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/irqflags.h>
10#include <linux/randomize_kstack.h>
11#include <linux/sched.h>
12#include <linux/sched/debug.h>
13#include <linux/sched/signal.h>
14#include <linux/signal.h>
15#include <linux/kdebug.h>
16#include <linux/uaccess.h>
17#include <linux/kprobes.h>
18#include <linux/uprobes.h>
19#include <asm/uprobes.h>
20#include <linux/mm.h>
21#include <linux/module.h>
22#include <linux/irq.h>
23#include <linux/kexec.h>
24#include <linux/entry-common.h>
25
26#include <asm/asm-prototypes.h>
27#include <asm/bug.h>
28#include <asm/cfi.h>
29#include <asm/csr.h>
30#include <asm/processor.h>
31#include <asm/ptrace.h>
32#include <asm/syscall.h>
33#include <asm/thread_info.h>
34#include <asm/vector.h>
35#include <asm/irq_stack.h>
36
37int show_unhandled_signals = 1;
38
39static DEFINE_RAW_SPINLOCK(die_lock);
40
41static int copy_code(struct pt_regs *regs, u16 *val, const u16 *insns)
42{
43 const void __user *uaddr = (__force const void __user *)insns;
44
45 if (!user_mode(regs))
46 return get_kernel_nofault(*val, insns);
47
48 /* The user space code from other tasks cannot be accessed. */
49 if (regs != task_pt_regs(current))
50 return -EPERM;
51
52 return copy_from_user_nofault(dst: val, src: uaddr, size: sizeof(*val));
53}
54
55static void dump_instr(const char *loglvl, struct pt_regs *regs)
56{
57 char str[sizeof("0000 ") * 12 + 2 + 1], *p = str;
58 const u16 *insns = (u16 *)instruction_pointer(regs);
59 long bad;
60 u16 val;
61 int i;
62
63 for (i = -10; i < 2; i++) {
64 bad = copy_code(regs, val: &val, insns: &insns[i]);
65 if (!bad) {
66 p += sprintf(buf: p, fmt: i == 0 ? "(%04hx) " : "%04hx ", val);
67 } else {
68 printk("%sCode: Unable to access instruction at 0x%px.\n",
69 loglvl, &insns[i]);
70 return;
71 }
72 }
73 printk("%sCode: %s\n", loglvl, str);
74}
75
76void die(struct pt_regs *regs, const char *str)
77{
78 static int die_counter;
79 int ret;
80 long cause;
81 unsigned long flags;
82
83 oops_enter();
84
85 raw_spin_lock_irqsave(&die_lock, flags);
86 console_verbose();
87 bust_spinlocks(yes: 1);
88
89 pr_emerg("%s [#%d]\n", str, ++die_counter);
90 print_modules();
91 if (regs) {
92 show_regs(regs);
93 dump_instr(KERN_EMERG, regs);
94 }
95
96 cause = regs ? regs->cause : -1;
97 ret = notify_die(val: DIE_OOPS, str, regs, err: 0, trap: cause, SIGSEGV);
98
99 if (kexec_should_crash(current))
100 crash_kexec(regs);
101
102 bust_spinlocks(yes: 0);
103 add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
104 raw_spin_unlock_irqrestore(&die_lock, flags);
105 oops_exit();
106
107 if (in_interrupt())
108 panic(fmt: "Fatal exception in interrupt");
109 if (panic_on_oops)
110 panic(fmt: "Fatal exception");
111 if (ret != NOTIFY_STOP)
112 make_task_dead(SIGSEGV);
113}
114
115void do_trap(struct pt_regs *regs, int signo, int code, unsigned long addr)
116{
117 struct task_struct *tsk = current;
118
119 if (show_unhandled_signals && unhandled_signal(tsk, sig: signo)
120 && printk_ratelimit()) {
121 pr_info("%s[%d]: unhandled signal %d code 0x%x at 0x" REG_FMT,
122 tsk->comm, task_pid_nr(tsk), signo, code, addr);
123 print_vma_addr(KERN_CONT " in ", rip: instruction_pointer(regs));
124 pr_cont("\n");
125 __show_regs(regs);
126 dump_instr(KERN_INFO, regs);
127 }
128
129 force_sig_fault(sig: signo, code, addr: (void __user *)addr);
130}
131
132static void do_trap_error(struct pt_regs *regs, int signo, int code,
133 unsigned long addr, const char *str)
134{
135 current->thread.bad_cause = regs->cause;
136
137 if (user_mode(regs)) {
138 do_trap(regs, signo, code, addr);
139 } else {
140 if (!fixup_exception(regs))
141 die(regs, str);
142 }
143}
144
145#if defined(CONFIG_XIP_KERNEL) && defined(CONFIG_RISCV_ALTERNATIVE)
146#define __trap_section __noinstr_section(".xip.traps")
147#else
148#define __trap_section noinstr
149#endif
150#define DO_ERROR_INFO(name, signo, code, str) \
151asmlinkage __visible __trap_section void name(struct pt_regs *regs) \
152{ \
153 if (user_mode(regs)) { \
154 irqentry_enter_from_user_mode(regs); \
155 local_irq_enable(); \
156 do_trap_error(regs, signo, code, regs->epc, "Oops - " str); \
157 local_irq_disable(); \
158 irqentry_exit_to_user_mode(regs); \
159 } else { \
160 irqentry_state_t state = irqentry_nmi_enter(regs); \
161 do_trap_error(regs, signo, code, regs->epc, "Oops - " str); \
162 irqentry_nmi_exit(regs, state); \
163 } \
164}
165
166DO_ERROR_INFO(do_trap_unknown,
167 SIGILL, ILL_ILLTRP, "unknown exception");
168DO_ERROR_INFO(do_trap_insn_misaligned,
169 SIGBUS, BUS_ADRALN, "instruction address misaligned");
170DO_ERROR_INFO(do_trap_insn_fault,
171 SIGSEGV, SEGV_ACCERR, "instruction access fault");
172
173asmlinkage __visible __trap_section void do_trap_insn_illegal(struct pt_regs *regs)
174{
175 bool handled;
176
177 if (user_mode(regs)) {
178 irqentry_enter_from_user_mode(regs);
179 local_irq_enable();
180
181 handled = riscv_v_first_use_handler(regs);
182 if (!handled)
183 do_trap_error(regs, SIGILL, ILL_ILLOPC, addr: regs->epc,
184 str: "Oops - illegal instruction");
185
186 local_irq_disable();
187 irqentry_exit_to_user_mode(regs);
188 } else {
189 irqentry_state_t state = irqentry_nmi_enter(regs);
190
191 do_trap_error(regs, SIGILL, ILL_ILLOPC, addr: regs->epc,
192 str: "Oops - illegal instruction");
193
194 irqentry_nmi_exit(regs, irq_state: state);
195 }
196}
197
198DO_ERROR_INFO(do_trap_load_fault,
199 SIGSEGV, SEGV_ACCERR, "load access fault");
200
201enum misaligned_access_type {
202 MISALIGNED_STORE,
203 MISALIGNED_LOAD,
204};
205static const struct {
206 const char *type_str;
207 int (*handler)(struct pt_regs *regs);
208} misaligned_handler[] = {
209 [MISALIGNED_STORE] = {
210 .type_str = "Oops - store (or AMO) address misaligned",
211 .handler = handle_misaligned_store,
212 },
213 [MISALIGNED_LOAD] = {
214 .type_str = "Oops - load address misaligned",
215 .handler = handle_misaligned_load,
216 },
217};
218
219static void do_trap_misaligned(struct pt_regs *regs, enum misaligned_access_type type)
220{
221 irqentry_state_t state;
222
223 if (user_mode(regs)) {
224 irqentry_enter_from_user_mode(regs);
225 local_irq_enable();
226 } else {
227 state = irqentry_nmi_enter(regs);
228 }
229
230 if (misaligned_handler[type].handler(regs))
231 do_trap_error(regs, SIGBUS, BUS_ADRALN, addr: regs->epc,
232 str: misaligned_handler[type].type_str);
233
234 if (user_mode(regs)) {
235 local_irq_disable();
236 irqentry_exit_to_user_mode(regs);
237 } else {
238 irqentry_nmi_exit(regs, irq_state: state);
239 }
240}
241
242asmlinkage __visible __trap_section void do_trap_load_misaligned(struct pt_regs *regs)
243{
244 do_trap_misaligned(regs, type: MISALIGNED_LOAD);
245}
246
247asmlinkage __visible __trap_section void do_trap_store_misaligned(struct pt_regs *regs)
248{
249 do_trap_misaligned(regs, type: MISALIGNED_STORE);
250}
251
252DO_ERROR_INFO(do_trap_store_fault,
253 SIGSEGV, SEGV_ACCERR, "store (or AMO) access fault");
254DO_ERROR_INFO(do_trap_ecall_s,
255 SIGILL, ILL_ILLTRP, "environment call from S-mode");
256DO_ERROR_INFO(do_trap_ecall_m,
257 SIGILL, ILL_ILLTRP, "environment call from M-mode");
258
259static inline unsigned long get_break_insn_length(unsigned long pc)
260{
261 bug_insn_t insn;
262
263 if (get_kernel_nofault(insn, (bug_insn_t *)pc))
264 return 0;
265
266 return GET_INSN_LENGTH(insn);
267}
268
269static bool probe_single_step_handler(struct pt_regs *regs)
270{
271 bool user = user_mode(regs);
272
273 return user ? uprobe_single_step_handler(regs) : kprobe_single_step_handler(regs);
274}
275
276static bool probe_breakpoint_handler(struct pt_regs *regs)
277{
278 bool user = user_mode(regs);
279
280 return user ? uprobe_breakpoint_handler(regs) : kprobe_breakpoint_handler(regs);
281}
282
283void handle_break(struct pt_regs *regs)
284{
285 if (probe_single_step_handler(regs))
286 return;
287
288 if (probe_breakpoint_handler(regs))
289 return;
290
291 current->thread.bad_cause = regs->cause;
292
293 if (user_mode(regs))
294 force_sig_fault(SIGTRAP, TRAP_BRKPT, addr: (void __user *)regs->epc);
295#ifdef CONFIG_KGDB
296 else if (notify_die(val: DIE_TRAP, str: "EBREAK", regs, err: 0, trap: regs->cause, SIGTRAP)
297 == NOTIFY_STOP)
298 return;
299#endif
300 else if (report_bug(bug_addr: regs->epc, regs) == BUG_TRAP_TYPE_WARN ||
301 handle_cfi_failure(regs) == BUG_TRAP_TYPE_WARN)
302 regs->epc += get_break_insn_length(pc: regs->epc);
303 else
304 die(regs, "Kernel BUG");
305}
306
307asmlinkage __visible __trap_section void do_trap_break(struct pt_regs *regs)
308{
309 if (user_mode(regs)) {
310 irqentry_enter_from_user_mode(regs);
311 local_irq_enable();
312
313 handle_break(regs);
314
315 local_irq_disable();
316 irqentry_exit_to_user_mode(regs);
317 } else {
318 irqentry_state_t state = irqentry_nmi_enter(regs);
319
320 handle_break(regs);
321
322 irqentry_nmi_exit(regs, irq_state: state);
323 }
324}
325
326asmlinkage __visible __trap_section __no_stack_protector
327void do_trap_ecall_u(struct pt_regs *regs)
328{
329 if (user_mode(regs)) {
330 long syscall = regs->a7;
331
332 regs->epc += 4;
333 regs->orig_a0 = regs->a0;
334 regs->a0 = -ENOSYS;
335
336 riscv_v_vstate_discard(regs);
337
338 syscall = syscall_enter_from_user_mode(regs, syscall);
339
340 add_random_kstack_offset();
341
342 if (syscall >= 0 && syscall < NR_syscalls) {
343 syscall = array_index_nospec(syscall, NR_syscalls);
344 syscall_handler(regs, syscall);
345 }
346
347 /*
348 * Ultimately, this value will get limited by KSTACK_OFFSET_MAX(),
349 * so the maximum stack offset is 1k bytes (10 bits).
350 *
351 * The actual entropy will be further reduced by the compiler when
352 * applying stack alignment constraints: 16-byte (i.e. 4-bit) aligned
353 * for RV32I or RV64I.
354 *
355 * The resulting 6 bits of entropy is seen in SP[9:4].
356 */
357 choose_random_kstack_offset(get_random_u16());
358
359 syscall_exit_to_user_mode(regs);
360 } else {
361 irqentry_state_t state = irqentry_nmi_enter(regs);
362
363 do_trap_error(regs, SIGILL, ILL_ILLTRP, addr: regs->epc,
364 str: "Oops - environment call from U-mode");
365
366 irqentry_nmi_exit(regs, irq_state: state);
367 }
368
369}
370
371#ifdef CONFIG_MMU
372asmlinkage __visible noinstr void do_page_fault(struct pt_regs *regs)
373{
374 irqentry_state_t state = irqentry_enter(regs);
375
376 handle_page_fault(regs);
377
378 local_irq_disable();
379
380 irqentry_exit(regs, state);
381}
382#endif
383
384static void noinstr handle_riscv_irq(struct pt_regs *regs)
385{
386 struct pt_regs *old_regs;
387
388 irq_enter_rcu();
389 old_regs = set_irq_regs(regs);
390 handle_arch_irq(regs);
391 set_irq_regs(old_regs);
392 irq_exit_rcu();
393}
394
395asmlinkage void noinstr do_irq(struct pt_regs *regs)
396{
397 irqentry_state_t state = irqentry_enter(regs);
398
399 if (IS_ENABLED(CONFIG_IRQ_STACKS) && on_thread_stack())
400 call_on_irq_stack(regs, handle_riscv_irq);
401 else
402 handle_riscv_irq(regs);
403
404 irqentry_exit(regs, state);
405}
406
407#ifdef CONFIG_GENERIC_BUG
408int is_valid_bugaddr(unsigned long pc)
409{
410 bug_insn_t insn;
411
412 if (pc < VMALLOC_START)
413 return 0;
414 if (get_kernel_nofault(insn, (bug_insn_t *)pc))
415 return 0;
416 if ((insn & __INSN_LENGTH_MASK) == __INSN_LENGTH_32)
417 return (insn == __BUG_INSN_32);
418 else
419 return ((insn & __COMPRESSED_INSN_MASK) == __BUG_INSN_16);
420}
421#endif /* CONFIG_GENERIC_BUG */
422
423#ifdef CONFIG_VMAP_STACK
424DEFINE_PER_CPU(unsigned long [OVERFLOW_STACK_SIZE/sizeof(long)],
425 overflow_stack)__aligned(16);
426
427asmlinkage void handle_bad_stack(struct pt_regs *regs)
428{
429 unsigned long tsk_stk = (unsigned long)current->stack;
430 unsigned long ovf_stk = (unsigned long)this_cpu_ptr(overflow_stack);
431
432 console_verbose();
433
434 pr_emerg("Insufficient stack space to handle exception!\n");
435 pr_emerg("Task stack: [0x%016lx..0x%016lx]\n",
436 tsk_stk, tsk_stk + THREAD_SIZE);
437 pr_emerg("Overflow stack: [0x%016lx..0x%016lx]\n",
438 ovf_stk, ovf_stk + OVERFLOW_STACK_SIZE);
439
440 __show_regs(regs);
441 panic(fmt: "Kernel stack overflow");
442
443 for (;;)
444 wait_for_interrupt();
445}
446#endif
447

source code of linux/arch/riscv/kernel/traps.c