1/*
  2 * Copyright (C) 2004-2006 Atmel Corporation
  3 *
  4 * Based on linux/arch/sh/mm/fault.c:
  5 *   Copyright (C) 1999  Niibe Yutaka
  6 *
  7 * This program is free software; you can redistribute it and/or modify
  8 * it under the terms of the GNU General Public License version 2 as
  9 * published by the Free Software Foundation.
 10 */
 11
 12#include <linux/mm.h>
 13#include <linux/module.h>
 14#include <linux/pagemap.h>
 15#include <linux/kdebug.h>
 16#include <linux/kprobes.h>
 17#include <linux/uaccess.h>
 18
 19#include <asm/mmu_context.h>
 20#include <asm/sysreg.h>
 21#include <asm/tlb.h>
 22
 23#ifdef CONFIG_KPROBES
 24static inline int notify_page_fault(struct pt_regs *regs, int trap)
 25{
 26	int ret = 0;
 27
 28	if (!user_mode(regs)) {
 29		if (kprobe_running() && kprobe_fault_handler(regs, trap))
 30			ret = 1;
 31	}
 32
 33	return ret;
 34}
 35#else
 36static inline int notify_page_fault(struct pt_regs *regs, int trap)
 37{
 38	return 0;
 39}
 40#endif
 41
 42int exception_trace = 1;
 43
 44/*
 45 * This routine handles page faults. It determines the address and the
 46 * problem, and then passes it off to one of the appropriate routines.
 47 *
 48 * ecr is the Exception Cause Register. Possible values are:
 49 *   6:  Protection fault (instruction access)
 50 *   15: Protection fault (read access)
 51 *   16: Protection fault (write access)
 52 *   20: Page not found (instruction access)
 53 *   24: Page not found (read access)
 54 *   28: Page not found (write access)
 55 */
 56asmlinkage void do_page_fault(unsigned long ecr, struct pt_regs *regs)
 57{
 58	struct task_struct *tsk;
 59	struct mm_struct *mm;
 60	struct vm_area_struct *vma;
 61	const struct exception_table_entry *fixup;
 62	unsigned long address;
 63	unsigned long page;
 64	long signr;
 65	int code;
 66	int fault;
 67	unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
 68
 69	if (notify_page_fault(regs, ecr))
 70		return;
 71
 72	address = sysreg_read(TLBEAR);
 73
 74	tsk = current;
 75	mm = tsk->mm;
 76
 77	signr = SIGSEGV;
 78	code = SEGV_MAPERR;
 79
 80	/*
 81	 * If we're in an interrupt or have no user context, we must
 82	 * not take the fault...
 83	 */
 84	if (faulthandler_disabled() || !mm || regs->sr & SYSREG_BIT(GM))
 85		goto no_context;
 86
 87	local_irq_enable();
 88
 89	if (user_mode(regs))
 90		flags |= FAULT_FLAG_USER;
 91retry:
 92	down_read(&mm->mmap_sem);
 93
 94	vma = find_vma(mm, address);
 95	if (!vma)
 96		goto bad_area;
 97	if (vma->vm_start <= address)
 98		goto good_area;
 99	if (!(vma->vm_flags & VM_GROWSDOWN))
100		goto bad_area;
101	if (expand_stack(vma, address))
102		goto bad_area;
103
104	/*
105	 * Ok, we have a good vm_area for this memory access, so we
106	 * can handle it...
107	 */
108good_area:
109	code = SEGV_ACCERR;
110
111	switch (ecr) {
112	case ECR_PROTECTION_X:
113	case ECR_TLB_MISS_X:
114		if (!(vma->vm_flags & VM_EXEC))
115			goto bad_area;
116		break;
117	case ECR_PROTECTION_R:
118	case ECR_TLB_MISS_R:
119		if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
120			goto bad_area;
121		break;
122	case ECR_PROTECTION_W:
123	case ECR_TLB_MISS_W:
124		if (!(vma->vm_flags & VM_WRITE))
125			goto bad_area;
126		flags |= FAULT_FLAG_WRITE;
127		break;
128	default:
129		panic("Unhandled case %lu in do_page_fault!", ecr);
130	}
131
132	/*
133	 * If for any reason at all we couldn't handle the fault, make
134	 * sure we exit gracefully rather than endlessly redo the
135	 * fault.
136	 */
137	fault = handle_mm_fault(mm, vma, address, flags);
138
139	if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
140		return;
141
142	if (unlikely(fault & VM_FAULT_ERROR)) {
143		if (fault & VM_FAULT_OOM)
144			goto out_of_memory;
145		else if (fault & VM_FAULT_SIGSEGV)
146			goto bad_area;
147		else if (fault & VM_FAULT_SIGBUS)
148			goto do_sigbus;
149		BUG();
150	}
151
152	if (flags & FAULT_FLAG_ALLOW_RETRY) {
153		if (fault & VM_FAULT_MAJOR)
154			tsk->maj_flt++;
155		else
156			tsk->min_flt++;
157		if (fault & VM_FAULT_RETRY) {
158			flags &= ~FAULT_FLAG_ALLOW_RETRY;
159			flags |= FAULT_FLAG_TRIED;
160
161			/*
162			 * No need to up_read(&mm->mmap_sem) as we would have
163			 * already released it in __lock_page_or_retry() in
164			 * mm/filemap.c.
165			 */
166			goto retry;
167		}
168	}
169
170	up_read(&mm->mmap_sem);
171	return;
172
173	/*
174	 * Something tried to access memory that isn't in our memory
175	 * map. Fix it, but check if it's kernel or user first...
176	 */
177bad_area:
178	up_read(&mm->mmap_sem);
179
180	if (user_mode(regs)) {
181		if (exception_trace && printk_ratelimit())
182			printk("%s%s[%d]: segfault at %08lx pc %08lx "
183			       "sp %08lx ecr %lu\n",
184			       is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
185			       tsk->comm, tsk->pid, address, regs->pc,
186			       regs->sp, ecr);
187		_exception(SIGSEGV, regs, code, address);
188		return;
189	}
190
191no_context:
192	/* Are we prepared to handle this kernel fault? */
193	fixup = search_exception_tables(regs->pc);
194	if (fixup) {
195		regs->pc = fixup->fixup;
196		return;
197	}
198
199	/*
200	 * Oops. The kernel tried to access some bad page. We'll have
201	 * to terminate things with extreme prejudice.
202	 */
203	if (address < PAGE_SIZE)
204		printk(KERN_ALERT
205		       "Unable to handle kernel NULL pointer dereference");
206	else
207		printk(KERN_ALERT
208		       "Unable to handle kernel paging request");
209	printk(" at virtual address %08lx\n", address);
210
211	page = sysreg_read(PTBR);
212	printk(KERN_ALERT "ptbr = %08lx", page);
213	if (address >= TASK_SIZE)
214		page = (unsigned long)swapper_pg_dir;
215	if (page) {
216		page = ((unsigned long *)page)[address >> 22];
217		printk(" pgd = %08lx", page);
218		if (page & _PAGE_PRESENT) {
219			page &= PAGE_MASK;
220			address &= 0x003ff000;
221			page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
222			printk(" pte = %08lx", page);
223		}
224	}
225	printk("\n");
226	die("Kernel access of bad area", regs, signr);
227	return;
228
229	/*
230	 * We ran out of memory, or some other thing happened to us
231	 * that made us unable to handle the page fault gracefully.
232	 */
233out_of_memory:
234	up_read(&mm->mmap_sem);
235	if (!user_mode(regs))
236		goto no_context;
237	pagefault_out_of_memory();
238	return;
239
240do_sigbus:
241	up_read(&mm->mmap_sem);
242
243	/* Kernel mode? Handle exceptions or die */
244	signr = SIGBUS;
245	code = BUS_ADRERR;
246	if (!user_mode(regs))
247		goto no_context;
248
249	if (exception_trace)
250		printk("%s%s[%d]: bus error at %08lx pc %08lx "
251		       "sp %08lx ecr %lu\n",
252		       is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
253		       tsk->comm, tsk->pid, address, regs->pc,
254		       regs->sp, ecr);
255
256	_exception(SIGBUS, regs, BUS_ADRERR, address);
257}
258
259asmlinkage void do_bus_error(unsigned long addr, int write_access,
260			     struct pt_regs *regs)
261{
262	printk(KERN_ALERT
263	       "Bus error at physical address 0x%08lx (%s access)\n",
264	       addr, write_access ? "write" : "read");
265	printk(KERN_INFO "DTLB dump:\n");
266	dump_dtlb();
267	die("Bus Error", regs, SIGKILL);
268}