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 #include <linux/perf_event.h> 33 #include <linux/magic.h> 34 #include <linux/ratelimit.h> 35 36 #include <asm/firmware.h> 37 #include <asm/page.h> 38 #include <asm/pgtable.h> 39 #include <asm/mmu.h> 40 #include <asm/mmu_context.h> 41 #include <asm/system.h> 42 #include <asm/uaccess.h> 43 #include <asm/tlbflush.h> 44 #include <asm/siginfo.h> 45 #include <mm/mmu_decl.h> 46 47 #include "icswx.h" 48 49 #ifdef CONFIG_KPROBES 50 static inline int notify_page_fault(struct pt_regs *regs) 51 { 52 int ret = 0; 53 54 /* kprobe_running() needs smp_processor_id() */ 55 if (!user_mode(regs)) { 56 preempt_disable(); 57 if (kprobe_running() && kprobe_fault_handler(regs, 11)) 58 ret = 1; 59 preempt_enable(); 60 } 61 62 return ret; 63 } 64 #else 65 static inline int notify_page_fault(struct pt_regs *regs) 66 { 67 return 0; 68 } 69 #endif 70 71 /* 72 * Check whether the instruction at regs->nip is a store using 73 * an update addressing form which will update r1. 74 */ 75 static int store_updates_sp(struct pt_regs *regs) 76 { 77 unsigned int inst; 78 79 if (get_user(inst, (unsigned int __user *)regs->nip)) 80 return 0; 81 /* check for 1 in the rA field */ 82 if (((inst >> 16) & 0x1f) != 1) 83 return 0; 84 /* check major opcode */ 85 switch (inst >> 26) { 86 case 37: /* stwu */ 87 case 39: /* stbu */ 88 case 45: /* sthu */ 89 case 53: /* stfsu */ 90 case 55: /* stfdu */ 91 return 1; 92 case 62: /* std or stdu */ 93 return (inst & 3) == 1; 94 case 31: 95 /* check minor opcode */ 96 switch ((inst >> 1) & 0x3ff) { 97 case 181: /* stdux */ 98 case 183: /* stwux */ 99 case 247: /* stbux */ 100 case 439: /* sthux */ 101 case 695: /* stfsux */ 102 case 759: /* stfdux */ 103 return 1; 104 } 105 } 106 return 0; 107 } 108 109 /* 110 * For 600- and 800-family processors, the error_code parameter is DSISR 111 * for a data fault, SRR1 for an instruction fault. For 400-family processors 112 * the error_code parameter is ESR for a data fault, 0 for an instruction 113 * fault. 114 * For 64-bit processors, the error_code parameter is 115 * - DSISR for a non-SLB data access fault, 116 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 117 * - 0 any SLB fault. 118 * 119 * The return value is 0 if the fault was handled, or the signal 120 * number if this is a kernel fault that can't be handled here. 121 */ 122 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 123 unsigned long error_code) 124 { 125 struct vm_area_struct * vma; 126 struct mm_struct *mm = current->mm; 127 siginfo_t info; 128 int code = SEGV_MAPERR; 129 int is_write = 0, ret; 130 int trap = TRAP(regs); 131 int is_exec = trap == 0x400; 132 133 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 134 /* 135 * Fortunately the bit assignments in SRR1 for an instruction 136 * fault and DSISR for a data fault are mostly the same for the 137 * bits we are interested in. But there are some bits which 138 * indicate errors in DSISR but can validly be set in SRR1. 139 */ 140 if (trap == 0x400) 141 error_code &= 0x48200000; 142 else 143 is_write = error_code & DSISR_ISSTORE; 144 #else 145 is_write = error_code & ESR_DST; 146 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 147 148 #ifdef CONFIG_PPC_ICSWX 149 /* 150 * we need to do this early because this "data storage 151 * interrupt" does not update the DAR/DEAR so we don't want to 152 * look at it 153 */ 154 if (error_code & ICSWX_DSI_UCT) { 155 int ret; 156 157 ret = acop_handle_fault(regs, address, error_code); 158 if (ret) 159 return ret; 160 } 161 #endif 162 163 if (notify_page_fault(regs)) 164 return 0; 165 166 if (unlikely(debugger_fault_handler(regs))) 167 return 0; 168 169 /* On a kernel SLB miss we can only check for a valid exception entry */ 170 if (!user_mode(regs) && (address >= TASK_SIZE)) 171 return SIGSEGV; 172 173 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \ 174 defined(CONFIG_PPC_BOOK3S_64)) 175 if (error_code & DSISR_DABRMATCH) { 176 /* DABR match */ 177 do_dabr(regs, address, error_code); 178 return 0; 179 } 180 #endif 181 182 if (in_atomic() || mm == NULL) { 183 if (!user_mode(regs)) 184 return SIGSEGV; 185 /* in_atomic() in user mode is really bad, 186 as is current->mm == NULL. */ 187 printk(KERN_EMERG "Page fault in user mode with " 188 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 189 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 190 regs->nip, regs->msr); 191 die("Weird page fault", regs, SIGSEGV); 192 } 193 194 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 195 196 /* When running in the kernel we expect faults to occur only to 197 * addresses in user space. All other faults represent errors in the 198 * kernel and should generate an OOPS. Unfortunately, in the case of an 199 * erroneous fault occurring in a code path which already holds mmap_sem 200 * we will deadlock attempting to validate the fault against the 201 * address space. Luckily the kernel only validly references user 202 * space from well defined areas of code, which are listed in the 203 * exceptions table. 204 * 205 * As the vast majority of faults will be valid we will only perform 206 * the source reference check when there is a possibility of a deadlock. 207 * Attempt to lock the address space, if we cannot we then validate the 208 * source. If this is invalid we can skip the address space check, 209 * thus avoiding the deadlock. 210 */ 211 if (!down_read_trylock(&mm->mmap_sem)) { 212 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 213 goto bad_area_nosemaphore; 214 215 down_read(&mm->mmap_sem); 216 } 217 218 vma = find_vma(mm, address); 219 if (!vma) 220 goto bad_area; 221 if (vma->vm_start <= address) 222 goto good_area; 223 if (!(vma->vm_flags & VM_GROWSDOWN)) 224 goto bad_area; 225 226 /* 227 * N.B. The POWER/Open ABI allows programs to access up to 228 * 288 bytes below the stack pointer. 229 * The kernel signal delivery code writes up to about 1.5kB 230 * below the stack pointer (r1) before decrementing it. 231 * The exec code can write slightly over 640kB to the stack 232 * before setting the user r1. Thus we allow the stack to 233 * expand to 1MB without further checks. 234 */ 235 if (address + 0x100000 < vma->vm_end) { 236 /* get user regs even if this fault is in kernel mode */ 237 struct pt_regs *uregs = current->thread.regs; 238 if (uregs == NULL) 239 goto bad_area; 240 241 /* 242 * A user-mode access to an address a long way below 243 * the stack pointer is only valid if the instruction 244 * is one which would update the stack pointer to the 245 * address accessed if the instruction completed, 246 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 247 * (or the byte, halfword, float or double forms). 248 * 249 * If we don't check this then any write to the area 250 * between the last mapped region and the stack will 251 * expand the stack rather than segfaulting. 252 */ 253 if (address + 2048 < uregs->gpr[1] 254 && (!user_mode(regs) || !store_updates_sp(regs))) 255 goto bad_area; 256 } 257 if (expand_stack(vma, address)) 258 goto bad_area; 259 260 good_area: 261 code = SEGV_ACCERR; 262 #if defined(CONFIG_6xx) 263 if (error_code & 0x95700000) 264 /* an error such as lwarx to I/O controller space, 265 address matching DABR, eciwx, etc. */ 266 goto bad_area; 267 #endif /* CONFIG_6xx */ 268 #if defined(CONFIG_8xx) 269 /* 8xx sometimes need to load a invalid/non-present TLBs. 270 * These must be invalidated separately as linux mm don't. 271 */ 272 if (error_code & 0x40000000) /* no translation? */ 273 _tlbil_va(address, 0, 0, 0); 274 275 /* The MPC8xx seems to always set 0x80000000, which is 276 * "undefined". Of those that can be set, this is the only 277 * one which seems bad. 278 */ 279 if (error_code & 0x10000000) 280 /* Guarded storage error. */ 281 goto bad_area; 282 #endif /* CONFIG_8xx */ 283 284 if (is_exec) { 285 #ifdef CONFIG_PPC_STD_MMU 286 /* Protection fault on exec go straight to failure on 287 * Hash based MMUs as they either don't support per-page 288 * execute permission, or if they do, it's handled already 289 * at the hash level. This test would probably have to 290 * be removed if we change the way this works to make hash 291 * processors use the same I/D cache coherency mechanism 292 * as embedded. 293 */ 294 if (error_code & DSISR_PROTFAULT) 295 goto bad_area; 296 #endif /* CONFIG_PPC_STD_MMU */ 297 298 /* 299 * Allow execution from readable areas if the MMU does not 300 * provide separate controls over reading and executing. 301 * 302 * Note: That code used to not be enabled for 4xx/BookE. 303 * It is now as I/D cache coherency for these is done at 304 * set_pte_at() time and I see no reason why the test 305 * below wouldn't be valid on those processors. This -may- 306 * break programs compiled with a really old ABI though. 307 */ 308 if (!(vma->vm_flags & VM_EXEC) && 309 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 310 !(vma->vm_flags & (VM_READ | VM_WRITE)))) 311 goto bad_area; 312 /* a write */ 313 } else if (is_write) { 314 if (!(vma->vm_flags & VM_WRITE)) 315 goto bad_area; 316 /* a read */ 317 } else { 318 /* protection fault */ 319 if (error_code & 0x08000000) 320 goto bad_area; 321 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 322 goto bad_area; 323 } 324 325 /* 326 * If for any reason at all we couldn't handle the fault, 327 * make sure we exit gracefully rather than endlessly redo 328 * the fault. 329 */ 330 ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 331 if (unlikely(ret & VM_FAULT_ERROR)) { 332 if (ret & VM_FAULT_OOM) 333 goto out_of_memory; 334 else if (ret & VM_FAULT_SIGBUS) 335 goto do_sigbus; 336 BUG(); 337 } 338 if (ret & VM_FAULT_MAJOR) { 339 current->maj_flt++; 340 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 341 regs, address); 342 #ifdef CONFIG_PPC_SMLPAR 343 if (firmware_has_feature(FW_FEATURE_CMO)) { 344 preempt_disable(); 345 get_lppaca()->page_ins += (1 << PAGE_FACTOR); 346 preempt_enable(); 347 } 348 #endif 349 } else { 350 current->min_flt++; 351 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 352 regs, address); 353 } 354 up_read(&mm->mmap_sem); 355 return 0; 356 357 bad_area: 358 up_read(&mm->mmap_sem); 359 360 bad_area_nosemaphore: 361 /* User mode accesses cause a SIGSEGV */ 362 if (user_mode(regs)) { 363 _exception(SIGSEGV, regs, code, address); 364 return 0; 365 } 366 367 if (is_exec && (error_code & DSISR_PROTFAULT)) 368 printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected" 369 " page (%lx) - exploit attempt? (uid: %d)\n", 370 address, current_uid()); 371 372 return SIGSEGV; 373 374 /* 375 * We ran out of memory, or some other thing happened to us that made 376 * us unable to handle the page fault gracefully. 377 */ 378 out_of_memory: 379 up_read(&mm->mmap_sem); 380 if (!user_mode(regs)) 381 return SIGKILL; 382 pagefault_out_of_memory(); 383 return 0; 384 385 do_sigbus: 386 up_read(&mm->mmap_sem); 387 if (user_mode(regs)) { 388 info.si_signo = SIGBUS; 389 info.si_errno = 0; 390 info.si_code = BUS_ADRERR; 391 info.si_addr = (void __user *)address; 392 force_sig_info(SIGBUS, &info, current); 393 return 0; 394 } 395 return SIGBUS; 396 } 397 398 /* 399 * bad_page_fault is called when we have a bad access from the kernel. 400 * It is called from the DSI and ISI handlers in head.S and from some 401 * of the procedures in traps.c. 402 */ 403 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 404 { 405 const struct exception_table_entry *entry; 406 unsigned long *stackend; 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 stackend = end_of_stack(current); 436 if (current != &init_task && *stackend != STACK_END_MAGIC) 437 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); 438 439 die("Kernel access of bad area", regs, sig); 440 } 441