/arch/unicore32/mm/fault.c

  1/*
  2 * linux/arch/unicore32/mm/fault.c
  3 *
  4 * Code specific to PKUnity SoC and UniCore ISA
  5 *
  6 * Copyright (C) 2001-2010 GUAN Xue-tao
  7 *
  8 * This program is free software; you can redistribute it and/or modify
  9 * it under the terms of the GNU General Public License version 2 as
 10 * published by the Free Software Foundation.
 11 */
 12#include <linux/module.h>
 13#include <linux/signal.h>
 14#include <linux/mm.h>
 15#include <linux/hardirq.h>
 16#include <linux/init.h>
 17#include <linux/kprobes.h>
 18#include <linux/uaccess.h>
 19#include <linux/page-flags.h>
 20#include <linux/sched.h>
 21#include <linux/io.h>
 22
 23#include <asm/system.h>
 24#include <asm/pgtable.h>
 25#include <asm/tlbflush.h>
 26
 27/*
 28 * Fault status register encodings.  We steal bit 31 for our own purposes.
 29 */
 30#define FSR_LNX_PF		(1 << 31)
 31
 32static inline int fsr_fs(unsigned int fsr)
 33{
 34	/* xyabcde will be abcde+xy */
 35	return (fsr & 31) + ((fsr & (3 << 5)) >> 5);
 36}
 37
 38/*
 39 * This is useful to dump out the page tables associated with
 40 * 'addr' in mm 'mm'.
 41 */
 42void show_pte(struct mm_struct *mm, unsigned long addr)
 43{
 44	pgd_t *pgd;
 45
 46	if (!mm)
 47		mm = &init_mm;
 48
 49	printk(KERN_ALERT "pgd = %p\n", mm->pgd);
 50	pgd = pgd_offset(mm, addr);
 51	printk(KERN_ALERT "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
 52
 53	do {
 54		pmd_t *pmd;
 55		pte_t *pte;
 56
 57		if (pgd_none(*pgd))
 58			break;
 59
 60		if (pgd_bad(*pgd)) {
 61			printk("(bad)");
 62			break;
 63		}
 64
 65		pmd = pmd_offset((pud_t *) pgd, addr);
 66		if (PTRS_PER_PMD != 1)
 67			printk(", *pmd=%08lx", pmd_val(*pmd));
 68
 69		if (pmd_none(*pmd))
 70			break;
 71
 72		if (pmd_bad(*pmd)) {
 73			printk("(bad)");
 74			break;
 75		}
 76
 77		/* We must not map this if we have highmem enabled */
 78		if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
 79			break;
 80
 81		pte = pte_offset_map(pmd, addr);
 82		printk(", *pte=%08lx", pte_val(*pte));
 83		pte_unmap(pte);
 84	} while (0);
 85
 86	printk("\n");
 87}
 88
 89/*
 90 * Oops.  The kernel tried to access some page that wasn't present.
 91 */
 92static void __do_kernel_fault(struct mm_struct *mm, unsigned long addr,
 93		unsigned int fsr, struct pt_regs *regs)
 94{
 95	/*
 96	 * Are we prepared to handle this kernel fault?
 97	 */
 98	if (fixup_exception(regs))
 99		return;
100
101	/*
102	 * No handler, we'll have to terminate things with extreme prejudice.
103	 */
104	bust_spinlocks(1);
105	printk(KERN_ALERT
106	       "Unable to handle kernel %s at virtual address %08lx\n",
107	       (addr < PAGE_SIZE) ? "NULL pointer dereference" :
108	       "paging request", addr);
109
110	show_pte(mm, addr);
111	die("Oops", regs, fsr);
112	bust_spinlocks(0);
113	do_exit(SIGKILL);
114}
115
116/*
117 * Something tried to access memory that isn't in our memory map..
118 * User mode accesses just cause a SIGSEGV
119 */
120static void __do_user_fault(struct task_struct *tsk, unsigned long addr,
121		unsigned int fsr, unsigned int sig, int code,
122		struct pt_regs *regs)
123{
124	struct siginfo si;
125
126	tsk->thread.address = addr;
127	tsk->thread.error_code = fsr;
128	tsk->thread.trap_no = 14;
129	si.si_signo = sig;
130	si.si_errno = 0;
131	si.si_code = code;
132	si.si_addr = (void __user *)addr;
133	force_sig_info(sig, &si, tsk);
134}
135
136void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
137{
138	struct task_struct *tsk = current;
139	struct mm_struct *mm = tsk->active_mm;
140
141	/*
142	 * If we are in kernel mode at this point, we
143	 * have no context to handle this fault with.
144	 */
145	if (user_mode(regs))
146		__do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
147	else
148		__do_kernel_fault(mm, addr, fsr, regs);
149}
150
151#define VM_FAULT_BADMAP		0x010000
152#define VM_FAULT_BADACCESS	0x020000
153
154/*
155 * Check that the permissions on the VMA allow for the fault which occurred.
156 * If we encountered a write fault, we must have write permission, otherwise
157 * we allow any permission.
158 */
159static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
160{
161	unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
162
163	if (!(fsr ^ 0x12))	/* write? */
164		mask = VM_WRITE;
165	if (fsr & FSR_LNX_PF)
166		mask = VM_EXEC;
167
168	return vma->vm_flags & mask ? false : true;
169}
170
171static int __do_pf(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
172		struct task_struct *tsk)
173{
174	struct vm_area_struct *vma;
175	int fault;
176
177	vma = find_vma(mm, addr);
178	fault = VM_FAULT_BADMAP;
179	if (unlikely(!vma))
180		goto out;
181	if (unlikely(vma->vm_start > addr))
182		goto check_stack;
183
184	/*
185	 * Ok, we have a good vm_area for this
186	 * memory access, so we can handle it.
187	 */
188good_area:
189	if (access_error(fsr, vma)) {
190		fault = VM_FAULT_BADACCESS;
191		goto out;
192	}
193
194	/*
195	 * If for any reason at all we couldn't handle the fault, make
196	 * sure we exit gracefully rather than endlessly redo the fault.
197	 */
198	fault = handle_mm_fault(mm, vma, addr & PAGE_MASK,
199			    (!(fsr ^ 0x12)) ? FAULT_FLAG_WRITE : 0);
200	if (unlikely(fault & VM_FAULT_ERROR))
201		return fault;
202	if (fault & VM_FAULT_MAJOR)
203		tsk->maj_flt++;
204	else
205		tsk->min_flt++;
206	return fault;
207
208check_stack:
209	if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
210		goto good_area;
211out:
212	return fault;
213}
214
215static int do_pf(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
216{
217	struct task_struct *tsk;
218	struct mm_struct *mm;
219	int fault, sig, code;
220
221	tsk = current;
222	mm = tsk->mm;
223
224	/*
225	 * If we're in an interrupt or have no user
226	 * context, we must not take the fault..
227	 */
228	if (in_atomic() || !mm)
229		goto no_context;
230
231	/*
232	 * As per x86, we may deadlock here.  However, since the kernel only
233	 * validly references user space from well defined areas of the code,
234	 * we can bug out early if this is from code which shouldn't.
235	 */
236	if (!down_read_trylock(&mm->mmap_sem)) {
237		if (!user_mode(regs)
238		    && !search_exception_tables(regs->UCreg_pc))
239			goto no_context;
240		down_read(&mm->mmap_sem);
241	} else {
242		/*
243		 * The above down_read_trylock() might have succeeded in
244		 * which case, we'll have missed the might_sleep() from
245		 * down_read()
246		 */
247		might_sleep();
248#ifdef CONFIG_DEBUG_VM
249		if (!user_mode(regs) &&
250		    !search_exception_tables(regs->UCreg_pc))
251			goto no_context;
252#endif
253	}
254
255	fault = __do_pf(mm, addr, fsr, tsk);
256	up_read(&mm->mmap_sem);
257
258	/*
259	 * Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
260	 */
261	if (likely(!(fault &
262	       (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
263		return 0;
264
265	if (fault & VM_FAULT_OOM) {
266		/*
267		 * We ran out of memory, call the OOM killer, and return to
268		 * userspace (which will retry the fault, or kill us if we
269		 * got oom-killed)
270		 */
271		pagefault_out_of_memory();
272		return 0;
273	}
274
275	/*
276	 * If we are in kernel mode at this point, we
277	 * have no context to handle this fault with.
278	 */
279	if (!user_mode(regs))
280		goto no_context;
281
282	if (fault & VM_FAULT_SIGBUS) {
283		/*
284		 * We had some memory, but were unable to
285		 * successfully fix up this page fault.
286		 */
287		sig = SIGBUS;
288		code = BUS_ADRERR;
289	} else {
290		/*
291		 * Something tried to access memory that
292		 * isn't in our memory map..
293		 */
294		sig = SIGSEGV;
295		code = fault == VM_FAULT_BADACCESS ? SEGV_ACCERR : SEGV_MAPERR;
296	}
297
298	__do_user_fault(tsk, addr, fsr, sig, code, regs);
299	return 0;
300
301no_context:
302	__do_kernel_fault(mm, addr, fsr, regs);
303	return 0;
304}
305
306/*
307 * First Level Translation Fault Handler
308 *
309 * We enter here because the first level page table doesn't contain
310 * a valid entry for the address.
311 *
312 * If the address is in kernel space (>= TASK_SIZE), then we are
313 * probably faulting in the vmalloc() area.
314 *
315 * If the init_task's first level page tables contains the relevant
316 * entry, we copy the it to this task.  If not, we send the process
317 * a signal, fixup the exception, or oops the kernel.
318 *
319 * NOTE! We MUST NOT take any locks for this case. We may be in an
320 * interrupt or a critical region, and should only copy the information
321 * from the master page table, nothing more.
322 */
323static int do_ifault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
324{
325	unsigned int index;
326	pgd_t *pgd, *pgd_k;
327	pmd_t *pmd, *pmd_k;
328
329	if (addr < TASK_SIZE)
330		return do_pf(addr, fsr, regs);
331
332	if (user_mode(regs))
333		goto bad_area;
334
335	index = pgd_index(addr);
336
337	pgd = cpu_get_pgd() + index;
338	pgd_k = init_mm.pgd + index;
339
340	if (pgd_none(*pgd_k))
341		goto bad_area;
342
343	pmd_k = pmd_offset((pud_t *) pgd_k, addr);
344	pmd = pmd_offset((pud_t *) pgd, addr);
345
346	if (pmd_none(*pmd_k))
347		goto bad_area;
348
349	set_pmd(pmd, *pmd_k);
350	flush_pmd_entry(pmd);
351	return 0;
352
353bad_area:
354	do_bad_area(addr, fsr, regs);
355	return 0;
356}
357
358/*
359 * This abort handler always returns "fault".
360 */
361static int do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
362{
363	return 1;
364}
365
366static int do_good(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
367{
368	unsigned int res1, res2;
369
370	printk("dabt exception but no error!\n");
371
372	__asm__ __volatile__(
373			"mff %0,f0\n"
374			"mff %1,f1\n"
375			: "=r"(res1), "=r"(res2)
376			:
377			: "memory");
378
379	printk(KERN_EMERG "r0 :%08x  r1 :%08x\n", res1, res2);
380	panic("shut up\n");
381	return 0;
382}
383
384static struct fsr_info {
385	int (*fn) (unsigned long addr, unsigned int fsr, struct pt_regs *regs);
386	int sig;
387	int code;
388	const char *name;
389} fsr_info[] = {
390	/*
391	 * The following are the standard Unicore-I and UniCore-II aborts.
392	 */
393	{ do_good,	SIGBUS,  0,		"no error"		},
394	{ do_bad,	SIGBUS,  BUS_ADRALN,	"alignment exception"	},
395	{ do_bad,	SIGBUS,  BUS_OBJERR,	"external exception"	},
396	{ do_bad,	SIGBUS,  0,		"burst operation"	},
397	{ do_bad,	SIGBUS,  0,		"unknown 00100"		},
398	{ do_ifault,	SIGSEGV, SEGV_MAPERR,	"2nd level pt non-exist"},
399	{ do_bad,	SIGBUS,  0,		"2nd lvl large pt non-exist" },
400	{ do_bad,	SIGBUS,  0,		"invalid pte"		},
401	{ do_pf,	SIGSEGV, SEGV_MAPERR,	"page miss"		},
402	{ do_bad,	SIGBUS,  0,		"middle page miss"	},
403	{ do_bad,	SIGBUS,	 0,		"large page miss"	},
404	{ do_pf,	SIGSEGV, SEGV_MAPERR,	"super page (section) miss" },
405	{ do_bad,	SIGBUS,  0,		"unknown 01100"		},
406	{ do_bad,	SIGBUS,  0,		"unknown 01101"		},
407	{ do_bad,	SIGBUS,  0,		"unknown 01110"		},
408	{ do_bad,	SIGBUS,  0,		"unknown 01111"		},
409	{ do_bad,	SIGBUS,  0,		"addr: up 3G or IO"	},
410	{ do_pf,	SIGSEGV, SEGV_ACCERR,	"read unreadable addr"	},
411	{ do_pf,	SIGSEGV, SEGV_ACCERR,	"write unwriteable addr"},
412	{ do_pf,	SIGSEGV, SEGV_ACCERR,	"exec unexecutable addr"},
413	{ do_bad,	SIGBUS,  0,		"unknown 10100"		},
414	{ do_bad,	SIGBUS,  0,		"unknown 10101"		},
415	{ do_bad,	SIGBUS,  0,		"unknown 10110"		},
416	{ do_bad,	SIGBUS,  0,		"unknown 10111"		},
417	{ do_bad,	SIGBUS,  0,		"unknown 11000"		},
418	{ do_bad,	SIGBUS,  0,		"unknown 11001"		},
419	{ do_bad,	SIGBUS,  0,		"unknown 11010"		},
420	{ do_bad,	SIGBUS,  0,		"unknown 11011"		},
421	{ do_bad,	SIGBUS,  0,		"unknown 11100"		},
422	{ do_bad,	SIGBUS,  0,		"unknown 11101"		},
423	{ do_bad,	SIGBUS,  0,		"unknown 11110"		},
424	{ do_bad,	SIGBUS,  0,		"unknown 11111"		}
425};
426
427void __init hook_fault_code(int nr,
428		int (*fn) (unsigned long, unsigned int, struct pt_regs *),
429		int sig, int code, const char *name)
430{
431	if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
432		BUG();
433
434	fsr_info[nr].fn   = fn;
435	fsr_info[nr].sig  = sig;
436	fsr_info[nr].code = code;
437	fsr_info[nr].name = name;
438}
439
440/*
441 * Dispatch a data abort to the relevant handler.
442 */
443asmlinkage void do_DataAbort(unsigned long addr, unsigned int fsr,
444			struct pt_regs *regs)
445{
446	const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
447	struct siginfo info;
448
449	if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
450		return;
451
452	printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
453	       inf->name, fsr, addr);
454
455	info.si_signo = inf->sig;
456	info.si_errno = 0;
457	info.si_code = inf->code;
458	info.si_addr = (void __user *)addr;
459	uc32_notify_die("", regs, &info, fsr, 0);
460}
461
462asmlinkage void do_PrefetchAbort(unsigned long addr,
463			unsigned int ifsr, struct pt_regs *regs)
464{
465	const struct fsr_info *inf = fsr_info + fsr_fs(ifsr);
466	struct siginfo info;
467
468	if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
469		return;
470
471	printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
472	       inf->name, ifsr, addr);
473
474	info.si_signo = inf->sig;
475	info.si_errno = 0;
476	info.si_code = inf->code;
477	info.si_addr = (void __user *)addr;
478	uc32_notify_die("", regs, &info, ifsr, 0);
479}