1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * Memory fault handling for Hexagon 4 * 5 * Copyright (c) 2010-2011, The Linux Foundation. All rights reserved. 6 */ 7 8 /* 9 * Page fault handling for the Hexagon Virtual Machine. 10 * Can also be called by a native port emulating the HVM 11 * execptions. 12 */ 13 14 #include <asm/traps.h> 15 #include <asm/vm_fault.h> 16 #include <linux/uaccess.h> 17 #include <linux/mm.h> 18 #include <linux/sched/signal.h> 19 #include <linux/signal.h> 20 #include <linux/extable.h> 21 #include <linux/hardirq.h> 22 #include <linux/perf_event.h> 23 24 /* 25 * Decode of hardware exception sends us to one of several 26 * entry points. At each, we generate canonical arguments 27 * for handling by the abstract memory management code. 28 */ 29 #define FLT_IFETCH -1 30 #define FLT_LOAD 0 31 #define FLT_STORE 1 32 33 34 /* 35 * Canonical page fault handler 36 */ 37 static void do_page_fault(unsigned long address, long cause, struct pt_regs *regs) 38 { 39 struct vm_area_struct *vma; 40 struct mm_struct *mm = current->mm; 41 int si_signo; 42 int si_code = SEGV_MAPERR; 43 vm_fault_t fault; 44 const struct exception_table_entry *fixup; 45 unsigned int flags = FAULT_FLAG_DEFAULT; 46 47 /* 48 * If we're in an interrupt or have no user context, 49 * then must not take the fault. 50 */ 51 if (unlikely(in_interrupt() || !mm)) 52 goto no_context; 53 54 local_irq_enable(); 55 56 if (user_mode(regs)) 57 flags |= FAULT_FLAG_USER; 58 59 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address); 60 retry: 61 vma = lock_mm_and_find_vma(mm, address, regs); 62 if (unlikely(!vma)) 63 goto bad_area_nosemaphore; 64 65 /* Address space is OK. Now check access rights. */ 66 si_code = SEGV_ACCERR; 67 68 switch (cause) { 69 case FLT_IFETCH: 70 if (!(vma->vm_flags & VM_EXEC)) 71 goto bad_area; 72 break; 73 case FLT_LOAD: 74 if (!(vma->vm_flags & VM_READ)) 75 goto bad_area; 76 break; 77 case FLT_STORE: 78 if (!(vma->vm_flags & VM_WRITE)) 79 goto bad_area; 80 flags |= FAULT_FLAG_WRITE; 81 break; 82 } 83 84 fault = handle_mm_fault(vma, address, flags, regs); 85 86 if (fault_signal_pending(fault, regs)) { 87 if (!user_mode(regs)) 88 goto no_context; 89 return; 90 } 91 92 /* The fault is fully completed (including releasing mmap lock) */ 93 if (fault & VM_FAULT_COMPLETED) 94 return; 95 96 /* The most common case -- we are done. */ 97 if (likely(!(fault & VM_FAULT_ERROR))) { 98 if (fault & VM_FAULT_RETRY) { 99 flags |= FAULT_FLAG_TRIED; 100 goto retry; 101 } 102 103 mmap_read_unlock(mm); 104 return; 105 } 106 107 mmap_read_unlock(mm); 108 109 /* Handle copyin/out exception cases */ 110 if (!user_mode(regs)) 111 goto no_context; 112 113 if (fault & VM_FAULT_OOM) { 114 pagefault_out_of_memory(); 115 return; 116 } 117 118 /* User-mode address is in the memory map, but we are 119 * unable to fix up the page fault. 120 */ 121 if (fault & VM_FAULT_SIGBUS) { 122 si_signo = SIGBUS; 123 si_code = BUS_ADRERR; 124 } 125 /* Address is not in the memory map */ 126 else { 127 si_signo = SIGSEGV; 128 si_code = SEGV_ACCERR; 129 } 130 force_sig_fault(si_signo, si_code, (void __user *)address); 131 return; 132 133 bad_area: 134 mmap_read_unlock(mm); 135 136 bad_area_nosemaphore: 137 if (user_mode(regs)) { 138 force_sig_fault(SIGSEGV, si_code, (void __user *)address); 139 return; 140 } 141 /* Kernel-mode fault falls through */ 142 143 no_context: 144 fixup = search_exception_tables(pt_elr(regs)); 145 if (fixup) { 146 pt_set_elr(regs, fixup->fixup); 147 return; 148 } 149 150 /* Things are looking very, very bad now */ 151 bust_spinlocks(1); 152 printk(KERN_EMERG "Unable to handle kernel paging request at " 153 "virtual address 0x%08lx, regs %p\n", address, regs); 154 die("Bad Kernel VA", regs, SIGKILL); 155 } 156 157 158 void read_protection_fault(struct pt_regs *regs) 159 { 160 unsigned long badvadr = pt_badva(regs); 161 162 do_page_fault(badvadr, FLT_LOAD, regs); 163 } 164 165 void write_protection_fault(struct pt_regs *regs) 166 { 167 unsigned long badvadr = pt_badva(regs); 168 169 do_page_fault(badvadr, FLT_STORE, regs); 170 } 171 172 void execute_protection_fault(struct pt_regs *regs) 173 { 174 unsigned long badvadr = pt_badva(regs); 175 176 do_page_fault(badvadr, FLT_IFETCH, regs); 177 } 178