1/* MN10300 MMU Fault handler
2 *
3 * Copyright (C) 2007 Matsushita Electric Industrial Co., Ltd.
4 * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
5 * Modified by David Howells (dhowells@redhat.com)
6 *
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public Licence
9 * as published by the Free Software Foundation; either version
10 * 2 of the Licence, or (at your option) any later version.
11 */
12
13#include <linux/signal.h>
14#include <linux/sched.h>
15#include <linux/kernel.h>
16#include <linux/errno.h>
17#include <linux/string.h>
18#include <linux/types.h>
19#include <linux/ptrace.h>
20#include <linux/mman.h>
21#include <linux/mm.h>
22#include <linux/smp.h>
23#include <linux/interrupt.h>
24#include <linux/init.h>
25#include <linux/vt_kern.h>		/* For unblank_screen() */
26
27#include <asm/uaccess.h>
28#include <asm/pgalloc.h>
29#include <asm/hardirq.h>
30#include <asm/cpu-regs.h>
31#include <asm/debugger.h>
32#include <asm/gdb-stub.h>
33
34/*
35 * Unlock any spinlocks which will prevent us from getting the
36 * message out
37 */
38void bust_spinlocks(int yes)
39{
40	if (yes) {
41		oops_in_progress = 1;
42	} else {
43		int loglevel_save = console_loglevel;
44#ifdef CONFIG_VT
45		unblank_screen();
46#endif
47		oops_in_progress = 0;
48		/*
49		 * OK, the message is on the console.  Now we call printk()
50		 * without oops_in_progress set so that printk will give klogd
51		 * a poke.  Hold onto your hats...
52		 */
53		console_loglevel = 15;	/* NMI oopser may have shut the console
54					 * up */
55		printk(" ");
56		console_loglevel = loglevel_save;
57	}
58}
59
60void do_BUG(const char *file, int line)
61{
62	bust_spinlocks(1);
63	printk(KERN_EMERG "------------[ cut here ]------------\n");
64	printk(KERN_EMERG "kernel BUG at %s:%d!\n", file, line);
65}
66
67#if 0
68static void print_pagetable_entries(pgd_t *pgdir, unsigned long address)
69{
70	pgd_t *pgd;
71	pmd_t *pmd;
72	pte_t *pte;
73
74	pgd = pgdir + __pgd_offset(address);
75	printk(KERN_DEBUG "pgd entry %p: %016Lx\n",
76	       pgd, (long long) pgd_val(*pgd));
77
78	if (!pgd_present(*pgd)) {
79		printk(KERN_DEBUG "... pgd not present!\n");
80		return;
81	}
82	pmd = pmd_offset(pgd, address);
83	printk(KERN_DEBUG "pmd entry %p: %016Lx\n",
84	       pmd, (long long)pmd_val(*pmd));
85
86	if (!pmd_present(*pmd)) {
87		printk(KERN_DEBUG "... pmd not present!\n");
88		return;
89	}
90	pte = pte_offset(pmd, address);
91	printk(KERN_DEBUG "pte entry %p: %016Lx\n",
92	       pte, (long long) pte_val(*pte));
93
94	if (!pte_present(*pte))
95		printk(KERN_DEBUG "... pte not present!\n");
96}
97#endif
98
99/*
100 * This routine handles page faults.  It determines the address,
101 * and the problem, and then passes it off to one of the appropriate
102 * routines.
103 *
104 * fault_code:
105 * - LSW: either MMUFCR_IFC or MMUFCR_DFC as appropriate
106 * - MSW: 0 if data access, 1 if instruction access
107 * - bit 0: TLB miss flag
108 * - bit 1: initial write
109 * - bit 2: page invalid
110 * - bit 3: protection violation
111 * - bit 4: accessor (0=user 1=kernel)
112 * - bit 5: 0=read 1=write
113 * - bit 6-8: page protection spec
114 * - bit 9: illegal address
115 * - bit 16: 0=data 1=ins
116 *
117 */
118asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long fault_code,
119			      unsigned long address)
120{
121	struct vm_area_struct *vma;
122	struct task_struct *tsk;
123	struct mm_struct *mm;
124	unsigned long page;
125	siginfo_t info;
126	int write, fault;
127
128#ifdef CONFIG_GDBSTUB
129	/* handle GDB stub causing a fault */
130	if (gdbstub_busy) {
131		gdbstub_exception(regs, TBR & TBR_INT_CODE);
132		return;
133	}
134#endif
135
136#if 0
137	printk(KERN_DEBUG "--- do_page_fault(%p,%s:%04lx,%08lx)\n",
138	       regs,
139	       fault_code & 0x10000 ? "ins" : "data",
140	       fault_code & 0xffff, address);
141#endif
142
143	tsk = current;
144
145	/*
146	 * We fault-in kernel-space virtual memory on-demand. The
147	 * 'reference' page table is init_mm.pgd.
148	 *
149	 * NOTE! We MUST NOT take any locks for this case. We may
150	 * be in an interrupt or a critical region, and should
151	 * only copy the information from the master page table,
152	 * nothing more.
153	 *
154	 * This verifies that the fault happens in kernel space
155	 * and that the fault was a page not present (invalid) error
156	 */
157	if (address >= VMALLOC_START && address < VMALLOC_END &&
158	    (fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR &&
159	    (fault_code & MMUFCR_xFC_PGINVAL) == MMUFCR_xFC_PGINVAL
160	    )
161		goto vmalloc_fault;
162
163	mm = tsk->mm;
164	info.si_code = SEGV_MAPERR;
165
166	/*
167	 * If we're in an interrupt or have no user
168	 * context, we must not take the fault..
169	 */
170	if (in_atomic() || !mm)
171		goto no_context;
172
173	down_read(&mm->mmap_sem);
174
175	vma = find_vma(mm, address);
176	if (!vma)
177		goto bad_area;
178	if (vma->vm_start <= address)
179		goto good_area;
180	if (!(vma->vm_flags & VM_GROWSDOWN))
181		goto bad_area;
182
183	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
184		/* accessing the stack below the stack pointer is always a
185		 * bug */
186		if ((address & PAGE_MASK) + 2 * PAGE_SIZE < regs->sp) {
187#if 0
188			printk(KERN_WARNING
189			       "[%d] ### Access below stack @%lx (sp=%lx)\n",
190			       current->pid, address, regs->sp);
191			printk(KERN_WARNING
192			       "vma [%08x - %08x]\n",
193			       vma->vm_start, vma->vm_end);
194			show_registers(regs);
195			printk(KERN_WARNING
196			       "[%d] ### Code: [%08lx]"
197			       " %02x %02x %02x %02x %02x %02x %02x %02x\n",
198			       current->pid,
199			       regs->pc,
200			       ((u8 *) regs->pc)[0],
201			       ((u8 *) regs->pc)[1],
202			       ((u8 *) regs->pc)[2],
203			       ((u8 *) regs->pc)[3],
204			       ((u8 *) regs->pc)[4],
205			       ((u8 *) regs->pc)[5],
206			       ((u8 *) regs->pc)[6],
207			       ((u8 *) regs->pc)[7]
208			       );
209#endif
210			goto bad_area;
211		}
212	}
213
214	if (expand_stack(vma, address))
215		goto bad_area;
216
217/*
218 * Ok, we have a good vm_area for this memory access, so
219 * we can handle it..
220 */
221good_area:
222	info.si_code = SEGV_ACCERR;
223	write = 0;
224	switch (fault_code & (MMUFCR_xFC_PGINVAL|MMUFCR_xFC_TYPE)) {
225	default:	/* 3: write, present */
226	case MMUFCR_xFC_TYPE_WRITE:
227#ifdef TEST_VERIFY_AREA
228		if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
229			printk(KERN_DEBUG "WP fault at %08lx\n", regs->pc);
230#endif
231		/* write to absent page */
232	case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_WRITE:
233		if (!(vma->vm_flags & VM_WRITE))
234			goto bad_area;
235		write++;
236		break;
237
238		/* read from protected page */
239	case MMUFCR_xFC_TYPE_READ:
240		goto bad_area;
241
242		/* read from absent page present */
243	case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_READ:
244		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
245			goto bad_area;
246		break;
247	}
248
249	/*
250	 * If for any reason at all we couldn't handle the fault,
251	 * make sure we exit gracefully rather than endlessly redo
252	 * the fault.
253	 */
254	fault = handle_mm_fault(mm, vma, address, write ? FAULT_FLAG_WRITE : 0);
255	if (unlikely(fault & VM_FAULT_ERROR)) {
256		if (fault & VM_FAULT_OOM)
257			goto out_of_memory;
258		else if (fault & VM_FAULT_SIGBUS)
259			goto do_sigbus;
260		BUG();
261	}
262	if (fault & VM_FAULT_MAJOR)
263		current->maj_flt++;
264	else
265		current->min_flt++;
266
267	up_read(&mm->mmap_sem);
268	return;
269
270/*
271 * Something tried to access memory that isn't in our memory map..
272 * Fix it, but check if it's kernel or user first..
273 */
274bad_area:
275	up_read(&mm->mmap_sem);
276
277	/* User mode accesses just cause a SIGSEGV */
278	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
279		info.si_signo = SIGSEGV;
280		info.si_errno = 0;
281		/* info.si_code has been set above */
282		info.si_addr = (void *)address;
283		force_sig_info(SIGSEGV, &info, tsk);
284		return;
285	}
286
287no_context:
288	/* Are we prepared to handle this kernel fault?  */
289	if (fixup_exception(regs))
290		return;
291
292/*
293 * Oops. The kernel tried to access some bad page. We'll have to
294 * terminate things with extreme prejudice.
295 */
296
297	bust_spinlocks(1);
298
299	if (address < PAGE_SIZE)
300		printk(KERN_ALERT
301		       "Unable to handle kernel NULL pointer dereference");
302	else
303		printk(KERN_ALERT
304		       "Unable to handle kernel paging request");
305	printk(" at virtual address %08lx\n", address);
306	printk(" printing pc:\n");
307	printk(KERN_ALERT "%08lx\n", regs->pc);
308
309	debugger_intercept(fault_code & 0x00010000 ? EXCEP_IAERROR : EXCEP_DAERROR,
310			   SIGSEGV, SEGV_ACCERR, regs);
311
312	page = PTBR;
313	page = ((unsigned long *) __va(page))[address >> 22];
314	printk(KERN_ALERT "*pde = %08lx\n", page);
315	if (page & 1) {
316		page &= PAGE_MASK;
317		address &= 0x003ff000;
318		page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
319		printk(KERN_ALERT "*pte = %08lx\n", page);
320	}
321
322	die("Oops", regs, fault_code);
323	do_exit(SIGKILL);
324
325/*
326 * We ran out of memory, or some other thing happened to us that made
327 * us unable to handle the page fault gracefully.
328 */
329out_of_memory:
330	up_read(&mm->mmap_sem);
331	printk(KERN_ALERT "VM: killing process %s\n", tsk->comm);
332	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR)
333		do_exit(SIGKILL);
334	goto no_context;
335
336do_sigbus:
337	up_read(&mm->mmap_sem);
338
339	/*
340	 * Send a sigbus, regardless of whether we were in kernel
341	 * or user mode.
342	 */
343	info.si_signo = SIGBUS;
344	info.si_errno = 0;
345	info.si_code = BUS_ADRERR;
346	info.si_addr = (void *)address;
347	force_sig_info(SIGBUS, &info, tsk);
348
349	/* Kernel mode? Handle exceptions or die */
350	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
351		goto no_context;
352	return;
353
354vmalloc_fault:
355	{
356		/*
357		 * Synchronize this task's top level page-table
358		 * with the 'reference' page table.
359		 *
360		 * Do _not_ use "tsk" here. We might be inside
361		 * an interrupt in the middle of a task switch..
362		 */
363		int index = pgd_index(address);
364		pgd_t *pgd, *pgd_k;
365		pud_t *pud, *pud_k;
366		pmd_t *pmd, *pmd_k;
367		pte_t *pte_k;
368
369		pgd_k = init_mm.pgd + index;
370
371		if (!pgd_present(*pgd_k))
372			goto no_context;
373
374		pud_k = pud_offset(pgd_k, address);
375		if (!pud_present(*pud_k))
376			goto no_context;
377
378		pmd_k = pmd_offset(pud_k, address);
379		if (!pmd_present(*pmd_k))
380			goto no_context;
381
382		pgd = (pgd_t *) PTBR + index;
383		pud = pud_offset(pgd, address);
384		pmd = pmd_offset(pud, address);
385		set_pmd(pmd, *pmd_k);
386
387		pte_k = pte_offset_kernel(pmd_k, address);
388		if (!pte_present(*pte_k))
389			goto no_context;
390		return;
391	}
392}
393