1 /* 2 * Copyright (C) 2000, 2001 Jeff Dike (jdike@karaya.com) 3 * Licensed under the GPL 4 */ 5 6 #include "linux/kernel.h" 7 #include "asm/errno.h" 8 #include "linux/sched.h" 9 #include "linux/mm.h" 10 #include "linux/spinlock.h" 11 #include "linux/init.h" 12 #include "linux/ptrace.h" 13 #include "asm/semaphore.h" 14 #include "asm/pgtable.h" 15 #include "asm/pgalloc.h" 16 #include "asm/tlbflush.h" 17 #include "asm/a.out.h" 18 #include "asm/current.h" 19 #include "asm/irq.h" 20 #include "sysdep/sigcontext.h" 21 #include "kern_util.h" 22 #include "as-layout.h" 23 #include "arch.h" 24 #include "kern.h" 25 #include "chan_kern.h" 26 #include "mconsole_kern.h" 27 #include "mem.h" 28 #include "mem_kern.h" 29 #include "sysdep/sigcontext.h" 30 #include "sysdep/ptrace.h" 31 #include "os.h" 32 #ifdef CONFIG_MODE_SKAS 33 #include "skas.h" 34 #endif 35 #include "os.h" 36 37 /* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by segv(). */ 38 int handle_page_fault(unsigned long address, unsigned long ip, 39 int is_write, int is_user, int *code_out) 40 { 41 struct mm_struct *mm = current->mm; 42 struct vm_area_struct *vma; 43 pgd_t *pgd; 44 pud_t *pud; 45 pmd_t *pmd; 46 pte_t *pte; 47 int err = -EFAULT; 48 49 *code_out = SEGV_MAPERR; 50 51 /* If the fault was during atomic operation, don't take the fault, just 52 * fail. */ 53 if (in_atomic()) 54 goto out_nosemaphore; 55 56 down_read(&mm->mmap_sem); 57 vma = find_vma(mm, address); 58 if(!vma) 59 goto out; 60 else if(vma->vm_start <= address) 61 goto good_area; 62 else if(!(vma->vm_flags & VM_GROWSDOWN)) 63 goto out; 64 else if(is_user && !ARCH_IS_STACKGROW(address)) 65 goto out; 66 else if(expand_stack(vma, address)) 67 goto out; 68 69 good_area: 70 *code_out = SEGV_ACCERR; 71 if(is_write && !(vma->vm_flags & VM_WRITE)) 72 goto out; 73 74 /* Don't require VM_READ|VM_EXEC for write faults! */ 75 if(!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC))) 76 goto out; 77 78 do { 79 int fault; 80 survive: 81 fault = handle_mm_fault(mm, vma, address, is_write); 82 if (unlikely(fault & VM_FAULT_ERROR)) { 83 if (fault & VM_FAULT_OOM) { 84 err = -ENOMEM; 85 goto out_of_memory; 86 } else if (fault & VM_FAULT_SIGBUS) { 87 err = -EACCES; 88 goto out; 89 } 90 BUG(); 91 } 92 if (fault & VM_FAULT_MAJOR) 93 current->maj_flt++; 94 else 95 current->min_flt++; 96 97 pgd = pgd_offset(mm, address); 98 pud = pud_offset(pgd, address); 99 pmd = pmd_offset(pud, address); 100 pte = pte_offset_kernel(pmd, address); 101 } while(!pte_present(*pte)); 102 err = 0; 103 /* The below warning was added in place of 104 * pte_mkyoung(); if (is_write) pte_mkdirty(); 105 * If it's triggered, we'd see normally a hang here (a clean pte is 106 * marked read-only to emulate the dirty bit). 107 * However, the generic code can mark a PTE writable but clean on a 108 * concurrent read fault, triggering this harmlessly. So comment it out. 109 */ 110 #if 0 111 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte))); 112 #endif 113 flush_tlb_page(vma, address); 114 out: 115 up_read(&mm->mmap_sem); 116 out_nosemaphore: 117 return(err); 118 119 /* 120 * We ran out of memory, or some other thing happened to us that made 121 * us unable to handle the page fault gracefully. 122 */ 123 out_of_memory: 124 if (is_init(current)) { 125 up_read(&mm->mmap_sem); 126 yield(); 127 down_read(&mm->mmap_sem); 128 goto survive; 129 } 130 goto out; 131 } 132 133 static void bad_segv(struct faultinfo fi, unsigned long ip) 134 { 135 struct siginfo si; 136 137 si.si_signo = SIGSEGV; 138 si.si_code = SEGV_ACCERR; 139 si.si_addr = (void __user *) FAULT_ADDRESS(fi); 140 current->thread.arch.faultinfo = fi; 141 force_sig_info(SIGSEGV, &si, current); 142 } 143 144 static void segv_handler(int sig, union uml_pt_regs *regs) 145 { 146 struct faultinfo * fi = UPT_FAULTINFO(regs); 147 148 if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){ 149 bad_segv(*fi, UPT_IP(regs)); 150 return; 151 } 152 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs); 153 } 154 155 /* 156 * We give a *copy* of the faultinfo in the regs to segv. 157 * This must be done, since nesting SEGVs could overwrite 158 * the info in the regs. A pointer to the info then would 159 * give us bad data! 160 */ 161 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 162 union uml_pt_regs *regs) 163 { 164 struct siginfo si; 165 void *catcher; 166 int err; 167 int is_write = FAULT_WRITE(fi); 168 unsigned long address = FAULT_ADDRESS(fi); 169 170 if(!is_user && (address >= start_vm) && (address < end_vm)){ 171 flush_tlb_kernel_vm(); 172 return 0; 173 } 174 else if(current->mm == NULL) { 175 show_regs(container_of(regs, struct pt_regs, regs)); 176 panic("Segfault with no mm"); 177 } 178 179 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi)) 180 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code); 181 else { 182 err = -EFAULT; 183 /* A thread accessed NULL, we get a fault, but CR2 is invalid. 184 * This code is used in __do_copy_from_user() of TT mode. */ 185 address = 0; 186 } 187 188 catcher = current->thread.fault_catcher; 189 if(!err) 190 return 0; 191 else if(catcher != NULL){ 192 current->thread.fault_addr = (void *) address; 193 do_longjmp(catcher, 1); 194 } 195 else if(current->thread.fault_addr != NULL) 196 panic("fault_addr set but no fault catcher"); 197 else if(!is_user && arch_fixup(ip, regs)) 198 return 0; 199 200 if(!is_user) { 201 show_regs(container_of(regs, struct pt_regs, regs)); 202 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx", 203 address, ip); 204 } 205 206 if (err == -EACCES) { 207 si.si_signo = SIGBUS; 208 si.si_errno = 0; 209 si.si_code = BUS_ADRERR; 210 si.si_addr = (void __user *)address; 211 current->thread.arch.faultinfo = fi; 212 force_sig_info(SIGBUS, &si, current); 213 } else if (err == -ENOMEM) { 214 printk("VM: killing process %s\n", current->comm); 215 do_exit(SIGKILL); 216 } else { 217 BUG_ON(err != -EFAULT); 218 si.si_signo = SIGSEGV; 219 si.si_addr = (void __user *) address; 220 current->thread.arch.faultinfo = fi; 221 force_sig_info(SIGSEGV, &si, current); 222 } 223 return 0; 224 } 225 226 void relay_signal(int sig, union uml_pt_regs *regs) 227 { 228 if(arch_handle_signal(sig, regs)) 229 return; 230 231 if(!UPT_IS_USER(regs)){ 232 if(sig == SIGBUS) 233 printk("Bus error - the host /dev/shm or /tmp mount " 234 "likely just ran out of space\n"); 235 panic("Kernel mode signal %d", sig); 236 } 237 238 current->thread.arch.faultinfo = *UPT_FAULTINFO(regs); 239 force_sig(sig, current); 240 } 241 242 static void bus_handler(int sig, union uml_pt_regs *regs) 243 { 244 if(current->thread.fault_catcher != NULL) 245 do_longjmp(current->thread.fault_catcher, 1); 246 else relay_signal(sig, regs); 247 } 248 249 static void winch(int sig, union uml_pt_regs *regs) 250 { 251 do_IRQ(WINCH_IRQ, regs); 252 } 253 254 const struct kern_handlers handlinfo_kern = { 255 .relay_signal = relay_signal, 256 .winch = winch, 257 .bus_handler = bus_handler, 258 .page_fault = segv_handler, 259 .sigio_handler = sigio_handler, 260 .timer_handler = timer_handler 261 }; 262 263 void trap_init(void) 264 { 265 } 266