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
|
/*
* linux/arch/m68k/mm/fault.c
*
* Copyright (C) 1995 Hamish Macdonald
*/
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/kernel.h>
#include <linux/ptrace.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <asm/setup.h>
#include <asm/traps.h>
#include <asm/uaccess.h>
#include <asm/pgalloc.h>
extern void die_if_kernel(char *, struct pt_regs *, long);
int send_fault_sig(struct pt_regs *regs)
{
siginfo_t siginfo = { 0, 0, 0, };
siginfo.si_signo = current->thread.signo;
siginfo.si_code = current->thread.code;
siginfo.si_addr = (void *)current->thread.faddr;
#ifdef DEBUG
printk("send_fault_sig: %p,%d,%d\n", siginfo.si_addr, siginfo.si_signo, siginfo.si_code);
#endif
if (user_mode(regs)) {
force_sig_info(siginfo.si_signo,
&siginfo, current);
} else {
if (handle_kernel_fault(regs))
return -1;
//if (siginfo.si_signo == SIGBUS)
// force_sig_info(siginfo.si_signo,
// &siginfo, current);
/*
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice.
*/
if ((unsigned long)siginfo.si_addr < PAGE_SIZE)
printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
else
printk(KERN_ALERT "Unable to handle kernel access");
printk(" at virtual address %p\n", siginfo.si_addr);
die_if_kernel("Oops", regs, 0 /*error_code*/);
do_exit(SIGKILL);
}
return 1;
}
/*
* This routine handles page faults. It determines the problem, and
* then passes it off to one of the appropriate routines.
*
* error_code:
* bit 0 == 0 means no page found, 1 means protection fault
* bit 1 == 0 means read, 1 means write
*
* If this routine detects a bad access, it returns 1, otherwise it
* returns 0.
*/
int do_page_fault(struct pt_regs *regs, unsigned long address,
unsigned long error_code)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct * vma;
int fault;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
#ifdef DEBUG
printk ("do page fault:\nregs->sr=%#x, regs->pc=%#lx, address=%#lx, %ld, %p\n",
regs->sr, regs->pc, address, error_code,
current->mm->pgd);
#endif
/*
* If we're in an interrupt or have no user
* context, we must not take the fault..
*/
if (in_atomic() || !mm)
goto no_context;
retry:
down_read(&mm->mmap_sem);
vma = find_vma(mm, address);
if (!vma)
goto map_err;
if (vma->vm_flags & VM_IO)
goto acc_err;
if (vma->vm_start <= address)
goto good_area;
if (!(vma->vm_flags & VM_GROWSDOWN))
goto map_err;
if (user_mode(regs)) {
/* Accessing the stack below usp is always a bug. The
"+ 256" is there due to some instructions doing
pre-decrement on the stack and that doesn't show up
until later. */
if (address + 256 < rdusp())
goto map_err;
}
if (expand_stack(vma, address))
goto map_err;
/*
* Ok, we have a good vm_area for this memory access, so
* we can handle it..
*/
good_area:
#ifdef DEBUG
printk("do_page_fault: good_area\n");
#endif
switch (error_code & 3) {
default: /* 3: write, present */
/* fall through */
case 2: /* write, not present */
if (!(vma->vm_flags & VM_WRITE))
goto acc_err;
flags |= FAULT_FLAG_WRITE;
break;
case 1: /* read, present */
goto acc_err;
case 0: /* read, not present */
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
goto acc_err;
}
/*
* 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);
#ifdef DEBUG
printk("handle_mm_fault returns %d\n",fault);
#endif
if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
return 0;
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
goto out_of_memory;
else if (fault & VM_FAULT_SIGBUS)
goto bus_err;
BUG();
}
/*
* Major/minor page fault accounting is only done on the
* initial attempt. If we go through a retry, it is extremely
* likely that the page will be found in page cache at that point.
*/
if (flags & FAULT_FLAG_ALLOW_RETRY) {
if (fault & VM_FAULT_MAJOR)
current->maj_flt++;
else
current->min_flt++;
if (fault & VM_FAULT_RETRY) {
/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
* of starvation. */
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 0;
/*
* 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);
if (!user_mode(regs))
goto no_context;
pagefault_out_of_memory();
return 0;
no_context:
current->thread.signo = SIGBUS;
current->thread.faddr = address;
return send_fault_sig(regs);
bus_err:
current->thread.signo = SIGBUS;
current->thread.code = BUS_ADRERR;
current->thread.faddr = address;
goto send_sig;
map_err:
current->thread.signo = SIGSEGV;
current->thread.code = SEGV_MAPERR;
current->thread.faddr = address;
goto send_sig;
acc_err:
current->thread.signo = SIGSEGV;
current->thread.code = SEGV_ACCERR;
current->thread.faddr = address;
send_sig:
up_read(&mm->mmap_sem);
return send_fault_sig(regs);
}
|
