1 /*
2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3 * Licensed under the GPL
4 */
5
6 #include <linux/mm.h>
7 #include <linux/sched.h>
8 #include <linux/hardirq.h>
9 #include <linux/module.h>
10 #include <asm/current.h>
11 #include <asm/pgtable.h>
12 #include <asm/tlbflush.h>
13 #include <arch.h>
14 #include <as-layout.h>
15 #include <kern_util.h>
16 #include <os.h>
17 #include <skas.h>
18
19 /*
20 * Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by
21 * segv().
22 */
handle_page_fault(unsigned long address,unsigned long ip,int is_write,int is_user,int * code_out)23 int handle_page_fault(unsigned long address, unsigned long ip,
24 int is_write, int is_user, int *code_out)
25 {
26 struct mm_struct *mm = current->mm;
27 struct vm_area_struct *vma;
28 pgd_t *pgd;
29 pud_t *pud;
30 pmd_t *pmd;
31 pte_t *pte;
32 int err = -EFAULT;
33 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
34
35 *code_out = SEGV_MAPERR;
36
37 /*
38 * If the fault was during atomic operation, don't take the fault, just
39 * fail.
40 */
41 if (in_atomic())
42 goto out_nosemaphore;
43
44 if (is_user)
45 flags |= FAULT_FLAG_USER;
46 retry:
47 down_read(&mm->mmap_sem);
48 vma = find_vma(mm, address);
49 if (!vma)
50 goto out;
51 else if (vma->vm_start <= address)
52 goto good_area;
53 else if (!(vma->vm_flags & VM_GROWSDOWN))
54 goto out;
55 else if (is_user && !ARCH_IS_STACKGROW(address))
56 goto out;
57 else if (expand_stack(vma, address))
58 goto out;
59
60 good_area:
61 *code_out = SEGV_ACCERR;
62 if (is_write) {
63 if (!(vma->vm_flags & VM_WRITE))
64 goto out;
65 flags |= FAULT_FLAG_WRITE;
66 } else {
67 /* Don't require VM_READ|VM_EXEC for write faults! */
68 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
69 goto out;
70 }
71
72 do {
73 int fault;
74
75 fault = handle_mm_fault(mm, vma, address, flags);
76
77 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
78 goto out_nosemaphore;
79
80 if (unlikely(fault & VM_FAULT_ERROR)) {
81 if (fault & VM_FAULT_OOM) {
82 goto out_of_memory;
83 } else if (fault & VM_FAULT_SIGSEGV) {
84 goto out;
85 } else if (fault & VM_FAULT_SIGBUS) {
86 err = -EACCES;
87 goto out;
88 }
89 BUG();
90 }
91 if (flags & FAULT_FLAG_ALLOW_RETRY) {
92 if (fault & VM_FAULT_MAJOR)
93 current->maj_flt++;
94 else
95 current->min_flt++;
96 if (fault & VM_FAULT_RETRY) {
97 flags &= ~FAULT_FLAG_ALLOW_RETRY;
98 flags |= FAULT_FLAG_TRIED;
99
100 goto retry;
101 }
102 }
103
104 pgd = pgd_offset(mm, address);
105 pud = pud_offset(pgd, address);
106 pmd = pmd_offset(pud, address);
107 pte = pte_offset_kernel(pmd, address);
108 } while (!pte_present(*pte));
109 err = 0;
110 /*
111 * The below warning was added in place of
112 * pte_mkyoung(); if (is_write) pte_mkdirty();
113 * If it's triggered, we'd see normally a hang here (a clean pte is
114 * marked read-only to emulate the dirty bit).
115 * However, the generic code can mark a PTE writable but clean on a
116 * concurrent read fault, triggering this harmlessly. So comment it out.
117 */
118 #if 0
119 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
120 #endif
121 flush_tlb_page(vma, address);
122 out:
123 up_read(&mm->mmap_sem);
124 out_nosemaphore:
125 return err;
126
127 out_of_memory:
128 /*
129 * We ran out of memory, call the OOM killer, and return the userspace
130 * (which will retry the fault, or kill us if we got oom-killed).
131 */
132 up_read(&mm->mmap_sem);
133 if (!is_user)
134 goto out_nosemaphore;
135 pagefault_out_of_memory();
136 return 0;
137 }
138 EXPORT_SYMBOL(handle_page_fault);
139
show_segv_info(struct uml_pt_regs * regs)140 static void show_segv_info(struct uml_pt_regs *regs)
141 {
142 struct task_struct *tsk = current;
143 struct faultinfo *fi = UPT_FAULTINFO(regs);
144
145 if (!unhandled_signal(tsk, SIGSEGV))
146 return;
147
148 if (!printk_ratelimit())
149 return;
150
151 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x",
152 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
153 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
154 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
155 fi->error_code);
156
157 print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
158 printk(KERN_CONT "\n");
159 }
160
bad_segv(struct faultinfo fi,unsigned long ip)161 static void bad_segv(struct faultinfo fi, unsigned long ip)
162 {
163 struct siginfo si;
164
165 si.si_signo = SIGSEGV;
166 si.si_code = SEGV_ACCERR;
167 si.si_addr = (void __user *) FAULT_ADDRESS(fi);
168 current->thread.arch.faultinfo = fi;
169 force_sig_info(SIGSEGV, &si, current);
170 }
171
fatal_sigsegv(void)172 void fatal_sigsegv(void)
173 {
174 force_sigsegv(SIGSEGV, current);
175 do_signal();
176 /*
177 * This is to tell gcc that we're not returning - do_signal
178 * can, in general, return, but in this case, it's not, since
179 * we just got a fatal SIGSEGV queued.
180 */
181 os_dump_core();
182 }
183
segv_handler(int sig,struct siginfo * unused_si,struct uml_pt_regs * regs)184 void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
185 {
186 struct faultinfo * fi = UPT_FAULTINFO(regs);
187
188 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
189 show_segv_info(regs);
190 bad_segv(*fi, UPT_IP(regs));
191 return;
192 }
193 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
194 }
195
196 /*
197 * We give a *copy* of the faultinfo in the regs to segv.
198 * This must be done, since nesting SEGVs could overwrite
199 * the info in the regs. A pointer to the info then would
200 * give us bad data!
201 */
segv(struct faultinfo fi,unsigned long ip,int is_user,struct uml_pt_regs * regs)202 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
203 struct uml_pt_regs *regs)
204 {
205 struct siginfo si;
206 jmp_buf *catcher;
207 int err;
208 int is_write = FAULT_WRITE(fi);
209 unsigned long address = FAULT_ADDRESS(fi);
210
211 if (!is_user && regs)
212 current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
213
214 if (!is_user && (address >= start_vm) && (address < end_vm)) {
215 flush_tlb_kernel_vm();
216 goto out;
217 }
218 else if (current->mm == NULL) {
219 show_regs(container_of(regs, struct pt_regs, regs));
220 panic("Segfault with no mm");
221 }
222
223 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
224 err = handle_page_fault(address, ip, is_write, is_user,
225 &si.si_code);
226 else {
227 err = -EFAULT;
228 /*
229 * A thread accessed NULL, we get a fault, but CR2 is invalid.
230 * This code is used in __do_copy_from_user() of TT mode.
231 * XXX tt mode is gone, so maybe this isn't needed any more
232 */
233 address = 0;
234 }
235
236 catcher = current->thread.fault_catcher;
237 if (!err)
238 goto out;
239 else if (catcher != NULL) {
240 current->thread.fault_addr = (void *) address;
241 UML_LONGJMP(catcher, 1);
242 }
243 else if (current->thread.fault_addr != NULL)
244 panic("fault_addr set but no fault catcher");
245 else if (!is_user && arch_fixup(ip, regs))
246 goto out;
247
248 if (!is_user) {
249 show_regs(container_of(regs, struct pt_regs, regs));
250 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
251 address, ip);
252 }
253
254 show_segv_info(regs);
255
256 if (err == -EACCES) {
257 si.si_signo = SIGBUS;
258 si.si_errno = 0;
259 si.si_code = BUS_ADRERR;
260 si.si_addr = (void __user *)address;
261 current->thread.arch.faultinfo = fi;
262 force_sig_info(SIGBUS, &si, current);
263 } else {
264 BUG_ON(err != -EFAULT);
265 si.si_signo = SIGSEGV;
266 si.si_addr = (void __user *) address;
267 current->thread.arch.faultinfo = fi;
268 force_sig_info(SIGSEGV, &si, current);
269 }
270
271 out:
272 if (regs)
273 current->thread.segv_regs = NULL;
274
275 return 0;
276 }
277
relay_signal(int sig,struct siginfo * si,struct uml_pt_regs * regs)278 void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
279 {
280 struct faultinfo *fi;
281 struct siginfo clean_si;
282
283 if (!UPT_IS_USER(regs)) {
284 if (sig == SIGBUS)
285 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
286 "mount likely just ran out of space\n");
287 panic("Kernel mode signal %d", sig);
288 }
289
290 arch_examine_signal(sig, regs);
291
292 memset(&clean_si, 0, sizeof(clean_si));
293 clean_si.si_signo = si->si_signo;
294 clean_si.si_errno = si->si_errno;
295 clean_si.si_code = si->si_code;
296 switch (sig) {
297 case SIGILL:
298 case SIGFPE:
299 case SIGSEGV:
300 case SIGBUS:
301 case SIGTRAP:
302 fi = UPT_FAULTINFO(regs);
303 clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi);
304 current->thread.arch.faultinfo = *fi;
305 #ifdef __ARCH_SI_TRAPNO
306 clean_si.si_trapno = si->si_trapno;
307 #endif
308 break;
309 default:
310 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n",
311 sig, si->si_code);
312 }
313
314 force_sig_info(sig, &clean_si, current);
315 }
316
bus_handler(int sig,struct siginfo * si,struct uml_pt_regs * regs)317 void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
318 {
319 if (current->thread.fault_catcher != NULL)
320 UML_LONGJMP(current->thread.fault_catcher, 1);
321 else
322 relay_signal(sig, si, regs);
323 }
324
winch(int sig,struct siginfo * unused_si,struct uml_pt_regs * regs)325 void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
326 {
327 do_IRQ(WINCH_IRQ, regs);
328 }
329
trap_init(void)330 void trap_init(void)
331 {
332 }
333