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