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 (trap == 0x300) { 171 if (debugger_fault_handler(regs)) 172 return 0; 173 } 174 175 /* On a kernel SLB miss we can only check for a valid exception entry */ 176 if (!user_mode(regs) && (address >= TASK_SIZE)) 177 return SIGSEGV; 178 179 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 180 if (error_code & DSISR_DABRMATCH) { 181 /* DABR match */ 182 do_dabr(regs, address, error_code); 183 return 0; 184 } 185 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 186 187 if (in_atomic() || mm == NULL) { 188 if (!user_mode(regs)) 189 return SIGSEGV; 190 /* in_atomic() in user mode is really bad, 191 as is current->mm == NULL. */ 192 printk(KERN_EMERG "Page fault in user mode with" 193 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 194 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 195 regs->nip, regs->msr); 196 die("Weird page fault", regs, SIGSEGV); 197 } 198 199 /* When running in the kernel we expect faults to occur only to 200 * addresses in user space. All other faults represent errors in the 201 * kernel and should generate an OOPS. Unfortunately, in the case of an 202 * erroneous fault occurring in a code path which already holds mmap_sem 203 * we will deadlock attempting to validate the fault against the 204 * address space. Luckily the kernel only validly references user 205 * space from well defined areas of code, which are listed in the 206 * exceptions table. 207 * 208 * As the vast majority of faults will be valid we will only perform 209 * the source reference check when there is a possibility of a deadlock. 210 * Attempt to lock the address space, if we cannot we then validate the 211 * source. If this is invalid we can skip the address space check, 212 * thus avoiding the deadlock. 213 */ 214 if (!down_read_trylock(&mm->mmap_sem)) { 215 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 216 goto bad_area_nosemaphore; 217 218 down_read(&mm->mmap_sem); 219 } 220 221 vma = find_vma(mm, address); 222 if (!vma) 223 goto bad_area; 224 if (vma->vm_start <= address) 225 goto good_area; 226 if (!(vma->vm_flags & VM_GROWSDOWN)) 227 goto bad_area; 228 229 /* 230 * N.B. The POWER/Open ABI allows programs to access up to 231 * 288 bytes below the stack pointer. 232 * The kernel signal delivery code writes up to about 1.5kB 233 * below the stack pointer (r1) before decrementing it. 234 * The exec code can write slightly over 640kB to the stack 235 * before setting the user r1. Thus we allow the stack to 236 * expand to 1MB without further checks. 237 */ 238 if (address + 0x100000 < vma->vm_end) { 239 /* get user regs even if this fault is in kernel mode */ 240 struct pt_regs *uregs = current->thread.regs; 241 if (uregs == NULL) 242 goto bad_area; 243 244 /* 245 * A user-mode access to an address a long way below 246 * the stack pointer is only valid if the instruction 247 * is one which would update the stack pointer to the 248 * address accessed if the instruction completed, 249 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 250 * (or the byte, halfword, float or double forms). 251 * 252 * If we don't check this then any write to the area 253 * between the last mapped region and the stack will 254 * expand the stack rather than segfaulting. 255 */ 256 if (address + 2048 < uregs->gpr[1] 257 && (!user_mode(regs) || !store_updates_sp(regs))) 258 goto bad_area; 259 } 260 if (expand_stack(vma, address)) 261 goto bad_area; 262 263 good_area: 264 code = SEGV_ACCERR; 265 #if defined(CONFIG_6xx) 266 if (error_code & 0x95700000) 267 /* an error such as lwarx to I/O controller space, 268 address matching DABR, eciwx, etc. */ 269 goto bad_area; 270 #endif /* CONFIG_6xx */ 271 #if defined(CONFIG_8xx) 272 /* The MPC8xx seems to always set 0x80000000, which is 273 * "undefined". Of those that can be set, this is the only 274 * one which seems bad. 275 */ 276 if (error_code & 0x10000000) 277 /* Guarded storage error. */ 278 goto bad_area; 279 #endif /* CONFIG_8xx */ 280 281 if (is_exec) { 282 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 283 /* protection fault */ 284 if (error_code & DSISR_PROTFAULT) 285 goto bad_area; 286 /* 287 * Allow execution from readable areas if the MMU does not 288 * provide separate controls over reading and executing. 289 */ 290 if (!(vma->vm_flags & VM_EXEC) && 291 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 292 !(vma->vm_flags & (VM_READ | VM_WRITE)))) 293 goto bad_area; 294 #else 295 pte_t *ptep; 296 pmd_t *pmdp; 297 298 /* Since 4xx/Book-E supports per-page execute permission, 299 * we lazily flush dcache to icache. */ 300 ptep = NULL; 301 if (get_pteptr(mm, address, &ptep, &pmdp)) { 302 spinlock_t *ptl = pte_lockptr(mm, pmdp); 303 spin_lock(ptl); 304 if (pte_present(*ptep)) { 305 struct page *page = pte_page(*ptep); 306 307 if (!test_bit(PG_arch_1, &page->flags)) { 308 flush_dcache_icache_page(page); 309 set_bit(PG_arch_1, &page->flags); 310 } 311 pte_update(ptep, 0, _PAGE_HWEXEC); 312 _tlbie(address); 313 pte_unmap_unlock(ptep, ptl); 314 up_read(&mm->mmap_sem); 315 return 0; 316 } 317 pte_unmap_unlock(ptep, ptl); 318 } 319 #endif 320 /* a write */ 321 } else if (is_write) { 322 if (!(vma->vm_flags & VM_WRITE)) 323 goto bad_area; 324 /* a read */ 325 } else { 326 /* protection fault */ 327 if (error_code & 0x08000000) 328 goto bad_area; 329 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 330 goto bad_area; 331 } 332 333 /* 334 * If for any reason at all we couldn't handle the fault, 335 * make sure we exit gracefully rather than endlessly redo 336 * the fault. 337 */ 338 survive: 339 ret = handle_mm_fault(mm, vma, address, is_write); 340 if (unlikely(ret & VM_FAULT_ERROR)) { 341 if (ret & VM_FAULT_OOM) 342 goto out_of_memory; 343 else if (ret & VM_FAULT_SIGBUS) 344 goto do_sigbus; 345 BUG(); 346 } 347 if (ret & VM_FAULT_MAJOR) 348 current->maj_flt++; 349 else 350 current->min_flt++; 351 up_read(&mm->mmap_sem); 352 return 0; 353 354 bad_area: 355 up_read(&mm->mmap_sem); 356 357 bad_area_nosemaphore: 358 /* User mode accesses cause a SIGSEGV */ 359 if (user_mode(regs)) { 360 _exception(SIGSEGV, regs, code, address); 361 return 0; 362 } 363 364 if (is_exec && (error_code & DSISR_PROTFAULT) 365 && printk_ratelimit()) 366 printk(KERN_CRIT "kernel tried to execute NX-protected" 367 " page (%lx) - exploit attempt? (uid: %d)\n", 368 address, current->uid); 369 370 return SIGSEGV; 371 372 /* 373 * We ran out of memory, or some other thing happened to us that made 374 * us unable to handle the page fault gracefully. 375 */ 376 out_of_memory: 377 up_read(&mm->mmap_sem); 378 if (is_global_init(current)) { 379 yield(); 380 down_read(&mm->mmap_sem); 381 goto survive; 382 } 383 printk("VM: killing process %s\n", current->comm); 384 if (user_mode(regs)) 385 do_group_exit(SIGKILL); 386 return SIGKILL; 387 388 do_sigbus: 389 up_read(&mm->mmap_sem); 390 if (user_mode(regs)) { 391 info.si_signo = SIGBUS; 392 info.si_errno = 0; 393 info.si_code = BUS_ADRERR; 394 info.si_addr = (void __user *)address; 395 force_sig_info(SIGBUS, &info, current); 396 return 0; 397 } 398 return SIGBUS; 399 } 400 401 /* 402 * bad_page_fault is called when we have a bad access from the kernel. 403 * It is called from the DSI and ISI handlers in head.S and from some 404 * of the procedures in traps.c. 405 */ 406 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 407 { 408 const struct exception_table_entry *entry; 409 410 /* Are we prepared to handle this fault? */ 411 if ((entry = search_exception_tables(regs->nip)) != NULL) { 412 regs->nip = entry->fixup; 413 return; 414 } 415 416 /* kernel has accessed a bad area */ 417 418 switch (regs->trap) { 419 case 0x300: 420 case 0x380: 421 printk(KERN_ALERT "Unable to handle kernel paging request for " 422 "data at address 0x%08lx\n", regs->dar); 423 break; 424 case 0x400: 425 case 0x480: 426 printk(KERN_ALERT "Unable to handle kernel paging request for " 427 "instruction fetch\n"); 428 break; 429 default: 430 printk(KERN_ALERT "Unable to handle kernel paging request for " 431 "unknown fault\n"); 432 break; 433 } 434 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 435 regs->nip); 436 437 die("Kernel access of bad area", regs, sig); 438 } 439