1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * MMU fault handling support. 4 * 5 * Copyright (C) 1998-2002 Hewlett-Packard Co 6 * David Mosberger-Tang <davidm@hpl.hp.com> 7 */ 8 #include <linux/sched/signal.h> 9 #include <linux/kernel.h> 10 #include <linux/mm.h> 11 #include <linux/extable.h> 12 #include <linux/interrupt.h> 13 #include <linux/kprobes.h> 14 #include <linux/kdebug.h> 15 #include <linux/prefetch.h> 16 #include <linux/uaccess.h> 17 18 #include <asm/pgtable.h> 19 #include <asm/processor.h> 20 #include <asm/exception.h> 21 22 extern int die(char *, struct pt_regs *, long); 23 24 #ifdef CONFIG_KPROBES 25 static inline int notify_page_fault(struct pt_regs *regs, int trap) 26 { 27 int ret = 0; 28 29 if (!user_mode(regs)) { 30 /* kprobe_running() needs smp_processor_id() */ 31 preempt_disable(); 32 if (kprobe_running() && kprobe_fault_handler(regs, trap)) 33 ret = 1; 34 preempt_enable(); 35 } 36 37 return ret; 38 } 39 #else 40 static inline int notify_page_fault(struct pt_regs *regs, int trap) 41 { 42 return 0; 43 } 44 #endif 45 46 /* 47 * Return TRUE if ADDRESS points at a page in the kernel's mapped segment 48 * (inside region 5, on ia64) and that page is present. 49 */ 50 static int 51 mapped_kernel_page_is_present (unsigned long address) 52 { 53 pgd_t *pgd; 54 pud_t *pud; 55 pmd_t *pmd; 56 pte_t *ptep, pte; 57 58 pgd = pgd_offset_k(address); 59 if (pgd_none(*pgd) || pgd_bad(*pgd)) 60 return 0; 61 62 pud = pud_offset(pgd, address); 63 if (pud_none(*pud) || pud_bad(*pud)) 64 return 0; 65 66 pmd = pmd_offset(pud, address); 67 if (pmd_none(*pmd) || pmd_bad(*pmd)) 68 return 0; 69 70 ptep = pte_offset_kernel(pmd, address); 71 if (!ptep) 72 return 0; 73 74 pte = *ptep; 75 return pte_present(pte); 76 } 77 78 # define VM_READ_BIT 0 79 # define VM_WRITE_BIT 1 80 # define VM_EXEC_BIT 2 81 82 void __kprobes 83 ia64_do_page_fault (unsigned long address, unsigned long isr, struct pt_regs *regs) 84 { 85 int signal = SIGSEGV, code = SEGV_MAPERR; 86 struct vm_area_struct *vma, *prev_vma; 87 struct mm_struct *mm = current->mm; 88 struct siginfo si; 89 unsigned long mask; 90 int fault; 91 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 92 93 mask = ((((isr >> IA64_ISR_X_BIT) & 1UL) << VM_EXEC_BIT) 94 | (((isr >> IA64_ISR_W_BIT) & 1UL) << VM_WRITE_BIT)); 95 96 /* mmap_sem is performance critical.... */ 97 prefetchw(&mm->mmap_sem); 98 99 /* 100 * If we're in an interrupt or have no user context, we must not take the fault.. 101 */ 102 if (faulthandler_disabled() || !mm) 103 goto no_context; 104 105 #ifdef CONFIG_VIRTUAL_MEM_MAP 106 /* 107 * If fault is in region 5 and we are in the kernel, we may already 108 * have the mmap_sem (pfn_valid macro is called during mmap). There 109 * is no vma for region 5 addr's anyway, so skip getting the semaphore 110 * and go directly to the exception handling code. 111 */ 112 113 if ((REGION_NUMBER(address) == 5) && !user_mode(regs)) 114 goto bad_area_no_up; 115 #endif 116 117 /* 118 * This is to handle the kprobes on user space access instructions 119 */ 120 if (notify_page_fault(regs, TRAP_BRKPT)) 121 return; 122 123 if (user_mode(regs)) 124 flags |= FAULT_FLAG_USER; 125 if (mask & VM_WRITE) 126 flags |= FAULT_FLAG_WRITE; 127 retry: 128 down_read(&mm->mmap_sem); 129 130 vma = find_vma_prev(mm, address, &prev_vma); 131 if (!vma && !prev_vma ) 132 goto bad_area; 133 134 /* 135 * find_vma_prev() returns vma such that address < vma->vm_end or NULL 136 * 137 * May find no vma, but could be that the last vm area is the 138 * register backing store that needs to expand upwards, in 139 * this case vma will be null, but prev_vma will ne non-null 140 */ 141 if (( !vma && prev_vma ) || (address < vma->vm_start) ) 142 goto check_expansion; 143 144 good_area: 145 code = SEGV_ACCERR; 146 147 /* OK, we've got a good vm_area for this memory area. Check the access permissions: */ 148 149 # if (((1 << VM_READ_BIT) != VM_READ || (1 << VM_WRITE_BIT) != VM_WRITE) \ 150 || (1 << VM_EXEC_BIT) != VM_EXEC) 151 # error File is out of sync with <linux/mm.h>. Please update. 152 # endif 153 154 if (((isr >> IA64_ISR_R_BIT) & 1UL) && (!(vma->vm_flags & (VM_READ | VM_WRITE)))) 155 goto bad_area; 156 157 if ((vma->vm_flags & mask) != mask) 158 goto bad_area; 159 160 /* 161 * If for any reason at all we couldn't handle the fault, make 162 * sure we exit gracefully rather than endlessly redo the 163 * fault. 164 */ 165 fault = handle_mm_fault(vma, address, flags); 166 167 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 168 return; 169 170 if (unlikely(fault & VM_FAULT_ERROR)) { 171 /* 172 * We ran out of memory, or some other thing happened 173 * to us that made us unable to handle the page fault 174 * gracefully. 175 */ 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 signal = SIGBUS; 182 goto bad_area; 183 } 184 BUG(); 185 } 186 187 if (flags & FAULT_FLAG_ALLOW_RETRY) { 188 if (fault & VM_FAULT_MAJOR) 189 current->maj_flt++; 190 else 191 current->min_flt++; 192 if (fault & VM_FAULT_RETRY) { 193 flags &= ~FAULT_FLAG_ALLOW_RETRY; 194 flags |= FAULT_FLAG_TRIED; 195 196 /* No need to up_read(&mm->mmap_sem) as we would 197 * have already released it in __lock_page_or_retry 198 * in mm/filemap.c. 199 */ 200 201 goto retry; 202 } 203 } 204 205 up_read(&mm->mmap_sem); 206 return; 207 208 check_expansion: 209 if (!(prev_vma && (prev_vma->vm_flags & VM_GROWSUP) && (address == prev_vma->vm_end))) { 210 if (!vma) 211 goto bad_area; 212 if (!(vma->vm_flags & VM_GROWSDOWN)) 213 goto bad_area; 214 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 215 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 216 goto bad_area; 217 if (expand_stack(vma, address)) 218 goto bad_area; 219 } else { 220 vma = prev_vma; 221 if (REGION_NUMBER(address) != REGION_NUMBER(vma->vm_start) 222 || REGION_OFFSET(address) >= RGN_MAP_LIMIT) 223 goto bad_area; 224 /* 225 * Since the register backing store is accessed sequentially, 226 * we disallow growing it by more than a page at a time. 227 */ 228 if (address > vma->vm_end + PAGE_SIZE - sizeof(long)) 229 goto bad_area; 230 if (expand_upwards(vma, address)) 231 goto bad_area; 232 } 233 goto good_area; 234 235 bad_area: 236 up_read(&mm->mmap_sem); 237 #ifdef CONFIG_VIRTUAL_MEM_MAP 238 bad_area_no_up: 239 #endif 240 if ((isr & IA64_ISR_SP) 241 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 242 { 243 /* 244 * This fault was due to a speculative load or lfetch.fault, set the "ed" 245 * bit in the psr to ensure forward progress. (Target register will get a 246 * NaT for ld.s, lfetch will be canceled.) 247 */ 248 ia64_psr(regs)->ed = 1; 249 return; 250 } 251 if (user_mode(regs)) { 252 si.si_signo = signal; 253 si.si_errno = 0; 254 si.si_code = code; 255 si.si_addr = (void __user *) address; 256 si.si_isr = isr; 257 si.si_flags = __ISR_VALID; 258 force_sig_info(signal, &si, current); 259 return; 260 } 261 262 no_context: 263 if ((isr & IA64_ISR_SP) 264 || ((isr & IA64_ISR_NA) && (isr & IA64_ISR_CODE_MASK) == IA64_ISR_CODE_LFETCH)) 265 { 266 /* 267 * This fault was due to a speculative load or lfetch.fault, set the "ed" 268 * bit in the psr to ensure forward progress. (Target register will get a 269 * NaT for ld.s, lfetch will be canceled.) 270 */ 271 ia64_psr(regs)->ed = 1; 272 return; 273 } 274 275 /* 276 * Since we have no vma's for region 5, we might get here even if the address is 277 * valid, due to the VHPT walker inserting a non present translation that becomes 278 * stale. If that happens, the non present fault handler already purged the stale 279 * translation, which fixed the problem. So, we check to see if the translation is 280 * valid, and return if it is. 281 */ 282 if (REGION_NUMBER(address) == 5 && mapped_kernel_page_is_present(address)) 283 return; 284 285 if (ia64_done_with_exception(regs)) 286 return; 287 288 /* 289 * Oops. The kernel tried to access some bad page. We'll have to terminate things 290 * with extreme prejudice. 291 */ 292 bust_spinlocks(1); 293 294 if (address < PAGE_SIZE) 295 printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference (address %016lx)\n", address); 296 else 297 printk(KERN_ALERT "Unable to handle kernel paging request at " 298 "virtual address %016lx\n", address); 299 if (die("Oops", regs, isr)) 300 regs = NULL; 301 bust_spinlocks(0); 302 if (regs) 303 do_exit(SIGKILL); 304 return; 305 306 out_of_memory: 307 up_read(&mm->mmap_sem); 308 if (!user_mode(regs)) 309 goto no_context; 310 pagefault_out_of_memory(); 311 } 312