1/*
  2 *  arch/cris/mm/fault.c
  3 *
  4 *  Copyright (C) 2000-2010  Axis Communications AB
  5 */
  6
  7#include <linux/mm.h>
  8#include <linux/interrupt.h>
  9#include <linux/module.h>
 10#include <linux/wait.h>
 11#include <asm/uaccess.h>
 12#include <arch/system.h>
 13
 14extern int find_fixup_code(struct pt_regs *);
 15extern void die_if_kernel(const char *, struct pt_regs *, long);
 16extern void show_registers(struct pt_regs *regs);
 17
 18/* debug of low-level TLB reload */
 19#undef DEBUG
 20
 21#ifdef DEBUG
 22#define D(x) x
 23#else
 24#define D(x)
 25#endif
 26
 27/* debug of higher-level faults */
 28#define DPG(x)
 29
 30/* current active page directory */
 31
 32DEFINE_PER_CPU(pgd_t *, current_pgd);
 33unsigned long cris_signal_return_page;
 34
 35/*
 36 * This routine handles page faults.  It determines the address,
 37 * and the problem, and then passes it off to one of the appropriate
 38 * routines.
 39 *
 40 * Notice that the address we're given is aligned to the page the fault
 41 * occurred in, since we only get the PFN in R_MMU_CAUSE not the complete
 42 * address.
 43 *
 44 * error_code:
 45 *      bit 0 == 0 means no page found, 1 means protection fault
 46 *      bit 1 == 0 means read, 1 means write
 47 *
 48 * If this routine detects a bad access, it returns 1, otherwise it
 49 * returns 0.
 50 */
 51
 52asmlinkage void
 53do_page_fault(unsigned long address, struct pt_regs *regs,
 54	      int protection, int writeaccess)
 55{
 56	struct task_struct *tsk;
 57	struct mm_struct *mm;
 58	struct vm_area_struct * vma;
 59	siginfo_t info;
 60	int fault;
 61	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
 62				((writeaccess & 1) ? FAULT_FLAG_WRITE : 0);
 63
 64	D(printk(KERN_DEBUG
 65		 "Page fault for %lX on %X at %lX, prot %d write %d\n",
 66		 address, smp_processor_id(), instruction_pointer(regs),
 67		 protection, writeaccess));
 68
 69	tsk = current;
 70
 71	/*
 72	 * We fault-in kernel-space virtual memory on-demand. The
 73	 * 'reference' page table is init_mm.pgd.
 74	 *
 75	 * NOTE! We MUST NOT take any locks for this case. We may
 76	 * be in an interrupt or a critical region, and should
 77	 * only copy the information from the master page table,
 78	 * nothing more.
 79	 *
 80	 * NOTE2: This is done so that, when updating the vmalloc
 81	 * mappings we don't have to walk all processes pgdirs and
 82	 * add the high mappings all at once. Instead we do it as they
 83	 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL
 84	 * bit set so sometimes the TLB can use a lingering entry.
 85	 *
 86	 * This verifies that the fault happens in kernel space
 87	 * and that the fault was not a protection error (error_code & 1).
 88	 */
 89
 90	if (address >= VMALLOC_START &&
 91	    !protection &&
 92	    !user_mode(regs))
 93		goto vmalloc_fault;
 94
 95	/* When stack execution is not allowed we store the signal
 96	 * trampolines in the reserved cris_signal_return_page.
 97	 * Handle this in the exact same way as vmalloc (we know
 98	 * that the mapping is there and is valid so no need to
 99	 * call handle_mm_fault).
100	 */
101	if (cris_signal_return_page &&
102	    address == cris_signal_return_page &&
103	    !protection && user_mode(regs))
104		goto vmalloc_fault;
105
106	/* we can and should enable interrupts at this point */
107	local_irq_enable();
108
109	mm = tsk->mm;
110	info.si_code = SEGV_MAPERR;
111
112	/*
113	 * If we're in an interrupt or "atomic" operation or have no
114	 * user context, we must not take the fault.
115	 */
116
117	if (in_atomic() || !mm)
118		goto no_context;
119
120retry:
121	down_read(&mm->mmap_sem);
122	vma = find_vma(mm, address);
123	if (!vma)
124		goto bad_area;
125	if (vma->vm_start <= address)
126		goto good_area;
127	if (!(vma->vm_flags & VM_GROWSDOWN))
128		goto bad_area;
129	if (user_mode(regs)) {
130		/*
131		 * accessing the stack below usp is always a bug.
132		 * we get page-aligned addresses so we can only check
133		 * if we're within a page from usp, but that might be
134		 * enough to catch brutal errors at least.
135		 */
136		if (address + PAGE_SIZE < rdusp())
137			goto bad_area;
138	}
139	if (expand_stack(vma, address))
140		goto bad_area;
141
142	/*
143	 * Ok, we have a good vm_area for this memory access, so
144	 * we can handle it..
145	 */
146
147 good_area:
148	info.si_code = SEGV_ACCERR;
149
150	/* first do some preliminary protection checks */
151
152	if (writeaccess == 2){
153		if (!(vma->vm_flags & VM_EXEC))
154			goto bad_area;
155	} else if (writeaccess == 1) {
156		if (!(vma->vm_flags & VM_WRITE))
157			goto bad_area;
158	} else {
159		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
160			goto bad_area;
161	}
162
163	/*
164	 * If for any reason at all we couldn't handle the fault,
165	 * make sure we exit gracefully rather than endlessly redo
166	 * the fault.
167	 */
168
169	fault = handle_mm_fault(mm, vma, address, flags);
170
171	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
172		return;
173
174	if (unlikely(fault & VM_FAULT_ERROR)) {
175		if (fault & VM_FAULT_OOM)
176			goto out_of_memory;
177		else if (fault & VM_FAULT_SIGBUS)
178			goto do_sigbus;
179		BUG();
180	}
181
182	if (flags & FAULT_FLAG_ALLOW_RETRY) {
183		if (fault & VM_FAULT_MAJOR)
184			tsk->maj_flt++;
185		else
186			tsk->min_flt++;
187		if (fault & VM_FAULT_RETRY) {
188			flags &= ~FAULT_FLAG_ALLOW_RETRY;
189
190			/*
191			 * No need to up_read(&mm->mmap_sem) as we would
192			 * have already released it in __lock_page_or_retry
193			 * in mm/filemap.c.
194			 */
195
196			goto retry;
197		}
198	}
199
200	up_read(&mm->mmap_sem);
201	return;
202
203	/*
204	 * Something tried to access memory that isn't in our memory map..
205	 * Fix it, but check if it's kernel or user first..
206	 */
207
208 bad_area:
209	up_read(&mm->mmap_sem);
210
211 bad_area_nosemaphore:
212	DPG(show_registers(regs));
213
214	/* User mode accesses just cause a SIGSEGV */
215
216	if (user_mode(regs)) {
217		printk(KERN_NOTICE "%s (pid %d) segfaults for page "
218			"address %08lx at pc %08lx\n",
219			tsk->comm, tsk->pid,
220			address, instruction_pointer(regs));
221
222		/* With DPG on, we've already dumped registers above.  */
223		DPG(if (0))
224			show_registers(regs);
225
226#ifdef CONFIG_NO_SEGFAULT_TERMINATION
227		DECLARE_WAIT_QUEUE_HEAD(wq);
228		wait_event_interruptible(wq, 0 == 1);
229#else
230		info.si_signo = SIGSEGV;
231		info.si_errno = 0;
232		/* info.si_code has been set above */
233		info.si_addr = (void *)address;
234		force_sig_info(SIGSEGV, &info, tsk);
235#endif
236		return;
237	}
238
239 no_context:
240
241	/* Are we prepared to handle this kernel fault?
242	 *
243	 * (The kernel has valid exception-points in the source
244	 *  when it accesses user-memory. When it fails in one
245	 *  of those points, we find it in a table and do a jump
246	 *  to some fixup code that loads an appropriate error
247	 *  code)
248	 */
249
250	if (find_fixup_code(regs))
251		return;
252
253	/*
254	 * Oops. The kernel tried to access some bad page. We'll have to
255	 * terminate things with extreme prejudice.
256	 */
257
258	if (!oops_in_progress) {
259		oops_in_progress = 1;
260		if ((unsigned long) (address) < PAGE_SIZE)
261			printk(KERN_ALERT "Unable to handle kernel NULL "
262				"pointer dereference");
263		else
264			printk(KERN_ALERT "Unable to handle kernel access"
265				" at virtual address %08lx\n", address);
266
267		die_if_kernel("Oops", regs, (writeaccess << 1) | protection);
268		oops_in_progress = 0;
269	}
270
271	do_exit(SIGKILL);
272
273	/*
274	 * We ran out of memory, or some other thing happened to us that made
275	 * us unable to handle the page fault gracefully.
276	 */
277
278 out_of_memory:
279	up_read(&mm->mmap_sem);
280	if (!user_mode(regs))
281		goto no_context;
282	pagefault_out_of_memory();
283	return;
284
285 do_sigbus:
286	up_read(&mm->mmap_sem);
287
288	/*
289	 * Send a sigbus, regardless of whether we were in kernel
290	 * or user mode.
291	 */
292	info.si_signo = SIGBUS;
293	info.si_errno = 0;
294	info.si_code = BUS_ADRERR;
295	info.si_addr = (void *)address;
296	force_sig_info(SIGBUS, &info, tsk);
297
298	/* Kernel mode? Handle exceptions or die */
299	if (!user_mode(regs))
300		goto no_context;
301	return;
302
303vmalloc_fault:
304	{
305		/*
306		 * Synchronize this task's top level page-table
307		 * with the 'reference' page table.
308		 *
309		 * Use current_pgd instead of tsk->active_mm->pgd
310		 * since the latter might be unavailable if this
311		 * code is executed in a misfortunately run irq
312		 * (like inside schedule() between switch_mm and
313		 *  switch_to...).
314		 */
315
316		int offset = pgd_index(address);
317		pgd_t *pgd, *pgd_k;
318		pud_t *pud, *pud_k;
319		pmd_t *pmd, *pmd_k;
320		pte_t *pte_k;
321
322		pgd = (pgd_t *)per_cpu(current_pgd, smp_processor_id()) + offset;
323		pgd_k = init_mm.pgd + offset;
324
325		/* Since we're two-level, we don't need to do both
326		 * set_pgd and set_pmd (they do the same thing). If
327		 * we go three-level at some point, do the right thing
328		 * with pgd_present and set_pgd here.
329		 *
330		 * Also, since the vmalloc area is global, we don't
331		 * need to copy individual PTE's, it is enough to
332		 * copy the pgd pointer into the pte page of the
333		 * root task. If that is there, we'll find our pte if
334		 * it exists.
335		 */
336
337		pud = pud_offset(pgd, address);
338		pud_k = pud_offset(pgd_k, address);
339		if (!pud_present(*pud_k))
340			goto no_context;
341
342		pmd = pmd_offset(pud, address);
343		pmd_k = pmd_offset(pud_k, address);
344
345		if (!pmd_present(*pmd_k))
346			goto bad_area_nosemaphore;
347
348		set_pmd(pmd, *pmd_k);
349
350		/* Make sure the actual PTE exists as well to
351		 * catch kernel vmalloc-area accesses to non-mapped
352		 * addresses. If we don't do this, this will just
353		 * silently loop forever.
354		 */
355
356		pte_k = pte_offset_kernel(pmd_k, address);
357		if (!pte_present(*pte_k))
358			goto no_context;
359
360		return;
361	}
362}
363
364/* Find fixup code. */
365int
366find_fixup_code(struct pt_regs *regs)
367{
368	const struct exception_table_entry *fixup;
369	/* in case of delay slot fault (v32) */
370	unsigned long ip = (instruction_pointer(regs) & ~0x1);
371
372	fixup = search_exception_tables(ip);
373	if (fixup != 0) {
374		/* Adjust the instruction pointer in the stackframe. */
375		instruction_pointer(regs) = fixup->fixup;
376		arch_fixup(regs);
377		return 1;
378	}
379
380	return 0;
381}