1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * fault.c: Page fault handlers for the Sparc. 4 * 5 * Copyright (C) 1995 David S. Miller (davem@caip.rutgers.edu) 6 * Copyright (C) 1996 Eddie C. Dost (ecd@skynet.be) 7 * Copyright (C) 1997 Jakub Jelinek (jj@sunsite.mff.cuni.cz) 8 */ 9 10 #include <asm/head.h> 11 12 #include <linux/string.h> 13 #include <linux/types.h> 14 #include <linux/sched.h> 15 #include <linux/ptrace.h> 16 #include <linux/mman.h> 17 #include <linux/threads.h> 18 #include <linux/kernel.h> 19 #include <linux/signal.h> 20 #include <linux/mm.h> 21 #include <linux/smp.h> 22 #include <linux/perf_event.h> 23 #include <linux/interrupt.h> 24 #include <linux/kdebug.h> 25 #include <linux/uaccess.h> 26 #include <linux/extable.h> 27 28 #include <asm/page.h> 29 #include <asm/openprom.h> 30 #include <asm/oplib.h> 31 #include <asm/setup.h> 32 #include <asm/smp.h> 33 #include <asm/traps.h> 34 35 #include "mm_32.h" 36 37 int show_unhandled_signals = 1; 38 39 static void __noreturn unhandled_fault(unsigned long address, 40 struct task_struct *tsk, 41 struct pt_regs *regs) 42 { 43 if ((unsigned long) address < PAGE_SIZE) { 44 printk(KERN_ALERT 45 "Unable to handle kernel NULL pointer dereference\n"); 46 } else { 47 printk(KERN_ALERT "Unable to handle kernel paging request at virtual address %08lx\n", 48 address); 49 } 50 printk(KERN_ALERT "tsk->{mm,active_mm}->context = %08lx\n", 51 (tsk->mm ? tsk->mm->context : tsk->active_mm->context)); 52 printk(KERN_ALERT "tsk->{mm,active_mm}->pgd = %08lx\n", 53 (tsk->mm ? (unsigned long) tsk->mm->pgd : 54 (unsigned long) tsk->active_mm->pgd)); 55 die_if_kernel("Oops", regs); 56 } 57 58 static inline void 59 show_signal_msg(struct pt_regs *regs, int sig, int code, 60 unsigned long address, struct task_struct *tsk) 61 { 62 if (!unhandled_signal(tsk, sig)) 63 return; 64 65 if (!printk_ratelimit()) 66 return; 67 68 printk("%s%s[%d]: segfault at %lx ip %px (rpc %px) sp %px error %x", 69 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 70 tsk->comm, task_pid_nr(tsk), address, 71 (void *)regs->pc, (void *)regs->u_regs[UREG_I7], 72 (void *)regs->u_regs[UREG_FP], code); 73 74 print_vma_addr(KERN_CONT " in ", regs->pc); 75 76 printk(KERN_CONT "\n"); 77 } 78 79 static void __do_fault_siginfo(int code, int sig, struct pt_regs *regs, 80 unsigned long addr) 81 { 82 if (unlikely(show_unhandled_signals)) 83 show_signal_msg(regs, sig, code, 84 addr, current); 85 86 force_sig_fault(sig, code, (void __user *) addr); 87 } 88 89 static unsigned long compute_si_addr(struct pt_regs *regs, int text_fault) 90 { 91 unsigned int insn; 92 93 if (text_fault) 94 return regs->pc; 95 96 if (regs->psr & PSR_PS) 97 insn = *(unsigned int *) regs->pc; 98 else 99 __get_user(insn, (unsigned int *) regs->pc); 100 101 return safe_compute_effective_address(regs, insn); 102 } 103 104 static noinline void do_fault_siginfo(int code, int sig, struct pt_regs *regs, 105 int text_fault) 106 { 107 unsigned long addr = compute_si_addr(regs, text_fault); 108 109 __do_fault_siginfo(code, sig, regs, addr); 110 } 111 112 asmlinkage void do_sparc_fault(struct pt_regs *regs, int text_fault, int write, 113 unsigned long address) 114 { 115 struct vm_area_struct *vma; 116 struct task_struct *tsk = current; 117 struct mm_struct *mm = tsk->mm; 118 int from_user = !(regs->psr & PSR_PS); 119 int code; 120 vm_fault_t fault; 121 unsigned int flags = FAULT_FLAG_DEFAULT; 122 123 if (text_fault) 124 address = regs->pc; 125 126 /* 127 * We fault-in kernel-space virtual memory on-demand. The 128 * 'reference' page table is init_mm.pgd. 129 * 130 * NOTE! We MUST NOT take any locks for this case. We may 131 * be in an interrupt or a critical region, and should 132 * only copy the information from the master page table, 133 * nothing more. 134 */ 135 code = SEGV_MAPERR; 136 if (address >= TASK_SIZE) 137 goto vmalloc_fault; 138 139 /* 140 * If we're in an interrupt or have no user 141 * context, we must not take the fault.. 142 */ 143 if (pagefault_disabled() || !mm) 144 goto no_context; 145 146 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 147 148 retry: 149 mmap_read_lock(mm); 150 151 if (!from_user && address >= PAGE_OFFSET) 152 goto bad_area; 153 154 vma = find_vma(mm, address); 155 if (!vma) 156 goto bad_area; 157 if (vma->vm_start <= address) 158 goto good_area; 159 if (!(vma->vm_flags & VM_GROWSDOWN)) 160 goto bad_area; 161 if (expand_stack(vma, address)) 162 goto bad_area; 163 /* 164 * Ok, we have a good vm_area for this memory access, so 165 * we can handle it.. 166 */ 167 good_area: 168 code = SEGV_ACCERR; 169 if (write) { 170 if (!(vma->vm_flags & VM_WRITE)) 171 goto bad_area; 172 } else { 173 /* Allow reads even for write-only mappings */ 174 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 175 goto bad_area; 176 } 177 178 if (from_user) 179 flags |= FAULT_FLAG_USER; 180 if (write) 181 flags |= FAULT_FLAG_WRITE; 182 183 /* 184 * If for any reason at all we couldn't handle the fault, 185 * make sure we exit gracefully rather than endlessly redo 186 * the fault. 187 */ 188 fault = handle_mm_fault(vma, address, flags, regs); 189 190 if (fault_signal_pending(fault, regs)) { 191 if (!from_user) 192 goto no_context; 193 return; 194 } 195 196 /* The fault is fully completed (including releasing mmap lock) */ 197 if (fault & VM_FAULT_COMPLETED) 198 return; 199 200 if (unlikely(fault & VM_FAULT_ERROR)) { 201 if (fault & VM_FAULT_OOM) 202 goto out_of_memory; 203 else if (fault & VM_FAULT_SIGSEGV) 204 goto bad_area; 205 else if (fault & VM_FAULT_SIGBUS) 206 goto do_sigbus; 207 BUG(); 208 } 209 210 if (fault & VM_FAULT_RETRY) { 211 flags |= FAULT_FLAG_TRIED; 212 213 /* No need to mmap_read_unlock(mm) as we would 214 * have already released it in __lock_page_or_retry 215 * in mm/filemap.c. 216 */ 217 218 goto retry; 219 } 220 221 mmap_read_unlock(mm); 222 return; 223 224 /* 225 * Something tried to access memory that isn't in our memory map.. 226 * Fix it, but check if it's kernel or user first.. 227 */ 228 bad_area: 229 mmap_read_unlock(mm); 230 231 bad_area_nosemaphore: 232 /* User mode accesses just cause a SIGSEGV */ 233 if (from_user) { 234 do_fault_siginfo(code, SIGSEGV, regs, text_fault); 235 return; 236 } 237 238 /* Is this in ex_table? */ 239 no_context: 240 if (!from_user) { 241 const struct exception_table_entry *entry; 242 243 entry = search_exception_tables(regs->pc); 244 #ifdef DEBUG_EXCEPTIONS 245 printk("Exception: PC<%08lx> faddr<%08lx>\n", 246 regs->pc, address); 247 printk("EX_TABLE: insn<%08lx> fixup<%08x>\n", 248 regs->pc, entry->fixup); 249 #endif 250 regs->pc = entry->fixup; 251 regs->npc = regs->pc + 4; 252 return; 253 } 254 255 unhandled_fault(address, tsk, regs); 256 257 /* 258 * We ran out of memory, or some other thing happened to us that made 259 * us unable to handle the page fault gracefully. 260 */ 261 out_of_memory: 262 mmap_read_unlock(mm); 263 if (from_user) { 264 pagefault_out_of_memory(); 265 return; 266 } 267 goto no_context; 268 269 do_sigbus: 270 mmap_read_unlock(mm); 271 do_fault_siginfo(BUS_ADRERR, SIGBUS, regs, text_fault); 272 if (!from_user) 273 goto no_context; 274 275 vmalloc_fault: 276 { 277 /* 278 * Synchronize this task's top level page-table 279 * with the 'reference' page table. 280 */ 281 int offset = pgd_index(address); 282 pgd_t *pgd, *pgd_k; 283 p4d_t *p4d, *p4d_k; 284 pud_t *pud, *pud_k; 285 pmd_t *pmd, *pmd_k; 286 287 pgd = tsk->active_mm->pgd + offset; 288 pgd_k = init_mm.pgd + offset; 289 290 if (!pgd_present(*pgd)) { 291 if (!pgd_present(*pgd_k)) 292 goto bad_area_nosemaphore; 293 pgd_val(*pgd) = pgd_val(*pgd_k); 294 return; 295 } 296 297 p4d = p4d_offset(pgd, address); 298 pud = pud_offset(p4d, address); 299 pmd = pmd_offset(pud, address); 300 301 p4d_k = p4d_offset(pgd_k, address); 302 pud_k = pud_offset(p4d_k, address); 303 pmd_k = pmd_offset(pud_k, address); 304 305 if (pmd_present(*pmd) || !pmd_present(*pmd_k)) 306 goto bad_area_nosemaphore; 307 308 *pmd = *pmd_k; 309 return; 310 } 311 } 312 313 /* This always deals with user addresses. */ 314 static void force_user_fault(unsigned long address, int write) 315 { 316 struct vm_area_struct *vma; 317 struct task_struct *tsk = current; 318 struct mm_struct *mm = tsk->mm; 319 unsigned int flags = FAULT_FLAG_USER; 320 int code; 321 322 code = SEGV_MAPERR; 323 324 mmap_read_lock(mm); 325 vma = find_vma(mm, address); 326 if (!vma) 327 goto bad_area; 328 if (vma->vm_start <= address) 329 goto good_area; 330 if (!(vma->vm_flags & VM_GROWSDOWN)) 331 goto bad_area; 332 if (expand_stack(vma, address)) 333 goto bad_area; 334 good_area: 335 code = SEGV_ACCERR; 336 if (write) { 337 if (!(vma->vm_flags & VM_WRITE)) 338 goto bad_area; 339 flags |= FAULT_FLAG_WRITE; 340 } else { 341 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 342 goto bad_area; 343 } 344 switch (handle_mm_fault(vma, address, flags, NULL)) { 345 case VM_FAULT_SIGBUS: 346 case VM_FAULT_OOM: 347 goto do_sigbus; 348 } 349 mmap_read_unlock(mm); 350 return; 351 bad_area: 352 mmap_read_unlock(mm); 353 __do_fault_siginfo(code, SIGSEGV, tsk->thread.kregs, address); 354 return; 355 356 do_sigbus: 357 mmap_read_unlock(mm); 358 __do_fault_siginfo(BUS_ADRERR, SIGBUS, tsk->thread.kregs, address); 359 } 360 361 static void check_stack_aligned(unsigned long sp) 362 { 363 if (sp & 0x7UL) 364 force_sig(SIGILL); 365 } 366 367 void window_overflow_fault(void) 368 { 369 unsigned long sp; 370 371 sp = current_thread_info()->rwbuf_stkptrs[0]; 372 if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK)) 373 force_user_fault(sp + 0x38, 1); 374 force_user_fault(sp, 1); 375 376 check_stack_aligned(sp); 377 } 378 379 void window_underflow_fault(unsigned long sp) 380 { 381 if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK)) 382 force_user_fault(sp + 0x38, 0); 383 force_user_fault(sp, 0); 384 385 check_stack_aligned(sp); 386 } 387 388 void window_ret_fault(struct pt_regs *regs) 389 { 390 unsigned long sp; 391 392 sp = regs->u_regs[UREG_FP]; 393 if (((sp + 0x38) & PAGE_MASK) != (sp & PAGE_MASK)) 394 force_user_fault(sp + 0x38, 0); 395 force_user_fault(sp, 0); 396 397 check_stack_aligned(sp); 398 } 399