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 fault, code = SEGV_MAPERR; 45 46 cause = regs->scause; 47 addr = regs->sbadaddr; 48 49 tsk = current; 50 mm = tsk->mm; 51 52 /* 53 * Fault-in kernel-space virtual memory on-demand. 54 * The 'reference' page table is init_mm.pgd. 55 * 56 * NOTE! We MUST NOT take any locks for this case. We may 57 * be in an interrupt or a critical region, and should 58 * only copy the information from the master page table, 59 * nothing more. 60 */ 61 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) 62 goto vmalloc_fault; 63 64 /* Enable interrupts if they were enabled in the parent context. */ 65 if (likely(regs->sstatus & SR_SPIE)) 66 local_irq_enable(); 67 68 /* 69 * If we're in an interrupt, have no user context, or are running 70 * in an atomic region, then we must not take the fault. 71 */ 72 if (unlikely(faulthandler_disabled() || !mm)) 73 goto no_context; 74 75 if (user_mode(regs)) 76 flags |= FAULT_FLAG_USER; 77 78 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 79 80 retry: 81 down_read(&mm->mmap_sem); 82 vma = find_vma(mm, addr); 83 if (unlikely(!vma)) 84 goto bad_area; 85 if (likely(vma->vm_start <= addr)) 86 goto good_area; 87 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 88 goto bad_area; 89 if (unlikely(expand_stack(vma, addr))) 90 goto bad_area; 91 92 /* 93 * Ok, we have a good vm_area for this memory access, so 94 * we can handle it. 95 */ 96 good_area: 97 code = SEGV_ACCERR; 98 99 switch (cause) { 100 case EXC_INST_PAGE_FAULT: 101 if (!(vma->vm_flags & VM_EXEC)) 102 goto bad_area; 103 break; 104 case EXC_LOAD_PAGE_FAULT: 105 if (!(vma->vm_flags & VM_READ)) 106 goto bad_area; 107 break; 108 case EXC_STORE_PAGE_FAULT: 109 if (!(vma->vm_flags & VM_WRITE)) 110 goto bad_area; 111 flags |= FAULT_FLAG_WRITE; 112 break; 113 default: 114 panic("%s: unhandled cause %lu", __func__, cause); 115 } 116 117 /* 118 * If for any reason at all we could not handle the fault, 119 * make sure we exit gracefully rather than endlessly redo 120 * the fault. 121 */ 122 fault = handle_mm_fault(vma, addr, flags); 123 124 /* 125 * If we need to retry but a fatal signal is pending, handle the 126 * signal first. We do not need to release the mmap_sem because it 127 * would already be released in __lock_page_or_retry in mm/filemap.c. 128 */ 129 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk)) 130 return; 131 132 if (unlikely(fault & VM_FAULT_ERROR)) { 133 if (fault & VM_FAULT_OOM) 134 goto out_of_memory; 135 else if (fault & VM_FAULT_SIGBUS) 136 goto do_sigbus; 137 BUG(); 138 } 139 140 /* 141 * Major/minor page fault accounting is only done on the 142 * initial attempt. If we go through a retry, it is extremely 143 * likely that the page will be found in page cache at that point. 144 */ 145 if (flags & FAULT_FLAG_ALLOW_RETRY) { 146 if (fault & VM_FAULT_MAJOR) { 147 tsk->maj_flt++; 148 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 149 1, regs, addr); 150 } else { 151 tsk->min_flt++; 152 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 153 1, regs, addr); 154 } 155 if (fault & VM_FAULT_RETRY) { 156 /* 157 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 158 * of starvation. 159 */ 160 flags &= ~(FAULT_FLAG_ALLOW_RETRY); 161 flags |= FAULT_FLAG_TRIED; 162 163 /* 164 * No need to up_read(&mm->mmap_sem) as we would 165 * have already released it in __lock_page_or_retry 166 * in mm/filemap.c. 167 */ 168 goto retry; 169 } 170 } 171 172 up_read(&mm->mmap_sem); 173 return; 174 175 /* 176 * Something tried to access memory that isn't in our memory map. 177 * Fix it, but check if it's kernel or user first. 178 */ 179 bad_area: 180 up_read(&mm->mmap_sem); 181 /* User mode accesses just cause a SIGSEGV */ 182 if (user_mode(regs)) { 183 do_trap(regs, SIGSEGV, code, addr, tsk); 184 return; 185 } 186 187 no_context: 188 /* Are we prepared to handle this kernel fault? */ 189 if (fixup_exception(regs)) 190 return; 191 192 /* 193 * Oops. The kernel tried to access some bad page. We'll have to 194 * terminate things with extreme prejudice. 195 */ 196 bust_spinlocks(1); 197 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", 198 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 199 "paging request", addr); 200 die(regs, "Oops"); 201 do_exit(SIGKILL); 202 203 /* 204 * We ran out of memory, call the OOM killer, and return the userspace 205 * (which will retry the fault, or kill us if we got oom-killed). 206 */ 207 out_of_memory: 208 up_read(&mm->mmap_sem); 209 if (!user_mode(regs)) 210 goto no_context; 211 pagefault_out_of_memory(); 212 return; 213 214 do_sigbus: 215 up_read(&mm->mmap_sem); 216 /* Kernel mode? Handle exceptions or die */ 217 if (!user_mode(regs)) 218 goto no_context; 219 do_trap(regs, SIGBUS, BUS_ADRERR, addr, tsk); 220 return; 221 222 vmalloc_fault: 223 { 224 pgd_t *pgd, *pgd_k; 225 pud_t *pud, *pud_k; 226 p4d_t *p4d, *p4d_k; 227 pmd_t *pmd, *pmd_k; 228 pte_t *pte_k; 229 int index; 230 231 if (user_mode(regs)) 232 goto bad_area; 233 234 /* 235 * Synchronize this task's top level page-table 236 * with the 'reference' page table. 237 * 238 * Do _not_ use "tsk->active_mm->pgd" here. 239 * We might be inside an interrupt in the middle 240 * of a task switch. 241 * 242 * Note: Use the old spbtr name instead of using the current 243 * satp name to support binutils 2.29 which doesn't know about 244 * the privileged ISA 1.10 yet. 245 */ 246 index = pgd_index(addr); 247 pgd = (pgd_t *)pfn_to_virt(csr_read(sptbr)) + index; 248 pgd_k = init_mm.pgd + index; 249 250 if (!pgd_present(*pgd_k)) 251 goto no_context; 252 set_pgd(pgd, *pgd_k); 253 254 p4d = p4d_offset(pgd, addr); 255 p4d_k = p4d_offset(pgd_k, addr); 256 if (!p4d_present(*p4d_k)) 257 goto no_context; 258 259 pud = pud_offset(p4d, addr); 260 pud_k = pud_offset(p4d_k, addr); 261 if (!pud_present(*pud_k)) 262 goto no_context; 263 264 /* 265 * Since the vmalloc area is global, it is unnecessary 266 * to copy individual PTEs 267 */ 268 pmd = pmd_offset(pud, addr); 269 pmd_k = pmd_offset(pud_k, addr); 270 if (!pmd_present(*pmd_k)) 271 goto no_context; 272 set_pmd(pmd, *pmd_k); 273 274 /* 275 * Make sure the actual PTE exists as well to 276 * catch kernel vmalloc-area accesses to non-mapped 277 * addresses. If we don't do this, this will just 278 * silently loop forever. 279 */ 280 pte_k = pte_offset_kernel(pmd_k, addr); 281 if (!pte_present(*pte_k)) 282 goto no_context; 283 return; 284 } 285 } 286