1 /* 2 * arch/ppc/mm/fault.c 3 * 4 * PowerPC version 5 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 6 * 7 * Derived from "arch/i386/mm/fault.c" 8 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 9 * 10 * Modified by Cort Dougan and Paul Mackerras. 11 * 12 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) 13 * 14 * This program is free software; you can redistribute it and/or 15 * modify it under the terms of the GNU General Public License 16 * as published by the Free Software Foundation; either version 17 * 2 of the License, or (at your option) any later version. 18 */ 19 20 #include <linux/config.h> 21 #include <linux/signal.h> 22 #include <linux/sched.h> 23 #include <linux/kernel.h> 24 #include <linux/errno.h> 25 #include <linux/string.h> 26 #include <linux/types.h> 27 #include <linux/ptrace.h> 28 #include <linux/mman.h> 29 #include <linux/mm.h> 30 #include <linux/interrupt.h> 31 #include <linux/highmem.h> 32 #include <linux/module.h> 33 #include <linux/kprobes.h> 34 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/kdebug.h> 43 #include <asm/siginfo.h> 44 45 /* 46 * Check whether the instruction at regs->nip is a store using 47 * an update addressing form which will update r1. 48 */ 49 static int store_updates_sp(struct pt_regs *regs) 50 { 51 unsigned int inst; 52 53 if (get_user(inst, (unsigned int __user *)regs->nip)) 54 return 0; 55 /* check for 1 in the rA field */ 56 if (((inst >> 16) & 0x1f) != 1) 57 return 0; 58 /* check major opcode */ 59 switch (inst >> 26) { 60 case 37: /* stwu */ 61 case 39: /* stbu */ 62 case 45: /* sthu */ 63 case 53: /* stfsu */ 64 case 55: /* stfdu */ 65 return 1; 66 case 62: /* std or stdu */ 67 return (inst & 3) == 1; 68 case 31: 69 /* check minor opcode */ 70 switch ((inst >> 1) & 0x3ff) { 71 case 181: /* stdux */ 72 case 183: /* stwux */ 73 case 247: /* stbux */ 74 case 439: /* sthux */ 75 case 695: /* stfsux */ 76 case 759: /* stfdux */ 77 return 1; 78 } 79 } 80 return 0; 81 } 82 83 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 84 static void do_dabr(struct pt_regs *regs, unsigned long address, 85 unsigned long error_code) 86 { 87 siginfo_t info; 88 89 if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code, 90 11, SIGSEGV) == NOTIFY_STOP) 91 return; 92 93 if (debugger_dabr_match(regs)) 94 return; 95 96 /* Clear the DABR */ 97 set_dabr(0); 98 99 /* Deliver the signal to userspace */ 100 info.si_signo = SIGTRAP; 101 info.si_errno = 0; 102 info.si_code = TRAP_HWBKPT; 103 info.si_addr = (void __user *)address; 104 force_sig_info(SIGTRAP, &info, current); 105 } 106 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 107 108 /* 109 * For 600- and 800-family processors, the error_code parameter is DSISR 110 * for a data fault, SRR1 for an instruction fault. For 400-family processors 111 * the error_code parameter is ESR for a data fault, 0 for an instruction 112 * fault. 113 * For 64-bit processors, the error_code parameter is 114 * - DSISR for a non-SLB data access fault, 115 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 116 * - 0 any SLB fault. 117 * 118 * The return value is 0 if the fault was handled, or the signal 119 * number if this is a kernel fault that can't be handled here. 120 */ 121 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 122 unsigned long error_code) 123 { 124 struct vm_area_struct * vma; 125 struct mm_struct *mm = current->mm; 126 siginfo_t info; 127 int code = SEGV_MAPERR; 128 int is_write = 0; 129 int trap = TRAP(regs); 130 int is_exec = trap == 0x400; 131 132 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 133 /* 134 * Fortunately the bit assignments in SRR1 for an instruction 135 * fault and DSISR for a data fault are mostly the same for the 136 * bits we are interested in. But there are some bits which 137 * indicate errors in DSISR but can validly be set in SRR1. 138 */ 139 if (trap == 0x400) 140 error_code &= 0x48200000; 141 else 142 is_write = error_code & DSISR_ISSTORE; 143 #else 144 is_write = error_code & ESR_DST; 145 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 146 147 if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code, 148 11, SIGSEGV) == NOTIFY_STOP) 149 return 0; 150 151 if (trap == 0x300) { 152 if (debugger_fault_handler(regs)) 153 return 0; 154 } 155 156 /* On a kernel SLB miss we can only check for a valid exception entry */ 157 if (!user_mode(regs) && (address >= TASK_SIZE)) 158 return SIGSEGV; 159 160 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 161 if (error_code & DSISR_DABRMATCH) { 162 /* DABR match */ 163 do_dabr(regs, address, error_code); 164 return 0; 165 } 166 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 167 168 if (in_atomic() || mm == NULL) { 169 if (!user_mode(regs)) 170 return SIGSEGV; 171 /* in_atomic() in user mode is really bad, 172 as is current->mm == NULL. */ 173 printk(KERN_EMERG "Page fault in user mode with" 174 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 175 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 176 regs->nip, regs->msr); 177 die("Weird page fault", regs, SIGSEGV); 178 } 179 180 /* When running in the kernel we expect faults to occur only to 181 * addresses in user space. All other faults represent errors in the 182 * kernel and should generate an OOPS. Unfortunatly, in the case of an 183 * erroneous fault occuring in a code path which already holds mmap_sem 184 * we will deadlock attempting to validate the fault against the 185 * address space. Luckily the kernel only validly references user 186 * space from well defined areas of code, which are listed in the 187 * exceptions table. 188 * 189 * As the vast majority of faults will be valid we will only perform 190 * the source reference check when there is a possibilty of a deadlock. 191 * Attempt to lock the address space, if we cannot we then validate the 192 * source. If this is invalid we can skip the address space check, 193 * thus avoiding the deadlock. 194 */ 195 if (!down_read_trylock(&mm->mmap_sem)) { 196 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 197 goto bad_area_nosemaphore; 198 199 down_read(&mm->mmap_sem); 200 } 201 202 vma = find_vma(mm, address); 203 if (!vma) 204 goto bad_area; 205 if (vma->vm_start <= address) 206 goto good_area; 207 if (!(vma->vm_flags & VM_GROWSDOWN)) 208 goto bad_area; 209 210 /* 211 * N.B. The POWER/Open ABI allows programs to access up to 212 * 288 bytes below the stack pointer. 213 * The kernel signal delivery code writes up to about 1.5kB 214 * below the stack pointer (r1) before decrementing it. 215 * The exec code can write slightly over 640kB to the stack 216 * before setting the user r1. Thus we allow the stack to 217 * expand to 1MB without further checks. 218 */ 219 if (address + 0x100000 < vma->vm_end) { 220 /* get user regs even if this fault is in kernel mode */ 221 struct pt_regs *uregs = current->thread.regs; 222 if (uregs == NULL) 223 goto bad_area; 224 225 /* 226 * A user-mode access to an address a long way below 227 * the stack pointer is only valid if the instruction 228 * is one which would update the stack pointer to the 229 * address accessed if the instruction completed, 230 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 231 * (or the byte, halfword, float or double forms). 232 * 233 * If we don't check this then any write to the area 234 * between the last mapped region and the stack will 235 * expand the stack rather than segfaulting. 236 */ 237 if (address + 2048 < uregs->gpr[1] 238 && (!user_mode(regs) || !store_updates_sp(regs))) 239 goto bad_area; 240 } 241 if (expand_stack(vma, address)) 242 goto bad_area; 243 244 good_area: 245 code = SEGV_ACCERR; 246 #if defined(CONFIG_6xx) 247 if (error_code & 0x95700000) 248 /* an error such as lwarx to I/O controller space, 249 address matching DABR, eciwx, etc. */ 250 goto bad_area; 251 #endif /* CONFIG_6xx */ 252 #if defined(CONFIG_8xx) 253 /* The MPC8xx seems to always set 0x80000000, which is 254 * "undefined". Of those that can be set, this is the only 255 * one which seems bad. 256 */ 257 if (error_code & 0x10000000) 258 /* Guarded storage error. */ 259 goto bad_area; 260 #endif /* CONFIG_8xx */ 261 262 if (is_exec) { 263 #ifdef CONFIG_PPC64 264 /* protection fault */ 265 if (error_code & DSISR_PROTFAULT) 266 goto bad_area; 267 if (!(vma->vm_flags & VM_EXEC)) 268 goto bad_area; 269 #endif 270 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) 271 pte_t *ptep; 272 273 /* Since 4xx/Book-E supports per-page execute permission, 274 * we lazily flush dcache to icache. */ 275 ptep = NULL; 276 if (get_pteptr(mm, address, &ptep) && pte_present(*ptep)) { 277 struct page *page = pte_page(*ptep); 278 279 if (! test_bit(PG_arch_1, &page->flags)) { 280 flush_dcache_icache_page(page); 281 set_bit(PG_arch_1, &page->flags); 282 } 283 pte_update(ptep, 0, _PAGE_HWEXEC); 284 _tlbie(address); 285 pte_unmap(ptep); 286 up_read(&mm->mmap_sem); 287 return 0; 288 } 289 if (ptep != NULL) 290 pte_unmap(ptep); 291 #endif 292 /* a write */ 293 } else if (is_write) { 294 if (!(vma->vm_flags & VM_WRITE)) 295 goto bad_area; 296 /* a read */ 297 } else { 298 /* protection fault */ 299 if (error_code & 0x08000000) 300 goto bad_area; 301 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 302 goto bad_area; 303 } 304 305 /* 306 * If for any reason at all we couldn't handle the fault, 307 * make sure we exit gracefully rather than endlessly redo 308 * the fault. 309 */ 310 survive: 311 switch (handle_mm_fault(mm, vma, address, is_write)) { 312 313 case VM_FAULT_MINOR: 314 current->min_flt++; 315 break; 316 case VM_FAULT_MAJOR: 317 current->maj_flt++; 318 break; 319 case VM_FAULT_SIGBUS: 320 goto do_sigbus; 321 case VM_FAULT_OOM: 322 goto out_of_memory; 323 default: 324 BUG(); 325 } 326 327 up_read(&mm->mmap_sem); 328 return 0; 329 330 bad_area: 331 up_read(&mm->mmap_sem); 332 333 bad_area_nosemaphore: 334 /* User mode accesses cause a SIGSEGV */ 335 if (user_mode(regs)) { 336 _exception(SIGSEGV, regs, code, address); 337 return 0; 338 } 339 340 if (is_exec && (error_code & DSISR_PROTFAULT) 341 && printk_ratelimit()) 342 printk(KERN_CRIT "kernel tried to execute NX-protected" 343 " page (%lx) - exploit attempt? (uid: %d)\n", 344 address, current->uid); 345 346 return SIGSEGV; 347 348 /* 349 * We ran out of memory, or some other thing happened to us that made 350 * us unable to handle the page fault gracefully. 351 */ 352 out_of_memory: 353 up_read(&mm->mmap_sem); 354 if (current->pid == 1) { 355 yield(); 356 down_read(&mm->mmap_sem); 357 goto survive; 358 } 359 printk("VM: killing process %s\n", current->comm); 360 if (user_mode(regs)) 361 do_exit(SIGKILL); 362 return SIGKILL; 363 364 do_sigbus: 365 up_read(&mm->mmap_sem); 366 if (user_mode(regs)) { 367 info.si_signo = SIGBUS; 368 info.si_errno = 0; 369 info.si_code = BUS_ADRERR; 370 info.si_addr = (void __user *)address; 371 force_sig_info(SIGBUS, &info, current); 372 return 0; 373 } 374 return SIGBUS; 375 } 376 377 /* 378 * bad_page_fault is called when we have a bad access from the kernel. 379 * It is called from the DSI and ISI handlers in head.S and from some 380 * of the procedures in traps.c. 381 */ 382 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 383 { 384 const struct exception_table_entry *entry; 385 386 /* Are we prepared to handle this fault? */ 387 if ((entry = search_exception_tables(regs->nip)) != NULL) { 388 regs->nip = entry->fixup; 389 return; 390 } 391 392 /* kernel has accessed a bad area */ 393 394 printk(KERN_ALERT "Unable to handle kernel paging request for "); 395 switch (regs->trap) { 396 case 0x300: 397 case 0x380: 398 printk("data at address 0x%08lx\n", regs->dar); 399 break; 400 case 0x400: 401 case 0x480: 402 printk("instruction fetch\n"); 403 break; 404 default: 405 printk("unknown fault\n"); 406 } 407 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 408 regs->nip); 409 410 die("Kernel access of bad area", regs, sig); 411 } 412