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 error_code) 85 { 86 siginfo_t info; 87 88 if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code, 89 11, SIGSEGV) == NOTIFY_STOP) 90 return; 91 92 if (debugger_dabr_match(regs)) 93 return; 94 95 /* Clear the DABR */ 96 set_dabr(0); 97 98 /* Deliver the signal to userspace */ 99 info.si_signo = SIGTRAP; 100 info.si_errno = 0; 101 info.si_code = TRAP_HWBKPT; 102 info.si_addr = (void __user *)regs->nip; 103 force_sig_info(SIGTRAP, &info, current); 104 } 105 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 106 107 /* 108 * For 600- and 800-family processors, the error_code parameter is DSISR 109 * for a data fault, SRR1 for an instruction fault. For 400-family processors 110 * the error_code parameter is ESR for a data fault, 0 for an instruction 111 * fault. 112 * For 64-bit processors, the error_code parameter is 113 * - DSISR for a non-SLB data access fault, 114 * - SRR1 & 0x08000000 for a non-SLB instruction access fault 115 * - 0 any SLB fault. 116 * 117 * The return value is 0 if the fault was handled, or the signal 118 * number if this is a kernel fault that can't be handled here. 119 */ 120 int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address, 121 unsigned long error_code) 122 { 123 struct vm_area_struct * vma; 124 struct mm_struct *mm = current->mm; 125 siginfo_t info; 126 int code = SEGV_MAPERR; 127 int is_write = 0; 128 int trap = TRAP(regs); 129 int is_exec = trap == 0x400; 130 131 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 132 /* 133 * Fortunately the bit assignments in SRR1 for an instruction 134 * fault and DSISR for a data fault are mostly the same for the 135 * bits we are interested in. But there are some bits which 136 * indicate errors in DSISR but can validly be set in SRR1. 137 */ 138 if (trap == 0x400) 139 error_code &= 0x48200000; 140 else 141 is_write = error_code & DSISR_ISSTORE; 142 #else 143 is_write = error_code & ESR_DST; 144 #endif /* CONFIG_4xx || CONFIG_BOOKE */ 145 146 if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code, 147 11, SIGSEGV) == NOTIFY_STOP) 148 return 0; 149 150 if (trap == 0x300) { 151 if (debugger_fault_handler(regs)) 152 return 0; 153 } 154 155 /* On a kernel SLB miss we can only check for a valid exception entry */ 156 if (!user_mode(regs) && (address >= TASK_SIZE)) 157 return SIGSEGV; 158 159 #if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE)) 160 if (error_code & DSISR_DABRMATCH) { 161 /* DABR match */ 162 do_dabr(regs, error_code); 163 return 0; 164 } 165 #endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/ 166 167 if (in_atomic() || mm == NULL) { 168 if (!user_mode(regs)) 169 return SIGSEGV; 170 /* in_atomic() in user mode is really bad, 171 as is current->mm == NULL. */ 172 printk(KERN_EMERG "Page fault in user mode with" 173 "in_atomic() = %d mm = %p\n", in_atomic(), mm); 174 printk(KERN_EMERG "NIP = %lx MSR = %lx\n", 175 regs->nip, regs->msr); 176 die("Weird page fault", regs, SIGSEGV); 177 } 178 179 /* When running in the kernel we expect faults to occur only to 180 * addresses in user space. All other faults represent errors in the 181 * kernel and should generate an OOPS. Unfortunatly, in the case of an 182 * erroneous fault occuring in a code path which already holds mmap_sem 183 * we will deadlock attempting to validate the fault against the 184 * address space. Luckily the kernel only validly references user 185 * space from well defined areas of code, which are listed in the 186 * exceptions table. 187 * 188 * As the vast majority of faults will be valid we will only perform 189 * the source reference check when there is a possibilty of a deadlock. 190 * Attempt to lock the address space, if we cannot we then validate the 191 * source. If this is invalid we can skip the address space check, 192 * thus avoiding the deadlock. 193 */ 194 if (!down_read_trylock(&mm->mmap_sem)) { 195 if (!user_mode(regs) && !search_exception_tables(regs->nip)) 196 goto bad_area_nosemaphore; 197 198 down_read(&mm->mmap_sem); 199 } 200 201 vma = find_vma(mm, address); 202 if (!vma) 203 goto bad_area; 204 if (vma->vm_start <= address) 205 goto good_area; 206 if (!(vma->vm_flags & VM_GROWSDOWN)) 207 goto bad_area; 208 209 /* 210 * N.B. The POWER/Open ABI allows programs to access up to 211 * 288 bytes below the stack pointer. 212 * The kernel signal delivery code writes up to about 1.5kB 213 * below the stack pointer (r1) before decrementing it. 214 * The exec code can write slightly over 640kB to the stack 215 * before setting the user r1. Thus we allow the stack to 216 * expand to 1MB without further checks. 217 */ 218 if (address + 0x100000 < vma->vm_end) { 219 /* get user regs even if this fault is in kernel mode */ 220 struct pt_regs *uregs = current->thread.regs; 221 if (uregs == NULL) 222 goto bad_area; 223 224 /* 225 * A user-mode access to an address a long way below 226 * the stack pointer is only valid if the instruction 227 * is one which would update the stack pointer to the 228 * address accessed if the instruction completed, 229 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 230 * (or the byte, halfword, float or double forms). 231 * 232 * If we don't check this then any write to the area 233 * between the last mapped region and the stack will 234 * expand the stack rather than segfaulting. 235 */ 236 if (address + 2048 < uregs->gpr[1] 237 && (!user_mode(regs) || !store_updates_sp(regs))) 238 goto bad_area; 239 } 240 if (expand_stack(vma, address)) 241 goto bad_area; 242 243 good_area: 244 code = SEGV_ACCERR; 245 #if defined(CONFIG_6xx) 246 if (error_code & 0x95700000) 247 /* an error such as lwarx to I/O controller space, 248 address matching DABR, eciwx, etc. */ 249 goto bad_area; 250 #endif /* CONFIG_6xx */ 251 #if defined(CONFIG_8xx) 252 /* The MPC8xx seems to always set 0x80000000, which is 253 * "undefined". Of those that can be set, this is the only 254 * one which seems bad. 255 */ 256 if (error_code & 0x10000000) 257 /* Guarded storage error. */ 258 goto bad_area; 259 #endif /* CONFIG_8xx */ 260 261 if (is_exec) { 262 #ifdef CONFIG_PPC64 263 /* protection fault */ 264 if (error_code & DSISR_PROTFAULT) 265 goto bad_area; 266 if (!(vma->vm_flags & VM_EXEC)) 267 goto bad_area; 268 #endif 269 #if defined(CONFIG_4xx) || defined(CONFIG_BOOKE) 270 pte_t *ptep; 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) && pte_present(*ptep)) { 276 struct page *page = pte_page(*ptep); 277 278 if (! test_bit(PG_arch_1, &page->flags)) { 279 flush_dcache_icache_page(page); 280 set_bit(PG_arch_1, &page->flags); 281 } 282 pte_update(ptep, 0, _PAGE_HWEXEC); 283 _tlbie(address); 284 pte_unmap(ptep); 285 up_read(&mm->mmap_sem); 286 return 0; 287 } 288 if (ptep != NULL) 289 pte_unmap(ptep); 290 #endif 291 /* a write */ 292 } else if (is_write) { 293 if (!(vma->vm_flags & VM_WRITE)) 294 goto bad_area; 295 /* a read */ 296 } else { 297 /* protection fault */ 298 if (error_code & 0x08000000) 299 goto bad_area; 300 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 301 goto bad_area; 302 } 303 304 /* 305 * If for any reason at all we couldn't handle the fault, 306 * make sure we exit gracefully rather than endlessly redo 307 * the fault. 308 */ 309 survive: 310 switch (handle_mm_fault(mm, vma, address, is_write)) { 311 312 case VM_FAULT_MINOR: 313 current->min_flt++; 314 break; 315 case VM_FAULT_MAJOR: 316 current->maj_flt++; 317 break; 318 case VM_FAULT_SIGBUS: 319 goto do_sigbus; 320 case VM_FAULT_OOM: 321 goto out_of_memory; 322 default: 323 BUG(); 324 } 325 326 up_read(&mm->mmap_sem); 327 return 0; 328 329 bad_area: 330 up_read(&mm->mmap_sem); 331 332 bad_area_nosemaphore: 333 /* User mode accesses cause a SIGSEGV */ 334 if (user_mode(regs)) { 335 _exception(SIGSEGV, regs, code, address); 336 return 0; 337 } 338 339 if (is_exec && (error_code & DSISR_PROTFAULT) 340 && printk_ratelimit()) 341 printk(KERN_CRIT "kernel tried to execute NX-protected" 342 " page (%lx) - exploit attempt? (uid: %d)\n", 343 address, current->uid); 344 345 return SIGSEGV; 346 347 /* 348 * We ran out of memory, or some other thing happened to us that made 349 * us unable to handle the page fault gracefully. 350 */ 351 out_of_memory: 352 up_read(&mm->mmap_sem); 353 if (current->pid == 1) { 354 yield(); 355 down_read(&mm->mmap_sem); 356 goto survive; 357 } 358 printk("VM: killing process %s\n", current->comm); 359 if (user_mode(regs)) 360 do_exit(SIGKILL); 361 return SIGKILL; 362 363 do_sigbus: 364 up_read(&mm->mmap_sem); 365 if (user_mode(regs)) { 366 info.si_signo = SIGBUS; 367 info.si_errno = 0; 368 info.si_code = BUS_ADRERR; 369 info.si_addr = (void __user *)address; 370 force_sig_info(SIGBUS, &info, current); 371 return 0; 372 } 373 return SIGBUS; 374 } 375 376 /* 377 * bad_page_fault is called when we have a bad access from the kernel. 378 * It is called from the DSI and ISI handlers in head.S and from some 379 * of the procedures in traps.c. 380 */ 381 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 382 { 383 const struct exception_table_entry *entry; 384 385 /* Are we prepared to handle this fault? */ 386 if ((entry = search_exception_tables(regs->nip)) != NULL) { 387 regs->nip = entry->fixup; 388 return; 389 } 390 391 /* kernel has accessed a bad area */ 392 393 printk(KERN_ALERT "Unable to handle kernel paging request for "); 394 switch (regs->trap) { 395 case 0x300: 396 case 0x380: 397 printk("data at address 0x%08lx\n", regs->dar); 398 break; 399 case 0x400: 400 case 0x480: 401 printk("instruction fetch\n"); 402 break; 403 default: 404 printk("unknown fault\n"); 405 } 406 printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n", 407 regs->nip); 408 409 die("Kernel access of bad area", regs, sig); 410 } 411