1 /* 2 * PowerPC version 3 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 4 * 5 * Derived from "arch/i386/mm/fault.c" 6 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 7 * 8 * Modified by Cort Dougan and Paul Mackerras. 9 * 10 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) 11 * 12 * This program is free software; you can redistribute it and/or 13 * modify it under the terms of the GNU General Public License 14 * as published by the Free Software Foundation; either version 15 * 2 of the License, or (at your option) any later version. 16 */ 17 18 #include <linux/config.h> 19 #include <linux/signal.h> 20 #include <linux/sched.h> 21 #include <linux/kernel.h> 22 #include <linux/errno.h> 23 #include <linux/string.h> 24 #include <linux/types.h> 25 #include <linux/ptrace.h> 26 #include <linux/mman.h> 27 #include <linux/mm.h> 28 #include <linux/interrupt.h> 29 #include <linux/highmem.h> 30 #include <linux/module.h> 31 #include <linux/kprobes.h> 32 33 #include <asm/page.h> 34 #include <asm/pgtable.h> 35 #include <asm/mmu.h> 36 #include <asm/mmu_context.h> 37 #include <asm/system.h> 38 #include <asm/uaccess.h> 39 #include <asm/tlbflush.h> 40 #include <asm/kdebug.h> 41 #include <asm/siginfo.h> 42 43 #ifdef CONFIG_KPROBES 44 ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain); 45 46 /* Hook to register for page fault notifications */ 47 int register_page_fault_notifier(struct notifier_block *nb) 48 { 49 return atomic_notifier_chain_register(¬ify_page_fault_chain, nb); 50 } 51 52 int unregister_page_fault_notifier(struct notifier_block *nb) 53 { 54 return atomic_notifier_chain_unregister(¬ify_page_fault_chain, nb); 55 } 56 57 static inline int notify_page_fault(enum die_val val, const char *str, 58 struct pt_regs *regs, long err, int trap, int sig) 59 { 60 struct die_args args = { 61 .regs = regs, 62 .str = str, 63 .err = err, 64 .trapnr = trap, 65 .signr = sig 66 }; 67 return atomic_notifier_call_chain(¬ify_page_fault_chain, val, &args); 68 } 69 #else 70 static inline int notify_page_fault(enum die_val val, const char *str, 71 struct pt_regs *regs, long err, int trap, int sig) 72 { 73 return NOTIFY_DONE; 74 } 75 #endif 76 77 /* 78 * Check whether the instruction at regs->nip is a store using 79 * an update addressing form which will update r1. 80 */ 81 static int store_updates_sp(struct pt_regs *regs) 82 { 83 unsigned int inst; 84 85 if (get_user(inst, (unsigned int __user *)regs->nip)) 86 return 0; 87 /* check for 1 in the rA field */ 88 if (((inst >> 16) & 0x1f) != 1) 89 return 0; 90 /* check major opcode */ 91 switch (inst >> 26) { 92 case 37: /* stwu */ 93 case 39: /* stbu */ 94 case 45: /* sthu */ 95 case 53: /* stfsu */ 96 case 55: /* stfdu */ 97 return 1; 98 case 62: /* std or stdu */ 99 return (inst & 3) == 1; 100 case 31: 101 /* check minor opcode */ 102 switch ((inst >> 1) & 0x3ff) { 103 case 181: /* stdux */ 104 case 183: /* stwux */ 105 case 247: /* stbux */ 106 case 439: /* sthux */ 107 case 695: /* stfsux */ 108 case 759: /* stfdux */ 109 return 1; 110 } 111 } 112 return 0; 113 } 114 115 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 116 static void do_dabr(struct pt_regs *regs, unsigned long address, 117 unsigned long error_code) 118 { 119 siginfo_t info; 120 121 if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code, 122 11, SIGSEGV) == NOTIFY_STOP) 123 return; 124 125 if (debugger_dabr_match(regs)) 126 return; 127 128 /* Clear the DABR */ 129 set_dabr(0); 130 131 /* Deliver the signal to userspace */ 132 info.si_signo = SIGTRAP; 133 info.si_errno = 0; 134 info.si_code = TRAP_HWBKPT; 135 info.si_addr = (void __user *)address; 136 force_sig_info(SIGTRAP, &info, current); 137 } 138 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 139 140 /* 141 * For 600- and 800-family processors, the error_code parameter is DSISR 142 * for a data fault, SRR1 for an instruction fault. For 400-family processors 143 * the error_code parameter is ESR for a data fault, 0 for an instruction 144 * fault. 145 * For 64-bit processors, the error_code parameter is 146 * - DSISR for a non-SLB data access fault, 147 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 148 * - 0 any SLB fault. 149 * 150 * The return value is 0 if the fault was handled, or the signal 151 * number if this is a kernel fault that can't be handled here. 152 */ 153 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 154 unsigned long error_code) 155 { 156 struct vm_area_struct * vma; 157 struct mm_struct *mm = current->mm; 158 siginfo_t info; 159 int code = SEGV_MAPERR; 160 int is_write = 0; 161 int trap = TRAP(regs); 162 int is_exec = trap == 0x400; 163 164 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 165 /* 166 * Fortunately the bit assignments in SRR1 for an instruction 167 * fault and DSISR for a data fault are mostly the same for the 168 * bits we are interested in. But there are some bits which 169 * indicate errors in DSISR but can validly be set in SRR1. 170 */ 171 if (trap == 0x400) 172 error_code &= 0x48200000; 173 else 174 is_write = error_code & DSISR_ISSTORE; 175 #else 176 is_write = error_code & ESR_DST; 177 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 178 179 if (notify_page_fault(DIE_PAGE_FAULT, "page_fault", regs, error_code, 180 11, SIGSEGV) == NOTIFY_STOP) 181 return 0; 182 183 if (trap == 0x300) { 184 if (debugger_fault_handler(regs)) 185 return 0; 186 } 187 188 /* On a kernel SLB miss we can only check for a valid exception entry */ 189 if (!user_mode(regs) && (address >= TASK_SIZE)) 190 return SIGSEGV; 191 192 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 193 if (error_code & DSISR_DABRMATCH) { 194 /* DABR match */ 195 do_dabr(regs, address, error_code); 196 return 0; 197 } 198 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 199 200 if (in_atomic() || mm == NULL) { 201 if (!user_mode(regs)) 202 return SIGSEGV; 203 /* in_atomic() in user mode is really bad, 204 as is current->mm == NULL. */ 205 printk(KERN_EMERG "Page fault in user mode with" 206 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 207 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 208 regs->nip, regs->msr); 209 die("Weird page fault", regs, SIGSEGV); 210 } 211 212 /* When running in the kernel we expect faults to occur only to 213 * addresses in user space. All other faults represent errors in the 214 * kernel and should generate an OOPS. Unfortunately, in the case of an 215 * erroneous fault occurring in a code path which already holds mmap_sem 216 * we will deadlock attempting to validate the fault against the 217 * address space. Luckily the kernel only validly references user 218 * space from well defined areas of code, which are listed in the 219 * exceptions table. 220 * 221 * As the vast majority of faults will be valid we will only perform 222 * the source reference check when there is a possibility of a deadlock. 223 * Attempt to lock the address space, if we cannot we then validate the 224 * source. If this is invalid we can skip the address space check, 225 * thus avoiding the deadlock. 226 */ 227 if (!down_read_trylock(&mm->mmap_sem)) { 228 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 229 goto bad_area_nosemaphore; 230 231 down_read(&mm->mmap_sem); 232 } 233 234 vma = find_vma(mm, address); 235 if (!vma) 236 goto bad_area; 237 if (vma->vm_start <= address) 238 goto good_area; 239 if (!(vma->vm_flags & VM_GROWSDOWN)) 240 goto bad_area; 241 242 /* 243 * N.B. The POWER/Open ABI allows programs to access up to 244 * 288 bytes below the stack pointer. 245 * The kernel signal delivery code writes up to about 1.5kB 246 * below the stack pointer (r1) before decrementing it. 247 * The exec code can write slightly over 640kB to the stack 248 * before setting the user r1. Thus we allow the stack to 249 * expand to 1MB without further checks. 250 */ 251 if (address + 0x100000 < vma->vm_end) { 252 /* get user regs even if this fault is in kernel mode */ 253 struct pt_regs *uregs = current->thread.regs; 254 if (uregs == NULL) 255 goto bad_area; 256 257 /* 258 * A user-mode access to an address a long way below 259 * the stack pointer is only valid if the instruction 260 * is one which would update the stack pointer to the 261 * address accessed if the instruction completed, 262 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 263 * (or the byte, halfword, float or double forms). 264 * 265 * If we don't check this then any write to the area 266 * between the last mapped region and the stack will 267 * expand the stack rather than segfaulting. 268 */ 269 if (address + 2048 < uregs->gpr[1] 270 && (!user_mode(regs) || !store_updates_sp(regs))) 271 goto bad_area; 272 } 273 if (expand_stack(vma, address)) 274 goto bad_area; 275 276 good_area: 277 code = SEGV_ACCERR; 278 #if defined(CONFIG_6xx) 279 if (error_code & 0x95700000) 280 /* an error such as lwarx to I/O controller space, 281 address matching DABR, eciwx, etc. */ 282 goto bad_area; 283 #endif /* CONFIG_6xx */ 284 #if defined(CONFIG_8xx) 285 /* The MPC8xx seems to always set 0x80000000, which is 286 * "undefined". Of those that can be set, this is the only 287 * one which seems bad. 288 */ 289 if (error_code & 0x10000000) 290 /* Guarded storage error. */ 291 goto bad_area; 292 #endif /* CONFIG_8xx */ 293 294 if (is_exec) { 295 #ifdef CONFIG_PPC64 296 /* protection fault */ 297 if (error_code & DSISR_PROTFAULT) 298 goto bad_area; 299 if (!(vma->vm_flags & VM_EXEC)) 300 goto bad_area; 301 #endif 302 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) 303 pte_t *ptep; 304 pmd_t *pmdp; 305 306 /* Since 4xx/Book-E supports per-page execute permission, 307 * we lazily flush dcache to icache. */ 308 ptep = NULL; 309 if (get_pteptr(mm, address, &ptep, &pmdp)) { 310 spinlock_t *ptl = pte_lockptr(mm, pmdp); 311 spin_lock(ptl); 312 if (pte_present(*ptep)) { 313 struct page *page = pte_page(*ptep); 314 315 if (!test_bit(PG_arch_1, &page->flags)) { 316 flush_dcache_icache_page(page); 317 set_bit(PG_arch_1, &page->flags); 318 } 319 pte_update(ptep, 0, _PAGE_HWEXEC); 320 _tlbie(address); 321 pte_unmap_unlock(ptep, ptl); 322 up_read(&mm->mmap_sem); 323 return 0; 324 } 325 pte_unmap_unlock(ptep, ptl); 326 } 327 #endif 328 /* a write */ 329 } else if (is_write) { 330 if (!(vma->vm_flags & VM_WRITE)) 331 goto bad_area; 332 /* a read */ 333 } else { 334 /* protection fault */ 335 if (error_code & 0x08000000) 336 goto bad_area; 337 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 338 goto bad_area; 339 } 340 341 /* 342 * If for any reason at all we couldn't handle the fault, 343 * make sure we exit gracefully rather than endlessly redo 344 * the fault. 345 */ 346 survive: 347 switch (handle_mm_fault(mm, vma, address, is_write)) { 348 349 case VM_FAULT_MINOR: 350 current->min_flt++; 351 break; 352 case VM_FAULT_MAJOR: 353 current->maj_flt++; 354 break; 355 case VM_FAULT_SIGBUS: 356 goto do_sigbus; 357 case VM_FAULT_OOM: 358 goto out_of_memory; 359 default: 360 BUG(); 361 } 362 363 up_read(&mm->mmap_sem); 364 return 0; 365 366 bad_area: 367 up_read(&mm->mmap_sem); 368 369 bad_area_nosemaphore: 370 /* User mode accesses cause a SIGSEGV */ 371 if (user_mode(regs)) { 372 _exception(SIGSEGV, regs, code, address); 373 return 0; 374 } 375 376 if (is_exec && (error_code & DSISR_PROTFAULT) 377 && printk_ratelimit()) 378 printk(KERN_CRIT "kernel tried to execute NX-protected" 379 " page (%lx) - exploit attempt? (uid: %d)\n", 380 address, current->uid); 381 382 return SIGSEGV; 383 384 /* 385 * We ran out of memory, or some other thing happened to us that made 386 * us unable to handle the page fault gracefully. 387 */ 388 out_of_memory: 389 up_read(&mm->mmap_sem); 390 if (current->pid == 1) { 391 yield(); 392 down_read(&mm->mmap_sem); 393 goto survive; 394 } 395 printk("VM: killing process %s\n", current->comm); 396 if (user_mode(regs)) 397 do_exit(SIGKILL); 398 return SIGKILL; 399 400 do_sigbus: 401 up_read(&mm->mmap_sem); 402 if (user_mode(regs)) { 403 info.si_signo = SIGBUS; 404 info.si_errno = 0; 405 info.si_code = BUS_ADRERR; 406 info.si_addr = (void __user *)address; 407 force_sig_info(SIGBUS, &info, current); 408 return 0; 409 } 410 return SIGBUS; 411 } 412 413 /* 414 * bad_page_fault is called when we have a bad access from the kernel. 415 * It is called from the DSI and ISI handlers in head.S and from some 416 * of the procedures in traps.c. 417 */ 418 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 419 { 420 const struct exception_table_entry *entry; 421 422 /* Are we prepared to handle this fault? */ 423 if ((entry = search_exception_tables(regs->nip)) != NULL) { 424 regs->nip = entry->fixup; 425 return; 426 } 427 428 /* kernel has accessed a bad area */ 429 430 printk(KERN_ALERT "Unable to handle kernel paging request for "); 431 switch (regs->trap) { 432 case 0x300: 433 case 0x380: 434 printk("data at address 0x%08lx\n", regs->dar); 435 break; 436 case 0x400: 437 case 0x480: 438 printk("instruction fetch\n"); 439 break; 440 default: 441 printk("unknown fault\n"); 442 } 443 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 444 regs->nip); 445 446 die("Kernel access of bad area", regs, sig); 447 } 448