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