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Linux/arch/um/kernel/trap.c

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  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  */
 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_SIGBUS) {
 84                                 err = -EACCES;
 85                                 goto out;
 86                         }
 87                         BUG();
 88                 }
 89                 if (flags & FAULT_FLAG_ALLOW_RETRY) {
 90                         if (fault & VM_FAULT_MAJOR)
 91                                 current->maj_flt++;
 92                         else
 93                                 current->min_flt++;
 94                         if (fault & VM_FAULT_RETRY) {
 95                                 flags &= ~FAULT_FLAG_ALLOW_RETRY;
 96                                 flags |= FAULT_FLAG_TRIED;
 97 
 98                                 goto retry;
 99                         }
100                 }
101 
102                 pgd = pgd_offset(mm, address);
103                 pud = pud_offset(pgd, address);
104                 pmd = pmd_offset(pud, address);
105                 pte = pte_offset_kernel(pmd, address);
106         } while (!pte_present(*pte));
107         err = 0;
108         /*
109          * The below warning was added in place of
110          *      pte_mkyoung(); if (is_write) pte_mkdirty();
111          * If it's triggered, we'd see normally a hang here (a clean pte is
112          * marked read-only to emulate the dirty bit).
113          * However, the generic code can mark a PTE writable but clean on a
114          * concurrent read fault, triggering this harmlessly. So comment it out.
115          */
116 #if 0
117         WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
118 #endif
119         flush_tlb_page(vma, address);
120 out:
121         up_read(&mm->mmap_sem);
122 out_nosemaphore:
123         return err;
124 
125 out_of_memory:
126         /*
127          * We ran out of memory, call the OOM killer, and return the userspace
128          * (which will retry the fault, or kill us if we got oom-killed).
129          */
130         up_read(&mm->mmap_sem);
131         if (!is_user)
132                 goto out_nosemaphore;
133         pagefault_out_of_memory();
134         return 0;
135 }
136 EXPORT_SYMBOL(handle_page_fault);
137 
138 static void show_segv_info(struct uml_pt_regs *regs)
139 {
140         struct task_struct *tsk = current;
141         struct faultinfo *fi = UPT_FAULTINFO(regs);
142 
143         if (!unhandled_signal(tsk, SIGSEGV))
144                 return;
145 
146         if (!printk_ratelimit())
147                 return;
148 
149         printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x",
150                 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG,
151                 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi),
152                 (void *)UPT_IP(regs), (void *)UPT_SP(regs),
153                 fi->error_code);
154 
155         print_vma_addr(KERN_CONT " in ", UPT_IP(regs));
156         printk(KERN_CONT "\n");
157 }
158 
159 static void bad_segv(struct faultinfo fi, unsigned long ip)
160 {
161         struct siginfo si;
162 
163         si.si_signo = SIGSEGV;
164         si.si_code = SEGV_ACCERR;
165         si.si_addr = (void __user *) FAULT_ADDRESS(fi);
166         current->thread.arch.faultinfo = fi;
167         force_sig_info(SIGSEGV, &si, current);
168 }
169 
170 void fatal_sigsegv(void)
171 {
172         force_sigsegv(SIGSEGV, current);
173         do_signal();
174         /*
175          * This is to tell gcc that we're not returning - do_signal
176          * can, in general, return, but in this case, it's not, since
177          * we just got a fatal SIGSEGV queued.
178          */
179         os_dump_core();
180 }
181 
182 void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
183 {
184         struct faultinfo * fi = UPT_FAULTINFO(regs);
185 
186         if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
187                 show_segv_info(regs);
188                 bad_segv(*fi, UPT_IP(regs));
189                 return;
190         }
191         segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
192 }
193 
194 /*
195  * We give a *copy* of the faultinfo in the regs to segv.
196  * This must be done, since nesting SEGVs could overwrite
197  * the info in the regs. A pointer to the info then would
198  * give us bad data!
199  */
200 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
201                    struct uml_pt_regs *regs)
202 {
203         struct siginfo si;
204         jmp_buf *catcher;
205         int err;
206         int is_write = FAULT_WRITE(fi);
207         unsigned long address = FAULT_ADDRESS(fi);
208 
209         if (regs)
210                 current->thread.segv_regs = container_of(regs, struct pt_regs, regs);
211 
212         if (!is_user && (address >= start_vm) && (address < end_vm)) {
213                 flush_tlb_kernel_vm();
214                 goto out;
215         }
216         else if (current->mm == NULL) {
217                 show_regs(container_of(regs, struct pt_regs, regs));
218                 panic("Segfault with no mm");
219         }
220 
221         if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
222                 err = handle_page_fault(address, ip, is_write, is_user,
223                                         &si.si_code);
224         else {
225                 err = -EFAULT;
226                 /*
227                  * A thread accessed NULL, we get a fault, but CR2 is invalid.
228                  * This code is used in __do_copy_from_user() of TT mode.
229                  * XXX tt mode is gone, so maybe this isn't needed any more
230                  */
231                 address = 0;
232         }
233 
234         catcher = current->thread.fault_catcher;
235         if (!err)
236                 goto out;
237         else if (catcher != NULL) {
238                 current->thread.fault_addr = (void *) address;
239                 UML_LONGJMP(catcher, 1);
240         }
241         else if (current->thread.fault_addr != NULL)
242                 panic("fault_addr set but no fault catcher");
243         else if (!is_user && arch_fixup(ip, regs))
244                 goto out;
245 
246         if (!is_user) {
247                 show_regs(container_of(regs, struct pt_regs, regs));
248                 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
249                       address, ip);
250         }
251 
252         show_segv_info(regs);
253 
254         if (err == -EACCES) {
255                 si.si_signo = SIGBUS;
256                 si.si_errno = 0;
257                 si.si_code = BUS_ADRERR;
258                 si.si_addr = (void __user *)address;
259                 current->thread.arch.faultinfo = fi;
260                 force_sig_info(SIGBUS, &si, current);
261         } else {
262                 BUG_ON(err != -EFAULT);
263                 si.si_signo = SIGSEGV;
264                 si.si_addr = (void __user *) address;
265                 current->thread.arch.faultinfo = fi;
266                 force_sig_info(SIGSEGV, &si, current);
267         }
268 
269 out:
270         if (regs)
271                 current->thread.segv_regs = NULL;
272 
273         return 0;
274 }
275 
276 void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs)
277 {
278         struct faultinfo *fi;
279         struct siginfo clean_si;
280 
281         if (!UPT_IS_USER(regs)) {
282                 if (sig == SIGBUS)
283                         printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
284                                "mount likely just ran out of space\n");
285                 panic("Kernel mode signal %d", sig);
286         }
287 
288         arch_examine_signal(sig, regs);
289 
290         memset(&clean_si, 0, sizeof(clean_si));
291         clean_si.si_signo = si->si_signo;
292         clean_si.si_errno = si->si_errno;
293         clean_si.si_code = si->si_code;
294         switch (sig) {
295         case SIGILL:
296         case SIGFPE:
297         case SIGSEGV:
298         case SIGBUS:
299         case SIGTRAP:
300                 fi = UPT_FAULTINFO(regs);
301                 clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi);
302                 current->thread.arch.faultinfo = *fi;
303 #ifdef __ARCH_SI_TRAPNO
304                 clean_si.si_trapno = si->si_trapno;
305 #endif
306                 break;
307         default:
308                 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n",
309                         sig, si->si_code);
310         }
311 
312         force_sig_info(sig, &clean_si, current);
313 }
314 
315 void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs)
316 {
317         if (current->thread.fault_catcher != NULL)
318                 UML_LONGJMP(current->thread.fault_catcher, 1);
319         else
320                 relay_signal(sig, si, regs);
321 }
322 
323 void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs)
324 {
325         do_IRQ(WINCH_IRQ, regs);
326 }
327 
328 void trap_init(void)
329 {
330 }
331 

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