xref: /openbmc/linux/arch/hexagon/kernel/traps.c (revision b4e18b29) 
1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * Kernel traps/events for Hexagon processor
4  *
5  * Copyright (c) 2010-2014, The Linux Foundation. All rights reserved.
6  */
7 
8 #include <linux/init.h>
9 #include <linux/sched/signal.h>
10 #include <linux/sched/debug.h>
11 #include <linux/sched/task_stack.h>
12 #include <linux/module.h>
13 #include <linux/kallsyms.h>
14 #include <linux/kdebug.h>
15 #include <linux/syscalls.h>
16 #include <linux/signal.h>
17 #include <linux/tracehook.h>
18 #include <asm/traps.h>
19 #include <asm/vm_fault.h>
20 #include <asm/syscall.h>
21 #include <asm/registers.h>
22 #include <asm/unistd.h>
23 #include <asm/sections.h>
24 #ifdef CONFIG_KGDB
25 # include <linux/kgdb.h>
26 #endif
27 
28 #define TRAP_SYSCALL	1
29 #define TRAP_DEBUG	0xdb
30 
31 void __init trap_init(void)
32 {
33 }
34 
35 #ifdef CONFIG_GENERIC_BUG
36 /* Maybe should resemble arch/sh/kernel/traps.c ?? */
37 int is_valid_bugaddr(unsigned long addr)
38 {
39 	return 1;
40 }
41 #endif /* CONFIG_GENERIC_BUG */
42 
43 static const char *ex_name(int ex)
44 {
45 	switch (ex) {
46 	case HVM_GE_C_XPROT:
47 	case HVM_GE_C_XUSER:
48 		return "Execute protection fault";
49 	case HVM_GE_C_RPROT:
50 	case HVM_GE_C_RUSER:
51 		return "Read protection fault";
52 	case HVM_GE_C_WPROT:
53 	case HVM_GE_C_WUSER:
54 		return "Write protection fault";
55 	case HVM_GE_C_XMAL:
56 		return "Misaligned instruction";
57 	case HVM_GE_C_WREG:
58 		return "Multiple writes to same register in packet";
59 	case HVM_GE_C_PCAL:
60 		return "Program counter values that are not properly aligned";
61 	case HVM_GE_C_RMAL:
62 		return "Misaligned data load";
63 	case HVM_GE_C_WMAL:
64 		return "Misaligned data store";
65 	case HVM_GE_C_INVI:
66 	case HVM_GE_C_PRIVI:
67 		return "Illegal instruction";
68 	case HVM_GE_C_BUS:
69 		return "Precise bus error";
70 	case HVM_GE_C_CACHE:
71 		return "Cache error";
72 
73 	case 0xdb:
74 		return "Debugger trap";
75 
76 	default:
77 		return "Unrecognized exception";
78 	}
79 }
80 
81 static void do_show_stack(struct task_struct *task, unsigned long *fp,
82 			  unsigned long ip, const char *loglvl)
83 {
84 	int kstack_depth_to_print = 24;
85 	unsigned long offset, size;
86 	const char *name = NULL;
87 	unsigned long *newfp;
88 	unsigned long low, high;
89 	char tmpstr[128];
90 	char *modname;
91 	int i;
92 
93 	if (task == NULL)
94 		task = current;
95 
96 	printk("%sCPU#%d, %s/%d, Call Trace:\n", loglvl, raw_smp_processor_id(),
97 		task->comm, task_pid_nr(task));
98 
99 	if (fp == NULL) {
100 		if (task == current) {
101 			asm("%0 = r30" : "=r" (fp));
102 		} else {
103 			fp = (unsigned long *)
104 			     ((struct hexagon_switch_stack *)
105 			     task->thread.switch_sp)->fp;
106 		}
107 	}
108 
109 	if ((((unsigned long) fp) & 0x3) || ((unsigned long) fp < 0x1000)) {
110 		printk("%s-- Corrupt frame pointer %p\n", loglvl, fp);
111 		return;
112 	}
113 
114 	/* Saved link reg is one word above FP */
115 	if (!ip)
116 		ip = *(fp+1);
117 
118 	/* Expect kernel stack to be in-bounds */
119 	low = (unsigned long)task_stack_page(task);
120 	high = low + THREAD_SIZE - 8;
121 	low += sizeof(struct thread_info);
122 
123 	for (i = 0; i < kstack_depth_to_print; i++) {
124 
125 		name = kallsyms_lookup(ip, &size, &offset, &modname, tmpstr);
126 
127 		printk("%s[%p] 0x%lx: %s + 0x%lx", loglvl, fp, ip, name, offset);
128 		if (((unsigned long) fp < low) || (high < (unsigned long) fp))
129 			printk(KERN_CONT " (FP out of bounds!)");
130 		if (modname)
131 			printk(KERN_CONT " [%s] ", modname);
132 		printk(KERN_CONT "\n");
133 
134 		newfp = (unsigned long *) *fp;
135 
136 		if (((unsigned long) newfp) & 0x3) {
137 			printk("%s-- Corrupt frame pointer %p\n", loglvl, newfp);
138 			break;
139 		}
140 
141 		/* Attempt to continue past exception. */
142 		if (0 == newfp) {
143 			struct pt_regs *regs = (struct pt_regs *) (((void *)fp)
144 						+ 8);
145 
146 			if (regs->syscall_nr != -1) {
147 				printk("%s-- trap0 -- syscall_nr: %ld", loglvl,
148 					regs->syscall_nr);
149 				printk(KERN_CONT "  psp: %lx  elr: %lx\n",
150 					 pt_psp(regs), pt_elr(regs));
151 				break;
152 			} else {
153 				/* really want to see more ... */
154 				kstack_depth_to_print += 6;
155 				printk("%s-- %s (0x%lx)  badva: %lx\n", loglvl,
156 					ex_name(pt_cause(regs)), pt_cause(regs),
157 					pt_badva(regs));
158 			}
159 
160 			newfp = (unsigned long *) regs->r30;
161 			ip = pt_elr(regs);
162 		} else {
163 			ip = *(newfp + 1);
164 		}
165 
166 		/* If link reg is null, we are done. */
167 		if (ip == 0x0)
168 			break;
169 
170 		/* If newfp isn't larger, we're tracing garbage. */
171 		if (newfp > fp)
172 			fp = newfp;
173 		else
174 			break;
175 	}
176 }
177 
178 void show_stack(struct task_struct *task, unsigned long *fp, const char *loglvl)
179 {
180 	/* Saved link reg is one word above FP */
181 	do_show_stack(task, fp, 0, loglvl);
182 }
183 
184 int die(const char *str, struct pt_regs *regs, long err)
185 {
186 	static struct {
187 		spinlock_t lock;
188 		int counter;
189 	} die = {
190 		.lock = __SPIN_LOCK_UNLOCKED(die.lock),
191 		.counter = 0
192 	};
193 
194 	console_verbose();
195 	oops_enter();
196 
197 	spin_lock_irq(&die.lock);
198 	bust_spinlocks(1);
199 	printk(KERN_EMERG "Oops: %s[#%d]:\n", str, ++die.counter);
200 
201 	if (notify_die(DIE_OOPS, str, regs, err, pt_cause(regs), SIGSEGV) ==
202 	    NOTIFY_STOP)
203 		return 1;
204 
205 	print_modules();
206 	show_regs(regs);
207 	do_show_stack(current, &regs->r30, pt_elr(regs), KERN_EMERG);
208 
209 	bust_spinlocks(0);
210 	add_taint(TAINT_DIE, LOCKDEP_NOW_UNRELIABLE);
211 
212 	spin_unlock_irq(&die.lock);
213 
214 	if (in_interrupt())
215 		panic("Fatal exception in interrupt");
216 
217 	if (panic_on_oops)
218 		panic("Fatal exception");
219 
220 	oops_exit();
221 	do_exit(err);
222 	return 0;
223 }
224 
225 int die_if_kernel(char *str, struct pt_regs *regs, long err)
226 {
227 	if (!user_mode(regs))
228 		return die(str, regs, err);
229 	else
230 		return 0;
231 }
232 
233 /*
234  * It's not clear that misaligned fetches are ever recoverable.
235  */
236 static void misaligned_instruction(struct pt_regs *regs)
237 {
238 	die_if_kernel("Misaligned Instruction", regs, 0);
239 	force_sig(SIGBUS);
240 }
241 
242 /*
243  * Misaligned loads and stores, on the other hand, can be
244  * emulated, and probably should be, some day.  But for now
245  * they will be considered fatal.
246  */
247 static void misaligned_data_load(struct pt_regs *regs)
248 {
249 	die_if_kernel("Misaligned Data Load", regs, 0);
250 	force_sig(SIGBUS);
251 }
252 
253 static void misaligned_data_store(struct pt_regs *regs)
254 {
255 	die_if_kernel("Misaligned Data Store", regs, 0);
256 	force_sig(SIGBUS);
257 }
258 
259 static void illegal_instruction(struct pt_regs *regs)
260 {
261 	die_if_kernel("Illegal Instruction", regs, 0);
262 	force_sig(SIGILL);
263 }
264 
265 /*
266  * Precise bus errors may be recoverable with a a retry,
267  * but for now, treat them as irrecoverable.
268  */
269 static void precise_bus_error(struct pt_regs *regs)
270 {
271 	die_if_kernel("Precise Bus Error", regs, 0);
272 	force_sig(SIGBUS);
273 }
274 
275 /*
276  * If anything is to be done here other than panic,
277  * it will probably be complex and migrate to another
278  * source module.  For now, just die.
279  */
280 static void cache_error(struct pt_regs *regs)
281 {
282 	die("Cache Error", regs, 0);
283 }
284 
285 /*
286  * General exception handler
287  */
288 void do_genex(struct pt_regs *regs)
289 {
290 	/*
291 	 * Decode Cause and Dispatch
292 	 */
293 	switch (pt_cause(regs)) {
294 	case HVM_GE_C_XPROT:
295 	case HVM_GE_C_XUSER:
296 		execute_protection_fault(regs);
297 		break;
298 	case HVM_GE_C_RPROT:
299 	case HVM_GE_C_RUSER:
300 		read_protection_fault(regs);
301 		break;
302 	case HVM_GE_C_WPROT:
303 	case HVM_GE_C_WUSER:
304 		write_protection_fault(regs);
305 		break;
306 	case HVM_GE_C_XMAL:
307 		misaligned_instruction(regs);
308 		break;
309 	case HVM_GE_C_WREG:
310 		illegal_instruction(regs);
311 		break;
312 	case HVM_GE_C_PCAL:
313 		misaligned_instruction(regs);
314 		break;
315 	case HVM_GE_C_RMAL:
316 		misaligned_data_load(regs);
317 		break;
318 	case HVM_GE_C_WMAL:
319 		misaligned_data_store(regs);
320 		break;
321 	case HVM_GE_C_INVI:
322 	case HVM_GE_C_PRIVI:
323 		illegal_instruction(regs);
324 		break;
325 	case HVM_GE_C_BUS:
326 		precise_bus_error(regs);
327 		break;
328 	case HVM_GE_C_CACHE:
329 		cache_error(regs);
330 		break;
331 	default:
332 		/* Halt and catch fire */
333 		panic("Unrecognized exception 0x%lx\n", pt_cause(regs));
334 		break;
335 	}
336 }
337 
338 /* Indirect system call dispatch */
339 long sys_syscall(void)
340 {
341 	printk(KERN_ERR "sys_syscall invoked!\n");
342 	return -ENOSYS;
343 }
344 
345 void do_trap0(struct pt_regs *regs)
346 {
347 	syscall_fn syscall;
348 
349 	switch (pt_cause(regs)) {
350 	case TRAP_SYSCALL:
351 		/* System call is trap0 #1 */
352 
353 		/* allow strace to catch syscall args  */
354 		if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE) &&
355 			tracehook_report_syscall_entry(regs)))
356 			return;  /*  return -ENOSYS somewhere?  */
357 
358 		/* Interrupts should be re-enabled for syscall processing */
359 		__vmsetie(VM_INT_ENABLE);
360 
361 		/*
362 		 * System call number is in r6, arguments in r0..r5.
363 		 * Fortunately, no Linux syscall has more than 6 arguments,
364 		 * and Hexagon ABI passes first 6 arguments in registers.
365 		 * 64-bit arguments are passed in odd/even register pairs.
366 		 * Fortunately, we have no system calls that take more
367 		 * than three arguments with more than one 64-bit value.
368 		 * Should that change, we'd need to redesign to copy
369 		 * between user and kernel stacks.
370 		 */
371 		regs->syscall_nr = regs->r06;
372 
373 		/*
374 		 * GPR R0 carries the first parameter, and is also used
375 		 * to report the return value.  We need a backup of
376 		 * the user's value in case we need to do a late restart
377 		 * of the system call.
378 		 */
379 		regs->restart_r0 = regs->r00;
380 
381 		if ((unsigned long) regs->syscall_nr >= __NR_syscalls) {
382 			regs->r00 = -1;
383 		} else {
384 			syscall = (syscall_fn)
385 				  (sys_call_table[regs->syscall_nr]);
386 			regs->r00 = syscall(regs->r00, regs->r01,
387 				   regs->r02, regs->r03,
388 				   regs->r04, regs->r05);
389 		}
390 
391 		/* allow strace to get the syscall return state  */
392 		if (unlikely(test_thread_flag(TIF_SYSCALL_TRACE)))
393 			tracehook_report_syscall_exit(regs, 0);
394 
395 		break;
396 	case TRAP_DEBUG:
397 		/* Trap0 0xdb is debug breakpoint */
398 		if (user_mode(regs)) {
399 			/*
400 			 * Some architecures add some per-thread state
401 			 * to distinguish between breakpoint traps and
402 			 * trace traps.  We may want to do that, and
403 			 * set the si_code value appropriately, or we
404 			 * may want to use a different trap0 flavor.
405 			 */
406 			force_sig_fault(SIGTRAP, TRAP_BRKPT,
407 					(void __user *) pt_elr(regs));
408 		} else {
409 #ifdef CONFIG_KGDB
410 			kgdb_handle_exception(pt_cause(regs), SIGTRAP,
411 					      TRAP_BRKPT, regs);
412 #endif
413 		}
414 		break;
415 	}
416 	/* Ignore other trap0 codes for now, especially 0 (Angel calls) */
417 }
418 
419 /*
420  * Machine check exception handler
421  */
422 void do_machcheck(struct pt_regs *regs)
423 {
424 	/* Halt and catch fire */
425 	__vmstop();
426 }
427 
428 /*
429  * Treat this like the old 0xdb trap.
430  */
431 
432 void do_debug_exception(struct pt_regs *regs)
433 {
434 	regs->hvmer.vmest &= ~HVM_VMEST_CAUSE_MSK;
435 	regs->hvmer.vmest |= (TRAP_DEBUG << HVM_VMEST_CAUSE_SFT);
436 	do_trap0(regs);
437 }
438