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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
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 int writeaccess;
65 long signr;
66 int code;
67 int fault;
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 down_read(&mm->mmap_sem);
90
91 vma = find_vma(mm, address);
92 if (!vma)
93 goto bad_area;
94 if (vma->vm_start <= address)
95 goto good_area;
96 if (!(vma->vm_flags & VM_GROWSDOWN))
97 goto bad_area;
98 if (expand_stack(vma, address))
99 goto bad_area;
100
101 /*
102 * Ok, we have a good vm_area for this memory access, so we
103 * can handle it...
104 */
105good_area:
106 code = SEGV_ACCERR;
107 writeaccess = 0;
108
109 switch (ecr) {
110 case ECR_PROTECTION_X:
111 case ECR_TLB_MISS_X:
112 if (!(vma->vm_flags & VM_EXEC))
113 goto bad_area;
114 break;
115 case ECR_PROTECTION_R:
116 case ECR_TLB_MISS_R:
117 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
118 goto bad_area;
119 break;
120 case ECR_PROTECTION_W:
121 case ECR_TLB_MISS_W:
122 if (!(vma->vm_flags & VM_WRITE))
123 goto bad_area;
124 writeaccess = 1;
125 break;
126 default:
127 panic("Unhandled case %lu in do_page_fault!", ecr);
128 }
129
130 /*
131 * If for any reason at all we couldn't handle the fault, make
132 * sure we exit gracefully rather than endlessly redo the
133 * fault.
134 */
135 fault = handle_mm_fault(mm, vma, address, writeaccess ? FAULT_FLAG_WRITE : 0);
136 if (unlikely(fault & VM_FAULT_ERROR)) {
137 if (fault & VM_FAULT_OOM)
138 goto out_of_memory;
139 else if (fault & VM_FAULT_SIGBUS)
140 goto do_sigbus;
141 BUG();
142 }
143 if (fault & VM_FAULT_MAJOR)
144 tsk->maj_flt++;
145 else
146 tsk->min_flt++;
147
148 up_read(&mm->mmap_sem);
149 return;
150
151 /*
152 * Something tried to access memory that isn't in our memory
153 * map. Fix it, but check if it's kernel or user first...
154 */
155bad_area:
156 up_read(&mm->mmap_sem);
157
158 if (user_mode(regs)) {
159 if (exception_trace && printk_ratelimit())
160 printk("%s%s[%d]: segfault at %08lx pc %08lx "
161 "sp %08lx ecr %lu\n",
162 is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
163 tsk->comm, tsk->pid, address, regs->pc,
164 regs->sp, ecr);
165 _exception(SIGSEGV, regs, code, address);
166 return;
167 }
168
169no_context:
170 /* Are we prepared to handle this kernel fault? */
171 fixup = search_exception_tables(regs->pc);
172 if (fixup) {
173 regs->pc = fixup->fixup;
174 return;
175 }
176
177 /*
178 * Oops. The kernel tried to access some bad page. We'll have
179 * to terminate things with extreme prejudice.
180 */
181 if (address < PAGE_SIZE)
182 printk(KERN_ALERT
183 "Unable to handle kernel NULL pointer dereference");
184 else
185 printk(KERN_ALERT
186 "Unable to handle kernel paging request");
187 printk(" at virtual address %08lx\n", address);
188
189 page = sysreg_read(PTBR);
190 printk(KERN_ALERT "ptbr = %08lx", page);
191 if (address >= TASK_SIZE)
192 page = (unsigned long)swapper_pg_dir;
193 if (page) {
194 page = ((unsigned long *)page)[address >> 22];
195 printk(" pgd = %08lx", page);
196 if (page & _PAGE_PRESENT) {
197 page &= PAGE_MASK;
198 address &= 0x003ff000;
199 page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
200 printk(" pte = %08lx", page);
201 }
202 }
203 printk("\n");
204 die("Kernel access of bad area", regs, signr);
205 return;
206
207 /*
208 * We ran out of memory, or some other thing happened to us
209 * that made us unable to handle the page fault gracefully.
210 */
211out_of_memory:
212 up_read(&mm->mmap_sem);
213 pagefault_out_of_memory();
214 if (!user_mode(regs))
215 goto no_context;
216 return;
217
218do_sigbus:
219 up_read(&mm->mmap_sem);
220
221 /* Kernel mode? Handle exceptions or die */
222 signr = SIGBUS;
223 code = BUS_ADRERR;
224 if (!user_mode(regs))
225 goto no_context;
226
227 if (exception_trace)
228 printk("%s%s[%d]: bus error at %08lx pc %08lx "
229 "sp %08lx ecr %lu\n",
230 is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
231 tsk->comm, tsk->pid, address, regs->pc,
232 regs->sp, ecr);
233
234 _exception(SIGBUS, regs, BUS_ADRERR, address);
235}
236
237asmlinkage void do_bus_error(unsigned long addr, int write_access,
238 struct pt_regs *regs)
239{
240 printk(KERN_ALERT
241 "Bus error at physical address 0x%08lx (%s access)\n",
242 addr, write_access ? "write" : "read");
243 printk(KERN_INFO "DTLB dump:\n");
244 dump_dtlb();
245 die("Bus Error", regs, SIGKILL);
246}