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