1/* $Id: fault.c,v 1.1.1.1 2007/08/03 18:52:19 Exp $
2 * arch/sparc64/mm/fault.c: Page fault handlers for the 64-bit Sparc.
3 *
4 * Copyright (C) 1996 David S. Miller (davem@caip.rutgers.edu)
5 * Copyright (C) 1997, 1999 Jakub Jelinek (jj@ultra.linux.cz)
6 */
7
8#include <asm/head.h>
9
10#include <linux/string.h>
11#include <linux/types.h>
12#include <linux/sched.h>
13#include <linux/ptrace.h>
14#include <linux/mman.h>
15#include <linux/signal.h>
16#include <linux/mm.h>
17#include <linux/module.h>
18#include <linux/init.h>
19#include <linux/interrupt.h>
20#include <linux/kprobes.h>
21#include <linux/kallsyms.h>
22#include <linux/kdebug.h>
23
24#include <asm/page.h>
25#include <asm/pgtable.h>
26#include <asm/openprom.h>
27#include <asm/oplib.h>
28#include <asm/uaccess.h>
29#include <asm/asi.h>
30#include <asm/lsu.h>
31#include <asm/sections.h>
32#include <asm/mmu_context.h>
33
34#ifdef CONFIG_KPROBES
35static inline int notify_page_fault(struct pt_regs *regs)
36{
37	int ret = 0;
38
39	/* kprobe_running() needs smp_processor_id() */
40	if (!user_mode(regs)) {
41		preempt_disable();
42		if (kprobe_running() && kprobe_fault_handler(regs, 0))
43			ret = 1;
44		preempt_enable();
45	}
46	return ret;
47}
48#else
49static inline int notify_page_fault(struct pt_regs *regs)
50{
51	return 0;
52}
53#endif
54
55/*
56 * To debug kernel to catch accesses to certain virtual/physical addresses.
57 * Mode = 0 selects physical watchpoints, mode = 1 selects virtual watchpoints.
58 * flags = VM_READ watches memread accesses, flags = VM_WRITE watches memwrite accesses.
59 * Caller passes in a 64bit aligned addr, with mask set to the bytes that need to be
60 * watched. This is only useful on a single cpu machine for now. After the watchpoint
61 * is detected, the process causing it will be killed, thus preventing an infinite loop.
62 */
63void set_brkpt(unsigned long addr, unsigned char mask, int flags, int mode)
64{
65	unsigned long lsubits;
66
67	__asm__ __volatile__("ldxa [%%g0] %1, %0"
68			     : "=r" (lsubits)
69			     : "i" (ASI_LSU_CONTROL));
70	lsubits &= ~(LSU_CONTROL_PM | LSU_CONTROL_VM |
71		     LSU_CONTROL_PR | LSU_CONTROL_VR |
72		     LSU_CONTROL_PW | LSU_CONTROL_VW);
73
74	__asm__ __volatile__("stxa	%0, [%1] %2\n\t"
75			     "membar	#Sync"
76			     : /* no outputs */
77			     : "r" (addr), "r" (mode ? VIRT_WATCHPOINT : PHYS_WATCHPOINT),
78			       "i" (ASI_DMMU));
79
80	lsubits |= ((unsigned long)mask << (mode ? 25 : 33));
81	if (flags & VM_READ)
82		lsubits |= (mode ? LSU_CONTROL_VR : LSU_CONTROL_PR);
83	if (flags & VM_WRITE)
84		lsubits |= (mode ? LSU_CONTROL_VW : LSU_CONTROL_PW);
85	__asm__ __volatile__("stxa %0, [%%g0] %1\n\t"
86			     "membar #Sync"
87			     : /* no outputs */
88			     : "r" (lsubits), "i" (ASI_LSU_CONTROL)
89			     : "memory");
90}
91
92static void __kprobes unhandled_fault(unsigned long address,
93				      struct task_struct *tsk,
94				      struct pt_regs *regs)
95{
96	if ((unsigned long) address < PAGE_SIZE) {
97		printk(KERN_ALERT "Unable to handle kernel NULL "
98		       "pointer dereference\n");
99	} else {
100		printk(KERN_ALERT "Unable to handle kernel paging request "
101		       "at virtual address %016lx\n", (unsigned long)address);
102	}
103	printk(KERN_ALERT "tsk->{mm,active_mm}->context = %016lx\n",
104	       (tsk->mm ?
105		CTX_HWBITS(tsk->mm->context) :
106		CTX_HWBITS(tsk->active_mm->context)));
107	printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %016lx\n",
108	       (tsk->mm ? (unsigned long) tsk->mm->pgd :
109		          (unsigned long) tsk->active_mm->pgd));
110	die_if_kernel("Oops", regs);
111}
112
113static void bad_kernel_pc(struct pt_regs *regs, unsigned long vaddr)
114{
115	unsigned long *ksp;
116
117	printk(KERN_CRIT "OOPS: Bogus kernel PC [%016lx] in fault handler\n",
118	       regs->tpc);
119	printk(KERN_CRIT "OOPS: RPC [%016lx]\n", regs->u_regs[15]);
120	print_symbol("RPC: <%s>\n", regs->u_regs[15]);
121	printk(KERN_CRIT "OOPS: Fault was to vaddr[%lx]\n", vaddr);
122	__asm__("mov %%sp, %0" : "=r" (ksp));
123	show_stack(current, ksp);
124	unhandled_fault(regs->tpc, current, regs);
125}
126
127/*
128 * We now make sure that mmap_sem is held in all paths that call
129 * this. Additionally, to prevent kswapd from ripping ptes from
130 * under us, raise interrupts around the time that we look at the
131 * pte, kswapd will have to wait to get his smp ipi response from
132 * us. vmtruncate likewise. This saves us having to get pte lock.
133 */
134static unsigned int get_user_insn(unsigned long tpc)
135{
136	pgd_t *pgdp = pgd_offset(current->mm, tpc);
137	pud_t *pudp;
138	pmd_t *pmdp;
139	pte_t *ptep, pte;
140	unsigned long pa;
141	u32 insn = 0;
142	unsigned long pstate;
143
144	if (pgd_none(*pgdp))
145		goto outret;
146	pudp = pud_offset(pgdp, tpc);
147	if (pud_none(*pudp))
148		goto outret;
149	pmdp = pmd_offset(pudp, tpc);
150	if (pmd_none(*pmdp))
151		goto outret;
152
153	/* This disables preemption for us as well. */
154	__asm__ __volatile__("rdpr %%pstate, %0" : "=r" (pstate));
155	__asm__ __volatile__("wrpr %0, %1, %%pstate"
156				: : "r" (pstate), "i" (PSTATE_IE));
157	ptep = pte_offset_map(pmdp, tpc);
158	pte = *ptep;
159	if (!pte_present(pte))
160		goto out;
161
162	pa  = (pte_pfn(pte) << PAGE_SHIFT);
163	pa += (tpc & ~PAGE_MASK);
164
165	/* Use phys bypass so we don't pollute dtlb/dcache. */
166	__asm__ __volatile__("lduwa [%1] %2, %0"
167			     : "=r" (insn)
168			     : "r" (pa), "i" (ASI_PHYS_USE_EC));
169
170out:
171	pte_unmap(ptep);
172	__asm__ __volatile__("wrpr %0, 0x0, %%pstate" : : "r" (pstate));
173outret:
174	return insn;
175}
176
177extern unsigned long compute_effective_address(struct pt_regs *, unsigned int, unsigned int);
178
179static void do_fault_siginfo(int code, int sig, struct pt_regs *regs,
180			     unsigned int insn, int fault_code)
181{
182	siginfo_t info;
183
184	info.si_code = code;
185	info.si_signo = sig;
186	info.si_errno = 0;
187	if (fault_code & FAULT_CODE_ITLB)
188		info.si_addr = (void __user *) regs->tpc;
189	else
190		info.si_addr = (void __user *)
191			compute_effective_address(regs, insn, 0);
192	info.si_trapno = 0;
193	force_sig_info(sig, &info, current);
194}
195
196extern int handle_ldf_stq(u32, struct pt_regs *);
197extern int handle_ld_nf(u32, struct pt_regs *);
198
199static unsigned int get_fault_insn(struct pt_regs *regs, unsigned int insn)
200{
201	if (!insn) {
202		if (!regs->tpc || (regs->tpc & 0x3))
203			return 0;
204		if (regs->tstate & TSTATE_PRIV) {
205			insn = *(unsigned int *) regs->tpc;
206		} else {
207			insn = get_user_insn(regs->tpc);
208		}
209	}
210	return insn;
211}
212
213static void do_kernel_fault(struct pt_regs *regs, int si_code, int fault_code,
214			    unsigned int insn, unsigned long address)
215{
216	unsigned char asi = ASI_P;
217
218	if ((!insn) && (regs->tstate & TSTATE_PRIV))
219		goto cannot_handle;
220
221	/* If user insn could be read (thus insn is zero), that
222	 * is fine.  We will just gun down the process with a signal
223	 * in that case.
224	 */
225
226	if (!(fault_code & (FAULT_CODE_WRITE|FAULT_CODE_ITLB)) &&
227	    (insn & 0xc0800000) == 0xc0800000) {
228		if (insn & 0x2000)
229			asi = (regs->tstate >> 24);
230		else
231			asi = (insn >> 5);
232		if ((asi & 0xf2) == 0x82) {
233			if (insn & 0x1000000) {
234				handle_ldf_stq(insn, regs);
235			} else {
236				/* This was a non-faulting load. Just clear the
237				 * destination register(s) and continue with the next
238				 * instruction. -jj
239				 */
240				handle_ld_nf(insn, regs);
241			}
242			return;
243		}
244	}
245
246	/* Is this in ex_table? */
247	if (regs->tstate & TSTATE_PRIV) {
248		const struct exception_table_entry *entry;
249
250		if (asi == ASI_P && (insn & 0xc0800000) == 0xc0800000) {
251			if (insn & 0x2000)
252				asi = (regs->tstate >> 24);
253			else
254				asi = (insn >> 5);
255		}
256
257		/* Look in asi.h: All _S asis have LS bit set */
258		if ((asi & 0x1) &&
259		    (entry = search_exception_tables(regs->tpc))) {
260			regs->tpc = entry->fixup;
261			regs->tnpc = regs->tpc + 4;
262			return;
263		}
264	} else {
265		/* The si_code was set to make clear whether
266		 * this was a SEGV_MAPERR or SEGV_ACCERR fault.
267		 */
268		do_fault_siginfo(si_code, SIGSEGV, regs, insn, fault_code);
269		return;
270	}
271
272cannot_handle:
273	unhandled_fault (address, current, regs);
274}
275
276asmlinkage void __kprobes do_sparc64_fault(struct pt_regs *regs)
277{
278	struct mm_struct *mm = current->mm;
279	struct vm_area_struct *vma;
280	unsigned int insn = 0;
281	int si_code, fault_code;
282	unsigned long address, mm_rss;
283
284	fault_code = get_thread_fault_code();
285
286	if (notify_page_fault(regs))
287		return;
288
289	si_code = SEGV_MAPERR;
290	address = current_thread_info()->fault_address;
291
292	if ((fault_code & FAULT_CODE_ITLB) &&
293	    (fault_code & FAULT_CODE_DTLB))
294		BUG();
295
296	if (regs->tstate & TSTATE_PRIV) {
297		unsigned long tpc = regs->tpc;
298
299		/* Sanity check the PC. */
300		if ((tpc >= KERNBASE && tpc < (unsigned long) _etext) ||
301		    (tpc >= MODULES_VADDR && tpc < MODULES_END)) {
302			/* Valid, no problems... */
303		} else {
304			bad_kernel_pc(regs, address);
305			return;
306		}
307	}
308
309	/*
310	 * If we're in an interrupt or have no user
311	 * context, we must not take the fault..
312	 */
313	if (in_atomic() || !mm)
314		goto intr_or_no_mm;
315
316	if (test_thread_flag(TIF_32BIT)) {
317		if (!(regs->tstate & TSTATE_PRIV))
318			regs->tpc &= 0xffffffff;
319		address &= 0xffffffff;
320	}
321
322	if (!down_read_trylock(&mm->mmap_sem)) {
323		if ((regs->tstate & TSTATE_PRIV) &&
324		    !search_exception_tables(regs->tpc)) {
325			insn = get_fault_insn(regs, insn);
326			goto handle_kernel_fault;
327		}
328		down_read(&mm->mmap_sem);
329	}
330
331	vma = find_vma(mm, address);
332	if (!vma)
333		goto bad_area;
334
335	/* Pure DTLB misses do not tell us whether the fault causing
336	 * load/store/atomic was a write or not, it only says that there
337	 * was no match.  So in such a case we (carefully) read the
338	 * instruction to try and figure this out.  It's an optimization
339	 * so it's ok if we can't do this.
340	 *
341	 * Special hack, window spill/fill knows the exact fault type.
342	 */
343	if (((fault_code &
344	      (FAULT_CODE_DTLB | FAULT_CODE_WRITE | FAULT_CODE_WINFIXUP)) == FAULT_CODE_DTLB) &&
345	    (vma->vm_flags & VM_WRITE) != 0) {
346		insn = get_fault_insn(regs, 0);
347		if (!insn)
348			goto continue_fault;
349		/* All loads, stores and atomics have bits 30 and 31 both set
350		 * in the instruction.  Bit 21 is set in all stores, but we
351		 * have to avoid prefetches which also have bit 21 set.
352		 */
353		if ((insn & 0xc0200000) == 0xc0200000 &&
354		    (insn & 0x01780000) != 0x01680000) {
355			/* Don't bother updating thread struct value,
356			 * because update_mmu_cache only cares which tlb
357			 * the access came from.
358			 */
359			fault_code |= FAULT_CODE_WRITE;
360		}
361	}
362continue_fault:
363
364	if (vma->vm_start <= address)
365		goto good_area;
366	if (!(vma->vm_flags & VM_GROWSDOWN))
367		goto bad_area;
368	if (!(fault_code & FAULT_CODE_WRITE)) {
369		/* Non-faulting loads shouldn't expand stack. */
370		insn = get_fault_insn(regs, insn);
371		if ((insn & 0xc0800000) == 0xc0800000) {
372			unsigned char asi;
373
374			if (insn & 0x2000)
375				asi = (regs->tstate >> 24);
376			else
377				asi = (insn >> 5);
378			if ((asi & 0xf2) == 0x82)
379				goto bad_area;
380		}
381	}
382	if (expand_stack(vma, address))
383		goto bad_area;
384	/*
385	 * Ok, we have a good vm_area for this memory access, so
386	 * we can handle it..
387	 */
388good_area:
389	si_code = SEGV_ACCERR;
390
391	/* If we took a ITLB miss on a non-executable page, catch
392	 * that here.
393	 */
394	if ((fault_code & FAULT_CODE_ITLB) && !(vma->vm_flags & VM_EXEC)) {
395		BUG_ON(address != regs->tpc);
396		BUG_ON(regs->tstate & TSTATE_PRIV);
397		goto bad_area;
398	}
399
400	if (fault_code & FAULT_CODE_WRITE) {
401		if (!(vma->vm_flags & VM_WRITE))
402			goto bad_area;
403
404		/* Spitfire has an icache which does not snoop
405		 * processor stores.  Later processors do...
406		 */
407		if (tlb_type == spitfire &&
408		    (vma->vm_flags & VM_EXEC) != 0 &&
409		    vma->vm_file != NULL)
410			set_thread_fault_code(fault_code |
411					      FAULT_CODE_BLKCOMMIT);
412	} else {
413		/* Allow reads even for write-only mappings */
414		if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
415			goto bad_area;
416	}
417
418	switch (handle_mm_fault(mm, vma, address, (fault_code & FAULT_CODE_WRITE))) {
419	case VM_FAULT_MINOR:
420		current->min_flt++;
421		break;
422	case VM_FAULT_MAJOR:
423		current->maj_flt++;
424		break;
425	case VM_FAULT_SIGBUS:
426		goto do_sigbus;
427	case VM_FAULT_OOM:
428		goto out_of_memory;
429	default:
430		BUG();
431	}
432
433	up_read(&mm->mmap_sem);
434
435	mm_rss = get_mm_rss(mm);
436#ifdef CONFIG_HUGETLB_PAGE
437	mm_rss -= (mm->context.huge_pte_count * (HPAGE_SIZE / PAGE_SIZE));
438#endif
439	if (unlikely(mm_rss >
440		     mm->context.tsb_block[MM_TSB_BASE].tsb_rss_limit))
441		tsb_grow(mm, MM_TSB_BASE, mm_rss);
442#ifdef CONFIG_HUGETLB_PAGE
443	mm_rss = mm->context.huge_pte_count;
444	if (unlikely(mm_rss >
445		     mm->context.tsb_block[MM_TSB_HUGE].tsb_rss_limit))
446		tsb_grow(mm, MM_TSB_HUGE, mm_rss);
447#endif
448	return;
449
450	/*
451	 * Something tried to access memory that isn't in our memory map..
452	 * Fix it, but check if it's kernel or user first..
453	 */
454bad_area:
455	insn = get_fault_insn(regs, insn);
456	up_read(&mm->mmap_sem);
457
458handle_kernel_fault:
459	do_kernel_fault(regs, si_code, fault_code, insn, address);
460	return;
461
462/*
463 * We ran out of memory, or some other thing happened to us that made
464 * us unable to handle the page fault gracefully.
465 */
466out_of_memory:
467	insn = get_fault_insn(regs, insn);
468	up_read(&mm->mmap_sem);
469	printk("VM: killing process %s\n", current->comm);
470	if (!(regs->tstate & TSTATE_PRIV))
471		do_exit(SIGKILL);
472	goto handle_kernel_fault;
473
474intr_or_no_mm:
475	insn = get_fault_insn(regs, 0);
476	goto handle_kernel_fault;
477
478do_sigbus:
479	insn = get_fault_insn(regs, insn);
480	up_read(&mm->mmap_sem);
481
482	/*
483	 * Send a sigbus, regardless of whether we were in kernel
484	 * or user mode.
485	 */
486	do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, insn, fault_code);
487
488	/* Kernel mode? Handle exceptions or die */
489	if (regs->tstate & TSTATE_PRIV)
490		goto handle_kernel_fault;
491}
492