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_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); 139 140 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 } 160 161 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 } 171 172 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 } 183 184 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 */ 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 } 277 278 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 } 316 317 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 } 324 325 void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs) 326 { 327 do_IRQ(WINCH_IRQ, regs); 328 } 329 330 void trap_init(void) 331 { 332 } 333