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