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 if (!user_mode(regs)) 167 goto no_context; 168 return; 169 } 170 171 /* The fault is fully completed (including releasing mmap lock) */ 172 if (fault & VM_FAULT_COMPLETED) 173 return; 174 175 if (unlikely(fault & VM_FAULT_ERROR)) { 176 if (fault & VM_FAULT_OOM) 177 goto out_of_memory; 178 else if (fault & VM_FAULT_SIGSEGV) 179 goto bad_area; 180 else if (fault & VM_FAULT_SIGBUS) 181 goto do_sigbus; 182 BUG(); 183 } 184 185 /*RGD modeled on Cris */ 186 if (fault & VM_FAULT_RETRY) { 187 flags |= FAULT_FLAG_TRIED; 188 189 /* No need to mmap_read_unlock(mm) as we would 190 * have already released it in __lock_page_or_retry 191 * in mm/filemap.c. 192 */ 193 194 goto retry; 195 } 196 197 mmap_read_unlock(mm); 198 return; 199 200 /* 201 * Something tried to access memory that isn't in our memory map.. 202 * Fix it, but check if it's kernel or user first.. 203 */ 204 205 bad_area: 206 mmap_read_unlock(mm); 207 208 bad_area_nosemaphore: 209 210 /* User mode accesses just cause a SIGSEGV */ 211 212 if (user_mode(regs)) { 213 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 214 return; 215 } 216 217 no_context: 218 219 /* Are we prepared to handle this kernel fault? 220 * 221 * (The kernel has valid exception-points in the source 222 * when it acesses user-memory. When it fails in one 223 * of those points, we find it in a table and do a jump 224 * to some fixup code that loads an appropriate error 225 * code) 226 */ 227 228 { 229 const struct exception_table_entry *entry; 230 231 if ((entry = search_exception_tables(regs->pc)) != NULL) { 232 /* Adjust the instruction pointer in the stackframe */ 233 regs->pc = entry->fixup; 234 return; 235 } 236 } 237 238 /* 239 * Oops. The kernel tried to access some bad page. We'll have to 240 * terminate things with extreme prejudice. 241 */ 242 243 if ((unsigned long)(address) < PAGE_SIZE) 244 printk(KERN_ALERT 245 "Unable to handle kernel NULL pointer dereference"); 246 else 247 printk(KERN_ALERT "Unable to handle kernel access"); 248 printk(" at virtual address 0x%08lx\n", address); 249 250 die("Oops", regs, write_acc); 251 252 /* 253 * We ran out of memory, or some other thing happened to us that made 254 * us unable to handle the page fault gracefully. 255 */ 256 257 out_of_memory: 258 mmap_read_unlock(mm); 259 if (!user_mode(regs)) 260 goto no_context; 261 pagefault_out_of_memory(); 262 return; 263 264 do_sigbus: 265 mmap_read_unlock(mm); 266 267 /* 268 * Send a sigbus, regardless of whether we were in kernel 269 * or user mode. 270 */ 271 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address); 272 273 /* Kernel mode? Handle exceptions or die */ 274 if (!user_mode(regs)) 275 goto no_context; 276 return; 277 278 vmalloc_fault: 279 { 280 /* 281 * Synchronize this task's top level page-table 282 * with the 'reference' page table. 283 * 284 * Use current_pgd instead of tsk->active_mm->pgd 285 * since the latter might be unavailable if this 286 * code is executed in a misfortunately run irq 287 * (like inside schedule() between switch_mm and 288 * switch_to...). 289 */ 290 291 int offset = pgd_index(address); 292 pgd_t *pgd, *pgd_k; 293 p4d_t *p4d, *p4d_k; 294 pud_t *pud, *pud_k; 295 pmd_t *pmd, *pmd_k; 296 pte_t *pte_k; 297 298 /* 299 phx_warn("do_page_fault(): vmalloc_fault will not work, " 300 "since current_pgd assign a proper value somewhere\n" 301 "anyhow we don't need this at the moment\n"); 302 303 phx_mmu("vmalloc_fault"); 304 */ 305 pgd = (pgd_t *)current_pgd[smp_processor_id()] + offset; 306 pgd_k = init_mm.pgd + offset; 307 308 /* Since we're two-level, we don't need to do both 309 * set_pgd and set_pmd (they do the same thing). If 310 * we go three-level at some point, do the right thing 311 * with pgd_present and set_pgd here. 312 * 313 * Also, since the vmalloc area is global, we don't 314 * need to copy individual PTE's, it is enough to 315 * copy the pgd pointer into the pte page of the 316 * root task. If that is there, we'll find our pte if 317 * it exists. 318 */ 319 320 p4d = p4d_offset(pgd, address); 321 p4d_k = p4d_offset(pgd_k, address); 322 if (!p4d_present(*p4d_k)) 323 goto no_context; 324 325 pud = pud_offset(p4d, address); 326 pud_k = pud_offset(p4d_k, address); 327 if (!pud_present(*pud_k)) 328 goto no_context; 329 330 pmd = pmd_offset(pud, address); 331 pmd_k = pmd_offset(pud_k, address); 332 333 if (!pmd_present(*pmd_k)) 334 goto bad_area_nosemaphore; 335 336 set_pmd(pmd, *pmd_k); 337 338 /* Make sure the actual PTE exists as well to 339 * catch kernel vmalloc-area accesses to non-mapped 340 * addresses. If we don't do this, this will just 341 * silently loop forever. 342 */ 343 344 pte_k = pte_offset_kernel(pmd_k, address); 345 if (!pte_present(*pte_k)) 346 goto no_context; 347 348 return; 349 } 350 } 351