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/config.h> 19 #include <linux/signal.h> 20 #include <linux/sched.h> 21 #include <linux/kernel.h> 22 #include <linux/errno.h> 23 #include <linux/string.h> 24 #include <linux/types.h> 25 #include <linux/ptrace.h> 26 #include <linux/mman.h> 27 #include <linux/mm.h> 28 #include <linux/interrupt.h> 29 #include <linux/highmem.h> 30 #include <linux/module.h> 31 #include <linux/kprobes.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/kdebug.h> 41 #include <asm/siginfo.h> 42 43 /* 44 * Check whether the instruction at regs->nip is a store using 45 * an update addressing form which will update r1. 46 */ 47 static int store_updates_sp(struct pt_regs *regs) 48 { 49 unsigned int inst; 50 51 if (get_user(inst, (unsigned int __user *)regs->nip)) 52 return 0; 53 /* check for 1 in the rA field */ 54 if (((inst >> 16) & 0x1f) != 1) 55 return 0; 56 /* check major opcode */ 57 switch (inst >> 26) { 58 case 37: /* stwu */ 59 case 39: /* stbu */ 60 case 45: /* sthu */ 61 case 53: /* stfsu */ 62 case 55: /* stfdu */ 63 return 1; 64 case 62: /* std or stdu */ 65 return (inst & 3) == 1; 66 case 31: 67 /* check minor opcode */ 68 switch ((inst >> 1) & 0x3ff) { 69 case 181: /* stdux */ 70 case 183: /* stwux */ 71 case 247: /* stbux */ 72 case 439: /* sthux */ 73 case 695: /* stfsux */ 74 case 759: /* stfdux */ 75 return 1; 76 } 77 } 78 return 0; 79 } 80 81 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 82 static void do_dabr(struct pt_regs *regs, unsigned long address, 83 unsigned long error_code) 84 { 85 siginfo_t info; 86 87 if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code, 88 11, SIGSEGV) == NOTIFY_STOP) 89 return; 90 91 if (debugger_dabr_match(regs)) 92 return; 93 94 /* Clear the DABR */ 95 set_dabr(0); 96 97 /* Deliver the signal to userspace */ 98 info.si_signo = SIGTRAP; 99 info.si_errno = 0; 100 info.si_code = TRAP_HWBKPT; 101 info.si_addr = (void __user *)address; 102 force_sig_info(SIGTRAP, &info, current); 103 } 104 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 105 106 /* 107 * For 600- and 800-family processors, the error_code parameter is DSISR 108 * for a data fault, SRR1 for an instruction fault. For 400-family processors 109 * the error_code parameter is ESR for a data fault, 0 for an instruction 110 * fault. 111 * For 64-bit processors, the error_code parameter is 112 * - DSISR for a non-SLB data access fault, 113 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 114 * - 0 any SLB fault. 115 * 116 * The return value is 0 if the fault was handled, or the signal 117 * number if this is a kernel fault that can't be handled here. 118 */ 119 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 120 unsigned long error_code) 121 { 122 struct vm_area_struct * vma; 123 struct mm_struct *mm = current->mm; 124 siginfo_t info; 125 int code = SEGV_MAPERR; 126 int is_write = 0; 127 int trap = TRAP(regs); 128 int is_exec = trap == 0x400; 129 130 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 131 /* 132 * Fortunately the bit assignments in SRR1 for an instruction 133 * fault and DSISR for a data fault are mostly the same for the 134 * bits we are interested in. But there are some bits which 135 * indicate errors in DSISR but can validly be set in SRR1. 136 */ 137 if (trap == 0x400) 138 error_code &= 0x48200000; 139 else 140 is_write = error_code & DSISR_ISSTORE; 141 #else 142 is_write = error_code & ESR_DST; 143 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 144 145 if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code, 146 11, SIGSEGV) == NOTIFY_STOP) 147 return 0; 148 149 if (trap == 0x300) { 150 if (debugger_fault_handler(regs)) 151 return 0; 152 } 153 154 /* On a kernel SLB miss we can only check for a valid exception entry */ 155 if (!user_mode(regs) && (address >= TASK_SIZE)) 156 return SIGSEGV; 157 158 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 159 if (error_code & DSISR_DABRMATCH) { 160 /* DABR match */ 161 do_dabr(regs, address, error_code); 162 return 0; 163 } 164 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 165 166 if (in_atomic() || mm == NULL) { 167 if (!user_mode(regs)) 168 return SIGSEGV; 169 /* in_atomic() in user mode is really bad, 170 as is current->mm == NULL. */ 171 printk(KERN_EMERG "Page fault in user mode with" 172 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 173 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 174 regs->nip, regs->msr); 175 die("Weird page fault", regs, SIGSEGV); 176 } 177 178 /* When running in the kernel we expect faults to occur only to 179 * addresses in user space. All other faults represent errors in the 180 * kernel and should generate an OOPS. Unfortunately, in the case of an 181 * erroneous fault occurring in a code path which already holds mmap_sem 182 * we will deadlock attempting to validate the fault against the 183 * address space. Luckily the kernel only validly references user 184 * space from well defined areas of code, which are listed in the 185 * exceptions table. 186 * 187 * As the vast majority of faults will be valid we will only perform 188 * the source reference check when there is a possibility of a deadlock. 189 * Attempt to lock the address space, if we cannot we then validate the 190 * source. If this is invalid we can skip the address space check, 191 * thus avoiding the deadlock. 192 */ 193 if (!down_read_trylock(&mm->mmap_sem)) { 194 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 195 goto bad_area_nosemaphore; 196 197 down_read(&mm->mmap_sem); 198 } 199 200 vma = find_vma(mm, address); 201 if (!vma) 202 goto bad_area; 203 if (vma->vm_start <= address) 204 goto good_area; 205 if (!(vma->vm_flags & VM_GROWSDOWN)) 206 goto bad_area; 207 208 /* 209 * N.B. The POWER/Open ABI allows programs to access up to 210 * 288 bytes below the stack pointer. 211 * The kernel signal delivery code writes up to about 1.5kB 212 * below the stack pointer (r1) before decrementing it. 213 * The exec code can write slightly over 640kB to the stack 214 * before setting the user r1. Thus we allow the stack to 215 * expand to 1MB without further checks. 216 */ 217 if (address + 0x100000 < vma->vm_end) { 218 /* get user regs even if this fault is in kernel mode */ 219 struct pt_regs *uregs = current->thread.regs; 220 if (uregs == NULL) 221 goto bad_area; 222 223 /* 224 * A user-mode access to an address a long way below 225 * the stack pointer is only valid if the instruction 226 * is one which would update the stack pointer to the 227 * address accessed if the instruction completed, 228 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 229 * (or the byte, halfword, float or double forms). 230 * 231 * If we don't check this then any write to the area 232 * between the last mapped region and the stack will 233 * expand the stack rather than segfaulting. 234 */ 235 if (address + 2048 < uregs->gpr[1] 236 && (!user_mode(regs) || !store_updates_sp(regs))) 237 goto bad_area; 238 } 239 if (expand_stack(vma, address)) 240 goto bad_area; 241 242 good_area: 243 code = SEGV_ACCERR; 244 #if defined(CONFIG_6xx) 245 if (error_code & 0x95700000) 246 /* an error such as lwarx to I/O controller space, 247 address matching DABR, eciwx, etc. */ 248 goto bad_area; 249 #endif /* CONFIG_6xx */ 250 #if defined(CONFIG_8xx) 251 /* The MPC8xx seems to always set 0x80000000, which is 252 * "undefined". Of those that can be set, this is the only 253 * one which seems bad. 254 */ 255 if (error_code & 0x10000000) 256 /* Guarded storage error. */ 257 goto bad_area; 258 #endif /* CONFIG_8xx */ 259 260 if (is_exec) { 261 #ifdef CONFIG_PPC64 262 /* protection fault */ 263 if (error_code & DSISR_PROTFAULT) 264 goto bad_area; 265 if (!(vma->vm_flags & VM_EXEC)) 266 goto bad_area; 267 #endif 268 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) 269 pte_t *ptep; 270 pmd_t *pmdp; 271 272 /* Since 4xx/Book-E supports per-page execute permission, 273 * we lazily flush dcache to icache. */ 274 ptep = NULL; 275 if (get_pteptr(mm, address, &ptep, &pmdp)) { 276 spinlock_t *ptl = pte_lockptr(mm, pmdp); 277 spin_lock(ptl); 278 if (pte_present(*ptep)) { 279 struct page *page = pte_page(*ptep); 280 281 if (!test_bit(PG_arch_1, &page->flags)) { 282 flush_dcache_icache_page(page); 283 set_bit(PG_arch_1, &page->flags); 284 } 285 pte_update(ptep, 0, _PAGE_HWEXEC); 286 _tlbie(address); 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))) 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 switch (handle_mm_fault(mm, vma, address, is_write)) { 314 315 case VM_FAULT_MINOR: 316 current->min_flt++; 317 break; 318 case VM_FAULT_MAJOR: 319 current->maj_flt++; 320 break; 321 case VM_FAULT_SIGBUS: 322 goto do_sigbus; 323 case VM_FAULT_OOM: 324 goto out_of_memory; 325 default: 326 BUG(); 327 } 328 329 up_read(&mm->mmap_sem); 330 return 0; 331 332 bad_area: 333 up_read(&mm->mmap_sem); 334 335 bad_area_nosemaphore: 336 /* User mode accesses cause a SIGSEGV */ 337 if (user_mode(regs)) { 338 _exception(SIGSEGV, regs, code, address); 339 return 0; 340 } 341 342 if (is_exec && (error_code & DSISR_PROTFAULT) 343 && printk_ratelimit()) 344 printk(KERN_CRIT "kernel tried to execute NX-protected" 345 " page (%lx) - exploit attempt? (uid: %d)\n", 346 address, current->uid); 347 348 return SIGSEGV; 349 350 /* 351 * We ran out of memory, or some other thing happened to us that made 352 * us unable to handle the page fault gracefully. 353 */ 354 out_of_memory: 355 up_read(&mm->mmap_sem); 356 if (current->pid == 1) { 357 yield(); 358 down_read(&mm->mmap_sem); 359 goto survive; 360 } 361 printk("VM: killing process %s\n", current->comm); 362 if (user_mode(regs)) 363 do_exit(SIGKILL); 364 return SIGKILL; 365 366 do_sigbus: 367 up_read(&mm->mmap_sem); 368 if (user_mode(regs)) { 369 info.si_signo = SIGBUS; 370 info.si_errno = 0; 371 info.si_code = BUS_ADRERR; 372 info.si_addr = (void __user *)address; 373 force_sig_info(SIGBUS, &info, current); 374 return 0; 375 } 376 return SIGBUS; 377 } 378 379 /* 380 * bad_page_fault is called when we have a bad access from the kernel. 381 * It is called from the DSI and ISI handlers in head.S and from some 382 * of the procedures in traps.c. 383 */ 384 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 385 { 386 const struct exception_table_entry *entry; 387 388 /* Are we prepared to handle this fault? */ 389 if ((entry = search_exception_tables(regs->nip)) != NULL) { 390 regs->nip = entry->fixup; 391 return; 392 } 393 394 /* kernel has accessed a bad area */ 395 396 printk(KERN_ALERT "Unable to handle kernel paging request for "); 397 switch (regs->trap) { 398 case 0x300: 399 case 0x380: 400 printk("data at address 0x%08lx\n", regs->dar); 401 break; 402 case 0x400: 403 case 0x480: 404 printk("instruction fetch\n"); 405 break; 406 default: 407 printk("unknown fault\n"); 408 } 409 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 410 regs->nip); 411 412 die("Kernel access of bad area", regs, sig); 413 } 414