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