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 <linux/uaccess.h>
11 #include <asm/current.h>
12 #include <asm/pgtable.h>
13 #include <asm/tlbflush.h>
14 #include <arch.h>
15 #include <as-layout.h>
16 #include <kern_util.h>
17 #include <os.h>
18 #include <skas.h>
19
20 /*
21 * Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by
22 * segv().
23 */
handle_page_fault(unsigned long address,unsigned long ip,int is_write,int is_user,int * code_out)24 int handle_page_fault(unsigned long address, unsigned long ip,
25 int is_write, int is_user, int *code_out)
26 {
27 struct mm_struct *mm = current->mm;
28 struct vm_area_struct *vma;
29 pgd_t *pgd;
30 pud_t *pud;
31 pmd_t *pmd;
32 pte_t *pte;
33 int err = -EFAULT;
34 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
35
36 *code_out = SEGV_MAPERR;
37
38 /*
39 * If the fault was with pagefaults disabled, don't take the fault, just
40 * fail.
41 */
42 if (faulthandler_disabled())
43 goto out_nosemaphore;
44
45 if (is_user)
46 flags |= FAULT_FLAG_USER;
47 retry:
48 down_read(&mm->mmap_sem);
49 vma = find_vma(mm, address);
50 if (!vma)
51 goto out;
52 else if (vma->vm_start <= address)
53 goto good_area;
54 else if (!(vma->vm_flags & VM_GROWSDOWN))
55 goto out;
56 else if (is_user && !ARCH_IS_STACKGROW(address))
57 goto out;
58 else if (expand_stack(vma, address))
59 goto out;
60
61 good_area:
62 *code_out = SEGV_ACCERR;
63 if (is_write) {
64 if (!(vma->vm_flags & VM_WRITE))
65 goto out;
66 flags |= FAULT_FLAG_WRITE;
67 } else {
68 /* Don't require VM_READ|VM_EXEC for write faults! */
69 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
70 goto out;
71 }
72
73 do {
74 int fault;
75
76 fault = handle_mm_fault(mm, vma, address, flags);
77
78 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
79 goto out_nosemaphore;
80
81 if (unlikely(fault & VM_FAULT_ERROR)) {
82 if (fault & VM_FAULT_OOM) {
83 goto out_of_memory;
84 } else if (fault & VM_FAULT_SIGSEGV) {
85 goto out;
86 } else if (fault & VM_FAULT_SIGBUS) {
87 err = -EACCES;
88 goto out;
89 }
90 BUG();
91 }
92 if (flags & FAULT_FLAG_ALLOW_RETRY) {
93 if (fault & VM_FAULT_MAJOR)
94 current->maj_flt++;
95 else
96 current->min_flt++;
97 if (fault & VM_FAULT_RETRY) {
98 flags &= ~FAULT_FLAG_ALLOW_RETRY;
99 flags |= FAULT_FLAG_TRIED;
100
101 goto retry;
102 }
103 }
104
105 pgd = pgd_offset(mm, address);
106 pud = pud_offset(pgd, address);
107 pmd = pmd_offset(pud, address);
108 pte = pte_offset_kernel(pmd, address);
109 } while (!pte_present(*pte));
110 err = 0;
111 /*
112 * The below warning was added in place of
113 * pte_mkyoung(); if (is_write) pte_mkdirty();
114 * If it's triggered, we'd see normally a hang here (a clean pte is
115 * marked read-only to emulate the dirty bit).
116 * However, the generic code can mark a PTE writable but clean on a
117 * concurrent read fault, triggering this harmlessly. So comment it out.
118 */
119 #if 0
120 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
121 #endif
122 flush_tlb_page(vma, address);
123 out:
124 up_read(&mm->mmap_sem);
125 out_nosemaphore:
126 return err;
127
128 out_of_memory:
129 /*
130 * We ran out of memory, call the OOM killer, and return the userspace
131 * (which will retry the fault, or kill us if we got oom-killed).
132 */
133 up_read(&mm->mmap_sem);
134 if (!is_user)
135 goto out_nosemaphore;
136 pagefault_out_of_memory();
137 return 0;
138 }
139 EXPORT_SYMBOL(handle_page_fault);
140
show_segv_info(struct uml_pt_regs * regs)141 static void show_segv_info(struct uml_pt_regs *regs)
142 {
143 struct task_struct *tsk = current;
144 struct faultinfo *fi = UPT_FAULTINFO(regs);
145
146 if (!unhandled_signal(tsk, SIGSEGV))
147 return;
148
149 if (!printk_ratelimit())
150 return;
151
152 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x",
153 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
154 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
155 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
156 fi->error_code);
157
158 print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
159 printk(KERN_CONT "\n");
160 }
161
bad_segv(struct faultinfo fi,unsigned long ip)162 static void bad_segv(struct faultinfo fi, unsigned long ip)
163 {
164 struct siginfo si;
165
166 si.si_signo = SIGSEGV;
167 si.si_code = SEGV_ACCERR;
168 si.si_addr = (void __user *) FAULT_ADDRESS(fi);
169 current->thread.arch.faultinfo = fi;
170 force_sig_info(SIGSEGV, &si, current);
171 }
172
fatal_sigsegv(void)173 void fatal_sigsegv(void)
174 {
175 force_sigsegv(SIGSEGV, current);
176 do_signal(¤t->thread.regs);
177 /*
178 * This is to tell gcc that we're not returning - do_signal
179 * can, in general, return, but in this case, it's not, since
180 * we just got a fatal SIGSEGV queued.
181 */
182 os_dump_core();
183 }
184
segv_handler(int sig,struct siginfo * unused_si,struct uml_pt_regs * regs)185 void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
186 {
187 struct faultinfo * fi = UPT_FAULTINFO(regs);
188
189 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
190 show_segv_info(regs);
191 bad_segv(*fi, UPT_IP(regs));
192 return;
193 }
194 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
195 }
196
197 /*
198 * We give a *copy* of the faultinfo in the regs to segv.
199 * This must be done, since nesting SEGVs could overwrite
200 * the info in the regs. A pointer to the info then would
201 * give us bad data!
202 */
segv(struct faultinfo fi,unsigned long ip,int is_user,struct uml_pt_regs * regs)203 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
204 struct uml_pt_regs *regs)
205 {
206 struct siginfo si;
207 jmp_buf *catcher;
208 int err;
209 int is_write = FAULT_WRITE(fi);
210 unsigned long address = FAULT_ADDRESS(fi);
211
212 if (!is_user && regs)
213 current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
214
215 if (!is_user && (address >= start_vm) && (address < end_vm)) {
216 flush_tlb_kernel_vm();
217 goto out;
218 }
219 else if (current->mm == NULL) {
220 show_regs(container_of(regs, struct pt_regs, regs));
221 panic("Segfault with no mm");
222 }
223 else if (!is_user && address > PAGE_SIZE && address < TASK_SIZE) {
224 show_regs(container_of(regs, struct pt_regs, regs));
225 panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx",
226 address, ip);
227 }
228
229 if (SEGV_IS_FIXABLE(&fi))
230 err = handle_page_fault(address, ip, is_write, is_user,
231 &si.si_code);
232 else {
233 err = -EFAULT;
234 /*
235 * A thread accessed NULL, we get a fault, but CR2 is invalid.
236 * This code is used in __do_copy_from_user() of TT mode.
237 * XXX tt mode is gone, so maybe this isn't needed any more
238 */
239 address = 0;
240 }
241
242 catcher = current->thread.fault_catcher;
243 if (!err)
244 goto out;
245 else if (catcher != NULL) {
246 current->thread.fault_addr = (void *) address;
247 UML_LONGJMP(catcher, 1);
248 }
249 else if (current->thread.fault_addr != NULL)
250 panic("fault_addr set but no fault catcher");
251 else if (!is_user && arch_fixup(ip, regs))
252 goto out;
253
254 if (!is_user) {
255 show_regs(container_of(regs, struct pt_regs, regs));
256 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
257 address, ip);
258 }
259
260 show_segv_info(regs);
261
262 if (err == -EACCES) {
263 si.si_signo = SIGBUS;
264 si.si_errno = 0;
265 si.si_code = BUS_ADRERR;
266 si.si_addr = (void __user *)address;
267 current->thread.arch.faultinfo = fi;
268 force_sig_info(SIGBUS, &si, current);
269 } else {
270 BUG_ON(err != -EFAULT);
271 si.si_signo = SIGSEGV;
272 si.si_addr = (void __user *) address;
273 current->thread.arch.faultinfo = fi;
274 force_sig_info(SIGSEGV, &si, current);
275 }
276
277 out:
278 if (regs)
279 current->thread.segv_regs = NULL;
280
281 return 0;
282 }
283
relay_signal(int sig,struct siginfo * si,struct uml_pt_regs * regs)284 void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
285 {
286 struct faultinfo *fi;
287 struct siginfo clean_si;
288
289 if (!UPT_IS_USER(regs)) {
290 if (sig == SIGBUS)
291 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
292 "mount likely just ran out of space\n");
293 panic("Kernel mode signal %d", sig);
294 }
295
296 arch_examine_signal(sig, regs);
297
298 memset(&clean_si, 0, sizeof(clean_si));
299 clean_si.si_signo = si->si_signo;
300 clean_si.si_errno = si->si_errno;
301 clean_si.si_code = si->si_code;
302 switch (sig) {
303 case SIGILL:
304 case SIGFPE:
305 case SIGSEGV:
306 case SIGBUS:
307 case SIGTRAP:
308 fi = UPT_FAULTINFO(regs);
309 clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi);
310 current->thread.arch.faultinfo = *fi;
311 #ifdef __ARCH_SI_TRAPNO
312 clean_si.si_trapno = si->si_trapno;
313 #endif
314 break;
315 default:
316 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n",
317 sig, si->si_code);
318 }
319
320 force_sig_info(sig, &clean_si, current);
321 }
322
bus_handler(int sig,struct siginfo * si,struct uml_pt_regs * regs)323 void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
324 {
325 if (current->thread.fault_catcher != NULL)
326 UML_LONGJMP(current->thread.fault_catcher, 1);
327 else
328 relay_signal(sig, si, regs);
329 }
330
winch(int sig,struct siginfo * unused_si,struct uml_pt_regs * regs)331 void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
332 {
333 do_IRQ(WINCH_IRQ, regs);
334 }
335
trap_init(void)336 void trap_init(void)
337 {
338 }
339