1 /* 2 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd. 3 * Lennox Wu <lennox.wu@sunplusct.com> 4 * Chen Liqin <liqin.chen@sunplusct.com> 5 * Copyright (C) 2012 Regents of the University of California 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation; either version 2 of the License, or 10 * (at your option) any later version. 11 * 12 * This program is distributed in the hope that it will be useful, 13 * but WITHOUT ANY WARRANTY; without even the implied warranty of 14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 15 * GNU General Public License for more details. 16 * 17 * You should have received a copy of the GNU General Public License 18 * along with this program; if not, see the file COPYING, or write 19 * to the Free Software Foundation, Inc., 20 */ 21 22 23 #include <linux/mm.h> 24 #include <linux/kernel.h> 25 #include <linux/interrupt.h> 26 #include <linux/perf_event.h> 27 #include <linux/signal.h> 28 #include <linux/uaccess.h> 29 30 #include <asm/pgalloc.h> 31 #include <asm/ptrace.h> 32 33 /* 34 * This routine handles page faults. It determines the address and the 35 * problem, and then passes it off to one of the appropriate routines. 36 */ 37 asmlinkage void do_page_fault(struct pt_regs *regs) 38 { 39 struct task_struct *tsk; 40 struct vm_area_struct *vma; 41 struct mm_struct *mm; 42 unsigned long addr, cause; 43 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 44 int code = SEGV_MAPERR; 45 vm_fault_t fault; 46 47 cause = regs->scause; 48 addr = regs->sbadaddr; 49 50 tsk = current; 51 mm = tsk->mm; 52 53 /* 54 * Fault-in kernel-space virtual memory on-demand. 55 * The 'reference' page table is init_mm.pgd. 56 * 57 * NOTE! We MUST NOT take any locks for this case. We may 58 * be in an interrupt or a critical region, and should 59 * only copy the information from the master page table, 60 * nothing more. 61 */ 62 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) 63 goto vmalloc_fault; 64 65 /* Enable interrupts if they were enabled in the parent context. */ 66 if (likely(regs->sstatus & SR_SPIE)) 67 local_irq_enable(); 68 69 /* 70 * If we're in an interrupt, have no user context, or are running 71 * in an atomic region, then we must not take the fault. 72 */ 73 if (unlikely(faulthandler_disabled() || !mm)) 74 goto no_context; 75 76 if (user_mode(regs)) 77 flags |= FAULT_FLAG_USER; 78 79 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 80 81 retry: 82 down_read(&mm->mmap_sem); 83 vma = find_vma(mm, addr); 84 if (unlikely(!vma)) 85 goto bad_area; 86 if (likely(vma->vm_start <= addr)) 87 goto good_area; 88 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 89 goto bad_area; 90 if (unlikely(expand_stack(vma, addr))) 91 goto bad_area; 92 93 /* 94 * Ok, we have a good vm_area for this memory access, so 95 * we can handle it. 96 */ 97 good_area: 98 code = SEGV_ACCERR; 99 100 switch (cause) { 101 case EXC_INST_PAGE_FAULT: 102 if (!(vma->vm_flags & VM_EXEC)) 103 goto bad_area; 104 break; 105 case EXC_LOAD_PAGE_FAULT: 106 if (!(vma->vm_flags & VM_READ)) 107 goto bad_area; 108 break; 109 case EXC_STORE_PAGE_FAULT: 110 if (!(vma->vm_flags & VM_WRITE)) 111 goto bad_area; 112 flags |= FAULT_FLAG_WRITE; 113 break; 114 default: 115 panic("%s: unhandled cause %lu", __func__, cause); 116 } 117 118 /* 119 * If for any reason at all we could not handle the fault, 120 * make sure we exit gracefully rather than endlessly redo 121 * the fault. 122 */ 123 fault = handle_mm_fault(vma, addr, flags); 124 125 /* 126 * If we need to retry but a fatal signal is pending, handle the 127 * signal first. We do not need to release the mmap_sem because it 128 * would already be released in __lock_page_or_retry in mm/filemap.c. 129 */ 130 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk)) 131 return; 132 133 if (unlikely(fault & VM_FAULT_ERROR)) { 134 if (fault & VM_FAULT_OOM) 135 goto out_of_memory; 136 else if (fault & VM_FAULT_SIGBUS) 137 goto do_sigbus; 138 BUG(); 139 } 140 141 /* 142 * Major/minor page fault accounting is only done on the 143 * initial attempt. If we go through a retry, it is extremely 144 * likely that the page will be found in page cache at that point. 145 */ 146 if (flags & FAULT_FLAG_ALLOW_RETRY) { 147 if (fault & VM_FAULT_MAJOR) { 148 tsk->maj_flt++; 149 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 150 1, regs, addr); 151 } else { 152 tsk->min_flt++; 153 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 154 1, regs, addr); 155 } 156 if (fault & VM_FAULT_RETRY) { 157 /* 158 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 159 * of starvation. 160 */ 161 flags &= ~(FAULT_FLAG_ALLOW_RETRY); 162 flags |= FAULT_FLAG_TRIED; 163 164 /* 165 * No need to up_read(&mm->mmap_sem) as we would 166 * have already released it in __lock_page_or_retry 167 * in mm/filemap.c. 168 */ 169 goto retry; 170 } 171 } 172 173 up_read(&mm->mmap_sem); 174 return; 175 176 /* 177 * Something tried to access memory that isn't in our memory map. 178 * Fix it, but check if it's kernel or user first. 179 */ 180 bad_area: 181 up_read(&mm->mmap_sem); 182 /* User mode accesses just cause a SIGSEGV */ 183 if (user_mode(regs)) { 184 do_trap(regs, SIGSEGV, code, addr, tsk); 185 return; 186 } 187 188 no_context: 189 /* Are we prepared to handle this kernel fault? */ 190 if (fixup_exception(regs)) 191 return; 192 193 /* 194 * Oops. The kernel tried to access some bad page. We'll have to 195 * terminate things with extreme prejudice. 196 */ 197 bust_spinlocks(1); 198 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", 199 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 200 "paging request", addr); 201 die(regs, "Oops"); 202 do_exit(SIGKILL); 203 204 /* 205 * We ran out of memory, call the OOM killer, and return the userspace 206 * (which will retry the fault, or kill us if we got oom-killed). 207 */ 208 out_of_memory: 209 up_read(&mm->mmap_sem); 210 if (!user_mode(regs)) 211 goto no_context; 212 pagefault_out_of_memory(); 213 return; 214 215 do_sigbus: 216 up_read(&mm->mmap_sem); 217 /* Kernel mode? Handle exceptions or die */ 218 if (!user_mode(regs)) 219 goto no_context; 220 do_trap(regs, SIGBUS, BUS_ADRERR, addr, tsk); 221 return; 222 223 vmalloc_fault: 224 { 225 pgd_t *pgd, *pgd_k; 226 pud_t *pud, *pud_k; 227 p4d_t *p4d, *p4d_k; 228 pmd_t *pmd, *pmd_k; 229 pte_t *pte_k; 230 int index; 231 232 if (user_mode(regs)) 233 goto bad_area; 234 235 /* 236 * Synchronize this task's top level page-table 237 * with the 'reference' page table. 238 * 239 * Do _not_ use "tsk->active_mm->pgd" here. 240 * We might be inside an interrupt in the middle 241 * of a task switch. 242 * 243 * Note: Use the old spbtr name instead of using the current 244 * satp name to support binutils 2.29 which doesn't know about 245 * the privileged ISA 1.10 yet. 246 */ 247 index = pgd_index(addr); 248 pgd = (pgd_t *)pfn_to_virt(csr_read(sptbr)) + index; 249 pgd_k = init_mm.pgd + index; 250 251 if (!pgd_present(*pgd_k)) 252 goto no_context; 253 set_pgd(pgd, *pgd_k); 254 255 p4d = p4d_offset(pgd, addr); 256 p4d_k = p4d_offset(pgd_k, addr); 257 if (!p4d_present(*p4d_k)) 258 goto no_context; 259 260 pud = pud_offset(p4d, addr); 261 pud_k = pud_offset(p4d_k, addr); 262 if (!pud_present(*pud_k)) 263 goto no_context; 264 265 /* 266 * Since the vmalloc area is global, it is unnecessary 267 * to copy individual PTEs 268 */ 269 pmd = pmd_offset(pud, addr); 270 pmd_k = pmd_offset(pud_k, addr); 271 if (!pmd_present(*pmd_k)) 272 goto no_context; 273 set_pmd(pmd, *pmd_k); 274 275 /* 276 * Make sure the actual PTE exists as well to 277 * catch kernel vmalloc-area accesses to non-mapped 278 * addresses. If we don't do this, this will just 279 * silently loop forever. 280 */ 281 pte_k = pte_offset_kernel(pmd_k, addr); 282 if (!pte_present(*pte_k)) 283 goto no_context; 284 return; 285 } 286 } 287