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