1 /* 2 * Copyright (C) 2009 Wind River Systems Inc 3 * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com 4 * 5 * based on arch/mips/mm/fault.c which is: 6 * 7 * Copyright (C) 1995-2000 Ralf Baechle 8 * 9 * This file is subject to the terms and conditions of the GNU General Public 10 * License. See the file "COPYING" in the main directory of this archive 11 * for more details. 12 */ 13 14 #include <linux/signal.h> 15 #include <linux/sched.h> 16 #include <linux/sched/debug.h> 17 #include <linux/interrupt.h> 18 #include <linux/kernel.h> 19 #include <linux/errno.h> 20 #include <linux/string.h> 21 #include <linux/types.h> 22 #include <linux/ptrace.h> 23 #include <linux/mman.h> 24 #include <linux/mm.h> 25 #include <linux/extable.h> 26 #include <linux/uaccess.h> 27 #include <linux/perf_event.h> 28 29 #include <asm/mmu_context.h> 30 #include <asm/traps.h> 31 32 #define EXC_SUPERV_INSN_ACCESS 9 /* Supervisor only instruction address */ 33 #define EXC_SUPERV_DATA_ACCESS 11 /* Supervisor only data address */ 34 #define EXC_X_PROTECTION_FAULT 13 /* TLB permission violation (x) */ 35 #define EXC_R_PROTECTION_FAULT 14 /* TLB permission violation (r) */ 36 #define EXC_W_PROTECTION_FAULT 15 /* TLB permission violation (w) */ 37 38 /* 39 * This routine handles page faults. It determines the address, 40 * and the problem, and then passes it off to one of the appropriate 41 * routines. 42 */ 43 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause, 44 unsigned long address) 45 { 46 struct vm_area_struct *vma = NULL; 47 struct task_struct *tsk = current; 48 struct mm_struct *mm = tsk->mm; 49 int code = SEGV_MAPERR; 50 vm_fault_t fault; 51 unsigned int flags = FAULT_FLAG_DEFAULT; 52 53 cause >>= 2; 54 55 /* Restart the instruction */ 56 regs->ea -= 4; 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 if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) { 68 if (user_mode(regs)) 69 goto bad_area_nosemaphore; 70 else 71 goto vmalloc_fault; 72 } 73 74 if (unlikely(address >= TASK_SIZE)) 75 goto bad_area_nosemaphore; 76 77 /* 78 * If we're in an interrupt or have no user 79 * context, we must not take the fault.. 80 */ 81 if (faulthandler_disabled() || !mm) 82 goto bad_area_nosemaphore; 83 84 if (user_mode(regs)) 85 flags |= FAULT_FLAG_USER; 86 87 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 88 89 if (!mmap_read_trylock(mm)) { 90 if (!user_mode(regs) && !search_exception_tables(regs->ea)) 91 goto bad_area_nosemaphore; 92 retry: 93 mmap_read_lock(mm); 94 } 95 96 vma = find_vma(mm, address); 97 if (!vma) 98 goto bad_area; 99 if (vma->vm_start <= address) 100 goto good_area; 101 if (!(vma->vm_flags & VM_GROWSDOWN)) 102 goto bad_area; 103 if (expand_stack(vma, address)) 104 goto bad_area; 105 /* 106 * Ok, we have a good vm_area for this memory access, so 107 * we can handle it.. 108 */ 109 good_area: 110 code = SEGV_ACCERR; 111 112 switch (cause) { 113 case EXC_SUPERV_INSN_ACCESS: 114 goto bad_area; 115 case EXC_SUPERV_DATA_ACCESS: 116 goto bad_area; 117 case EXC_X_PROTECTION_FAULT: 118 if (!(vma->vm_flags & VM_EXEC)) 119 goto bad_area; 120 break; 121 case EXC_R_PROTECTION_FAULT: 122 if (!(vma->vm_flags & VM_READ)) 123 goto bad_area; 124 break; 125 case EXC_W_PROTECTION_FAULT: 126 if (!(vma->vm_flags & VM_WRITE)) 127 goto bad_area; 128 flags = FAULT_FLAG_WRITE; 129 break; 130 } 131 132 /* 133 * If for any reason at all we couldn't handle the fault, 134 * make sure we exit gracefully rather than endlessly redo 135 * the fault. 136 */ 137 fault = handle_mm_fault(vma, address, flags, regs); 138 139 if (fault_signal_pending(fault, regs)) { 140 if (!user_mode(regs)) 141 goto no_context; 142 return; 143 } 144 145 /* The fault is fully completed (including releasing mmap lock) */ 146 if (fault & VM_FAULT_COMPLETED) 147 return; 148 149 if (unlikely(fault & VM_FAULT_ERROR)) { 150 if (fault & VM_FAULT_OOM) 151 goto out_of_memory; 152 else if (fault & VM_FAULT_SIGSEGV) 153 goto bad_area; 154 else if (fault & VM_FAULT_SIGBUS) 155 goto do_sigbus; 156 BUG(); 157 } 158 159 if (fault & VM_FAULT_RETRY) { 160 flags |= FAULT_FLAG_TRIED; 161 162 /* 163 * No need to mmap_read_unlock(mm) as we would 164 * have already released it in __lock_page_or_retry 165 * in mm/filemap.c. 166 */ 167 168 goto retry; 169 } 170 171 mmap_read_unlock(mm); 172 return; 173 174 /* 175 * Something tried to access memory that isn't in our memory map.. 176 * Fix it, but check if it's kernel or user first.. 177 */ 178 bad_area: 179 mmap_read_unlock(mm); 180 181 bad_area_nosemaphore: 182 /* User mode accesses just cause a SIGSEGV */ 183 if (user_mode(regs)) { 184 if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) { 185 pr_info("%s: unhandled page fault (%d) at 0x%08lx, " 186 "cause %ld\n", current->comm, SIGSEGV, address, cause); 187 show_regs(regs); 188 } 189 _exception(SIGSEGV, regs, code, address); 190 return; 191 } 192 193 no_context: 194 /* Are we prepared to handle this kernel fault? */ 195 if (fixup_exception(regs)) 196 return; 197 198 /* 199 * Oops. The kernel tried to access some bad page. We'll have to 200 * terminate things with extreme prejudice. 201 */ 202 bust_spinlocks(1); 203 204 pr_alert("Unable to handle kernel %s at virtual address %08lx", 205 address < PAGE_SIZE ? "NULL pointer dereference" : 206 "paging request", address); 207 pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra, 208 cause); 209 panic("Oops"); 210 return; 211 212 /* 213 * We ran out of memory, or some other thing happened to us that made 214 * us unable to handle the page fault gracefully. 215 */ 216 out_of_memory: 217 mmap_read_unlock(mm); 218 if (!user_mode(regs)) 219 goto no_context; 220 pagefault_out_of_memory(); 221 return; 222 223 do_sigbus: 224 mmap_read_unlock(mm); 225 226 /* Kernel mode? Handle exceptions or die */ 227 if (!user_mode(regs)) 228 goto no_context; 229 230 _exception(SIGBUS, regs, BUS_ADRERR, address); 231 return; 232 233 vmalloc_fault: 234 { 235 /* 236 * Synchronize this task's top level page-table 237 * with the 'reference' page table. 238 * 239 * Do _not_ use "tsk" here. We might be inside 240 * an interrupt in the middle of a task switch.. 241 */ 242 int offset = pgd_index(address); 243 pgd_t *pgd, *pgd_k; 244 p4d_t *p4d, *p4d_k; 245 pud_t *pud, *pud_k; 246 pmd_t *pmd, *pmd_k; 247 pte_t *pte_k; 248 249 pgd = pgd_current + offset; 250 pgd_k = init_mm.pgd + offset; 251 252 if (!pgd_present(*pgd_k)) 253 goto no_context; 254 set_pgd(pgd, *pgd_k); 255 256 p4d = p4d_offset(pgd, address); 257 p4d_k = p4d_offset(pgd_k, address); 258 if (!p4d_present(*p4d_k)) 259 goto no_context; 260 pud = pud_offset(p4d, address); 261 pud_k = pud_offset(p4d_k, address); 262 if (!pud_present(*pud_k)) 263 goto no_context; 264 pmd = pmd_offset(pud, address); 265 pmd_k = pmd_offset(pud_k, address); 266 if (!pmd_present(*pmd_k)) 267 goto no_context; 268 set_pmd(pmd, *pmd_k); 269 270 pte_k = pte_offset_kernel(pmd_k, address); 271 if (!pte_present(*pte_k)) 272 goto no_context; 273 274 flush_tlb_kernel_page(address); 275 return; 276 } 277 } 278