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
18 #include <asm/mmu_context.h>
19 #include <asm/sysreg.h>
20 #include <asm/tlb.h>
21 #include <asm/uaccess.h>
22
23 #ifdef CONFIG_KPROBES
notify_page_fault(struct pt_regs * regs,int trap)24 static 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
notify_page_fault(struct pt_regs * regs,int trap)36 static inline int notify_page_fault(struct pt_regs *regs, int trap)
37 {
38 return 0;
39 }
40 #endif
41
42 int 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 */
do_page_fault(unsigned long ecr,struct pt_regs * regs)56 asmlinkage 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 (in_atomic() || !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;
91 retry:
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 */
108 good_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 */
177 bad_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
191 no_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 */
233 out_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
240 do_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
do_bus_error(unsigned long addr,int write_access,struct pt_regs * regs)259 asmlinkage 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 }
269