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/page.h> 34 #include <asm/pgtable.h> 35 #include <asm/mmu.h> 36 #include <asm/mmu_context.h> 37 #include <asm/system.h> 38 #include <asm/uaccess.h> 39 #include <asm/tlbflush.h> 40 #include <asm/siginfo.h> 41 42 43 #ifdef CONFIG_KPROBES 44 static inline int notify_page_fault(struct pt_regs *regs) 45 { 46 int ret = 0; 47 48 /* kprobe_running() needs smp_processor_id() */ 49 if (!user_mode(regs)) { 50 preempt_disable(); 51 if (kprobe_running() && kprobe_fault_handler(regs, 11)) 52 ret = 1; 53 preempt_enable(); 54 } 55 56 return ret; 57 } 58 #else 59 static inline int notify_page_fault(struct pt_regs *regs) 60 { 61 return 0; 62 } 63 #endif 64 65 /* 66 * Check whether the instruction at regs->nip is a store using 67 * an update addressing form which will update r1. 68 */ 69 static int store_updates_sp(struct pt_regs *regs) 70 { 71 unsigned int inst; 72 73 if (get_user(inst, (unsigned int __user *)regs->nip)) 74 return 0; 75 /* check for 1 in the rA field */ 76 if (((inst >> 16) & 0x1f) != 1) 77 return 0; 78 /* check major opcode */ 79 switch (inst >> 26) { 80 case 37: /* stwu */ 81 case 39: /* stbu */ 82 case 45: /* sthu */ 83 case 53: /* stfsu */ 84 case 55: /* stfdu */ 85 return 1; 86 case 62: /* std or stdu */ 87 return (inst & 3) == 1; 88 case 31: 89 /* check minor opcode */ 90 switch ((inst >> 1) & 0x3ff) { 91 case 181: /* stdux */ 92 case 183: /* stwux */ 93 case 247: /* stbux */ 94 case 439: /* sthux */ 95 case 695: /* stfsux */ 96 case 759: /* stfdux */ 97 return 1; 98 } 99 } 100 return 0; 101 } 102 103 /* 104 * For 600- and 800-family processors, the error_code parameter is DSISR 105 * for a data fault, SRR1 for an instruction fault. For 400-family processors 106 * the error_code parameter is ESR for a data fault, 0 for an instruction 107 * fault. 108 * For 64-bit processors, the error_code parameter is 109 * - DSISR for a non-SLB data access fault, 110 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 111 * - 0 any SLB fault. 112 * 113 * The return value is 0 if the fault was handled, or the signal 114 * number if this is a kernel fault that can't be handled here. 115 */ 116 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 117 unsigned long error_code) 118 { 119 struct vm_area_struct * vma; 120 struct mm_struct *mm = current->mm; 121 siginfo_t info; 122 int code = SEGV_MAPERR; 123 int is_write = 0, ret; 124 int trap = TRAP(regs); 125 int is_exec = trap == 0x400; 126 127 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 128 /* 129 * Fortunately the bit assignments in SRR1 for an instruction 130 * fault and DSISR for a data fault are mostly the same for the 131 * bits we are interested in. But there are some bits which 132 * indicate errors in DSISR but can validly be set in SRR1. 133 */ 134 if (trap == 0x400) 135 error_code &= 0x48200000; 136 else 137 is_write = error_code & DSISR_ISSTORE; 138 #else 139 is_write = error_code & ESR_DST; 140 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 141 142 if (notify_page_fault(regs)) 143 return 0; 144 145 if (unlikely(debugger_fault_handler(regs))) 146 return 0; 147 148 /* On a kernel SLB miss we can only check for a valid exception entry */ 149 if (!user_mode(regs) && (address >= TASK_SIZE)) 150 return SIGSEGV; 151 152 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 153 if (error_code & DSISR_DABRMATCH) { 154 /* DABR match */ 155 do_dabr(regs, address, error_code); 156 return 0; 157 } 158 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 159 160 if (in_atomic() || mm == NULL) { 161 if (!user_mode(regs)) 162 return SIGSEGV; 163 /* in_atomic() in user mode is really bad, 164 as is current->mm == NULL. */ 165 printk(KERN_EMERG "Page fault in user mode with " 166 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 167 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 168 regs->nip, regs->msr); 169 die("Weird page fault", regs, SIGSEGV); 170 } 171 172 /* When running in the kernel we expect faults to occur only to 173 * addresses in user space. All other faults represent errors in the 174 * kernel and should generate an OOPS. Unfortunately, in the case of an 175 * erroneous fault occurring in a code path which already holds mmap_sem 176 * we will deadlock attempting to validate the fault against the 177 * address space. Luckily the kernel only validly references user 178 * space from well defined areas of code, which are listed in the 179 * exceptions table. 180 * 181 * As the vast majority of faults will be valid we will only perform 182 * the source reference check when there is a possibility of a deadlock. 183 * Attempt to lock the address space, if we cannot we then validate the 184 * source. If this is invalid we can skip the address space check, 185 * thus avoiding the deadlock. 186 */ 187 if (!down_read_trylock(&mm->mmap_sem)) { 188 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 189 goto bad_area_nosemaphore; 190 191 down_read(&mm->mmap_sem); 192 } 193 194 vma = find_vma(mm, address); 195 if (!vma) 196 goto bad_area; 197 if (vma->vm_start <= address) 198 goto good_area; 199 if (!(vma->vm_flags & VM_GROWSDOWN)) 200 goto bad_area; 201 202 /* 203 * N.B. The POWER/Open ABI allows programs to access up to 204 * 288 bytes below the stack pointer. 205 * The kernel signal delivery code writes up to about 1.5kB 206 * below the stack pointer (r1) before decrementing it. 207 * The exec code can write slightly over 640kB to the stack 208 * before setting the user r1. Thus we allow the stack to 209 * expand to 1MB without further checks. 210 */ 211 if (address + 0x100000 < vma->vm_end) { 212 /* get user regs even if this fault is in kernel mode */ 213 struct pt_regs *uregs = current->thread.regs; 214 if (uregs == NULL) 215 goto bad_area; 216 217 /* 218 * A user-mode access to an address a long way below 219 * the stack pointer is only valid if the instruction 220 * is one which would update the stack pointer to the 221 * address accessed if the instruction completed, 222 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 223 * (or the byte, halfword, float or double forms). 224 * 225 * If we don't check this then any write to the area 226 * between the last mapped region and the stack will 227 * expand the stack rather than segfaulting. 228 */ 229 if (address + 2048 < uregs->gpr[1] 230 && (!user_mode(regs) || !store_updates_sp(regs))) 231 goto bad_area; 232 } 233 if (expand_stack(vma, address)) 234 goto bad_area; 235 236 good_area: 237 code = SEGV_ACCERR; 238 #if defined(CONFIG_6xx) 239 if (error_code & 0x95700000) 240 /* an error such as lwarx to I/O controller space, 241 address matching DABR, eciwx, etc. */ 242 goto bad_area; 243 #endif /* CONFIG_6xx */ 244 #if defined(CONFIG_8xx) 245 /* The MPC8xx seems to always set 0x80000000, which is 246 * "undefined". Of those that can be set, this is the only 247 * one which seems bad. 248 */ 249 if (error_code & 0x10000000) 250 /* Guarded storage error. */ 251 goto bad_area; 252 #endif /* CONFIG_8xx */ 253 254 if (is_exec) { 255 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 256 /* protection fault */ 257 if (error_code & DSISR_PROTFAULT) 258 goto bad_area; 259 /* 260 * Allow execution from readable areas if the MMU does not 261 * provide separate controls over reading and executing. 262 */ 263 if (!(vma->vm_flags & VM_EXEC) && 264 (cpu_has_feature(CPU_FTR_NOEXECUTE) || 265 !(vma->vm_flags & (VM_READ | VM_WRITE)))) 266 goto bad_area; 267 #else 268 pte_t *ptep; 269 pmd_t *pmdp; 270 271 /* Since 4xx/Book-E supports per-page execute permission, 272 * we lazily flush dcache to icache. */ 273 ptep = NULL; 274 if (get_pteptr(mm, address, &ptep, &pmdp)) { 275 spinlock_t *ptl = pte_lockptr(mm, pmdp); 276 spin_lock(ptl); 277 if (pte_present(*ptep)) { 278 struct page *page = pte_page(*ptep); 279 280 if (!test_bit(PG_arch_1, &page->flags)) { 281 flush_dcache_icache_page(page); 282 set_bit(PG_arch_1, &page->flags); 283 } 284 pte_update(ptep, 0, _PAGE_HWEXEC | 285 _PAGE_ACCESSED); 286 _tlbie(address, mm->context.id); 287 pte_unmap_unlock(ptep, ptl); 288 up_read(&mm->mmap_sem); 289 return 0; 290 } 291 pte_unmap_unlock(ptep, ptl); 292 } 293 #endif 294 /* a write */ 295 } else if (is_write) { 296 if (!(vma->vm_flags & VM_WRITE)) 297 goto bad_area; 298 /* a read */ 299 } else { 300 /* protection fault */ 301 if (error_code & 0x08000000) 302 goto bad_area; 303 if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE))) 304 goto bad_area; 305 } 306 307 /* 308 * If for any reason at all we couldn't handle the fault, 309 * make sure we exit gracefully rather than endlessly redo 310 * the fault. 311 */ 312 survive: 313 ret = handle_mm_fault(mm, vma, address, is_write); 314 if (unlikely(ret & VM_FAULT_ERROR)) { 315 if (ret & VM_FAULT_OOM) 316 goto out_of_memory; 317 else if (ret & VM_FAULT_SIGBUS) 318 goto do_sigbus; 319 BUG(); 320 } 321 if (ret & VM_FAULT_MAJOR) 322 current->maj_flt++; 323 else 324 current->min_flt++; 325 up_read(&mm->mmap_sem); 326 return 0; 327 328 bad_area: 329 up_read(&mm->mmap_sem); 330 331 bad_area_nosemaphore: 332 /* User mode accesses cause a SIGSEGV */ 333 if (user_mode(regs)) { 334 _exception(SIGSEGV, regs, code, address); 335 return 0; 336 } 337 338 if (is_exec && (error_code & DSISR_PROTFAULT) 339 && printk_ratelimit()) 340 printk(KERN_CRIT "kernel tried to execute NX-protected" 341 " page (%lx) - exploit attempt? (uid: %d)\n", 342 address, current->uid); 343 344 return SIGSEGV; 345 346 /* 347 * We ran out of memory, or some other thing happened to us that made 348 * us unable to handle the page fault gracefully. 349 */ 350 out_of_memory: 351 up_read(&mm->mmap_sem); 352 if (is_global_init(current)) { 353 yield(); 354 down_read(&mm->mmap_sem); 355 goto survive; 356 } 357 printk("VM: killing process %s\n", current->comm); 358 if (user_mode(regs)) 359 do_group_exit(SIGKILL); 360 return SIGKILL; 361 362 do_sigbus: 363 up_read(&mm->mmap_sem); 364 if (user_mode(regs)) { 365 info.si_signo = SIGBUS; 366 info.si_errno = 0; 367 info.si_code = BUS_ADRERR; 368 info.si_addr = (void __user *)address; 369 force_sig_info(SIGBUS, &info, current); 370 return 0; 371 } 372 return SIGBUS; 373 } 374 375 /* 376 * bad_page_fault is called when we have a bad access from the kernel. 377 * It is called from the DSI and ISI handlers in head.S and from some 378 * of the procedures in traps.c. 379 */ 380 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 381 { 382 const struct exception_table_entry *entry; 383 384 /* Are we prepared to handle this fault? */ 385 if ((entry = search_exception_tables(regs->nip)) != NULL) { 386 regs->nip = entry->fixup; 387 return; 388 } 389 390 /* kernel has accessed a bad area */ 391 392 switch (regs->trap) { 393 case 0x300: 394 case 0x380: 395 printk(KERN_ALERT "Unable to handle kernel paging request for " 396 "data at address 0x%08lx\n", regs->dar); 397 break; 398 case 0x400: 399 case 0x480: 400 printk(KERN_ALERT "Unable to handle kernel paging request for " 401 "instruction fetch\n"); 402 break; 403 default: 404 printk(KERN_ALERT "Unable to handle kernel paging request for " 405 "unknown fault\n"); 406 break; 407 } 408 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 409 regs->nip); 410 411 die("Kernel access of bad area", regs, sig); 412 } 413