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 retry: 90 vma = lock_mm_and_find_vma(mm, address, regs); 91 if (!vma) 92 goto bad_area_nosemaphore; 93 /* 94 * Ok, we have a good vm_area for this memory access, so 95 * we can handle it.. 96 */ 97 code = SEGV_ACCERR; 98 99 switch (cause) { 100 case EXC_SUPERV_INSN_ACCESS: 101 goto bad_area; 102 case EXC_SUPERV_DATA_ACCESS: 103 goto bad_area; 104 case EXC_X_PROTECTION_FAULT: 105 if (!(vma->vm_flags & VM_EXEC)) 106 goto bad_area; 107 break; 108 case EXC_R_PROTECTION_FAULT: 109 if (!(vma->vm_flags & VM_READ)) 110 goto bad_area; 111 break; 112 case EXC_W_PROTECTION_FAULT: 113 if (!(vma->vm_flags & VM_WRITE)) 114 goto bad_area; 115 flags = FAULT_FLAG_WRITE; 116 break; 117 } 118 119 /* 120 * If for any reason at all we couldn't handle the fault, 121 * make sure we exit gracefully rather than endlessly redo 122 * the fault. 123 */ 124 fault = handle_mm_fault(vma, address, flags, regs); 125 126 if (fault_signal_pending(fault, regs)) { 127 if (!user_mode(regs)) 128 goto no_context; 129 return; 130 } 131 132 /* The fault is fully completed (including releasing mmap lock) */ 133 if (fault & VM_FAULT_COMPLETED) 134 return; 135 136 if (unlikely(fault & VM_FAULT_ERROR)) { 137 if (fault & VM_FAULT_OOM) 138 goto out_of_memory; 139 else if (fault & VM_FAULT_SIGSEGV) 140 goto bad_area; 141 else if (fault & VM_FAULT_SIGBUS) 142 goto do_sigbus; 143 BUG(); 144 } 145 146 if (fault & VM_FAULT_RETRY) { 147 flags |= FAULT_FLAG_TRIED; 148 149 /* 150 * No need to mmap_read_unlock(mm) as we would 151 * have already released it in __lock_page_or_retry 152 * in mm/filemap.c. 153 */ 154 155 goto retry; 156 } 157 158 mmap_read_unlock(mm); 159 return; 160 161 /* 162 * Something tried to access memory that isn't in our memory map.. 163 * Fix it, but check if it's kernel or user first.. 164 */ 165 bad_area: 166 mmap_read_unlock(mm); 167 168 bad_area_nosemaphore: 169 /* User mode accesses just cause a SIGSEGV */ 170 if (user_mode(regs)) { 171 if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) { 172 pr_info("%s: unhandled page fault (%d) at 0x%08lx, " 173 "cause %ld\n", current->comm, SIGSEGV, address, cause); 174 show_regs(regs); 175 } 176 _exception(SIGSEGV, regs, code, address); 177 return; 178 } 179 180 no_context: 181 /* Are we prepared to handle this kernel fault? */ 182 if (fixup_exception(regs)) 183 return; 184 185 /* 186 * Oops. The kernel tried to access some bad page. We'll have to 187 * terminate things with extreme prejudice. 188 */ 189 bust_spinlocks(1); 190 191 pr_alert("Unable to handle kernel %s at virtual address %08lx", 192 address < PAGE_SIZE ? "NULL pointer dereference" : 193 "paging request", address); 194 pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra, 195 cause); 196 panic("Oops"); 197 return; 198 199 /* 200 * We ran out of memory, or some other thing happened to us that made 201 * us unable to handle the page fault gracefully. 202 */ 203 out_of_memory: 204 mmap_read_unlock(mm); 205 if (!user_mode(regs)) 206 goto no_context; 207 pagefault_out_of_memory(); 208 return; 209 210 do_sigbus: 211 mmap_read_unlock(mm); 212 213 /* Kernel mode? Handle exceptions or die */ 214 if (!user_mode(regs)) 215 goto no_context; 216 217 _exception(SIGBUS, regs, BUS_ADRERR, address); 218 return; 219 220 vmalloc_fault: 221 { 222 /* 223 * Synchronize this task's top level page-table 224 * with the 'reference' page table. 225 * 226 * Do _not_ use "tsk" here. We might be inside 227 * an interrupt in the middle of a task switch.. 228 */ 229 int offset = pgd_index(address); 230 pgd_t *pgd, *pgd_k; 231 p4d_t *p4d, *p4d_k; 232 pud_t *pud, *pud_k; 233 pmd_t *pmd, *pmd_k; 234 pte_t *pte_k; 235 236 pgd = pgd_current + offset; 237 pgd_k = init_mm.pgd + offset; 238 239 if (!pgd_present(*pgd_k)) 240 goto no_context; 241 set_pgd(pgd, *pgd_k); 242 243 p4d = p4d_offset(pgd, address); 244 p4d_k = p4d_offset(pgd_k, address); 245 if (!p4d_present(*p4d_k)) 246 goto no_context; 247 pud = pud_offset(p4d, address); 248 pud_k = pud_offset(p4d_k, address); 249 if (!pud_present(*pud_k)) 250 goto no_context; 251 pmd = pmd_offset(pud, address); 252 pmd_k = pmd_offset(pud_k, address); 253 if (!pmd_present(*pmd_k)) 254 goto no_context; 255 set_pmd(pmd, *pmd_k); 256 257 pte_k = pte_offset_kernel(pmd_k, address); 258 if (!pte_present(*pte_k)) 259 goto no_context; 260 261 flush_tlb_kernel_page(address); 262 return; 263 } 264 } 265