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6#include <linux/mm.h>
7#include <linux/sched/signal.h>
8#include <linux/hardirq.h>
9#include <linux/module.h>
10#include <linux/uaccess.h>
11#include <linux/sched/debug.h>
12#include <asm/current.h>
13#include <asm/pgtable.h>
14#include <asm/tlbflush.h>
15#include <arch.h>
16#include <as-layout.h>
17#include <kern_util.h>
18#include <os.h>
19#include <skas.h>
20
21
22
23
24
25int handle_page_fault(unsigned long address, unsigned long ip,
26 int is_write, int is_user, int *code_out)
27{
28 struct mm_struct *mm = current->mm;
29 struct vm_area_struct *vma;
30 pgd_t *pgd;
31 pud_t *pud;
32 pmd_t *pmd;
33 pte_t *pte;
34 int err = -EFAULT;
35 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
36
37 *code_out = SEGV_MAPERR;
38
39
40
41
42
43 if (faulthandler_disabled())
44 goto out_nosemaphore;
45
46 if (is_user)
47 flags |= FAULT_FLAG_USER;
48retry:
49 down_read(&mm->mmap_sem);
50 vma = find_vma(mm, address);
51 if (!vma)
52 goto out;
53 else if (vma->vm_start <= address)
54 goto good_area;
55 else if (!(vma->vm_flags & VM_GROWSDOWN))
56 goto out;
57 else if (is_user && !ARCH_IS_STACKGROW(address))
58 goto out;
59 else if (expand_stack(vma, address))
60 goto out;
61
62good_area:
63 *code_out = SEGV_ACCERR;
64 if (is_write) {
65 if (!(vma->vm_flags & VM_WRITE))
66 goto out;
67 flags |= FAULT_FLAG_WRITE;
68 } else {
69
70 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
71 goto out;
72 }
73
74 do {
75 int fault;
76
77 fault = handle_mm_fault(vma, address, flags);
78
79 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
80 goto out_nosemaphore;
81
82 if (unlikely(fault & VM_FAULT_ERROR)) {
83 if (fault & VM_FAULT_OOM) {
84 goto out_of_memory;
85 } else if (fault & VM_FAULT_SIGSEGV) {
86 goto out;
87 } else if (fault & VM_FAULT_SIGBUS) {
88 err = -EACCES;
89 goto out;
90 }
91 BUG();
92 }
93 if (flags & FAULT_FLAG_ALLOW_RETRY) {
94 if (fault & VM_FAULT_MAJOR)
95 current->maj_flt++;
96 else
97 current->min_flt++;
98 if (fault & VM_FAULT_RETRY) {
99 flags &= ~FAULT_FLAG_ALLOW_RETRY;
100 flags |= FAULT_FLAG_TRIED;
101
102 goto retry;
103 }
104 }
105
106 pgd = pgd_offset(mm, address);
107 pud = pud_offset(pgd, address);
108 pmd = pmd_offset(pud, address);
109 pte = pte_offset_kernel(pmd, address);
110 } while (!pte_present(*pte));
111 err = 0;
112
113
114
115
116
117
118
119
120#if 0
121 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
122#endif
123 flush_tlb_page(vma, address);
124out:
125 up_read(&mm->mmap_sem);
126out_nosemaphore:
127 return err;
128
129out_of_memory:
130
131
132
133
134 up_read(&mm->mmap_sem);
135 if (!is_user)
136 goto out_nosemaphore;
137 pagefault_out_of_memory();
138 return 0;
139}
140EXPORT_SYMBOL(handle_page_fault);
141
142static void show_segv_info(struct uml_pt_regs *regs)
143{
144 struct task_struct *tsk = current;
145 struct faultinfo *fi = UPT_FAULTINFO(regs);
146
147 if (!unhandled_signal(tsk, SIGSEGV))
148 return;
149
150 if (!printk_ratelimit())
151 return;
152
153 printk("%s%s[%d]: segfault at %lx ip %px sp %px error %x",
154 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
155 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
156 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
157 fi->error_code);
158
159 print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
160 printk(KERN_CONT "\n");
161}
162
163static void bad_segv(struct faultinfo fi, unsigned long ip)
164{
165 current->thread.arch.faultinfo = fi;
166 force_sig_fault(SIGSEGV, SEGV_ACCERR, (void __user *) FAULT_ADDRESS(fi),
167 current);
168}
169
170void fatal_sigsegv(void)
171{
172 force_sigsegv(SIGSEGV, current);
173 do_signal(¤t->thread.regs);
174
175
176
177
178
179 os_dump_core();
180}
181
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189
190
191
192void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
193{
194 struct faultinfo * fi = UPT_FAULTINFO(regs);
195
196 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
197 show_segv_info(regs);
198 bad_segv(*fi, UPT_IP(regs));
199 return;
200 }
201 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
202}
203
204
205
206
207
208
209
210unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
211 struct uml_pt_regs *regs)
212{
213 jmp_buf *catcher;
214 int si_code;
215 int err;
216 int is_write = FAULT_WRITE(fi);
217 unsigned long address = FAULT_ADDRESS(fi);
218
219 if (!is_user && regs)
220 current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
221
222 if (!is_user && (address >= start_vm) && (address < end_vm)) {
223 flush_tlb_kernel_vm();
224 goto out;
225 }
226 else if (current->mm == NULL) {
227 show_regs(container_of(regs, struct pt_regs, regs));
228 panic("Segfault with no mm");
229 }
230 else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
231 show_regs(container_of(regs, struct pt_regs, regs));
232 panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx",
233 address, ip);
234 }
235
236 if (SEGV_IS_FIXABLE(&fi))
237 err = handle_page_fault(address, ip, is_write, is_user,
238 &si_code);
239 else {
240 err = -EFAULT;
241
242
243
244
245
246 address = 0;
247 }
248
249 catcher = current->thread.fault_catcher;
250 if (!err)
251 goto out;
252 else if (catcher != NULL) {
253 current->thread.fault_addr = (void *) address;
254 UML_LONGJMP(catcher, 1);
255 }
256 else if (current->thread.fault_addr != NULL)
257 panic("fault_addr set but no fault catcher");
258 else if (!is_user && arch_fixup(ip, regs))
259 goto out;
260
261 if (!is_user) {
262 show_regs(container_of(regs, struct pt_regs, regs));
263 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
264 address, ip);
265 }
266
267 show_segv_info(regs);
268
269 if (err == -EACCES) {
270 current->thread.arch.faultinfo = fi;
271 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address,
272 current);
273 } else {
274 BUG_ON(err != -EFAULT);
275 current->thread.arch.faultinfo = fi;
276 force_sig_fault(SIGSEGV, si_code, (void __user *) address,
277 current);
278 }
279
280out:
281 if (regs)
282 current->thread.segv_regs = NULL;
283
284 return 0;
285}
286
287void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
288{
289 int code, err;
290 if (!UPT_IS_USER(regs)) {
291 if (sig == SIGBUS)
292 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
293 "mount likely just ran out of space\n");
294 panic("Kernel mode signal %d", sig);
295 }
296
297 arch_examine_signal(sig, regs);
298
299
300
301
302 code = si->si_code;
303 err = si->si_errno;
304 if ((err == 0) && (siginfo_layout(sig, code) == SIL_FAULT)) {
305 struct faultinfo *fi = UPT_FAULTINFO(regs);
306 current->thread.arch.faultinfo = *fi;
307 force_sig_fault(sig, code, (void __user *)FAULT_ADDRESS(*fi),
308 current);
309 } else {
310 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d) with errno %d\n",
311 sig, code, err);
312 force_sig(sig, current);
313 }
314}
315
316void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
317{
318 if (current->thread.fault_catcher != NULL)
319 UML_LONGJMP(current->thread.fault_catcher, 1);
320 else
321 relay_signal(sig, si, regs);
322}
323
324void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
325{
326 do_IRQ(WINCH_IRQ, regs);
327}
328
329void trap_init(void)
330{
331}
332