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