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 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 #include <mm/mmu_decl.h> 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 defined(CONFIG_PPC_BOOK3S_64)) 156 if (error_code & DSISR_DABRMATCH) { 157 /* DABR match */ 158 do_dabr(regs, address, error_code); 159 return 0; 160 } 161 #endif 162 163 if (in_atomic() || mm == NULL) { 164 if (!user_mode(regs)) 165 return SIGSEGV; 166 /* in_atomic() in user mode is really bad, 167 as is current->mm == NULL. */ 168 printk(KERN_EMERG "Page fault in user mode with " 169 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 170 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 171 regs->nip, regs->msr); 172 die("Weird page fault", regs, SIGSEGV); 173 } 174 175 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, 0, regs, address); 176 177 /* When running in the kernel we expect faults to occur only to 178 * addresses in user space. All other faults represent errors in the 179 * kernel and should generate an OOPS. Unfortunately, in the case of an 180 * erroneous fault occurring in a code path which already holds mmap_sem 181 * we will deadlock attempting to validate the fault against the 182 * address space. Luckily the kernel only validly references user 183 * space from well defined areas of code, which are listed in the 184 * exceptions table. 185 * 186 * As the vast majority of faults will be valid we will only perform 187 * the source reference check when there is a possibility of a deadlock. 188 * Attempt to lock the address space, if we cannot we then validate the 189 * source. If this is invalid we can skip the address space check, 190 * thus avoiding the deadlock. 191 */ 192 if (!down_read_trylock(&mm->mmap_sem)) { 193 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 194 goto bad_area_nosemaphore; 195 196 down_read(&mm->mmap_sem); 197 } 198 199 vma = find_vma(mm, address); 200 if (!vma) 201 goto bad_area; 202 if (vma->vm_start <= address) 203 goto good_area; 204 if (!(vma->vm_flags & VM_GROWSDOWN)) 205 goto bad_area; 206 207 /* 208 * N.B. The POWER/Open ABI allows programs to access up to 209 * 288 bytes below the stack pointer. 210 * The kernel signal delivery code writes up to about 1.5kB 211 * below the stack pointer (r1) before decrementing it. 212 * The exec code can write slightly over 640kB to the stack 213 * before setting the user r1. Thus we allow the stack to 214 * expand to 1MB without further checks. 215 */ 216 if (address + 0x100000 < vma->vm_end) { 217 /* get user regs even if this fault is in kernel mode */ 218 struct pt_regs *uregs = current->thread.regs; 219 if (uregs == NULL) 220 goto bad_area; 221 222 /* 223 * A user-mode access to an address a long way below 224 * the stack pointer is only valid if the instruction 225 * is one which would update the stack pointer to the 226 * address accessed if the instruction completed, 227 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 228 * (or the byte, halfword, float or double forms). 229 * 230 * If we don't check this then any write to the area 231 * between the last mapped region and the stack will 232 * expand the stack rather than segfaulting. 233 */ 234 if (address + 2048 < uregs->gpr[1] 235 && (!user_mode(regs) || !store_updates_sp(regs))) 236 goto bad_area; 237 } 238 if (expand_stack(vma, address)) 239 goto bad_area; 240 241 good_area: 242 code = SEGV_ACCERR; 243 #if defined(CONFIG_6xx) 244 if (error_code & 0x95700000) 245 /* an error such as lwarx to I/O controller space, 246 address matching DABR, eciwx, etc. */ 247 goto bad_area; 248 #endif /* CONFIG_6xx */ 249 #if defined(CONFIG_8xx) 250 /* 8xx sometimes need to load a invalid/non-present TLBs. 251 * These must be invalidated separately as linux mm don't. 252 */ 253 if (error_code & 0x40000000) /* no translation? */ 254 _tlbil_va(address, 0, 0, 0); 255 256 /* The MPC8xx seems to always set 0x80000000, which is 257 * "undefined". Of those that can be set, this is the only 258 * one which seems bad. 259 */ 260 if (error_code & 0x10000000) 261 /* Guarded storage error. */ 262 goto bad_area; 263 #endif /* CONFIG_8xx */ 264 265 if (is_exec) { 266 #ifdef CONFIG_PPC_STD_MMU 267 /* Protection fault on exec go straight to failure on 268 * Hash based MMUs as they either don't support per-page 269 * execute permission, or if they do, it's handled already 270 * at the hash level. This test would probably have to 271 * be removed if we change the way this works to make hash 272 * processors use the same I/D cache coherency mechanism 273 * as embedded. 274 */ 275 if (error_code & DSISR_PROTFAULT) 276 goto bad_area; 277 #endif /* CONFIG_PPC_STD_MMU */ 278 279 /* 280 * Allow execution from readable areas if the MMU does not 281 * provide separate controls over reading and executing. 282 * 283 * Note: That code used to not be enabled for 4xx/BookE. 284 * It is now as I/D cache coherency for these is done at 285 * set_pte_at() time and I see no reason why the test 286 * below wouldn't be valid on those processors. This -may- 287 * break programs compiled with a really old ABI though. 288 */ 289 if (!(vma->vm_flags & VM_EXEC) && 290 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 291 !(vma->vm_flags & (VM_READ | VM_WRITE)))) 292 goto bad_area; 293 /* a write */ 294 } else if (is_write) { 295 if (!(vma->vm_flags & VM_WRITE)) 296 goto bad_area; 297 /* a read */ 298 } else { 299 /* protection fault */ 300 if (error_code & 0x08000000) 301 goto bad_area; 302 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 303 goto bad_area; 304 } 305 306 /* 307 * If for any reason at all we couldn't handle the fault, 308 * make sure we exit gracefully rather than endlessly redo 309 * the fault. 310 */ 311 ret = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 312 if (unlikely(ret & VM_FAULT_ERROR)) { 313 if (ret & VM_FAULT_OOM) 314 goto out_of_memory; 315 else if (ret & VM_FAULT_SIGBUS) 316 goto do_sigbus; 317 BUG(); 318 } 319 if (ret & VM_FAULT_MAJOR) { 320 current->maj_flt++; 321 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, 0, 322 regs, address); 323 #ifdef CONFIG_PPC_SMLPAR 324 if (firmware_has_feature(FW_FEATURE_CMO)) { 325 preempt_disable(); 326 get_lppaca()->page_ins += (1 << PAGE_FACTOR); 327 preempt_enable(); 328 } 329 #endif 330 } else { 331 current->min_flt++; 332 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, 0, 333 regs, address); 334 } 335 up_read(&mm->mmap_sem); 336 return 0; 337 338 bad_area: 339 up_read(&mm->mmap_sem); 340 341 bad_area_nosemaphore: 342 /* User mode accesses cause a SIGSEGV */ 343 if (user_mode(regs)) { 344 _exception(SIGSEGV, regs, code, address); 345 return 0; 346 } 347 348 if (is_exec && (error_code & DSISR_PROTFAULT) 349 && printk_ratelimit()) 350 printk(KERN_CRIT "kernel tried to execute NX-protected" 351 " page (%lx) - exploit attempt? (uid: %d)\n", 352 address, current_uid()); 353 354 return SIGSEGV; 355 356 /* 357 * We ran out of memory, or some other thing happened to us that made 358 * us unable to handle the page fault gracefully. 359 */ 360 out_of_memory: 361 up_read(&mm->mmap_sem); 362 if (!user_mode(regs)) 363 return SIGKILL; 364 pagefault_out_of_memory(); 365 return 0; 366 367 do_sigbus: 368 up_read(&mm->mmap_sem); 369 if (user_mode(regs)) { 370 info.si_signo = SIGBUS; 371 info.si_errno = 0; 372 info.si_code = BUS_ADRERR; 373 info.si_addr = (void __user *)address; 374 force_sig_info(SIGBUS, &info, current); 375 return 0; 376 } 377 return SIGBUS; 378 } 379 380 /* 381 * bad_page_fault is called when we have a bad access from the kernel. 382 * It is called from the DSI and ISI handlers in head.S and from some 383 * of the procedures in traps.c. 384 */ 385 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 386 { 387 const struct exception_table_entry *entry; 388 389 /* Are we prepared to handle this fault? */ 390 if ((entry = search_exception_tables(regs->nip)) != NULL) { 391 regs->nip = entry->fixup; 392 return; 393 } 394 395 /* kernel has accessed a bad area */ 396 397 switch (regs->trap) { 398 case 0x300: 399 case 0x380: 400 printk(KERN_ALERT "Unable to handle kernel paging request for " 401 "data at address 0x%08lx\n", regs->dar); 402 break; 403 case 0x400: 404 case 0x480: 405 printk(KERN_ALERT "Unable to handle kernel paging request for " 406 "instruction fetch\n"); 407 break; 408 default: 409 printk(KERN_ALERT "Unable to handle kernel paging request for " 410 "unknown fault\n"); 411 break; 412 } 413 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 414 regs->nip); 415 416 die("Kernel access of bad area", regs, sig); 417 } 418