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 #ifdef CONFIG_KPROBES 48 static inline int notify_page_fault(struct pt_regs *regs) 49 { 50 int ret = 0; 51 52 /* kprobe_running() needs smp_processor_id() */ 53 if (!user_mode(regs)) { 54 preempt_disable(); 55 if (kprobe_running() && kprobe_fault_handler(regs, 11)) 56 ret = 1; 57 preempt_enable(); 58 } 59 60 return ret; 61 } 62 #else 63 static inline int notify_page_fault(struct pt_regs *regs) 64 { 65 return 0; 66 } 67 #endif 68 69 /* 70 * Check whether the instruction at regs->nip is a store using 71 * an update addressing form which will update r1. 72 */ 73 static int store_updates_sp(struct pt_regs *regs) 74 { 75 unsigned int inst; 76 77 if (get_user(inst, (unsigned int __user *)regs->nip)) 78 return 0; 79 /* check for 1 in the rA field */ 80 if (((inst >> 16) & 0x1f) != 1) 81 return 0; 82 /* check major opcode */ 83 switch (inst >> 26) { 84 case 37: /* stwu */ 85 case 39: /* stbu */ 86 case 45: /* sthu */ 87 case 53: /* stfsu */ 88 case 55: /* stfdu */ 89 return 1; 90 case 62: /* std or stdu */ 91 return (inst & 3) == 1; 92 case 31: 93 /* check minor opcode */ 94 switch ((inst >> 1) & 0x3ff) { 95 case 181: /* stdux */ 96 case 183: /* stwux */ 97 case 247: /* stbux */ 98 case 439: /* sthux */ 99 case 695: /* stfsux */ 100 case 759: /* stfdux */ 101 return 1; 102 } 103 } 104 return 0; 105 } 106 107 /* 108 * For 600- and 800-family processors, the error_code parameter is DSISR 109 * for a data fault, SRR1 for an instruction fault. For 400-family processors 110 * the error_code parameter is ESR for a data fault, 0 for an instruction 111 * fault. 112 * For 64-bit processors, the error_code parameter is 113 * - DSISR for a non-SLB data access fault, 114 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 115 * - 0 any SLB fault. 116 * 117 * The return value is 0 if the fault was handled, or the signal 118 * number if this is a kernel fault that can't be handled here. 119 */ 120 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 121 unsigned long error_code) 122 { 123 struct vm_area_struct * vma; 124 struct mm_struct *mm = current->mm; 125 siginfo_t info; 126 int code = SEGV_MAPERR; 127 int is_write = 0, ret; 128 int trap = TRAP(regs); 129 int is_exec = trap == 0x400; 130 131 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 132 /* 133 * Fortunately the bit assignments in SRR1 for an instruction 134 * fault and DSISR for a data fault are mostly the same for the 135 * bits we are interested in. But there are some bits which 136 * indicate errors in DSISR but can validly be set in SRR1. 137 */ 138 if (trap == 0x400) 139 error_code &= 0x48200000; 140 else 141 is_write = error_code & DSISR_ISSTORE; 142 #else 143 is_write = error_code & ESR_DST; 144 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 145 146 if (notify_page_fault(regs)) 147 return 0; 148 149 if (unlikely(debugger_fault_handler(regs))) 150 return 0; 151 152 /* On a kernel SLB miss we can only check for a valid exception entry */ 153 if (!user_mode(regs) && (address >= TASK_SIZE)) 154 return SIGSEGV; 155 156 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \ 157 defined(CONFIG_PPC_BOOK3S_64)) 158 if (error_code & DSISR_DABRMATCH) { 159 /* DABR match */ 160 do_dabr(regs, address, error_code); 161 return 0; 162 } 163 #endif 164 165 if (in_atomic() || mm == NULL) { 166 if (!user_mode(regs)) 167 return SIGSEGV; 168 /* in_atomic() in user mode is really bad, 169 as is current->mm == NULL. */ 170 printk(KERN_EMERG "Page fault in user mode with " 171 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 172 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 173 regs->nip, regs->msr); 174 die("Weird page fault", regs, SIGSEGV); 175 } 176 177 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 178 179 /* When running in the kernel we expect faults to occur only to 180 * addresses in user space. All other faults represent errors in the 181 * kernel and should generate an OOPS. Unfortunately, in the case of an 182 * erroneous fault occurring in a code path which already holds mmap_sem 183 * we will deadlock attempting to validate the fault against the 184 * address space. Luckily the kernel only validly references user 185 * space from well defined areas of code, which are listed in the 186 * exceptions table. 187 * 188 * As the vast majority of faults will be valid we will only perform 189 * the source reference check when there is a possibility of a deadlock. 190 * Attempt to lock the address space, if we cannot we then validate the 191 * source. If this is invalid we can skip the address space check, 192 * thus avoiding the deadlock. 193 */ 194 if (!down_read_trylock(&mm->mmap_sem)) { 195 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 196 goto bad_area_nosemaphore; 197 198 down_read(&mm->mmap_sem); 199 } 200 201 vma = find_vma(mm, address); 202 if (!vma) 203 goto bad_area; 204 if (vma->vm_start <= address) 205 goto good_area; 206 if (!(vma->vm_flags & VM_GROWSDOWN)) 207 goto bad_area; 208 209 /* 210 * N.B. The POWER/Open ABI allows programs to access up to 211 * 288 bytes below the stack pointer. 212 * The kernel signal delivery code writes up to about 1.5kB 213 * below the stack pointer (r1) before decrementing it. 214 * The exec code can write slightly over 640kB to the stack 215 * before setting the user r1. Thus we allow the stack to 216 * expand to 1MB without further checks. 217 */ 218 if (address + 0x100000 < vma->vm_end) { 219 /* get user regs even if this fault is in kernel mode */ 220 struct pt_regs *uregs = current->thread.regs; 221 if (uregs == NULL) 222 goto bad_area; 223 224 /* 225 * A user-mode access to an address a long way below 226 * the stack pointer is only valid if the instruction 227 * is one which would update the stack pointer to the 228 * address accessed if the instruction completed, 229 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 230 * (or the byte, halfword, float or double forms). 231 * 232 * If we don't check this then any write to the area 233 * between the last mapped region and the stack will 234 * expand the stack rather than segfaulting. 235 */ 236 if (address + 2048 < uregs->gpr[1] 237 && (!user_mode(regs) || !store_updates_sp(regs))) 238 goto bad_area; 239 } 240 if (expand_stack(vma, address)) 241 goto bad_area; 242 243 good_area: 244 code = SEGV_ACCERR; 245 #if defined(CONFIG_6xx) 246 if (error_code & 0x95700000) 247 /* an error such as lwarx to I/O controller space, 248 address matching DABR, eciwx, etc. */ 249 goto bad_area; 250 #endif /* CONFIG_6xx */ 251 #if defined(CONFIG_8xx) 252 /* 8xx sometimes need to load a invalid/non-present TLBs. 253 * These must be invalidated separately as linux mm don't. 254 */ 255 if (error_code & 0x40000000) /* no translation? */ 256 _tlbil_va(address, 0, 0, 0); 257 258 /* The MPC8xx seems to always set 0x80000000, which is 259 * "undefined". Of those that can be set, this is the only 260 * one which seems bad. 261 */ 262 if (error_code & 0x10000000) 263 /* Guarded storage error. */ 264 goto bad_area; 265 #endif /* CONFIG_8xx */ 266 267 if (is_exec) { 268 #ifdef CONFIG_PPC_STD_MMU 269 /* Protection fault on exec go straight to failure on 270 * Hash based MMUs as they either don't support per-page 271 * execute permission, or if they do, it's handled already 272 * at the hash level. This test would probably have to 273 * be removed if we change the way this works to make hash 274 * processors use the same I/D cache coherency mechanism 275 * as embedded. 276 */ 277 if (error_code & DSISR_PROTFAULT) 278 goto bad_area; 279 #endif /* CONFIG_PPC_STD_MMU */ 280 281 /* 282 * Allow execution from readable areas if the MMU does not 283 * provide separate controls over reading and executing. 284 * 285 * Note: That code used to not be enabled for 4xx/BookE. 286 * It is now as I/D cache coherency for these is done at 287 * set_pte_at() time and I see no reason why the test 288 * below wouldn't be valid on those processors. This -may- 289 * break programs compiled with a really old ABI though. 290 */ 291 if (!(vma->vm_flags & VM_EXEC) && 292 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 293 !(vma->vm_flags & (VM_READ | VM_WRITE)))) 294 goto bad_area; 295 /* a write */ 296 } else if (is_write) { 297 if (!(vma->vm_flags & VM_WRITE)) 298 goto bad_area; 299 /* a read */ 300 } else { 301 /* protection fault */ 302 if (error_code & 0x08000000) 303 goto bad_area; 304 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 305 goto bad_area; 306 } 307 308 /* 309 * If for any reason at all we couldn't handle the fault, 310 * make sure we exit gracefully rather than endlessly redo 311 * the fault. 312 */ 313 ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 314 if (unlikely(ret & VM_FAULT_ERROR)) { 315 if (ret & VM_FAULT_OOM) 316 goto out_of_memory; 317 else if (ret & VM_FAULT_SIGBUS) 318 goto do_sigbus; 319 BUG(); 320 } 321 if (ret & VM_FAULT_MAJOR) { 322 current->maj_flt++; 323 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 324 regs, address); 325 #ifdef CONFIG_PPC_SMLPAR 326 if (firmware_has_feature(FW_FEATURE_CMO)) { 327 preempt_disable(); 328 get_lppaca()->page_ins += (1 << PAGE_FACTOR); 329 preempt_enable(); 330 } 331 #endif 332 } else { 333 current->min_flt++; 334 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 335 regs, address); 336 } 337 up_read(&mm->mmap_sem); 338 return 0; 339 340 bad_area: 341 up_read(&mm->mmap_sem); 342 343 bad_area_nosemaphore: 344 /* User mode accesses cause a SIGSEGV */ 345 if (user_mode(regs)) { 346 _exception(SIGSEGV, regs, code, address); 347 return 0; 348 } 349 350 if (is_exec && (error_code & DSISR_PROTFAULT)) 351 printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected" 352 " page (%lx) - exploit attempt? (uid: %d)\n", 353 address, current_uid()); 354 355 return SIGSEGV; 356 357 /* 358 * We ran out of memory, or some other thing happened to us that made 359 * us unable to handle the page fault gracefully. 360 */ 361 out_of_memory: 362 up_read(&mm->mmap_sem); 363 if (!user_mode(regs)) 364 return SIGKILL; 365 pagefault_out_of_memory(); 366 return 0; 367 368 do_sigbus: 369 up_read(&mm->mmap_sem); 370 if (user_mode(regs)) { 371 info.si_signo = SIGBUS; 372 info.si_errno = 0; 373 info.si_code = BUS_ADRERR; 374 info.si_addr = (void __user *)address; 375 force_sig_info(SIGBUS, &info, current); 376 return 0; 377 } 378 return SIGBUS; 379 } 380 381 /* 382 * bad_page_fault is called when we have a bad access from the kernel. 383 * It is called from the DSI and ISI handlers in head.S and from some 384 * of the procedures in traps.c. 385 */ 386 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 387 { 388 const struct exception_table_entry *entry; 389 unsigned long *stackend; 390 391 /* Are we prepared to handle this fault? */ 392 if ((entry = search_exception_tables(regs->nip)) != NULL) { 393 regs->nip = entry->fixup; 394 return; 395 } 396 397 /* kernel has accessed a bad area */ 398 399 switch (regs->trap) { 400 case 0x300: 401 case 0x380: 402 printk(KERN_ALERT "Unable to handle kernel paging request for " 403 "data at address 0x%08lx\n", regs->dar); 404 break; 405 case 0x400: 406 case 0x480: 407 printk(KERN_ALERT "Unable to handle kernel paging request for " 408 "instruction fetch\n"); 409 break; 410 default: 411 printk(KERN_ALERT "Unable to handle kernel paging request for " 412 "unknown fault\n"); 413 break; 414 } 415 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 416 regs->nip); 417 418 stackend = end_of_stack(current); 419 if (current != &init_task && *stackend != STACK_END_MAGIC) 420 printk(KERN_ALERT "Thread overran stack, or stack corrupted\n"); 421 422 die("Kernel access of bad area", regs, sig); 423 } 424