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 #include "../kernel/head.h" 22 23 /* 24 * This routine handles page faults. It determines the address and the 25 * problem, and then passes it off to one of the appropriate routines. 26 */ 27 asmlinkage void do_page_fault(struct pt_regs *regs) 28 { 29 struct task_struct *tsk; 30 struct vm_area_struct *vma; 31 struct mm_struct *mm; 32 unsigned long addr, cause; 33 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 34 int code = SEGV_MAPERR; 35 vm_fault_t fault; 36 37 cause = regs->cause; 38 addr = regs->badaddr; 39 40 tsk = current; 41 mm = tsk->mm; 42 43 /* 44 * Fault-in kernel-space virtual memory on-demand. 45 * The 'reference' page table is init_mm.pgd. 46 * 47 * NOTE! We MUST NOT take any locks for this case. We may 48 * be in an interrupt or a critical region, and should 49 * only copy the information from the master page table, 50 * nothing more. 51 */ 52 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) 53 goto vmalloc_fault; 54 55 /* Enable interrupts if they were enabled in the parent context. */ 56 if (likely(regs->status & SR_PIE)) 57 local_irq_enable(); 58 59 /* 60 * If we're in an interrupt, have no user context, or are running 61 * in an atomic region, then we must not take the fault. 62 */ 63 if (unlikely(faulthandler_disabled() || !mm)) 64 goto no_context; 65 66 if (user_mode(regs)) 67 flags |= FAULT_FLAG_USER; 68 69 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 70 71 retry: 72 down_read(&mm->mmap_sem); 73 vma = find_vma(mm, addr); 74 if (unlikely(!vma)) 75 goto bad_area; 76 if (likely(vma->vm_start <= addr)) 77 goto good_area; 78 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 79 goto bad_area; 80 if (unlikely(expand_stack(vma, addr))) 81 goto bad_area; 82 83 /* 84 * Ok, we have a good vm_area for this memory access, so 85 * we can handle it. 86 */ 87 good_area: 88 code = SEGV_ACCERR; 89 90 switch (cause) { 91 case EXC_INST_PAGE_FAULT: 92 if (!(vma->vm_flags & VM_EXEC)) 93 goto bad_area; 94 break; 95 case EXC_LOAD_PAGE_FAULT: 96 if (!(vma->vm_flags & VM_READ)) 97 goto bad_area; 98 break; 99 case EXC_STORE_PAGE_FAULT: 100 if (!(vma->vm_flags & VM_WRITE)) 101 goto bad_area; 102 flags |= FAULT_FLAG_WRITE; 103 break; 104 default: 105 panic("%s: unhandled cause %lu", __func__, cause); 106 } 107 108 /* 109 * If for any reason at all we could not handle the fault, 110 * make sure we exit gracefully rather than endlessly redo 111 * the fault. 112 */ 113 fault = handle_mm_fault(vma, addr, flags); 114 115 /* 116 * If we need to retry but a fatal signal is pending, handle the 117 * signal first. We do not need to release the mmap_sem because it 118 * would already be released in __lock_page_or_retry in mm/filemap.c. 119 */ 120 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(tsk)) 121 return; 122 123 if (unlikely(fault & VM_FAULT_ERROR)) { 124 if (fault & VM_FAULT_OOM) 125 goto out_of_memory; 126 else if (fault & VM_FAULT_SIGBUS) 127 goto do_sigbus; 128 BUG(); 129 } 130 131 /* 132 * Major/minor page fault accounting is only done on the 133 * initial attempt. If we go through a retry, it is extremely 134 * likely that the page will be found in page cache at that point. 135 */ 136 if (flags & FAULT_FLAG_ALLOW_RETRY) { 137 if (fault & VM_FAULT_MAJOR) { 138 tsk->maj_flt++; 139 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 140 1, regs, addr); 141 } else { 142 tsk->min_flt++; 143 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 144 1, regs, addr); 145 } 146 if (fault & VM_FAULT_RETRY) { 147 /* 148 * Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk 149 * of starvation. 150 */ 151 flags &= ~(FAULT_FLAG_ALLOW_RETRY); 152 flags |= FAULT_FLAG_TRIED; 153 154 /* 155 * No need to up_read(&mm->mmap_sem) as we would 156 * have already released it in __lock_page_or_retry 157 * in mm/filemap.c. 158 */ 159 goto retry; 160 } 161 } 162 163 up_read(&mm->mmap_sem); 164 return; 165 166 /* 167 * Something tried to access memory that isn't in our memory map. 168 * Fix it, but check if it's kernel or user first. 169 */ 170 bad_area: 171 up_read(&mm->mmap_sem); 172 /* User mode accesses just cause a SIGSEGV */ 173 if (user_mode(regs)) { 174 do_trap(regs, SIGSEGV, code, addr); 175 return; 176 } 177 178 no_context: 179 /* Are we prepared to handle this kernel fault? */ 180 if (fixup_exception(regs)) 181 return; 182 183 /* 184 * Oops. The kernel tried to access some bad page. We'll have to 185 * terminate things with extreme prejudice. 186 */ 187 bust_spinlocks(1); 188 pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n", 189 (addr < PAGE_SIZE) ? "NULL pointer dereference" : 190 "paging request", addr); 191 die(regs, "Oops"); 192 do_exit(SIGKILL); 193 194 /* 195 * We ran out of memory, call the OOM killer, and return the userspace 196 * (which will retry the fault, or kill us if we got oom-killed). 197 */ 198 out_of_memory: 199 up_read(&mm->mmap_sem); 200 if (!user_mode(regs)) 201 goto no_context; 202 pagefault_out_of_memory(); 203 return; 204 205 do_sigbus: 206 up_read(&mm->mmap_sem); 207 /* Kernel mode? Handle exceptions or die */ 208 if (!user_mode(regs)) 209 goto no_context; 210 do_trap(regs, SIGBUS, BUS_ADRERR, addr); 211 return; 212 213 vmalloc_fault: 214 { 215 pgd_t *pgd, *pgd_k; 216 pud_t *pud, *pud_k; 217 p4d_t *p4d, *p4d_k; 218 pmd_t *pmd, *pmd_k; 219 pte_t *pte_k; 220 int index; 221 222 /* User mode accesses just cause a SIGSEGV */ 223 if (user_mode(regs)) 224 return do_trap(regs, SIGSEGV, code, addr); 225 226 /* 227 * Synchronize this task's top level page-table 228 * with the 'reference' page table. 229 * 230 * Do _not_ use "tsk->active_mm->pgd" here. 231 * We might be inside an interrupt in the middle 232 * of a task switch. 233 */ 234 index = pgd_index(addr); 235 pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + index; 236 pgd_k = init_mm.pgd + index; 237 238 if (!pgd_present(*pgd_k)) 239 goto no_context; 240 set_pgd(pgd, *pgd_k); 241 242 p4d = p4d_offset(pgd, addr); 243 p4d_k = p4d_offset(pgd_k, addr); 244 if (!p4d_present(*p4d_k)) 245 goto no_context; 246 247 pud = pud_offset(p4d, addr); 248 pud_k = pud_offset(p4d_k, addr); 249 if (!pud_present(*pud_k)) 250 goto no_context; 251 252 /* 253 * Since the vmalloc area is global, it is unnecessary 254 * to copy individual PTEs 255 */ 256 pmd = pmd_offset(pud, addr); 257 pmd_k = pmd_offset(pud_k, addr); 258 if (!pmd_present(*pmd_k)) 259 goto no_context; 260 set_pmd(pmd, *pmd_k); 261 262 /* 263 * Make sure the actual PTE exists as well to 264 * catch kernel vmalloc-area accesses to non-mapped 265 * addresses. If we don't do this, this will just 266 * silently loop forever. 267 */ 268 pte_k = pte_offset_kernel(pmd_k, addr); 269 if (!pte_present(*pte_k)) 270 goto no_context; 271 272 /* 273 * The kernel assumes that TLBs don't cache invalid 274 * entries, but in RISC-V, SFENCE.VMA specifies an 275 * ordering constraint, not a cache flush; it is 276 * necessary even after writing invalid entries. 277 */ 278 local_flush_tlb_page(addr); 279 280 return; 281 } 282 } 283