1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * OpenRISC fault.c 4 * 5 * Linux architectural port borrowing liberally from similar works of 6 * others. All original copyrights apply as per the original source 7 * declaration. 8 * 9 * Modifications for the OpenRISC architecture: 10 * Copyright (C) 2003 Matjaz Breskvar <phoenix@bsemi.com> 11 * Copyright (C) 2010-2011 Jonas Bonn <jonas@southpole.se> 12 */ 13 14 #include <linux/mm.h> 15 #include <linux/interrupt.h> 16 #include <linux/extable.h> 17 #include <linux/sched/signal.h> 18 #include <linux/perf_event.h> 19 20 #include <linux/uaccess.h> 21 #include <asm/siginfo.h> 22 #include <asm/signal.h> 23 24 #define NUM_TLB_ENTRIES 64 25 #define TLB_OFFSET(add) (((add) >> PAGE_SHIFT) & (NUM_TLB_ENTRIES-1)) 26 27 unsigned long pte_misses; /* updated by do_page_fault() */ 28 unsigned long pte_errors; /* updated by do_page_fault() */ 29 30 /* __PHX__ :: - check the vmalloc_fault in do_page_fault() 31 * - also look into include/asm/mmu_context.h 32 */ 33 volatile pgd_t *current_pgd[NR_CPUS]; 34 35 extern void __noreturn die(char *, struct pt_regs *, long); 36 37 /* 38 * This routine handles page faults. It determines the address, 39 * and the problem, and then passes it off to one of the appropriate 40 * routines. 41 * 42 * If this routine detects a bad access, it returns 1, otherwise it 43 * returns 0. 44 */ 45 46 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long address, 47 unsigned long vector, int write_acc) 48 { 49 struct task_struct *tsk; 50 struct mm_struct *mm; 51 struct vm_area_struct *vma; 52 int si_code; 53 vm_fault_t fault; 54 unsigned int flags = FAULT_FLAG_DEFAULT; 55 56 tsk = current; 57 58 /* 59 * We fault-in kernel-space virtual memory on-demand. The 60 * 'reference' page table is init_mm.pgd. 61 * 62 * NOTE! We MUST NOT take any locks for this case. We may 63 * be in an interrupt or a critical region, and should 64 * only copy the information from the master page table, 65 * nothing more. 66 * 67 * NOTE2: This is done so that, when updating the vmalloc 68 * mappings we don't have to walk all processes pgdirs and 69 * add the high mappings all at once. Instead we do it as they 70 * are used. However vmalloc'ed page entries have the PAGE_GLOBAL 71 * bit set so sometimes the TLB can use a lingering entry. 72 * 73 * This verifies that the fault happens in kernel space 74 * and that the fault was not a protection error. 75 */ 76 77 if (address >= VMALLOC_START && 78 (vector != 0x300 && vector != 0x400) && 79 !user_mode(regs)) 80 goto vmalloc_fault; 81 82 /* If exceptions were enabled, we can reenable them here */ 83 if (user_mode(regs)) { 84 /* Exception was in userspace: reenable interrupts */ 85 local_irq_enable(); 86 flags |= FAULT_FLAG_USER; 87 } else { 88 /* If exception was in a syscall, then IRQ's may have 89 * been enabled or disabled. If they were enabled, 90 * reenable them. 91 */ 92 if (regs->sr && (SPR_SR_IEE | SPR_SR_TEE)) 93 local_irq_enable(); 94 } 95 96 mm = tsk->mm; 97 si_code = SEGV_MAPERR; 98 99 /* 100 * If we're in an interrupt or have no user 101 * context, we must not take the fault.. 102 */ 103 104 if (in_interrupt() || !mm) 105 goto no_context; 106 107 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 108 109 retry: 110 mmap_read_lock(mm); 111 vma = find_vma(mm, address); 112 113 if (!vma) 114 goto bad_area; 115 116 if (vma->vm_start <= address) 117 goto good_area; 118 119 if (!(vma->vm_flags & VM_GROWSDOWN)) 120 goto bad_area; 121 122 if (user_mode(regs)) { 123 /* 124 * accessing the stack below usp is always a bug. 125 * we get page-aligned addresses so we can only check 126 * if we're within a page from usp, but that might be 127 * enough to catch brutal errors at least. 128 */ 129 if (address + PAGE_SIZE < regs->sp) 130 goto bad_area; 131 } 132 if (expand_stack(vma, address)) 133 goto bad_area; 134 135 /* 136 * Ok, we have a good vm_area for this memory access, so 137 * we can handle it.. 138 */ 139 140 good_area: 141 si_code = SEGV_ACCERR; 142 143 /* first do some preliminary protection checks */ 144 145 if (write_acc) { 146 if (!(vma->vm_flags & VM_WRITE)) 147 goto bad_area; 148 flags |= FAULT_FLAG_WRITE; 149 } else { 150 /* not present */ 151 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 152 goto bad_area; 153 } 154 155 /* are we trying to execute nonexecutable area */ 156 if ((vector == 0x400) && !(vma->vm_page_prot.pgprot & _PAGE_EXEC)) 157 goto bad_area; 158 159 /* 160 * If for any reason at all we couldn't handle the fault, 161 * make sure we exit gracefully rather than endlessly redo 162 * the fault. 163 */ 164 165 fault = handle_mm_fault(vma, address, flags, regs); 166 167 if (fault_signal_pending(fault, regs)) 168 return; 169 170 if (unlikely(fault & VM_FAULT_ERROR)) { 171 if (fault & VM_FAULT_OOM) 172 goto out_of_memory; 173 else if (fault & VM_FAULT_SIGSEGV) 174 goto bad_area; 175 else if (fault & VM_FAULT_SIGBUS) 176 goto do_sigbus; 177 BUG(); 178 } 179 180 if (flags & FAULT_FLAG_ALLOW_RETRY) { 181 /*RGD modeled on Cris */ 182 if (fault & VM_FAULT_RETRY) { 183 flags |= FAULT_FLAG_TRIED; 184 185 /* No need to mmap_read_unlock(mm) as we would 186 * have already released it in __lock_page_or_retry 187 * in mm/filemap.c. 188 */ 189 190 goto retry; 191 } 192 } 193 194 mmap_read_unlock(mm); 195 return; 196 197 /* 198 * Something tried to access memory that isn't in our memory map.. 199 * Fix it, but check if it's kernel or user first.. 200 */ 201 202 bad_area: 203 mmap_read_unlock(mm); 204 205 bad_area_nosemaphore: 206 207 /* User mode accesses just cause a SIGSEGV */ 208 209 if (user_mode(regs)) { 210 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 211 return; 212 } 213 214 no_context: 215 216 /* Are we prepared to handle this kernel fault? 217 * 218 * (The kernel has valid exception-points in the source 219 * when it acesses user-memory. When it fails in one 220 * of those points, we find it in a table and do a jump 221 * to some fixup code that loads an appropriate error 222 * code) 223 */ 224 225 { 226 const struct exception_table_entry *entry; 227 228 __asm__ __volatile__("l.nop 42"); 229 230 if ((entry = search_exception_tables(regs->pc)) != NULL) { 231 /* Adjust the instruction pointer in the stackframe */ 232 regs->pc = entry->fixup; 233 return; 234 } 235 } 236 237 /* 238 * Oops. The kernel tried to access some bad page. We'll have to 239 * terminate things with extreme prejudice. 240 */ 241 242 if ((unsigned long)(address) < PAGE_SIZE) 243 printk(KERN_ALERT 244 "Unable to handle kernel NULL pointer dereference"); 245 else 246 printk(KERN_ALERT "Unable to handle kernel access"); 247 printk(" at virtual address 0x%08lx\n", address); 248 249 die("Oops", regs, write_acc); 250 251 /* 252 * We ran out of memory, or some other thing happened to us that made 253 * us unable to handle the page fault gracefully. 254 */ 255 256 out_of_memory: 257 __asm__ __volatile__("l.nop 42"); 258 __asm__ __volatile__("l.nop 1"); 259 260 mmap_read_unlock(mm); 261 if (!user_mode(regs)) 262 goto no_context; 263 pagefault_out_of_memory(); 264 return; 265 266 do_sigbus: 267 mmap_read_unlock(mm); 268 269 /* 270 * Send a sigbus, regardless of whether we were in kernel 271 * or user mode. 272 */ 273 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 274 275 /* Kernel mode? Handle exceptions or die */ 276 if (!user_mode(regs)) 277 goto no_context; 278 return; 279 280 vmalloc_fault: 281 { 282 /* 283 * Synchronize this task's top level page-table 284 * with the 'reference' page table. 285 * 286 * Use current_pgd instead of tsk->active_mm->pgd 287 * since the latter might be unavailable if this 288 * code is executed in a misfortunately run irq 289 * (like inside schedule() between switch_mm and 290 * switch_to...). 291 */ 292 293 int offset = pgd_index(address); 294 pgd_t *pgd, *pgd_k; 295 p4d_t *p4d, *p4d_k; 296 pud_t *pud, *pud_k; 297 pmd_t *pmd, *pmd_k; 298 pte_t *pte_k; 299 300 /* 301 phx_warn("do_page_fault(): vmalloc_fault will not work, " 302 "since current_pgd assign a proper value somewhere\n" 303 "anyhow we don't need this at the moment\n"); 304 305 phx_mmu("vmalloc_fault"); 306 */ 307 pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset; 308 pgd_k = init_mm.pgd + offset; 309 310 /* Since we're two-level, we don't need to do both 311 * set_pgd and set_pmd (they do the same thing). If 312 * we go three-level at some point, do the right thing 313 * with pgd_present and set_pgd here. 314 * 315 * Also, since the vmalloc area is global, we don't 316 * need to copy individual PTE's, it is enough to 317 * copy the pgd pointer into the pte page of the 318 * root task. If that is there, we'll find our pte if 319 * it exists. 320 */ 321 322 p4d = p4d_offset(pgd, address); 323 p4d_k = p4d_offset(pgd_k, address); 324 if (!p4d_present(*p4d_k)) 325 goto no_context; 326 327 pud = pud_offset(p4d, address); 328 pud_k = pud_offset(p4d_k, address); 329 if (!pud_present(*pud_k)) 330 goto no_context; 331 332 pmd = pmd_offset(pud, address); 333 pmd_k = pmd_offset(pud_k, address); 334 335 if (!pmd_present(*pmd_k)) 336 goto bad_area_nosemaphore; 337 338 set_pmd(pmd, *pmd_k); 339 340 /* Make sure the actual PTE exists as well to 341 * catch kernel vmalloc-area accesses to non-mapped 342 * addresses. If we don't do this, this will just 343 * silently loop forever. 344 */ 345 346 pte_k = pte_offset_kernel(pmd_k, address); 347 if (!pte_present(*pte_k)) 348 goto no_context; 349 350 return; 351 } 352 } 353