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
|
/*
* Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com)
* Licensed under the GPL
*/
#include "linux/kernel.h"
#include "asm/errno.h"
#include "linux/sched.h"
#include "linux/mm.h"
#include "linux/spinlock.h"
#include "linux/config.h"
#include "linux/init.h"
#include "linux/ptrace.h"
#include "asm/semaphore.h"
#include "asm/pgtable.h"
#include "asm/pgalloc.h"
#include "asm/tlbflush.h"
#include "asm/a.out.h"
#include "asm/current.h"
#include "asm/irq.h"
#include "sysdep/sigcontext.h"
#include "user_util.h"
#include "kern_util.h"
#include "kern.h"
#include "chan_kern.h"
#include "mconsole_kern.h"
#include "mem.h"
#include "mem_kern.h"
#ifdef CONFIG_MODE_SKAS
#include "skas.h"
#endif
/* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */
int handle_page_fault(unsigned long address, unsigned long ip,
int is_write, int is_user, int *code_out)
{
struct mm_struct *mm = current->mm;
struct vm_area_struct *vma;
pgd_t *pgd;
pud_t *pud;
pmd_t *pmd;
pte_t *pte;
int err = -EFAULT;
*code_out = SEGV_MAPERR;
/* If the fault was during atomic operation, don't take the fault, just
* fail. */
if (in_atomic())
goto out_nosemaphore;
down_read(&mm->mmap_sem);
vma = find_vma(mm, address);
if(!vma)
goto out;
else if(vma->vm_start <= address)
goto good_area;
else if(!(vma->vm_flags & VM_GROWSDOWN))
goto out;
else if(is_user && !ARCH_IS_STACKGROW(address))
goto out;
else if(expand_stack(vma, address))
goto out;
good_area:
*code_out = SEGV_ACCERR;
if(is_write && !(vma->vm_flags & VM_WRITE))
goto out;
/* Don't require VM_READ|VM_EXEC for write faults! */
if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
goto out;
do {
survive:
switch (handle_mm_fault(mm, vma, address, is_write)){
case VM_FAULT_MINOR:
current->min_flt++;
break;
case VM_FAULT_MAJOR:
current->maj_flt++;
break;
case VM_FAULT_SIGBUS:
err = -EACCES;
goto out;
case VM_FAULT_OOM:
err = -ENOMEM;
goto out_of_memory;
default:
BUG();
}
pgd = pgd_offset(mm, address);
pud = pud_offset(pgd, address);
pmd = pmd_offset(pud, address);
pte = pte_offset_kernel(pmd, address);
} while(!pte_present(*pte));
err = 0;
/* The below warning was added in place of
* pte_mkyoung(); if (is_write) pte_mkdirty();
* If it's triggered, we'd see normally a hang here (a clean pte is
* marked read-only to emulate the dirty bit).
* However, the generic code can mark a PTE writable but clean on a
* concurrent read fault, triggering this harmlessly. So comment it out.
*/
#if 0
WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
#endif
flush_tlb_page(vma, address);
out:
up_read(&mm->mmap_sem);
out_nosemaphore:
return(err);
/*
* 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:
if (current->pid == 1) {
up_read(&mm->mmap_sem);
yield();
down_read(&mm->mmap_sem);
goto survive;
}
goto out;
}
/*
* We give a *copy* of the faultinfo in the regs to segv.
* This must be done, since nesting SEGVs could overwrite
* the info in the regs. A pointer to the info then would
* give us bad data!
*/
unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, void *sc)
{
struct siginfo si;
void *catcher;
int err;
int is_write = FAULT_WRITE(fi);
unsigned long address = FAULT_ADDRESS(fi);
if(!is_user && (address >= start_vm) && (address < end_vm)){
flush_tlb_kernel_vm();
return(0);
}
else if(current->mm == NULL)
panic("Segfault with no mm");
if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
err = handle_page_fault(address, ip, is_write, is_user, &si.si_code);
else {
err = -EFAULT;
/* A thread accessed NULL, we get a fault, but CR2 is invalid.
* This code is used in __do_copy_from_user() of TT mode. */
address = 0;
}
catcher = current->thread.fault_catcher;
if(!err)
return(0);
else if(catcher != NULL){
current->thread.fault_addr = (void *) address;
do_longjmp(catcher, 1);
}
else if(current->thread.fault_addr != NULL)
panic("fault_addr set but no fault catcher");
else if(!is_user && arch_fixup(ip, sc))
return(0);
if(!is_user)
panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
address, ip);
if (err == -EACCES) {
si.si_signo = SIGBUS;
si.si_errno = 0;
si.si_code = BUS_ADRERR;
si.si_addr = (void *)address;
current->thread.arch.faultinfo = fi;
force_sig_info(SIGBUS, &si, current);
} else if (err == -ENOMEM) {
printk("VM: killing process %s\n", current->comm);
do_exit(SIGKILL);
} else {
BUG_ON(err != -EFAULT);
si.si_signo = SIGSEGV;
si.si_addr = (void *) address;
current->thread.arch.faultinfo = fi;
force_sig_info(SIGSEGV, &si, current);
}
return(0);
}
void bad_segv(struct faultinfo fi, unsigned long ip)
{
struct siginfo si;
si.si_signo = SIGSEGV;
si.si_code = SEGV_ACCERR;
si.si_addr = (void *) FAULT_ADDRESS(fi);
current->thread.arch.faultinfo = fi;
force_sig_info(SIGSEGV, &si, current);
}
void relay_signal(int sig, union uml_pt_regs *regs)
{
if(arch_handle_signal(sig, regs)) return;
if(!UPT_IS_USER(regs))
panic("Kernel mode signal %d", sig);
current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
force_sig(sig, current);
}
void bus_handler(int sig, union uml_pt_regs *regs)
{
if(current->thread.fault_catcher != NULL)
do_longjmp(current->thread.fault_catcher, 1);
else relay_signal(sig, regs);
}
void winch(int sig, union uml_pt_regs *regs)
{
do_IRQ(WINCH_IRQ, regs);
}
void trap_init(void)
{
}
|
