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 #include <asm/tlbflush.h> 20 21 /* 22 * This routine handles page faults. It determines the address and the 23 * problem, and then passes it off to one of the appropriate routines. 24 */ 25 asmlinkage void do_page_fault(struct pt_regs *regs) 26 { 27 struct task_struct *tsk; 28 struct vm_area_struct *vma; 29 struct mm_struct *mm; 30 unsigned long addr, cause; 31 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 32 int code = SEGV_MAPERR; 33 vm_fault_t fault; 34 35 cause = regs->scause; 36 addr = regs->sbadaddr; 37 38 tsk = current; 39 mm = tsk->mm; 40 41 /* 42 * Fault-in kernel-space virtual memory on-demand. 43 * The 'reference' page table is init_mm.pgd. 44 * 45 * NOTE! We MUST NOT take any locks for this case. We may 46 * be in an interrupt or a critical region, and should 47 * only copy the information from the master page table, 48 * nothing more. 49 */ 50 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) 51 goto vmalloc_fault; 52 53 /* Enable interrupts if they were enabled in the parent context. */ 54 if (likely(regs->sstatus & SR_SPIE)) 55 local_irq_enable(); 56 57 /* 58 * If we're in an interrupt, have no user context, or are running 59 * in an atomic region, then we must not take the fault. 60 */ 61 if (unlikely(faulthandler_disabled() || !mm)) 62 goto no_context; 63 64 if (user_mode(regs)) 65 flags |= FAULT_FLAG_USER; 66 67 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 68 69 retry: 70 down_read(&mm->mmap_sem); 71 vma = find_vma(mm, addr); 72 if (unlikely(!vma)) 73 goto bad_area; 74 if (likely(vma->vm_start <= addr)) 75 goto good_area; 76 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 77 goto bad_area; 78 if (unlikely(expand_stack(vma, addr))) 79 goto bad_area; 80 81 /* 82 * Ok, we have a good vm_area for this memory access, so 83 * we can handle it. 84 */ 85 good_area: 86 code = SEGV_ACCERR; 87 88 switch (cause) { 89 case EXC_INST_PAGE_FAULT: 90 if (!(vma->vm_flags & VM_EXEC)) 91 goto bad_area; 92 break; 93 case EXC_LOAD_PAGE_FAULT: 94 if (!(vma->vm_flags & VM_READ)) 95 goto bad_area; 96 break; 97 case EXC_STORE_PAGE_FAULT: 98 if (!(vma->vm_flags & VM_WRITE)) 99 goto bad_area; 100 flags |= FAULT_FLAG_WRITE; 101 break; 102 default: 103 panic("%s: unhandled cause %lu", __func__, cause); 104 } 105 106 /* 107 * If for any reason at all we could not handle the fault, 108 * make sure we exit gracefully rather than endlessly redo 109 * the fault. 110 */ 111 fault = handle_mm_fault(vma, addr, flags); 112 113 /* 114 * If we need to retry but a fatal signal is pending, handle the 115 * signal first. We do not need to release the mmap_sem because it 116 * would already be released in __lock_page_or_retry in mm/filemap.c. 117 */ 118 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk)) 119 return; 120 121 if (unlikely(fault & VM_FAULT_ERROR)) { 122 if (fault & VM_FAULT_OOM) 123 goto out_of_memory; 124 else if (fault & VM_FAULT_SIGBUS) 125 goto do_sigbus; 126 BUG(); 127 } 128 129 /* 130 * Major/minor page fault accounting is only done on the 131 * initial attempt. If we go through a retry, it is extremely 132 * likely that the page will be found in page cache at that point. 133 */ 134 if (flags & FAULT_FLAG_ALLOW_RETRY) { 135 if (fault & VM_FAULT_MAJOR) { 136 tsk->maj_flt++; 137 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 138 1, regs, addr); 139 } else { 140 tsk->min_flt++; 141 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 142 1, regs, addr); 143 } 144 if (fault & VM_FAULT_RETRY) { 145 /* 146 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 147 * of starvation. 148 */ 149 flags &= ~(FAULT_FLAG_ALLOW_RETRY); 150 flags |= FAULT_FLAG_TRIED; 151 152 /* 153 * No need to up_read(&mm->mmap_sem) as we would 154 * have already released it in __lock_page_or_retry 155 * in mm/filemap.c. 156 */ 157 goto retry; 158 } 159 } 160 161 up_read(&mm->mmap_sem); 162 return; 163 164 /* 165 * Something tried to access memory that isn't in our memory map. 166 * Fix it, but check if it's kernel or user first. 167 */ 168 bad_area: 169 up_read(&mm->mmap_sem); 170 /* User mode accesses just cause a SIGSEGV */ 171 if (user_mode(regs)) { 172 do_trap(regs, SIGSEGV, code, addr); 173 return; 174 } 175 176 no_context: 177 /* Are we prepared to handle this kernel fault? */ 178 if (fixup_exception(regs)) 179 return; 180 181 /* 182 * Oops. The kernel tried to access some bad page. We'll have to 183 * terminate things with extreme prejudice. 184 */ 185 bust_spinlocks(1); 186 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", 187 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 188 "paging request", addr); 189 die(regs, "Oops"); 190 do_exit(SIGKILL); 191 192 /* 193 * We ran out of memory, call the OOM killer, and return the userspace 194 * (which will retry the fault, or kill us if we got oom-killed). 195 */ 196 out_of_memory: 197 up_read(&mm->mmap_sem); 198 if (!user_mode(regs)) 199 goto no_context; 200 pagefault_out_of_memory(); 201 return; 202 203 do_sigbus: 204 up_read(&mm->mmap_sem); 205 /* Kernel mode? Handle exceptions or die */ 206 if (!user_mode(regs)) 207 goto no_context; 208 do_trap(regs, SIGBUS, BUS_ADRERR, addr); 209 return; 210 211 vmalloc_fault: 212 { 213 pgd_t *pgd, *pgd_k; 214 pud_t *pud, *pud_k; 215 p4d_t *p4d, *p4d_k; 216 pmd_t *pmd, *pmd_k; 217 pte_t *pte_k; 218 int index; 219 220 /* User mode accesses just cause a SIGSEGV */ 221 if (user_mode(regs)) 222 return do_trap(regs, SIGSEGV, code, addr); 223 224 /* 225 * Synchronize this task's top level page-table 226 * with the 'reference' page table. 227 * 228 * Do _not_ use "tsk->active_mm->pgd" here. 229 * We might be inside an interrupt in the middle 230 * of a task switch. 231 */ 232 index = pgd_index(addr); 233 pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index; 234 pgd_k = init_mm.pgd + index; 235 236 if (!pgd_present(*pgd_k)) 237 goto no_context; 238 set_pgd(pgd, *pgd_k); 239 240 p4d = p4d_offset(pgd, addr); 241 p4d_k = p4d_offset(pgd_k, addr); 242 if (!p4d_present(*p4d_k)) 243 goto no_context; 244 245 pud = pud_offset(p4d, addr); 246 pud_k = pud_offset(p4d_k, addr); 247 if (!pud_present(*pud_k)) 248 goto no_context; 249 250 /* 251 * Since the vmalloc area is global, it is unnecessary 252 * to copy individual PTEs 253 */ 254 pmd = pmd_offset(pud, addr); 255 pmd_k = pmd_offset(pud_k, addr); 256 if (!pmd_present(*pmd_k)) 257 goto no_context; 258 set_pmd(pmd, *pmd_k); 259 260 /* 261 * Make sure the actual PTE exists as well to 262 * catch kernel vmalloc-area accesses to non-mapped 263 * addresses. If we don't do this, this will just 264 * silently loop forever. 265 */ 266 pte_k = pte_offset_kernel(pmd_k, addr); 267 if (!pte_present(*pte_k)) 268 goto no_context; 269 270 /* 271 * The kernel assumes that TLBs don't cache invalid 272 * entries, but in RISC-V, SFENCE.VMA specifies an 273 * ordering constraint, not a cache flush; it is 274 * necessary even after writing invalid entries. 275 */ 276 local_flush_tlb_page(addr); 277 278 return; 279 } 280 } 281