1 /* 2 * arch/s390/mm/fault.c 3 * 4 * S390 version 5 * Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation 6 * Author(s): Hartmut Penner (hp@de.ibm.com) 7 * Ulrich Weigand (uweigand@de.ibm.com) 8 * 9 * Derived from "arch/i386/mm/fault.c" 10 * Copyright (C) 1995 Linus Torvalds 11 */ 12 13 #include <linux/config.h> 14 #include <linux/signal.h> 15 #include <linux/sched.h> 16 #include <linux/kernel.h> 17 #include <linux/errno.h> 18 #include <linux/string.h> 19 #include <linux/types.h> 20 #include <linux/ptrace.h> 21 #include <linux/mman.h> 22 #include <linux/mm.h> 23 #include <linux/smp.h> 24 #include <linux/smp_lock.h> 25 #include <linux/init.h> 26 #include <linux/console.h> 27 #include <linux/module.h> 28 #include <linux/hardirq.h> 29 30 #include <asm/system.h> 31 #include <asm/uaccess.h> 32 #include <asm/pgtable.h> 33 34 #ifndef CONFIG_64BIT 35 #define __FAIL_ADDR_MASK 0x7ffff000 36 #define __FIXUP_MASK 0x7fffffff 37 #define __SUBCODE_MASK 0x0200 38 #define __PF_RES_FIELD 0ULL 39 #else /* CONFIG_64BIT */ 40 #define __FAIL_ADDR_MASK -4096L 41 #define __FIXUP_MASK ~0L 42 #define __SUBCODE_MASK 0x0600 43 #define __PF_RES_FIELD 0x8000000000000000ULL 44 #endif /* CONFIG_64BIT */ 45 46 #ifdef CONFIG_SYSCTL 47 extern int sysctl_userprocess_debug; 48 #endif 49 50 extern void die(const char *,struct pt_regs *,long); 51 52 extern spinlock_t timerlist_lock; 53 54 /* 55 * Unlock any spinlocks which will prevent us from getting the 56 * message out (timerlist_lock is acquired through the 57 * console unblank code) 58 */ 59 void bust_spinlocks(int yes) 60 { 61 if (yes) { 62 oops_in_progress = 1; 63 } else { 64 int loglevel_save = console_loglevel; 65 console_unblank(); 66 oops_in_progress = 0; 67 /* 68 * OK, the message is on the console. Now we call printk() 69 * without oops_in_progress set so that printk will give klogd 70 * a poke. Hold onto your hats... 71 */ 72 console_loglevel = 15; 73 printk(" "); 74 console_loglevel = loglevel_save; 75 } 76 } 77 78 /* 79 * Check which address space is addressed by the access 80 * register in S390_lowcore.exc_access_id. 81 * Returns 1 for user space and 0 for kernel space. 82 */ 83 static int __check_access_register(struct pt_regs *regs, int error_code) 84 { 85 int areg = S390_lowcore.exc_access_id; 86 87 if (areg == 0) 88 /* Access via access register 0 -> kernel address */ 89 return 0; 90 save_access_regs(current->thread.acrs); 91 if (regs && areg < NUM_ACRS && current->thread.acrs[areg] <= 1) 92 /* 93 * access register contains 0 -> kernel address, 94 * access register contains 1 -> user space address 95 */ 96 return current->thread.acrs[areg]; 97 98 /* Something unhealthy was done with the access registers... */ 99 die("page fault via unknown access register", regs, error_code); 100 do_exit(SIGKILL); 101 return 0; 102 } 103 104 /* 105 * Check which address space the address belongs to. 106 * Returns 1 for user space and 0 for kernel space. 107 */ 108 static inline int check_user_space(struct pt_regs *regs, int error_code) 109 { 110 /* 111 * The lowest two bits of S390_lowcore.trans_exc_code indicate 112 * which paging table was used: 113 * 0: Primary Segment Table Descriptor 114 * 1: STD determined via access register 115 * 2: Secondary Segment Table Descriptor 116 * 3: Home Segment Table Descriptor 117 */ 118 int descriptor = S390_lowcore.trans_exc_code & 3; 119 if (unlikely(descriptor == 1)) 120 return __check_access_register(regs, error_code); 121 if (descriptor == 2) 122 return current->thread.mm_segment.ar4; 123 return descriptor != 0; 124 } 125 126 /* 127 * Send SIGSEGV to task. This is an external routine 128 * to keep the stack usage of do_page_fault small. 129 */ 130 static void do_sigsegv(struct pt_regs *regs, unsigned long error_code, 131 int si_code, unsigned long address) 132 { 133 struct siginfo si; 134 135 #if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG) 136 #if defined(CONFIG_SYSCTL) 137 if (sysctl_userprocess_debug) 138 #endif 139 { 140 printk("User process fault: interruption code 0x%lX\n", 141 error_code); 142 printk("failing address: %lX\n", address); 143 show_regs(regs); 144 } 145 #endif 146 si.si_signo = SIGSEGV; 147 si.si_code = si_code; 148 si.si_addr = (void *) address; 149 force_sig_info(SIGSEGV, &si, current); 150 } 151 152 /* 153 * This routine handles page faults. It determines the address, 154 * and the problem, and then passes it off to one of the appropriate 155 * routines. 156 * 157 * error_code: 158 * 04 Protection -> Write-Protection (suprression) 159 * 10 Segment translation -> Not present (nullification) 160 * 11 Page translation -> Not present (nullification) 161 * 3b Region third trans. -> Not present (nullification) 162 */ 163 static inline void 164 do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection) 165 { 166 struct task_struct *tsk; 167 struct mm_struct *mm; 168 struct vm_area_struct * vma; 169 unsigned long address; 170 int user_address; 171 const struct exception_table_entry *fixup; 172 int si_code = SEGV_MAPERR; 173 174 tsk = current; 175 mm = tsk->mm; 176 177 /* 178 * Check for low-address protection. This needs to be treated 179 * as a special case because the translation exception code 180 * field is not guaranteed to contain valid data in this case. 181 */ 182 if (is_protection && !(S390_lowcore.trans_exc_code & 4)) { 183 184 /* Low-address protection hit in kernel mode means 185 NULL pointer write access in kernel mode. */ 186 if (!(regs->psw.mask & PSW_MASK_PSTATE)) { 187 address = 0; 188 user_address = 0; 189 goto no_context; 190 } 191 192 /* Low-address protection hit in user mode 'cannot happen'. */ 193 die ("Low-address protection", regs, error_code); 194 do_exit(SIGKILL); 195 } 196 197 /* 198 * get the failing address 199 * more specific the segment and page table portion of 200 * the address 201 */ 202 address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK; 203 user_address = check_user_space(regs, error_code); 204 205 /* 206 * Verify that the fault happened in user space, that 207 * we are not in an interrupt and that there is a 208 * user context. 209 */ 210 if (user_address == 0 || in_atomic() || !mm) 211 goto no_context; 212 213 /* 214 * When we get here, the fault happened in the current 215 * task's user address space, so we can switch on the 216 * interrupts again and then search the VMAs 217 */ 218 local_irq_enable(); 219 220 down_read(&mm->mmap_sem); 221 222 vma = find_vma(mm, address); 223 if (!vma) 224 goto bad_area; 225 if (vma->vm_start <= address) 226 goto good_area; 227 if (!(vma->vm_flags & VM_GROWSDOWN)) 228 goto bad_area; 229 if (expand_stack(vma, address)) 230 goto bad_area; 231 /* 232 * Ok, we have a good vm_area for this memory access, so 233 * we can handle it.. 234 */ 235 good_area: 236 si_code = SEGV_ACCERR; 237 if (!is_protection) { 238 /* page not present, check vm flags */ 239 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 240 goto bad_area; 241 } else { 242 if (!(vma->vm_flags & VM_WRITE)) 243 goto bad_area; 244 } 245 246 survive: 247 /* 248 * If for any reason at all we couldn't handle the fault, 249 * make sure we exit gracefully rather than endlessly redo 250 * the fault. 251 */ 252 switch (handle_mm_fault(mm, vma, address, is_protection)) { 253 case VM_FAULT_MINOR: 254 tsk->min_flt++; 255 break; 256 case VM_FAULT_MAJOR: 257 tsk->maj_flt++; 258 break; 259 case VM_FAULT_SIGBUS: 260 goto do_sigbus; 261 case VM_FAULT_OOM: 262 goto out_of_memory; 263 default: 264 BUG(); 265 } 266 267 up_read(&mm->mmap_sem); 268 /* 269 * The instruction that caused the program check will 270 * be repeated. Don't signal single step via SIGTRAP. 271 */ 272 clear_tsk_thread_flag(current, TIF_SINGLE_STEP); 273 return; 274 275 /* 276 * Something tried to access memory that isn't in our memory map.. 277 * Fix it, but check if it's kernel or user first.. 278 */ 279 bad_area: 280 up_read(&mm->mmap_sem); 281 282 /* User mode accesses just cause a SIGSEGV */ 283 if (regs->psw.mask & PSW_MASK_PSTATE) { 284 tsk->thread.prot_addr = address; 285 tsk->thread.trap_no = error_code; 286 do_sigsegv(regs, error_code, si_code, address); 287 return; 288 } 289 290 no_context: 291 /* Are we prepared to handle this kernel fault? */ 292 fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK); 293 if (fixup) { 294 regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE; 295 return; 296 } 297 298 /* 299 * Oops. The kernel tried to access some bad page. We'll have to 300 * terminate things with extreme prejudice. 301 */ 302 if (user_address == 0) 303 printk(KERN_ALERT "Unable to handle kernel pointer dereference" 304 " at virtual kernel address %p\n", (void *)address); 305 else 306 printk(KERN_ALERT "Unable to handle kernel paging request" 307 " at virtual user address %p\n", (void *)address); 308 309 die("Oops", regs, error_code); 310 do_exit(SIGKILL); 311 312 313 /* 314 * We ran out of memory, or some other thing happened to us that made 315 * us unable to handle the page fault gracefully. 316 */ 317 out_of_memory: 318 up_read(&mm->mmap_sem); 319 if (tsk->pid == 1) { 320 yield(); 321 goto survive; 322 } 323 printk("VM: killing process %s\n", tsk->comm); 324 if (regs->psw.mask & PSW_MASK_PSTATE) 325 do_exit(SIGKILL); 326 goto no_context; 327 328 do_sigbus: 329 up_read(&mm->mmap_sem); 330 331 /* 332 * Send a sigbus, regardless of whether we were in kernel 333 * or user mode. 334 */ 335 tsk->thread.prot_addr = address; 336 tsk->thread.trap_no = error_code; 337 force_sig(SIGBUS, tsk); 338 339 /* Kernel mode? Handle exceptions or die */ 340 if (!(regs->psw.mask & PSW_MASK_PSTATE)) 341 goto no_context; 342 } 343 344 void do_protection_exception(struct pt_regs *regs, unsigned long error_code) 345 { 346 regs->psw.addr -= (error_code >> 16); 347 do_exception(regs, 4, 1); 348 } 349 350 void do_dat_exception(struct pt_regs *regs, unsigned long error_code) 351 { 352 do_exception(regs, error_code & 0xff, 0); 353 } 354 355 #ifdef CONFIG_PFAULT 356 /* 357 * 'pfault' pseudo page faults routines. 358 */ 359 static int pfault_disable = 0; 360 361 static int __init nopfault(char *str) 362 { 363 pfault_disable = 1; 364 return 1; 365 } 366 367 __setup("nopfault", nopfault); 368 369 typedef struct { 370 __u16 refdiagc; 371 __u16 reffcode; 372 __u16 refdwlen; 373 __u16 refversn; 374 __u64 refgaddr; 375 __u64 refselmk; 376 __u64 refcmpmk; 377 __u64 reserved; 378 } __attribute__ ((packed)) pfault_refbk_t; 379 380 int pfault_init(void) 381 { 382 pfault_refbk_t refbk = 383 { 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48, 384 __PF_RES_FIELD }; 385 int rc; 386 387 if (pfault_disable) 388 return -1; 389 __asm__ __volatile__( 390 " diag %1,%0,0x258\n" 391 "0: j 2f\n" 392 "1: la %0,8\n" 393 "2:\n" 394 ".section __ex_table,\"a\"\n" 395 " .align 4\n" 396 #ifndef CONFIG_64BIT 397 " .long 0b,1b\n" 398 #else /* CONFIG_64BIT */ 399 " .quad 0b,1b\n" 400 #endif /* CONFIG_64BIT */ 401 ".previous" 402 : "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc" ); 403 __ctl_set_bit(0, 9); 404 return rc; 405 } 406 407 void pfault_fini(void) 408 { 409 pfault_refbk_t refbk = 410 { 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL }; 411 412 if (pfault_disable) 413 return; 414 __ctl_clear_bit(0,9); 415 __asm__ __volatile__( 416 " diag %0,0,0x258\n" 417 "0:\n" 418 ".section __ex_table,\"a\"\n" 419 " .align 4\n" 420 #ifndef CONFIG_64BIT 421 " .long 0b,0b\n" 422 #else /* CONFIG_64BIT */ 423 " .quad 0b,0b\n" 424 #endif /* CONFIG_64BIT */ 425 ".previous" 426 : : "a" (&refbk), "m" (refbk) : "cc" ); 427 } 428 429 asmlinkage void 430 pfault_interrupt(struct pt_regs *regs, __u16 error_code) 431 { 432 struct task_struct *tsk; 433 __u16 subcode; 434 435 /* 436 * Get the external interruption subcode & pfault 437 * initial/completion signal bit. VM stores this 438 * in the 'cpu address' field associated with the 439 * external interrupt. 440 */ 441 subcode = S390_lowcore.cpu_addr; 442 if ((subcode & 0xff00) != __SUBCODE_MASK) 443 return; 444 445 /* 446 * Get the token (= address of the task structure of the affected task). 447 */ 448 tsk = *(struct task_struct **) __LC_PFAULT_INTPARM; 449 450 if (subcode & 0x0080) { 451 /* signal bit is set -> a page has been swapped in by VM */ 452 if (xchg(&tsk->thread.pfault_wait, -1) != 0) { 453 /* Initial interrupt was faster than the completion 454 * interrupt. pfault_wait is valid. Set pfault_wait 455 * back to zero and wake up the process. This can 456 * safely be done because the task is still sleeping 457 * and can't produce new pfaults. */ 458 tsk->thread.pfault_wait = 0; 459 wake_up_process(tsk); 460 put_task_struct(tsk); 461 } 462 } else { 463 /* signal bit not set -> a real page is missing. */ 464 get_task_struct(tsk); 465 set_task_state(tsk, TASK_UNINTERRUPTIBLE); 466 if (xchg(&tsk->thread.pfault_wait, 1) != 0) { 467 /* Completion interrupt was faster than the initial 468 * interrupt (swapped in a -1 for pfault_wait). Set 469 * pfault_wait back to zero and exit. This can be 470 * done safely because tsk is running in kernel 471 * mode and can't produce new pfaults. */ 472 tsk->thread.pfault_wait = 0; 473 set_task_state(tsk, TASK_RUNNING); 474 put_task_struct(tsk); 475 } else 476 set_tsk_need_resched(tsk); 477 } 478 } 479 #endif 480 481