 	bust_spinlocks(0);
101 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
102 	spin_unlock_irqrestore(&die_lock, flags);
103 	oops_exit();
104 
105 	if (in_interrupt())
106 		panic("Fatal exception in interrupt");
107 	if (panic_on_oops)
108 		panic("Fatal exception");
109 	if (ret != NOTIFY_STOP)
110 		make_task_dead(SIGSEGV);
111 }
112 
113 void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
114 {
115 	struct task_struct *tsk = current;
116 
117 	if (show_unhandled_signals && unhandled_signal(tsk, signo)
118 	    && printk_ratelimit()) {
119 		pr_info("%s[%d]: unhandled signal %d code 0x%x at 0x" REG_FMT,
120 			tsk->comm, task_pid_nr(tsk), signo, code, addr);
121 		print_vma_addr(KERN_CONT " in ", instruction_pointer(regs));
122 		pr_cont("\n");
123 		__show_regs(regs);
124 		dump_instr(KERN_EMERG, regs);
125 	}
126 
127 	force_sig_fault(signo, code, (void __user *)addr);
128 }
129 
130 static void do_trap_error(struct pt_regs *regs, int signo, int code,
131 	unsigned long addr, const char *str)
132 {
133 	current->thread.bad_cause = regs->cause;
134 
135 	if (user_mode(regs)) {
136 		do_trap(regs, signo, code, addr);
137 	} else {
138 		if (!fixup_exception(regs))
139 			die(regs, str);
140 	}
141 }
142 
143 #if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_RISCV_ALTERNATIVE)
144 #define __trap_section __noinstr_section(".xip.traps")
145 #else
146 #define __trap_section noinstr
147 #endif
148 #define DO_ERROR_INFO(name, signo, code, str)					\
149 asmlinkage __visible __trap_section void name(struct pt_regs *regs)		\
150 {										\
151 	if (user_mode(regs)) {							\
152 		irqentry_enter_from_user_mode(regs);				\
153 		do_trap_error(regs, signo, code, regs->epc, "Oops - " str);	\
154 		irqentry_exit_to_user_mode(regs);				\
155 	} else {								\
156 		irqentry_state_t state = irqentry_nmi_enter(regs);		\
157 		do_trap_error(regs, signo, code, regs->epc, "Oops - " str);	\
158 		irqentry_nmi_exit(regs, state);					\
159 	}									\
160 }
161 
162 DO_ERROR_INFO(do_trap_unknown,
163 	SIGILL, ILL_ILLTRP, "unknown exception");
164 DO_ERROR_INFO(do_trap_insn_misaligned,
165 	SIGBUS, BUS_ADRALN, "instruction address misaligned");
166 DO_ERROR_INFO(do_trap_insn_fault,
167 	SIGSEGV, SEGV_ACCERR, "instruction access fault");
168 
169 asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *regs)
170 {
171 	bool handled;
172 
173 	if (user_mode(regs)) {
174 		irqentry_enter_from_user_mode(regs);
175 
176 		local_irq_enable();
177 
178 		handled = riscv_v_first_use_handler(regs);
179 
180 		local_irq_disable();
181 
182 		if (!handled)
183 			do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc,
184 				      "Oops - illegal instruction");
185 
186 		irqentry_exit_to_user_mode(regs);
187 	} else {
188 		irqentry_state_t state = irqentry_nmi_enter(regs);
189 
190 		do_trap_error(regs, SIGILL, ILL_ILLOPC, regs->epc,
191 			      "Oops - illegal instruction");
192 
193 		irqentry_nmi_exit(regs, state);
194 	}
195 }
196 
197 DO_ERROR_INFO(do_trap_load_fault,
198 	SIGSEGV, SEGV_ACCERR, "load access fault");
199 
200 asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
201 {
202 	if (user_mode(regs)) {
203 		irqentry_enter_from_user_mode(regs);
204 
205 		if (handle_misaligned_load(regs))
206 			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
207 			      "Oops - load address misaligned");
208 
209 		irqentry_exit_to_user_mode(regs);
210 	} else {
211 		irqentry_state_t state = irqentry_nmi_enter(regs);
212 
213 		if (handle_misaligned_load(regs))
214 			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
215 			      "Oops - load address misaligned");
216 
217 		irqentry_nmi_exit(regs, state);
218 	}
219 }
220 
221 asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs *regs)
222 {
223 	if (user_mode(regs)) {
224 		irqentry_enter_from_user_mode(regs);
225 
226 		if (handle_misaligned_store(regs))
227 			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
228 				"Oops - store (or AMO) address misaligned");
229 
230 		irqentry_exit_to_user_mode(regs);
231 	} else {
232 		irqentry_state_t state = irqentry_nmi_enter(regs);
233 
234 		if (handle_misaligned_store(regs))
235 			do_trap_error(regs, SIGBUS, BUS_ADRALN, regs->epc,
236 				"Oops - store (or AMO) address misaligned");
237 
238 		irqentry_nmi_exit(regs, state);
239 	}
240 }
241 DO_ERROR_INFO(do_trap_store_fault,
242 	SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
243 DO_ERROR_INFO(do_trap_ecall_s,
244 	SIGILL, ILL_ILLTRP, "environment call from S-mode");
245 DO_ERROR_INFO(do_trap_ecall_m,
246 	SIGILL, ILL_ILLTRP, "environment call from M-mode");
247 
248 static inline unsigned long get_break_insn_length(unsigned long pc)
249 {
250 	bug_insn_t insn;
251 
252 	if (get_kernel_nofault(insn, (bug_insn_t *)pc))
253 		return 0;
254 
255 	return GET_INSN_LENGTH(insn);
256 }
257 
258 static bool probe_single_step_handler(struct pt_regs *regs)
259 {
260 	bool user = user_mode(regs);
261 
262 	return user ? uprobe_single_step_handler(regs) : kprobe_single_step_handler(regs);
263 }
264 
265 static bool probe_breakpoint_handler(struct pt_regs *regs)
266 {
267 	bool user = user_mode(regs);
268 
269 	return user ? uprobe_breakpoint_handler(regs) : kprobe_breakpoint_handler(regs);
270 }
271 
272 void handle_break(struct pt_regs *regs)
273 {
274 	if (probe_single_step_handler(regs))
275 		return;
276 
277 	if (probe_breakpoint_handler(regs))
278 		return;
279 
280 	current->thread.bad_cause = regs->cause;
281 
282 	if (user_mode(regs))
283 		force_sig_fault(SIGTRAP, TRAP_BRKPT, (void __user *)regs->epc);
284 #ifdef CONFIG_KGDB
285 	else if (notify_die(DIE_TRAP, "EBREAK", regs, 0, regs->cause, SIGTRAP)
286 								== NOTIFY_STOP)
287 		return;
288 #endif
289 	else if (report_bug(regs->epc, regs) == BUG_TRAP_TYPE_WARN ||
290 		 handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN)
291 		regs->epc += get_break_insn_length(regs->epc);
292 	else
293 		die(regs, "Kernel BUG");
294 }
295 
296 asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
297 {
298 	if (user_mode(regs)) {
299 		irqentry_enter_from_user_mode(regs);
300 
301 		handle_break(regs);
302 
303 		irqentry_exit_to_user_mode(regs);
304 	} else {
305 		irqentry_state_t state = irqentry_nmi_enter(regs);
306 
307 		handle_break(regs);
308 
309 		irqentry_nmi_exit(regs, state);
310 	}
311 }
312 
313 asmlinkage __visible __trap_section void do_trap_ecall_u(struct pt_regs *regs)
314 {
315 	if (user_mode(regs)) {
316 		long syscall = regs->a7;
317 
318 		regs->epc += 4;
319 		regs->orig_a0 = regs->a0;
320 
321 		riscv_v_vstate_discard(regs);
322 
323 		syscall = syscall_enter_from_user_mode(regs, syscall);
324 
325 		if (syscall >= 0 && syscall < NR_syscalls)
326 			syscall_handler(regs, syscall);
327 		else if (syscall != -1)
328 			regs->a0 = -ENOSYS;
329 
330 		syscall_exit_to_user_mode(regs);
331 	} else {
332 		irqentry_state_t state = irqentry_nmi_enter(regs);
333 
334 		do_trap_error(regs, SIGILL, ILL_ILLTRP, regs->epc,
335 			"Oops - environment call from U-mode");
336 
337 		irqentry_nmi_exit(regs, state);
338 	}
339 
340 }
341 
342 #ifdef CONFIG_MMU
343 asmlinkage __visible noinstr void do_page_fault(struct pt_regs *regs)
344 {
345 	irqentry_state_t state = irqentry_enter(regs);
346 
347 	handle_page_fault(regs);
348 
349 	local_irq_disable();
350 
351 	irqentry_exit(regs, state);
352 }
353 #endif
354 
355 static void noinstr handle_riscv_irq(struct pt_regs *regs)
356 {
357 	struct pt_regs *old_regs;
358 
359 	irq_enter_rcu();
360 	old_regs = set_irq_regs(regs);
361 	handle_arch_irq(regs);
362 	set_irq_regs(old_regs);
363 	irq_exit_rcu();
364 }
365 
366 asmlinkage void noinstr do_irq(struct pt_regs *regs)
367 {
368 	irqentry_state_t state = irqentry_enter(regs);
369 
370 	if (IS_ENABLED(CONFIG_IRQ_STACKS) && on_thread_stack())
371 		call_on_irq_stack(regs, handle_riscv_irq);
372 	else
373 		handle_riscv_irq(regs);
374 
375 	irqentry_exit(regs, state);
376 }
377 
378 #ifdef CONFIG_GENERIC_BUG
379 int is_valid_bugaddr(unsigned long pc)
380 {
381 	bug_insn_t insn;
382 
383 	if (pc < VMALLOC_START)
384 		return 0;
385 	if (get_kernel_nofault(insn, (bug_insn_t *)pc))
386 		return 0;
387 	if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
388 		return (insn == __BUG_INSN_32);
389 	else
390 		return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
391 }
392 #endif /* CONFIG_GENERIC_BUG */
393 
394 #ifdef CONFIG_VMAP_STACK
395 DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
396 		overflow_stack)__aligned(16);
397 
398 asmlinkage void handle_bad_stack(struct pt_regs *regs)
399 {
400 	unsigned long tsk_stk = (unsigned long)current->stack;
401 	unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack);
402 
403 	console_verbose();
404 
405 	pr_emerg("Insufficient stack space to handle exception!\n");
406 	pr_emerg("Task stack:     [0x%016lx..0x%016lx]\n",
407 			tsk_stk, tsk_stk + THREAD_SIZE);
408 	pr_emerg("Overflow stack: [0x%016lx..0x%016lx]\n",
409 			ovf_stk, ovf_stk + OVERFLOW_STACK_SIZE);
410 
411 	__show_regs(regs);
412 	panic("Kernel stack overflow");
413 
414 	for (;;)
415 		wait_for_interrupt();
416 }
417 #endif
418