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_counter.h> 33 34 #include <asm/firmware.h> 35 #include <asm/page.h> 36 #include <asm/pgtable.h> 37 #include <asm/mmu.h> 38 #include <asm/mmu_context.h> 39 #include <asm/system.h> 40 #include <asm/uaccess.h> 41 #include <asm/tlbflush.h> 42 #include <asm/siginfo.h> 43 44 45 #ifdef CONFIG_KPROBES 46 static inline int notify_page_fault(struct pt_regs *regs) 47 { 48 int ret = 0; 49 50 /* kprobe_running() needs smp_processor_id() */ 51 if (!user_mode(regs)) { 52 preempt_disable(); 53 if (kprobe_running() && kprobe_fault_handler(regs, 11)) 54 ret = 1; 55 preempt_enable(); 56 } 57 58 return ret; 59 } 60 #else 61 static inline int notify_page_fault(struct pt_regs *regs) 62 { 63 return 0; 64 } 65 #endif 66 67 /* 68 * Check whether the instruction at regs->nip is a store using 69 * an update addressing form which will update r1. 70 */ 71 static int store_updates_sp(struct pt_regs *regs) 72 { 73 unsigned int inst; 74 75 if (get_user(inst, (unsigned int __user *)regs->nip)) 76 return 0; 77 /* check for 1 in the rA field */ 78 if (((inst >> 16) & 0x1f) != 1) 79 return 0; 80 /* check major opcode */ 81 switch (inst >> 26) { 82 case 37: /* stwu */ 83 case 39: /* stbu */ 84 case 45: /* sthu */ 85 case 53: /* stfsu */ 86 case 55: /* stfdu */ 87 return 1; 88 case 62: /* std or stdu */ 89 return (inst & 3) == 1; 90 case 31: 91 /* check minor opcode */ 92 switch ((inst >> 1) & 0x3ff) { 93 case 181: /* stdux */ 94 case 183: /* stwux */ 95 case 247: /* stbux */ 96 case 439: /* sthux */ 97 case 695: /* stfsux */ 98 case 759: /* stfdux */ 99 return 1; 100 } 101 } 102 return 0; 103 } 104 105 /* 106 * For 600- and 800-family processors, the error_code parameter is DSISR 107 * for a data fault, SRR1 for an instruction fault. For 400-family processors 108 * the error_code parameter is ESR for a data fault, 0 for an instruction 109 * fault. 110 * For 64-bit processors, the error_code parameter is 111 * - DSISR for a non-SLB data access fault, 112 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 113 * - 0 any SLB fault. 114 * 115 * The return value is 0 if the fault was handled, or the signal 116 * number if this is a kernel fault that can't be handled here. 117 */ 118 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 119 unsigned long error_code) 120 { 121 struct vm_area_struct * vma; 122 struct mm_struct *mm = current->mm; 123 siginfo_t info; 124 int code = SEGV_MAPERR; 125 int is_write = 0, ret; 126 int trap = TRAP(regs); 127 int is_exec = trap == 0x400; 128 129 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 130 /* 131 * Fortunately the bit assignments in SRR1 for an instruction 132 * fault and DSISR for a data fault are mostly the same for the 133 * bits we are interested in. But there are some bits which 134 * indicate errors in DSISR but can validly be set in SRR1. 135 */ 136 if (trap == 0x400) 137 error_code &= 0x48200000; 138 else 139 is_write = error_code & DSISR_ISSTORE; 140 #else 141 is_write = error_code & ESR_DST; 142 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 143 144 if (notify_page_fault(regs)) 145 return 0; 146 147 if (unlikely(debugger_fault_handler(regs))) 148 return 0; 149 150 /* On a kernel SLB miss we can only check for a valid exception entry */ 151 if (!user_mode(regs) && (address >= TASK_SIZE)) 152 return SIGSEGV; 153 154 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 155 if (error_code & DSISR_DABRMATCH) { 156 /* DABR match */ 157 do_dabr(regs, address, error_code); 158 return 0; 159 } 160 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 161 162 if (in_atomic() || mm == NULL) { 163 if (!user_mode(regs)) 164 return SIGSEGV; 165 /* in_atomic() in user mode is really bad, 166 as is current->mm == NULL. */ 167 printk(KERN_EMERG "Page fault in user mode with " 168 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 169 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 170 regs->nip, regs->msr); 171 die("Weird page fault", regs, SIGSEGV); 172 } 173 174 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address); 175 176 /* When running in the kernel we expect faults to occur only to 177 * addresses in user space. All other faults represent errors in the 178 * kernel and should generate an OOPS. Unfortunately, in the case of an 179 * erroneous fault occurring in a code path which already holds mmap_sem 180 * we will deadlock attempting to validate the fault against the 181 * address space. Luckily the kernel only validly references user 182 * space from well defined areas of code, which are listed in the 183 * exceptions table. 184 * 185 * As the vast majority of faults will be valid we will only perform 186 * the source reference check when there is a possibility of a deadlock. 187 * Attempt to lock the address space, if we cannot we then validate the 188 * source. If this is invalid we can skip the address space check, 189 * thus avoiding the deadlock. 190 */ 191 if (!down_read_trylock(&mm->mmap_sem)) { 192 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 193 goto bad_area_nosemaphore; 194 195 down_read(&mm->mmap_sem); 196 } 197 198 vma = find_vma(mm, address); 199 if (!vma) 200 goto bad_area; 201 if (vma->vm_start <= address) 202 goto good_area; 203 if (!(vma->vm_flags & VM_GROWSDOWN)) 204 goto bad_area; 205 206 /* 207 * N.B. The POWER/Open ABI allows programs to access up to 208 * 288 bytes below the stack pointer. 209 * The kernel signal delivery code writes up to about 1.5kB 210 * below the stack pointer (r1) before decrementing it. 211 * The exec code can write slightly over 640kB to the stack 212 * before setting the user r1. Thus we allow the stack to 213 * expand to 1MB without further checks. 214 */ 215 if (address + 0x100000 < vma->vm_end) { 216 /* get user regs even if this fault is in kernel mode */ 217 struct pt_regs *uregs = current->thread.regs; 218 if (uregs == NULL) 219 goto bad_area; 220 221 /* 222 * A user-mode access to an address a long way below 223 * the stack pointer is only valid if the instruction 224 * is one which would update the stack pointer to the 225 * address accessed if the instruction completed, 226 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 227 * (or the byte, halfword, float or double forms). 228 * 229 * If we don't check this then any write to the area 230 * between the last mapped region and the stack will 231 * expand the stack rather than segfaulting. 232 */ 233 if (address + 2048 < uregs->gpr[1] 234 && (!user_mode(regs) || !store_updates_sp(regs))) 235 goto bad_area; 236 } 237 if (expand_stack(vma, address)) 238 goto bad_area; 239 240 good_area: 241 code = SEGV_ACCERR; 242 #if defined(CONFIG_6xx) 243 if (error_code & 0x95700000) 244 /* an error such as lwarx to I/O controller space, 245 address matching DABR, eciwx, etc. */ 246 goto bad_area; 247 #endif /* CONFIG_6xx */ 248 #if defined(CONFIG_8xx) 249 /* The MPC8xx seems to always set 0x80000000, which is 250 * "undefined". Of those that can be set, this is the only 251 * one which seems bad. 252 */ 253 if (error_code & 0x10000000) 254 /* Guarded storage error. */ 255 goto bad_area; 256 #endif /* CONFIG_8xx */ 257 258 if (is_exec) { 259 #ifdef CONFIG_PPC_STD_MMU 260 /* Protection fault on exec go straight to failure on 261 * Hash based MMUs as they either don't support per-page 262 * execute permission, or if they do, it's handled already 263 * at the hash level. This test would probably have to 264 * be removed if we change the way this works to make hash 265 * processors use the same I/D cache coherency mechanism 266 * as embedded. 267 */ 268 if (error_code & DSISR_PROTFAULT) 269 goto bad_area; 270 #endif /* CONFIG_PPC_STD_MMU */ 271 272 /* 273 * Allow execution from readable areas if the MMU does not 274 * provide separate controls over reading and executing. 275 * 276 * Note: That code used to not be enabled for 4xx/BookE. 277 * It is now as I/D cache coherency for these is done at 278 * set_pte_at() time and I see no reason why the test 279 * below wouldn't be valid on those processors. This -may- 280 * break programs compiled with a really old ABI though. 281 */ 282 if (!(vma->vm_flags & VM_EXEC) && 283 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 284 !(vma->vm_flags & (VM_READ | VM_WRITE)))) 285 goto bad_area; 286 /* a write */ 287 } else if (is_write) { 288 if (!(vma->vm_flags & VM_WRITE)) 289 goto bad_area; 290 /* a read */ 291 } else { 292 /* protection fault */ 293 if (error_code & 0x08000000) 294 goto bad_area; 295 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 296 goto bad_area; 297 } 298 299 /* 300 * If for any reason at all we couldn't handle the fault, 301 * make sure we exit gracefully rather than endlessly redo 302 * the fault. 303 */ 304 survive: 305 ret = handle_mm_fault(mm, vma, address, is_write); 306 if (unlikely(ret & VM_FAULT_ERROR)) { 307 if (ret & VM_FAULT_OOM) 308 goto out_of_memory; 309 else if (ret & VM_FAULT_SIGBUS) 310 goto do_sigbus; 311 BUG(); 312 } 313 if (ret & VM_FAULT_MAJOR) { 314 current->maj_flt++; 315 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0, 316 regs, address); 317 #ifdef CONFIG_PPC_SMLPAR 318 if (firmware_has_feature(FW_FEATURE_CMO)) { 319 preempt_disable(); 320 get_lppaca()->page_ins += (1 << PAGE_FACTOR); 321 preempt_enable(); 322 } 323 #endif 324 } else { 325 current->min_flt++; 326 perf_swcounter_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0, 327 regs, address); 328 } 329 up_read(&mm->mmap_sem); 330 return 0; 331 332 bad_area: 333 up_read(&mm->mmap_sem); 334 335 bad_area_nosemaphore: 336 /* User mode accesses cause a SIGSEGV */ 337 if (user_mode(regs)) { 338 _exception(SIGSEGV, regs, code, address); 339 return 0; 340 } 341 342 if (is_exec && (error_code & DSISR_PROTFAULT) 343 && printk_ratelimit()) 344 printk(KERN_CRIT "kernel tried to execute NX-protected" 345 " page (%lx) - exploit attempt? (uid: %d)\n", 346 address, current_uid()); 347 348 return SIGSEGV; 349 350 /* 351 * We ran out of memory, or some other thing happened to us that made 352 * us unable to handle the page fault gracefully. 353 */ 354 out_of_memory: 355 up_read(&mm->mmap_sem); 356 if (is_global_init(current)) { 357 yield(); 358 down_read(&mm->mmap_sem); 359 goto survive; 360 } 361 printk("VM: killing process %s\n", current->comm); 362 if (user_mode(regs)) 363 do_group_exit(SIGKILL); 364 return SIGKILL; 365 366 do_sigbus: 367 up_read(&mm->mmap_sem); 368 if (user_mode(regs)) { 369 info.si_signo = SIGBUS; 370 info.si_errno = 0; 371 info.si_code = BUS_ADRERR; 372 info.si_addr = (void __user *)address; 373 force_sig_info(SIGBUS, &info, current); 374 return 0; 375 } 376 return SIGBUS; 377 } 378 379 /* 380 * bad_page_fault is called when we have a bad access from the kernel. 381 * It is called from the DSI and ISI handlers in head.S and from some 382 * of the procedures in traps.c. 383 */ 384 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 385 { 386 const struct exception_table_entry *entry; 387 388 /* Are we prepared to handle this fault? */ 389 if ((entry = search_exception_tables(regs->nip)) != NULL) { 390 regs->nip = entry->fixup; 391 return; 392 } 393 394 /* kernel has accessed a bad area */ 395 396 switch (regs->trap) { 397 case 0x300: 398 case 0x380: 399 printk(KERN_ALERT "Unable to handle kernel paging request for " 400 "data at address 0x%08lx\n", regs->dar); 401 break; 402 case 0x400: 403 case 0x480: 404 printk(KERN_ALERT "Unable to handle kernel paging request for " 405 "instruction fetch\n"); 406 break; 407 default: 408 printk(KERN_ALERT "Unable to handle kernel paging request for " 409 "unknown fault\n"); 410 break; 411 } 412 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 413 regs->nip); 414 415 die("Kernel access of bad area", regs, sig); 416 } 417