1 // SPDX-License-Identifier: GPL-2.0 2 // Copyright (C) 2018 Hangzhou C-SKY Microsystems co.,ltd. 3 4 #include <linux/extable.h> 5 #include <linux/kprobes.h> 6 #include <linux/mmu_context.h> 7 #include <linux/perf_event.h> 8 9 int fixup_exception(struct pt_regs *regs) 10 { 11 const struct exception_table_entry *fixup; 12 13 fixup = search_exception_tables(instruction_pointer(regs)); 14 if (fixup) { 15 regs->pc = fixup->fixup; 16 17 return 1; 18 } 19 20 return 0; 21 } 22 23 static inline bool is_write(struct pt_regs *regs) 24 { 25 switch (trap_no(regs)) { 26 case VEC_TLBINVALIDS: 27 return true; 28 case VEC_TLBMODIFIED: 29 return true; 30 } 31 32 return false; 33 } 34 35 #ifdef CONFIG_CPU_HAS_LDSTEX 36 static inline void csky_cmpxchg_fixup(struct pt_regs *regs) 37 { 38 return; 39 } 40 #else 41 extern unsigned long csky_cmpxchg_ldw; 42 extern unsigned long csky_cmpxchg_stw; 43 static inline void csky_cmpxchg_fixup(struct pt_regs *regs) 44 { 45 if (trap_no(regs) != VEC_TLBMODIFIED) 46 return; 47 48 if (instruction_pointer(regs) == csky_cmpxchg_stw) 49 instruction_pointer_set(regs, csky_cmpxchg_ldw); 50 return; 51 } 52 #endif 53 54 static inline void no_context(struct pt_regs *regs, unsigned long addr) 55 { 56 current->thread.trap_no = trap_no(regs); 57 58 /* Are we prepared to handle this kernel fault? */ 59 if (fixup_exception(regs)) 60 return; 61 62 /* 63 * Oops. The kernel tried to access some bad page. We'll have to 64 * terminate things with extreme prejudice. 65 */ 66 bust_spinlocks(1); 67 pr_alert("Unable to handle kernel paging request at virtual " 68 "addr 0x%08lx, pc: 0x%08lx\n", addr, regs->pc); 69 die(regs, "Oops"); 70 make_task_dead(SIGKILL); 71 } 72 73 static inline void mm_fault_error(struct pt_regs *regs, unsigned long addr, vm_fault_t fault) 74 { 75 current->thread.trap_no = trap_no(regs); 76 77 if (fault & VM_FAULT_OOM) { 78 /* 79 * We ran out of memory, call the OOM killer, and return the userspace 80 * (which will retry the fault, or kill us if we got oom-killed). 81 */ 82 if (!user_mode(regs)) { 83 no_context(regs, addr); 84 return; 85 } 86 pagefault_out_of_memory(); 87 return; 88 } else if (fault & VM_FAULT_SIGBUS) { 89 /* Kernel mode? Handle exceptions or die */ 90 if (!user_mode(regs)) { 91 no_context(regs, addr); 92 return; 93 } 94 do_trap(regs, SIGBUS, BUS_ADRERR, addr); 95 return; 96 } 97 BUG(); 98 } 99 100 static inline void bad_area_nosemaphore(struct pt_regs *regs, struct mm_struct *mm, int code, unsigned long addr) 101 { 102 /* 103 * Something tried to access memory that isn't in our memory map. 104 * Fix it, but check if it's kernel or user first. 105 */ 106 /* User mode accesses just cause a SIGSEGV */ 107 if (user_mode(regs)) { 108 do_trap(regs, SIGSEGV, code, addr); 109 return; 110 } 111 112 no_context(regs, addr); 113 } 114 115 static inline void vmalloc_fault(struct pt_regs *regs, int code, unsigned long addr) 116 { 117 pgd_t *pgd, *pgd_k; 118 pud_t *pud, *pud_k; 119 pmd_t *pmd, *pmd_k; 120 pte_t *pte_k; 121 int offset; 122 123 /* User mode accesses just cause a SIGSEGV */ 124 if (user_mode(regs)) { 125 do_trap(regs, SIGSEGV, code, addr); 126 return; 127 } 128 129 /* 130 * Synchronize this task's top level page-table 131 * with the 'reference' page table. 132 * 133 * Do _not_ use "tsk" here. We might be inside 134 * an interrupt in the middle of a task switch.. 135 */ 136 offset = pgd_index(addr); 137 138 pgd = get_pgd() + offset; 139 pgd_k = init_mm.pgd + offset; 140 141 if (!pgd_present(*pgd_k)) { 142 no_context(regs, addr); 143 return; 144 } 145 set_pgd(pgd, *pgd_k); 146 147 pud = (pud_t *)pgd; 148 pud_k = (pud_t *)pgd_k; 149 if (!pud_present(*pud_k)) { 150 no_context(regs, addr); 151 return; 152 } 153 154 pmd = pmd_offset(pud, addr); 155 pmd_k = pmd_offset(pud_k, addr); 156 if (!pmd_present(*pmd_k)) { 157 no_context(regs, addr); 158 return; 159 } 160 set_pmd(pmd, *pmd_k); 161 162 pte_k = pte_offset_kernel(pmd_k, addr); 163 if (!pte_present(*pte_k)) { 164 no_context(regs, addr); 165 return; 166 } 167 168 flush_tlb_one(addr); 169 } 170 171 static inline bool access_error(struct pt_regs *regs, struct vm_area_struct *vma) 172 { 173 if (is_write(regs)) { 174 if (!(vma->vm_flags & VM_WRITE)) 175 return true; 176 } else { 177 if (unlikely(!vma_is_accessible(vma))) 178 return true; 179 } 180 return false; 181 } 182 183 /* 184 * This routine handles page faults. It determines the address and the 185 * problem, and then passes it off to one of the appropriate routines. 186 */ 187 asmlinkage void do_page_fault(struct pt_regs *regs) 188 { 189 struct task_struct *tsk; 190 struct vm_area_struct *vma; 191 struct mm_struct *mm; 192 unsigned long addr = read_mmu_entryhi() & PAGE_MASK; 193 unsigned int flags = FAULT_FLAG_DEFAULT; 194 int code = SEGV_MAPERR; 195 vm_fault_t fault; 196 197 tsk = current; 198 mm = tsk->mm; 199 200 csky_cmpxchg_fixup(regs); 201 202 if (kprobe_page_fault(regs, tsk->thread.trap_no)) 203 return; 204 205 /* 206 * Fault-in kernel-space virtual memory on-demand. 207 * The 'reference' page table is init_mm.pgd. 208 * 209 * NOTE! We MUST NOT take any locks for this case. We may 210 * be in an interrupt or a critical region, and should 211 * only copy the information from the master page table, 212 * nothing more. 213 */ 214 if (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END))) { 215 vmalloc_fault(regs, code, addr); 216 return; 217 } 218 219 /* Enable interrupts if they were enabled in the parent context. */ 220 if (likely(regs->sr & BIT(6))) 221 local_irq_enable(); 222 223 /* 224 * If we're in an interrupt, have no user context, or are running 225 * in an atomic region, then we must not take the fault. 226 */ 227 if (unlikely(faulthandler_disabled() || !mm)) { 228 no_context(regs, addr); 229 return; 230 } 231 232 if (user_mode(regs)) 233 flags |= FAULT_FLAG_USER; 234 235 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); 236 237 if (is_write(regs)) 238 flags |= FAULT_FLAG_WRITE; 239 retry: 240 vma = lock_mm_and_find_vma(mm, addr, regs); 241 if (unlikely(!vma)) { 242 bad_area_nosemaphore(regs, mm, code, addr); 243 return; 244 } 245 246 /* 247 * Ok, we have a good vm_area for this memory access, so 248 * we can handle it. 249 */ 250 code = SEGV_ACCERR; 251 252 if (unlikely(access_error(regs, vma))) { 253 mmap_read_unlock(mm); 254 bad_area_nosemaphore(regs, mm, code, addr); 255 return; 256 } 257 258 /* 259 * If for any reason at all we could not handle the fault, 260 * make sure we exit gracefully rather than endlessly redo 261 * the fault. 262 */ 263 fault = handle_mm_fault(vma, addr, flags, regs); 264 265 /* 266 * If we need to retry but a fatal signal is pending, handle the 267 * signal first. We do not need to release the mmap_lock because it 268 * would already be released in __lock_page_or_retry in mm/filemap.c. 269 */ 270 if (fault_signal_pending(fault, regs)) { 271 if (!user_mode(regs)) 272 no_context(regs, addr); 273 return; 274 } 275 276 /* The fault is fully completed (including releasing mmap lock) */ 277 if (fault & VM_FAULT_COMPLETED) 278 return; 279 280 if (unlikely((fault & VM_FAULT_RETRY) && (flags & FAULT_FLAG_ALLOW_RETRY))) { 281 flags |= FAULT_FLAG_TRIED; 282 283 /* 284 * No need to mmap_read_unlock(mm) as we would 285 * have already released it in __lock_page_or_retry 286 * in mm/filemap.c. 287 */ 288 goto retry; 289 } 290 291 mmap_read_unlock(mm); 292 293 if (unlikely(fault & VM_FAULT_ERROR)) { 294 mm_fault_error(regs, addr, fault); 295 return; 296 } 297 return; 298 } 299