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 return; 141 142 /* The fault is fully completed (including releasing mmap lock) */ 143 if (fault & VM_FAULT_COMPLETED) 144 return; 145 146 if (unlikely(fault & VM_FAULT_ERROR)) { 147 if (fault & VM_FAULT_OOM) 148 goto out_of_memory; 149 else if (fault & VM_FAULT_SIGSEGV) 150 goto bad_area; 151 else if (fault & VM_FAULT_SIGBUS) 152 goto do_sigbus; 153 BUG(); 154 } 155 156 if (fault & VM_FAULT_RETRY) { 157 flags |= FAULT_FLAG_TRIED; 158 159 /* 160 * No need to mmap_read_unlock(mm) as we would 161 * have already released it in __lock_page_or_retry 162 * in mm/filemap.c. 163 */ 164 165 goto retry; 166 } 167 168 mmap_read_unlock(mm); 169 return; 170 171 /* 172 * Something tried to access memory that isn't in our memory map.. 173 * Fix it, but check if it's kernel or user first.. 174 */ 175 bad_area: 176 mmap_read_unlock(mm); 177 178 bad_area_nosemaphore: 179 /* User mode accesses just cause a SIGSEGV */ 180 if (user_mode(regs)) { 181 if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) { 182 pr_info("%s: unhandled page fault (%d) at 0x%08lx, " 183 "cause %ld\n", current->comm, SIGSEGV, address, cause); 184 show_regs(regs); 185 } 186 _exception(SIGSEGV, regs, code, address); 187 return; 188 } 189 190 no_context: 191 /* Are we prepared to handle this kernel fault? */ 192 if (fixup_exception(regs)) 193 return; 194 195 /* 196 * Oops. The kernel tried to access some bad page. We'll have to 197 * terminate things with extreme prejudice. 198 */ 199 bust_spinlocks(1); 200 201 pr_alert("Unable to handle kernel %s at virtual address %08lx", 202 address < PAGE_SIZE ? "NULL pointer dereference" : 203 "paging request", address); 204 pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra, 205 cause); 206 panic("Oops"); 207 return; 208 209 /* 210 * We ran out of memory, or some other thing happened to us that made 211 * us unable to handle the page fault gracefully. 212 */ 213 out_of_memory: 214 mmap_read_unlock(mm); 215 if (!user_mode(regs)) 216 goto no_context; 217 pagefault_out_of_memory(); 218 return; 219 220 do_sigbus: 221 mmap_read_unlock(mm); 222 223 /* Kernel mode? Handle exceptions or die */ 224 if (!user_mode(regs)) 225 goto no_context; 226 227 _exception(SIGBUS, regs, BUS_ADRERR, address); 228 return; 229 230 vmalloc_fault: 231 { 232 /* 233 * Synchronize this task's top level page-table 234 * with the 'reference' page table. 235 * 236 * Do _not_ use "tsk" here. We might be inside 237 * an interrupt in the middle of a task switch.. 238 */ 239 int offset = pgd_index(address); 240 pgd_t *pgd, *pgd_k; 241 p4d_t *p4d, *p4d_k; 242 pud_t *pud, *pud_k; 243 pmd_t *pmd, *pmd_k; 244 pte_t *pte_k; 245 246 pgd = pgd_current + offset; 247 pgd_k = init_mm.pgd + offset; 248 249 if (!pgd_present(*pgd_k)) 250 goto no_context; 251 set_pgd(pgd, *pgd_k); 252 253 p4d = p4d_offset(pgd, address); 254 p4d_k = p4d_offset(pgd_k, address); 255 if (!p4d_present(*p4d_k)) 256 goto no_context; 257 pud = pud_offset(p4d, address); 258 pud_k = pud_offset(p4d_k, address); 259 if (!pud_present(*pud_k)) 260 goto no_context; 261 pmd = pmd_offset(pud, address); 262 pmd_k = pmd_offset(pud_k, address); 263 if (!pmd_present(*pmd_k)) 264 goto no_context; 265 set_pmd(pmd, *pmd_k); 266 267 pte_k = pte_offset_kernel(pmd_k, address); 268 if (!pte_present(*pte_k)) 269 goto no_context; 270 271 flush_tlb_kernel_page(address); 272 return; 273 } 274 } 275