1/*
2 * fault.c:  Page fault handlers for the Sparc.
3 *
4 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu)
5 * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be)
6 * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz)
7 */
8
9#include <asm/head.h>
10
11#include <linux/string.h>
12#include <linux/types.h>
13#include <linux/sched.h>
14#include <linux/ptrace.h>
15#include <linux/mman.h>
16#include <linux/threads.h>
17#include <linux/kernel.h>
18#include <linux/signal.h>
19#include <linux/mm.h>
20#include <linux/smp.h>
21#include <linux/perf_event.h>
22#include <linux/interrupt.h>
23#include <linux/kdebug.h>
24#include <linux/uaccess.h>
25
26#include <asm/page.h>
27#include <asm/pgtable.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
36int show_unhandled_signals = 1;
37
38static 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
57asmlinkage 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
105static inline void
106show_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 %p (rpc %p) sp %p 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
126static void __do_fault_siginfo(int code, int sig, struct pt_regs *regs,
127			       unsigned long addr)
128{
129	siginfo_t info;
130
131	info.si_signo = sig;
132	info.si_code = code;
133	info.si_errno = 0;
134	info.si_addr = (void __user *) addr;
135	info.si_trapno = 0;
136
137	if (unlikely(show_unhandled_signals))
138		show_signal_msg(regs, sig, info.si_code,
139				addr, current);
140
141	force_sig_info (sig, &info, current);
142}
143
144static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault)
145{
146	unsigned int insn;
147
148	if (text_fault)
149		return regs->pc;
150
151	if (regs->psr & PSR_PS)
152		insn = *(unsigned int *) regs->pc;
153	else
154		__get_user(insn, (unsigned int *) regs->pc);
155
156	return safe_compute_effective_address(regs, insn);
157}
158
159static noinline void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
160				      int text_fault)
161{
162	unsigned long addr = compute_si_addr(regs, text_fault);
163
164	__do_fault_siginfo(code, sig, regs, addr);
165}
166
167asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write,
168			       unsigned long address)
169{
170	struct vm_area_struct *vma;
171	struct task_struct *tsk = current;
172	struct mm_struct *mm = tsk->mm;
173	unsigned int fixup;
174	unsigned long g2;
175	int from_user = !(regs->psr & PSR_PS);
176	int fault, code;
177	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
178
179	if (text_fault)
180		address = regs->pc;
181
182	/*
183	 * We fault-in kernel-space virtual memory on-demand. The
184	 * 'reference' page table is init_mm.pgd.
185	 *
186	 * NOTE! We MUST NOT take any locks for this case. We may
187	 * be in an interrupt or a critical region, and should
188	 * only copy the information from the master page table,
189	 * nothing more.
190	 */
191	code = SEGV_MAPERR;
192	if (address >= TASK_SIZE)
193		goto vmalloc_fault;
194
195	/*
196	 * If we're in an interrupt or have no user
197	 * context, we must not take the fault..
198	 */
199	if (pagefault_disabled() || !mm)
200		goto no_context;
201
202	perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
203
204retry:
205	down_read(&mm->mmap_sem);
206
207	if (!from_user && address >= PAGE_OFFSET)
208		goto bad_area;
209
210	vma = find_vma(mm, address);
211	if (!vma)
212		goto bad_area;
213	if (vma->vm_start <= address)
214		goto good_area;
215	if (!(vma->vm_flags & VM_GROWSDOWN))
216		goto bad_area;
217	if (expand_stack(vma, address))
218		goto bad_area;
219	/*
220	 * Ok, we have a good vm_area for this memory access, so
221	 * we can handle it..
222	 */
223good_area:
224	code = SEGV_ACCERR;
225	if (write) {
226		if (!(vma->vm_flags & VM_WRITE))
227			goto bad_area;
228	} else {
229		/* Allow reads even for write-only mappings */
230		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
231			goto bad_area;
232	}
233
234	if (from_user)
235		flags |= FAULT_FLAG_USER;
236	if (write)
237		flags |= FAULT_FLAG_WRITE;
238
239	/*
240	 * If for any reason at all we couldn't handle the fault,
241	 * make sure we exit gracefully rather than endlessly redo
242	 * the fault.
243	 */
244	fault = handle_mm_fault(mm, vma, address, flags);
245
246	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
247		return;
248
249	if (unlikely(fault & VM_FAULT_ERROR)) {
250		if (fault & VM_FAULT_OOM)
251			goto out_of_memory;
252		else if (fault & VM_FAULT_SIGSEGV)
253			goto bad_area;
254		else if (fault & VM_FAULT_SIGBUS)
255			goto do_sigbus;
256		BUG();
257	}
258
259	if (flags & FAULT_FLAG_ALLOW_RETRY) {
260		if (fault & VM_FAULT_MAJOR) {
261			current->maj_flt++;
262			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
263				      1, regs, address);
264		} else {
265			current->min_flt++;
266			perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
267				      1, regs, address);
268		}
269		if (fault & VM_FAULT_RETRY) {
270			flags &= ~FAULT_FLAG_ALLOW_RETRY;
271			flags |= FAULT_FLAG_TRIED;
272
273			/* No need to up_read(&mm->mmap_sem) as we would
274			 * have already released it in __lock_page_or_retry
275			 * in mm/filemap.c.
276			 */
277
278			goto retry;
279		}
280	}
281
282	up_read(&mm->mmap_sem);
283	return;
284
285	/*
286	 * Something tried to access memory that isn't in our memory map..
287	 * Fix it, but check if it's kernel or user first..
288	 */
289bad_area:
290	up_read(&mm->mmap_sem);
291
292bad_area_nosemaphore:
293	/* User mode accesses just cause a SIGSEGV */
294	if (from_user) {
295		do_fault_siginfo(code, SIGSEGV, regs, text_fault);
296		return;
297	}
298
299	/* Is this in ex_table? */
300no_context:
301	g2 = regs->u_regs[UREG_G2];
302	if (!from_user) {
303		fixup = search_extables_range(regs->pc, &g2);
304		/* Values below 10 are reserved for other things */
305		if (fixup > 10) {
306			extern const unsigned __memset_start[];
307			extern const unsigned __memset_end[];
308			extern const unsigned __csum_partial_copy_start[];
309			extern const unsigned __csum_partial_copy_end[];
310
311#ifdef DEBUG_EXCEPTIONS
312			printk("Exception: PC<%08lx> faddr<%08lx>\n",
313			       regs->pc, address);
314			printk("EX_TABLE: insn<%08lx> fixup<%08x> g2<%08lx>\n",
315				regs->pc, fixup, g2);
316#endif
317			if ((regs->pc >= (unsigned long)__memset_start &&
318			     regs->pc < (unsigned long)__memset_end) ||
319			    (regs->pc >= (unsigned long)__csum_partial_copy_start &&
320			     regs->pc < (unsigned long)__csum_partial_copy_end)) {
321				regs->u_regs[UREG_I4] = address;
322				regs->u_regs[UREG_I5] = regs->pc;
323			}
324			regs->u_regs[UREG_G2] = g2;
325			regs->pc = fixup;
326			regs->npc = regs->pc + 4;
327			return;
328		}
329	}
330
331	unhandled_fault(address, tsk, regs);
332	do_exit(SIGKILL);
333
334/*
335 * We ran out of memory, or some other thing happened to us that made
336 * us unable to handle the page fault gracefully.
337 */
338out_of_memory:
339	up_read(&mm->mmap_sem);
340	if (from_user) {
341		pagefault_out_of_memory();
342		return;
343	}
344	goto no_context;
345
346do_sigbus:
347	up_read(&mm->mmap_sem);
348	do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, text_fault);
349	if (!from_user)
350		goto no_context;
351
352vmalloc_fault:
353	{
354		/*
355		 * Synchronize this task's top level page-table
356		 * with the 'reference' page table.
357		 */
358		int offset = pgd_index(address);
359		pgd_t *pgd, *pgd_k;
360		pmd_t *pmd, *pmd_k;
361
362		pgd = tsk->active_mm->pgd + offset;
363		pgd_k = init_mm.pgd + offset;
364
365		if (!pgd_present(*pgd)) {
366			if (!pgd_present(*pgd_k))
367				goto bad_area_nosemaphore;
368			pgd_val(*pgd) = pgd_val(*pgd_k);
369			return;
370		}
371
372		pmd = pmd_offset(pgd, address);
373		pmd_k = pmd_offset(pgd_k, address);
374
375		if (pmd_present(*pmd) || !pmd_present(*pmd_k))
376			goto bad_area_nosemaphore;
377
378		*pmd = *pmd_k;
379		return;
380	}
381}
382
383/* This always deals with user addresses. */
384static void force_user_fault(unsigned long address, int write)
385{
386	struct vm_area_struct *vma;
387	struct task_struct *tsk = current;
388	struct mm_struct *mm = tsk->mm;
389	unsigned int flags = FAULT_FLAG_USER;
390	int code;
391
392	code = SEGV_MAPERR;
393
394	down_read(&mm->mmap_sem);
395	vma = find_vma(mm, address);
396	if (!vma)
397		goto bad_area;
398	if (vma->vm_start <= address)
399		goto good_area;
400	if (!(vma->vm_flags & VM_GROWSDOWN))
401		goto bad_area;
402	if (expand_stack(vma, address))
403		goto bad_area;
404good_area:
405	code = SEGV_ACCERR;
406	if (write) {
407		if (!(vma->vm_flags & VM_WRITE))
408			goto bad_area;
409		flags |= FAULT_FLAG_WRITE;
410	} else {
411		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
412			goto bad_area;
413	}
414	switch (handle_mm_fault(mm, vma, address, flags)) {
415	case VM_FAULT_SIGBUS:
416	case VM_FAULT_OOM:
417		goto do_sigbus;
418	}
419	up_read(&mm->mmap_sem);
420	return;
421bad_area:
422	up_read(&mm->mmap_sem);
423	__do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address);
424	return;
425
426do_sigbus:
427	up_read(&mm->mmap_sem);
428	__do_fault_siginfo(BUS_ADRERR, SIGBUS, tsk->thread.kregs, address);
429}
430
431static void check_stack_aligned(unsigned long sp)
432{
433	if (sp & 0x7UL)
434		force_sig(SIGILL, current);
435}
436
437void window_overflow_fault(void)
438{
439	unsigned long sp;
440
441	sp = current_thread_info()->rwbuf_stkptrs[0];
442	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
443		force_user_fault(sp + 0x38, 1);
444	force_user_fault(sp, 1);
445
446	check_stack_aligned(sp);
447}
448
449void window_underflow_fault(unsigned long sp)
450{
451	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
452		force_user_fault(sp + 0x38, 0);
453	force_user_fault(sp, 0);
454
455	check_stack_aligned(sp);
456}
457
458void window_ret_fault(struct pt_regs *regs)
459{
460	unsigned long sp;
461
462	sp = regs->u_regs[UREG_FP];
463	if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK))
464		force_user_fault(sp + 0x38, 0);
465	force_user_fault(sp, 0);
466
467	check_stack_aligned(sp);
468}
469