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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/smp_lock.h>
24 #include <linux/interrupt.h>
25 #include <linux/init.h>
26 #include <linux/vt_kern.h>		/* For unblank_screen() */
27 
28 #include <asm/system.h>
29 #include <asm/uaccess.h>
30 #include <asm/pgalloc.h>
31 #include <asm/hardirq.h>
32 #include <asm/gdb-stub.h>
33 #include <asm/cpu-regs.h>
34 
35 /*
36  * Unlock any spinlocks which will prevent us from getting the
37  * message out
38  */
bust_spinlocks(int yes)39 void bust_spinlocks(int yes)
40 {
41 	if (yes) {
42 		oops_in_progress = 1;
43 #ifdef CONFIG_SMP
44 		/* Many serial drivers do __global_cli() */
45 		global_irq_lock = 0;
46 #endif
47 	} else {
48 		int loglevel_save = console_loglevel;
49 #ifdef CONFIG_VT
50 		unblank_screen();
51 #endif
52 		oops_in_progress = 0;
53 		/*
54 		 * OK, the message is on the console.  Now we call printk()
55 		 * without oops_in_progress set so that printk will give klogd
56 		 * a poke.  Hold onto your hats...
57 		 */
58 		console_loglevel = 15;	/* NMI oopser may have shut the console
59 					 * up */
60 		printk(" ");
61 		console_loglevel = loglevel_save;
62 	}
63 }
64 
do_BUG(const char * file,int line)65 void do_BUG(const char *file, int line)
66 {
67 	bust_spinlocks(1);
68 	printk(KERN_EMERG "------------[ cut here ]------------\n");
69 	printk(KERN_EMERG "kernel BUG at %s:%d!\n", file, line);
70 }
71 
72 #if 0
73 static void print_pagetable_entries(pgd_t *pgdir, unsigned long address)
74 {
75 	pgd_t *pgd;
76 	pmd_t *pmd;
77 	pte_t *pte;
78 
79 	pgd = pgdir + __pgd_offset(address);
80 	printk(KERN_DEBUG "pgd entry %p: %016Lx\n",
81 	       pgd, (long long) pgd_val(*pgd));
82 
83 	if (!pgd_present(*pgd)) {
84 		printk(KERN_DEBUG "... pgd not present!\n");
85 		return;
86 	}
87 	pmd = pmd_offset(pgd, address);
88 	printk(KERN_DEBUG "pmd entry %p: %016Lx\n",
89 	       pmd, (long long)pmd_val(*pmd));
90 
91 	if (!pmd_present(*pmd)) {
92 		printk(KERN_DEBUG "... pmd not present!\n");
93 		return;
94 	}
95 	pte = pte_offset(pmd, address);
96 	printk(KERN_DEBUG "pte entry %p: %016Lx\n",
97 	       pte, (long long) pte_val(*pte));
98 
99 	if (!pte_present(*pte))
100 		printk(KERN_DEBUG "... pte not present!\n");
101 }
102 #endif
103 
104 asmlinkage void monitor_signal(struct pt_regs *);
105 
106 /*
107  * This routine handles page faults.  It determines the address,
108  * and the problem, and then passes it off to one of the appropriate
109  * routines.
110  *
111  * fault_code:
112  * - LSW: either MMUFCR_IFC or MMUFCR_DFC as appropriate
113  * - MSW: 0 if data access, 1 if instruction access
114  * - bit 0: TLB miss flag
115  * - bit 1: initial write
116  * - bit 2: page invalid
117  * - bit 3: protection violation
118  * - bit 4: accessor (0=user 1=kernel)
119  * - bit 5: 0=read 1=write
120  * - bit 6-8: page protection spec
121  * - bit 9: illegal address
122  * - bit 16: 0=data 1=ins
123  *
124  */
do_page_fault(struct pt_regs * regs,unsigned long fault_code,unsigned long address)125 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long fault_code,
126 			      unsigned long address)
127 {
128 	struct vm_area_struct *vma;
129 	struct task_struct *tsk;
130 	struct mm_struct *mm;
131 	unsigned long page;
132 	siginfo_t info;
133 	int write, fault;
134 
135 #ifdef CONFIG_GDBSTUB
136 	/* handle GDB stub causing a fault */
137 	if (gdbstub_busy) {
138 		gdbstub_exception(regs, TBR & TBR_INT_CODE);
139 		return;
140 	}
141 #endif
142 
143 #if 0
144 	printk(KERN_DEBUG "--- do_page_fault(%p,%s:%04lx,%08lx)\n",
145 	       regs,
146 	       fault_code & 0x10000 ? "ins" : "data",
147 	       fault_code & 0xffff, address);
148 #endif
149 
150 	tsk = current;
151 
152 	/*
153 	 * We fault-in kernel-space virtual memory on-demand. The
154 	 * 'reference' page table is init_mm.pgd.
155 	 *
156 	 * NOTE! We MUST NOT take any locks for this case. We may
157 	 * be in an interrupt or a critical region, and should
158 	 * only copy the information from the master page table,
159 	 * nothing more.
160 	 *
161 	 * This verifies that the fault happens in kernel space
162 	 * and that the fault was a page not present (invalid) error
163 	 */
164 	if (address >= VMALLOC_START && address < VMALLOC_END &&
165 	    (fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR &&
166 	    (fault_code & MMUFCR_xFC_PGINVAL) == MMUFCR_xFC_PGINVAL
167 	    )
168 		goto vmalloc_fault;
169 
170 	mm = tsk->mm;
171 	info.si_code = SEGV_MAPERR;
172 
173 	/*
174 	 * If we're in an interrupt or have no user
175 	 * context, we must not take the fault..
176 	 */
177 	if (in_atomic() || !mm)
178 		goto no_context;
179 
180 	down_read(&mm->mmap_sem);
181 
182 	vma = find_vma(mm, address);
183 	if (!vma)
184 		goto bad_area;
185 	if (vma->vm_start <= address)
186 		goto good_area;
187 	if (!(vma->vm_flags & VM_GROWSDOWN))
188 		goto bad_area;
189 
190 	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
191 		/* accessing the stack below the stack pointer is always a
192 		 * bug */
193 		if ((address & PAGE_MASK) + 2 * PAGE_SIZE < regs->sp) {
194 #if 0
195 			printk(KERN_WARNING
196 			       "[%d] ### Access below stack @%lx (sp=%lx)\n",
197 			       current->pid, address, regs->sp);
198 			printk(KERN_WARNING
199 			       "vma [%08x - %08x]\n",
200 			       vma->vm_start, vma->vm_end);
201 			show_registers(regs);
202 			printk(KERN_WARNING
203 			       "[%d] ### Code: [%08lx]"
204 			       " %02x %02x %02x %02x %02x %02x %02x %02x\n",
205 			       current->pid,
206 			       regs->pc,
207 			       ((u8 *) regs->pc)[0],
208 			       ((u8 *) regs->pc)[1],
209 			       ((u8 *) regs->pc)[2],
210 			       ((u8 *) regs->pc)[3],
211 			       ((u8 *) regs->pc)[4],
212 			       ((u8 *) regs->pc)[5],
213 			       ((u8 *) regs->pc)[6],
214 			       ((u8 *) regs->pc)[7]
215 			       );
216 #endif
217 			goto bad_area;
218 		}
219 	}
220 
221 	if (expand_stack(vma, address))
222 		goto bad_area;
223 
224 /*
225  * Ok, we have a good vm_area for this memory access, so
226  * we can handle it..
227  */
228 good_area:
229 	info.si_code = SEGV_ACCERR;
230 	write = 0;
231 	switch (fault_code & (MMUFCR_xFC_PGINVAL|MMUFCR_xFC_TYPE)) {
232 	default:	/* 3: write, present */
233 	case MMUFCR_xFC_TYPE_WRITE:
234 #ifdef TEST_VERIFY_AREA
235 		if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
236 			printk(KERN_DEBUG "WP fault at %08lx\n", regs->pc);
237 #endif
238 		/* write to absent page */
239 	case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_WRITE:
240 		if (!(vma->vm_flags & VM_WRITE))
241 			goto bad_area;
242 		write++;
243 		break;
244 
245 		/* read from protected page */
246 	case MMUFCR_xFC_TYPE_READ:
247 		goto bad_area;
248 
249 		/* read from absent page present */
250 	case MMUFCR_xFC_PGINVAL | MMUFCR_xFC_TYPE_READ:
251 		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
252 			goto bad_area;
253 		break;
254 	}
255 
256 	/*
257 	 * If for any reason at all we couldn't handle the fault,
258 	 * make sure we exit gracefully rather than endlessly redo
259 	 * the fault.
260 	 */
261 	fault = handle_mm_fault(mm, vma, address, write);
262 	if (unlikely(fault & VM_FAULT_ERROR)) {
263 		if (fault & VM_FAULT_OOM)
264 			goto out_of_memory;
265 		else if (fault & VM_FAULT_SIGBUS)
266 			goto do_sigbus;
267 		BUG();
268 	}
269 	if (fault & VM_FAULT_MAJOR)
270 		current->maj_flt++;
271 	else
272 		current->min_flt++;
273 
274 	up_read(&mm->mmap_sem);
275 	return;
276 
277 /*
278  * Something tried to access memory that isn't in our memory map..
279  * Fix it, but check if it's kernel or user first..
280  */
281 bad_area:
282 	up_read(&mm->mmap_sem);
283 	monitor_signal(regs);
284 
285 	/* User mode accesses just cause a SIGSEGV */
286 	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR) {
287 		info.si_signo = SIGSEGV;
288 		info.si_errno = 0;
289 		/* info.si_code has been set above */
290 		info.si_addr = (void *)address;
291 		force_sig_info(SIGSEGV, &info, tsk);
292 		return;
293 	}
294 
295 no_context:
296 	monitor_signal(regs);
297 	/* Are we prepared to handle this kernel fault?  */
298 	if (fixup_exception(regs))
299 		return;
300 
301 /*
302  * Oops. The kernel tried to access some bad page. We'll have to
303  * terminate things with extreme prejudice.
304  */
305 
306 	bust_spinlocks(1);
307 
308 	if (address < PAGE_SIZE)
309 		printk(KERN_ALERT
310 		       "Unable to handle kernel NULL pointer dereference");
311 	else
312 		printk(KERN_ALERT
313 		       "Unable to handle kernel paging request");
314 	printk(" at virtual address %08lx\n", address);
315 	printk(" printing pc:\n");
316 	printk(KERN_ALERT "%08lx\n", regs->pc);
317 
318 #ifdef CONFIG_GDBSTUB
319 	gdbstub_intercept(
320 		regs, fault_code & 0x00010000 ? EXCEP_IAERROR : EXCEP_DAERROR);
321 #endif
322 
323 	page = PTBR;
324 	page = ((unsigned long *) __va(page))[address >> 22];
325 	printk(KERN_ALERT "*pde = %08lx\n", page);
326 	if (page & 1) {
327 		page &= PAGE_MASK;
328 		address &= 0x003ff000;
329 		page = ((unsigned long *) __va(page))[address >> PAGE_SHIFT];
330 		printk(KERN_ALERT "*pte = %08lx\n", page);
331 	}
332 
333 	die("Oops", regs, fault_code);
334 	do_exit(SIGKILL);
335 
336 /*
337  * We ran out of memory, or some other thing happened to us that made
338  * us unable to handle the page fault gracefully.
339  */
340 out_of_memory:
341 	up_read(&mm->mmap_sem);
342 	monitor_signal(regs);
343 	printk(KERN_ALERT "VM: killing process %s\n", tsk->comm);
344 	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_USR)
345 		do_exit(SIGKILL);
346 	goto no_context;
347 
348 do_sigbus:
349 	up_read(&mm->mmap_sem);
350 	monitor_signal(regs);
351 
352 	/*
353 	 * Send a sigbus, regardless of whether we were in kernel
354 	 * or user mode.
355 	 */
356 	info.si_signo = SIGBUS;
357 	info.si_errno = 0;
358 	info.si_code = BUS_ADRERR;
359 	info.si_addr = (void *)address;
360 	force_sig_info(SIGBUS, &info, tsk);
361 
362 	/* Kernel mode? Handle exceptions or die */
363 	if ((fault_code & MMUFCR_xFC_ACCESS) == MMUFCR_xFC_ACCESS_SR)
364 		goto no_context;
365 	return;
366 
367 vmalloc_fault:
368 	{
369 		/*
370 		 * Synchronize this task's top level page-table
371 		 * with the 'reference' page table.
372 		 *
373 		 * Do _not_ use "tsk" here. We might be inside
374 		 * an interrupt in the middle of a task switch..
375 		 */
376 		int index = pgd_index(address);
377 		pgd_t *pgd, *pgd_k;
378 		pud_t *pud, *pud_k;
379 		pmd_t *pmd, *pmd_k;
380 		pte_t *pte_k;
381 
382 		pgd_k = init_mm.pgd + index;
383 
384 		if (!pgd_present(*pgd_k))
385 			goto no_context;
386 
387 		pud_k = pud_offset(pgd_k, address);
388 		if (!pud_present(*pud_k))
389 			goto no_context;
390 
391 		pmd_k = pmd_offset(pud_k, address);
392 		if (!pmd_present(*pmd_k))
393 			goto no_context;
394 
395 		pgd = (pgd_t *) PTBR + index;
396 		pud = pud_offset(pgd, address);
397 		pmd = pmd_offset(pud, address);
398 		set_pmd(pmd, *pmd_k);
399 
400 		pte_k = pte_offset_kernel(pmd_k, address);
401 		if (!pte_present(*pte_k))
402 			goto no_context;
403 		return;
404 	}
405 }
406