1 // SPDX-License-Identifier: GPL-2.0-or-later 2 /* 3 * Copyright (C) 2009 Sunplus Core Technology Co., Ltd. 4 * Lennox Wu <lennox.wu@sunplusct.com> 5 * Chen Liqin <liqin.chen@sunplusct.com> 6 * Copyright (C) 2012 Regents of the University of California 7 */ 8 9 10 #include <linux/mm.h> 11 #include <linux/kernel.h> 12 #include <linux/interrupt.h> 13 #include <linux/perf_event.h> 14 #include <linux/signal.h> 15 #include <linux/uaccess.h> 16 17 #include <asm/pgalloc.h> 18 #include <asm/ptrace.h> 19 20 /* 21 * This routine handles page faults. It determines the address and the 22 * problem, and then passes it off to one of the appropriate routines. 23 */ 24 asmlinkage void do_page_fault(struct pt_regs *regs) 25 { 26 struct task_struct *tsk; 27 struct vm_area_struct *vma; 28 struct mm_struct *mm; 29 unsigned long addr, cause; 30 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 31 int code = SEGV_MAPERR; 32 vm_fault_t fault; 33 34 cause = regs->scause; 35 addr = regs->sbadaddr; 36 37 tsk = current; 38 mm = tsk->mm; 39 40 /* 41 * Fault-in kernel-space virtual memory on-demand. 42 * The 'reference' page table is init_mm.pgd. 43 * 44 * NOTE! We MUST NOT take any locks for this case. We may 45 * be in an interrupt or a critical region, and should 46 * only copy the information from the master page table, 47 * nothing more. 48 */ 49 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) 50 goto vmalloc_fault; 51 52 /* Enable interrupts if they were enabled in the parent context. */ 53 if (likely(regs->sstatus & SR_SPIE)) 54 local_irq_enable(); 55 56 /* 57 * If we're in an interrupt, have no user context, or are running 58 * in an atomic region, then we must not take the fault. 59 */ 60 if (unlikely(faulthandler_disabled() || !mm)) 61 goto no_context; 62 63 if (user_mode(regs)) 64 flags |= FAULT_FLAG_USER; 65 66 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 67 68 retry: 69 down_read(&mm->mmap_sem); 70 vma = find_vma(mm, addr); 71 if (unlikely(!vma)) 72 goto bad_area; 73 if (likely(vma->vm_start <= addr)) 74 goto good_area; 75 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 76 goto bad_area; 77 if (unlikely(expand_stack(vma, addr))) 78 goto bad_area; 79 80 /* 81 * Ok, we have a good vm_area for this memory access, so 82 * we can handle it. 83 */ 84 good_area: 85 code = SEGV_ACCERR; 86 87 switch (cause) { 88 case EXC_INST_PAGE_FAULT: 89 if (!(vma->vm_flags & VM_EXEC)) 90 goto bad_area; 91 break; 92 case EXC_LOAD_PAGE_FAULT: 93 if (!(vma->vm_flags & VM_READ)) 94 goto bad_area; 95 break; 96 case EXC_STORE_PAGE_FAULT: 97 if (!(vma->vm_flags & VM_WRITE)) 98 goto bad_area; 99 flags |= FAULT_FLAG_WRITE; 100 break; 101 default: 102 panic("%s: unhandled cause %lu", __func__, cause); 103 } 104 105 /* 106 * If for any reason at all we could not handle the fault, 107 * make sure we exit gracefully rather than endlessly redo 108 * the fault. 109 */ 110 fault = handle_mm_fault(vma, addr, flags); 111 112 /* 113 * If we need to retry but a fatal signal is pending, handle the 114 * signal first. We do not need to release the mmap_sem because it 115 * would already be released in __lock_page_or_retry in mm/filemap.c. 116 */ 117 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk)) 118 return; 119 120 if (unlikely(fault & VM_FAULT_ERROR)) { 121 if (fault & VM_FAULT_OOM) 122 goto out_of_memory; 123 else if (fault & VM_FAULT_SIGBUS) 124 goto do_sigbus; 125 BUG(); 126 } 127 128 /* 129 * Major/minor page fault accounting is only done on the 130 * initial attempt. If we go through a retry, it is extremely 131 * likely that the page will be found in page cache at that point. 132 */ 133 if (flags & FAULT_FLAG_ALLOW_RETRY) { 134 if (fault & VM_FAULT_MAJOR) { 135 tsk->maj_flt++; 136 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 137 1, regs, addr); 138 } else { 139 tsk->min_flt++; 140 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 141 1, regs, addr); 142 } 143 if (fault & VM_FAULT_RETRY) { 144 /* 145 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 146 * of starvation. 147 */ 148 flags &= ~(FAULT_FLAG_ALLOW_RETRY); 149 flags |= FAULT_FLAG_TRIED; 150 151 /* 152 * No need to up_read(&mm->mmap_sem) as we would 153 * have already released it in __lock_page_or_retry 154 * in mm/filemap.c. 155 */ 156 goto retry; 157 } 158 } 159 160 up_read(&mm->mmap_sem); 161 return; 162 163 /* 164 * Something tried to access memory that isn't in our memory map. 165 * Fix it, but check if it's kernel or user first. 166 */ 167 bad_area: 168 up_read(&mm->mmap_sem); 169 /* User mode accesses just cause a SIGSEGV */ 170 if (user_mode(regs)) { 171 do_trap(regs, SIGSEGV, code, addr, tsk); 172 return; 173 } 174 175 no_context: 176 /* Are we prepared to handle this kernel fault? */ 177 if (fixup_exception(regs)) 178 return; 179 180 /* 181 * Oops. The kernel tried to access some bad page. We'll have to 182 * terminate things with extreme prejudice. 183 */ 184 bust_spinlocks(1); 185 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", 186 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 187 "paging request", addr); 188 die(regs, "Oops"); 189 do_exit(SIGKILL); 190 191 /* 192 * We ran out of memory, call the OOM killer, and return the userspace 193 * (which will retry the fault, or kill us if we got oom-killed). 194 */ 195 out_of_memory: 196 up_read(&mm->mmap_sem); 197 if (!user_mode(regs)) 198 goto no_context; 199 pagefault_out_of_memory(); 200 return; 201 202 do_sigbus: 203 up_read(&mm->mmap_sem); 204 /* Kernel mode? Handle exceptions or die */ 205 if (!user_mode(regs)) 206 goto no_context; 207 do_trap(regs, SIGBUS, BUS_ADRERR, addr, tsk); 208 return; 209 210 vmalloc_fault: 211 { 212 pgd_t *pgd, *pgd_k; 213 pud_t *pud, *pud_k; 214 p4d_t *p4d, *p4d_k; 215 pmd_t *pmd, *pmd_k; 216 pte_t *pte_k; 217 int index; 218 219 /* User mode accesses just cause a SIGSEGV */ 220 if (user_mode(regs)) 221 return do_trap(regs, SIGSEGV, code, addr, tsk); 222 223 /* 224 * Synchronize this task's top level page-table 225 * with the 'reference' page table. 226 * 227 * Do _not_ use "tsk->active_mm->pgd" here. 228 * We might be inside an interrupt in the middle 229 * of a task switch. 230 */ 231 index = pgd_index(addr); 232 pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index; 233 pgd_k = init_mm.pgd + index; 234 235 if (!pgd_present(*pgd_k)) 236 goto no_context; 237 set_pgd(pgd, *pgd_k); 238 239 p4d = p4d_offset(pgd, addr); 240 p4d_k = p4d_offset(pgd_k, addr); 241 if (!p4d_present(*p4d_k)) 242 goto no_context; 243 244 pud = pud_offset(p4d, addr); 245 pud_k = pud_offset(p4d_k, addr); 246 if (!pud_present(*pud_k)) 247 goto no_context; 248 249 /* 250 * Since the vmalloc area is global, it is unnecessary 251 * to copy individual PTEs 252 */ 253 pmd = pmd_offset(pud, addr); 254 pmd_k = pmd_offset(pud_k, addr); 255 if (!pmd_present(*pmd_k)) 256 goto no_context; 257 set_pmd(pmd, *pmd_k); 258 259 /* 260 * Make sure the actual PTE exists as well to 261 * catch kernel vmalloc-area accesses to non-mapped 262 * addresses. If we don't do this, this will just 263 * silently loop forever. 264 */ 265 pte_k = pte_offset_kernel(pmd_k, addr); 266 if (!pte_present(*pte_k)) 267 goto no_context; 268 return; 269 } 270 } 271