xref: /openbmc/linux/arch/sparc/mm/fault_32.c (revision 842ed298) 
1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  * fault.c:  Page fault handlers for the Sparc.
4  *
5  * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
6  * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
7  * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
8  */
9 
10 #include <asm/head.h>
11 
12 #include <linux/string.h>
13 #include <linux/types.h>
14 #include <linux/sched.h>
15 #include <linux/ptrace.h>
16 #include <linux/mman.h>
17 #include <linux/threads.h>
18 #include <linux/kernel.h>
19 #include <linux/signal.h>
20 #include <linux/mm.h>
21 #include <linux/smp.h>
22 #include <linux/perf_event.h>
23 #include <linux/interrupt.h>
24 #include <linux/kdebug.h>
25 #include <linux/uaccess.h>
26 
27 #include <asm/page.h>
28 #include <asm/openprom.h>
29 #include <asm/oplib.h>
30 #include <asm/setup.h>
31 #include <asm/smp.h>
32 #include <asm/traps.h>
33 
34 #include "mm_32.h"
35 
36 int show_unhandled_signals = 1;
37 
38 static void __noreturn unhandled_fault(unsigned long address,
39 				       struct task_struct *tsk,
40 				       struct pt_regs *regs)
41 {
42 	if ((unsigned long) address < PAGE_SIZE) {
43 		printk(KERN_ALERT
44 		    "Unable to handle kernel NULL pointer dereference\n");
45 	} else {
46 		printk(KERN_ALERT "Unable to handle kernel paging request at virtual address %08lx\n",
47 		       address);
48 	}
49 	printk(KERN_ALERT "tsk->{mm,active_mm}->context = %08lx\n",
50 		(tsk->mm ? tsk->mm->context : tsk->active_mm->context));
51 	printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %08lx\n",
52 		(tsk->mm ? (unsigned long) tsk->mm->pgd :
53 			(unsigned long) tsk->active_mm->pgd));
54 	die_if_kernel("Oops", regs);
55 }
56 
57 asmlinkage int lookup_fault(unsigned long pc, unsigned long ret_pc,
58 			    unsigned long address)
59 {
60 	struct pt_regs regs;
61 	unsigned long g2;
62 	unsigned int insn;
63 	int i;
64 
65 	i = search_extables_range(ret_pc, &g2);
66 	switch (i) {
67 	case 3:
68 		/* load & store will be handled by fixup */
69 		return 3;
70 
71 	case 1:
72 		/* store will be handled by fixup, load will bump out */
73 		/* for _to_ macros */
74 		insn = *((unsigned int *) pc);
75 		if ((insn >> 21) & 1)
76 			return 1;
77 		break;
78 
79 	case 2:
80 		/* load will be handled by fixup, store will bump out */
81 		/* for _from_ macros */
82 		insn = *((unsigned int *) pc);
83 		if (!((insn >> 21) & 1) || ((insn>>19)&0x3f) == 15)
84 			return 2;
85 		break;
86 
87 	default:
88 		break;
89 	}
90 
91 	memset(&regs, 0, sizeof(regs));
92 	regs.pc = pc;
93 	regs.npc = pc + 4;
94 	__asm__ __volatile__(
95 		"rd %%psr, %0\n\t"
96 		"nop\n\t"
97 		"nop\n\t"
98 		"nop\n" : "=r" (regs.psr));
99 	unhandled_fault(address, current, &regs);
100 
101 	/* Not reached */
102 	return 0;
103 }
104 
105 static inline void
106 show_signal_msg(struct pt_regs *regs, int sig, int code,
107 		unsigned long address, struct task_struct *tsk)
108 {
109 	if (!unhandled_signal(tsk, sig))
110 		return;
111 
112 	if (!printk_ratelimit())
113 		return;
114 
115 	printk("%s%s[%d]: segfault at %lx ip %px (rpc %px) sp %px error %x",
116 	       task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
117 	       tsk->comm, task_pid_nr(tsk), address,
118 	       (void *)regs->pc, (void *)regs->u_regs[UREG_I7],
119 	       (void *)regs->u_regs[UREG_FP], code);
120 
121 	print_vma_addr(KERN_CONT " in ", regs->pc);
122 
123 	printk(KERN_CONT "\n");
124 }
125 
126 static void __do_fault_siginfo(int code, int sig, struct pt_regs *regs,
127 			       unsigned long addr)
128 {
129 	if (unlikely(show_unhandled_signals))
130 		show_signal_msg(regs, sig, code,
131 				addr, current);
132 
133 	force_sig_fault(sig, code, (void __user *) addr, 0);
134 }
135 
136 static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault)
137 {
138 	unsigned int insn;
139 
140 	if (text_fault)
141 		return regs->pc;
142 
143 	if (regs->psr & PSR_PS)
144 		insn = *(unsigned int *) regs->pc;
145 	else
146 		__get_user(insn, (unsigned int *) regs->pc);
147 
148 	return safe_compute_effective_address(regs, insn);
149 }
150 
151 static noinline void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
152 				      int text_fault)
153 {
154 	unsigned long addr = compute_si_addr(regs, text_fault);
155 
156 	__do_fault_siginfo(code, sig, regs, addr);
157 }
158 
159 asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
160 			       unsigned long address)
161 {
162 	struct vm_area_struct *vma;
163 	struct task_struct *tsk = current;
164 	struct mm_struct *mm = tsk->mm;
165 	unsigned int fixup;
166 	unsigned long g2;
167 	int from_user = !(regs->psr & PSR_PS);
168 	int code;
169 	vm_fault_t fault;
170 	unsigned int flags = FAULT_FLAG_DEFAULT;
171 
172 	if (text_fault)
173 		address = regs->pc;
174 
175 	/*
176 	 * We fault-in kernel-space virtual memory on-demand. The
177 	 * 'reference' page table is init_mm.pgd.
178 	 *
179 	 * NOTE! We MUST NOT take any locks for this case. We may
180 	 * be in an interrupt or a critical region, and should
181 	 * only copy the information from the master page table,
182 	 * nothing more.
183 	 */
184 	code = SEGV_MAPERR;
185 	if (address >= TASK_SIZE)
186 		goto vmalloc_fault;
187 
188 	/*
189 	 * If we're in an interrupt or have no user
190 	 * context, we must not take the fault..
191 	 */
192 	if (pagefault_disabled() || !mm)
193 		goto no_context;
194 
195 	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
196 
197 retry:
198 	mmap_read_lock(mm);
199 
200 	if (!from_user && address >= PAGE_OFFSET)
201 		goto bad_area;
202 
203 	vma = find_vma(mm, address);
204 	if (!vma)
205 		goto bad_area;
206 	if (vma->vm_start <= address)
207 		goto good_area;
208 	if (!(vma->vm_flags & VM_GROWSDOWN))
209 		goto bad_area;
210 	if (expand_stack(vma, address))
211 		goto bad_area;
212 	/*
213 	 * Ok, we have a good vm_area for this memory access, so
214 	 * we can handle it..
215 	 */
216 good_area:
217 	code = SEGV_ACCERR;
218 	if (write) {
219 		if (!(vma->vm_flags & VM_WRITE))
220 			goto bad_area;
221 	} else {
222 		/* Allow reads even for write-only mappings */
223 		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
224 			goto bad_area;
225 	}
226 
227 	if (from_user)
228 		flags |= FAULT_FLAG_USER;
229 	if (write)
230 		flags |= FAULT_FLAG_WRITE;
231 
232 	/*
233 	 * If for any reason at all we couldn't handle the fault,
234 	 * make sure we exit gracefully rather than endlessly redo
235 	 * the fault.
236 	 */
237 	fault = handle_mm_fault(vma, address, flags, regs);
238 
239 	if (fault_signal_pending(fault, regs))
240 		return;
241 
242 	if (unlikely(fault & VM_FAULT_ERROR)) {
243 		if (fault & VM_FAULT_OOM)
244 			goto out_of_memory;
245 		else if (fault & VM_FAULT_SIGSEGV)
246 			goto bad_area;
247 		else if (fault & VM_FAULT_SIGBUS)
248 			goto do_sigbus;
249 		BUG();
250 	}
251 
252 	if (flags & FAULT_FLAG_ALLOW_RETRY) {
253 		if (fault & VM_FAULT_RETRY) {
254 			flags |= FAULT_FLAG_TRIED;
255 
256 			/* No need to mmap_read_unlock(mm) as we would
257 			 * have already released it in __lock_page_or_retry
258 			 * in mm/filemap.c.
259 			 */
260 
261 			goto retry;
262 		}
263 	}
264 
265 	mmap_read_unlock(mm);
266 	return;
267 
268 	/*
269 	 * Something tried to access memory that isn't in our memory map..
270 	 * Fix it, but check if it's kernel or user first..
271 	 */
272 bad_area:
273 	mmap_read_unlock(mm);
274 
275 bad_area_nosemaphore:
276 	/* User mode accesses just cause a SIGSEGV */
277 	if (from_user) {
278 		do_fault_siginfo(code, SIGSEGV, regs, text_fault);
279 		return;
280 	}
281 
282 	/* Is this in ex_table? */
283 no_context:
284 	g2 = regs->u_regs[UREG_G2];
285 	if (!from_user) {
286 		fixup = search_extables_range(regs->pc, &g2);
287 		/* Values below 10 are reserved for other things */
288 		if (fixup > 10) {
289 			extern const unsigned int __memset_start[];
290 			extern const unsigned int __memset_end[];
291 
292 #ifdef DEBUG_EXCEPTIONS
293 			printk("Exception: PC<%08lx> faddr<%08lx>\n",
294 			       regs->pc, address);
295 			printk("EX_TABLE: insn<%08lx> fixup<%08x> g2<%08lx>\n",
296 				regs->pc, fixup, g2);
297 #endif
298 			if ((regs->pc >= (unsigned long)__memset_start &&
299 			     regs->pc < (unsigned long)__memset_end)) {
300 				regs->u_regs[UREG_I4] = address;
301 				regs->u_regs[UREG_I5] = regs->pc;
302 			}
303 			regs->u_regs[UREG_G2] = g2;
304 			regs->pc = fixup;
305 			regs->npc = regs->pc + 4;
306 			return;
307 		}
308 	}
309 
310 	unhandled_fault(address, tsk, regs);
311 	do_exit(SIGKILL);
312 
313 /*
314  * We ran out of memory, or some other thing happened to us that made
315  * us unable to handle the page fault gracefully.
316  */
317 out_of_memory:
318 	mmap_read_unlock(mm);
319 	if (from_user) {
320 		pagefault_out_of_memory();
321 		return;
322 	}
323 	goto no_context;
324 
325 do_sigbus:
326 	mmap_read_unlock(mm);
327 	do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, text_fault);
328 	if (!from_user)
329 		goto no_context;
330 
331 vmalloc_fault:
332 	{
333 		/*
334 		 * Synchronize this task's top level page-table
335 		 * with the 'reference' page table.
336 		 */
337 		int offset = pgd_index(address);
338 		pgd_t *pgd, *pgd_k;
339 		p4d_t *p4d, *p4d_k;
340 		pud_t *pud, *pud_k;
341 		pmd_t *pmd, *pmd_k;
342 
343 		pgd = tsk->active_mm->pgd + offset;
344 		pgd_k = init_mm.pgd + offset;
345 
346 		if (!pgd_present(*pgd)) {
347 			if (!pgd_present(*pgd_k))
348 				goto bad_area_nosemaphore;
349 			pgd_val(*pgd) = pgd_val(*pgd_k);
350 			return;
351 		}
352 
353 		p4d = p4d_offset(pgd, address);
354 		pud = pud_offset(p4d, address);
355 		pmd = pmd_offset(pud, address);
356 
357 		p4d_k = p4d_offset(pgd_k, address);
358 		pud_k = pud_offset(p4d_k, address);
359 		pmd_k = pmd_offset(pud_k, address);
360 
361 		if (pmd_present(*pmd) || !pmd_present(*pmd_k))
362 			goto bad_area_nosemaphore;
363 
364 		*pmd = *pmd_k;
365 		return;
366 	}
367 }
368 
369 /* This always deals with user addresses. */
370 static void force_user_fault(unsigned long address, int write)
371 {
372 	struct vm_area_struct *vma;
373 	struct task_struct *tsk = current;
374 	struct mm_struct *mm = tsk->mm;
375 	unsigned int flags = FAULT_FLAG_USER;
376 	int code;
377 
378 	code = SEGV_MAPERR;
379 
380 	mmap_read_lock(mm);
381 	vma = find_vma(mm, address);
382 	if (!vma)
383 		goto bad_area;
384 	if (vma->vm_start <= address)
385 		goto good_area;
386 	if (!(vma->vm_flags & VM_GROWSDOWN))
387 		goto bad_area;
388 	if (expand_stack(vma, address))
389 		goto bad_area;
390 good_area:
391 	code = SEGV_ACCERR;
392 	if (write) {
393 		if (!(vma->vm_flags & VM_WRITE))
394 			goto bad_area;
395 		flags |= FAULT_FLAG_WRITE;
396 	} else {
397 		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
398 			goto bad_area;
399 	}
400 	switch (handle_mm_fault(vma, address, flags, NULL)) {
401 	case VM_FAULT_SIGBUS:
402 	case VM_FAULT_OOM:
403 		goto do_sigbus;
404 	}
405 	mmap_read_unlock(mm);
406 	return;
407 bad_area:
408 	mmap_read_unlock(mm);
409 	__do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address);
410 	return;
411 
412 do_sigbus:
413 	mmap_read_unlock(mm);
414 	__do_fault_siginfo(BUS_ADRERR, SIGBUS, tsk->thread.kregs, address);
415 }
416 
417 static void check_stack_aligned(unsigned long sp)
418 {
419 	if (sp & 0x7UL)
420 		force_sig(SIGILL);
421 }
422 
423 void window_overflow_fault(void)
424 {
425 	unsigned long sp;
426 
427 	sp = current_thread_info()->rwbuf_stkptrs[0];
428 	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
429 		force_user_fault(sp + 0x38, 1);
430 	force_user_fault(sp, 1);
431 
432 	check_stack_aligned(sp);
433 }
434 
435 void window_underflow_fault(unsigned long sp)
436 {
437 	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
438 		force_user_fault(sp + 0x38, 0);
439 	force_user_fault(sp, 0);
440 
441 	check_stack_aligned(sp);
442 }
443 
444 void window_ret_fault(struct pt_regs *regs)
445 {
446 	unsigned long sp;
447 
448 	sp = regs->u_regs[UREG_FP];
449 	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
450 		force_user_fault(sp + 0x38, 0);
451 	force_user_fault(sp, 0);
452 
453 	check_stack_aligned(sp);
454 }
455