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