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 survive: 80 switch (handle_mm_fault(mm, vma, address, is_write)){ 81 case VM_FAULT_MINOR: 82 current->min_flt++; 83 break; 84 case VM_FAULT_MAJOR: 85 current->maj_flt++; 86 break; 87 case VM_FAULT_SIGBUS: 88 err = -EACCES; 89 goto out; 90 case VM_FAULT_OOM: 91 err = -ENOMEM; 92 goto out_of_memory; 93 default: 94 BUG(); 95 } 96 pgd = pgd_offset(mm, address); 97 pud = pud_offset(pgd, address); 98 pmd = pmd_offset(pud, address); 99 pte = pte_offset_kernel(pmd, address); 100 } while(!pte_present(*pte)); 101 err = 0; 102 /* The below warning was added in place of 103 * pte_mkyoung(); if (is_write) pte_mkdirty(); 104 * If it's triggered, we'd see normally a hang here (a clean pte is 105 * marked read-only to emulate the dirty bit). 106 * However, the generic code can mark a PTE writable but clean on a 107 * concurrent read fault, triggering this harmlessly. So comment it out. 108 */ 109 #if 0 110 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte))); 111 #endif 112 flush_tlb_page(vma, address); 113 out: 114 up_read(&mm->mmap_sem); 115 out_nosemaphore: 116 return(err); 117 118 /* 119 * We ran out of memory, or some other thing happened to us that made 120 * us unable to handle the page fault gracefully. 121 */ 122 out_of_memory: 123 if (is_init(current)) { 124 up_read(&mm->mmap_sem); 125 yield(); 126 down_read(&mm->mmap_sem); 127 goto survive; 128 } 129 goto out; 130 } 131 132 static void bad_segv(struct faultinfo fi, unsigned long ip) 133 { 134 struct siginfo si; 135 136 si.si_signo = SIGSEGV; 137 si.si_code = SEGV_ACCERR; 138 si.si_addr = (void __user *) FAULT_ADDRESS(fi); 139 current->thread.arch.faultinfo = fi; 140 force_sig_info(SIGSEGV, &si, current); 141 } 142 143 static void segv_handler(int sig, union uml_pt_regs *regs) 144 { 145 struct faultinfo * fi = UPT_FAULTINFO(regs); 146 147 if(UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)){ 148 bad_segv(*fi, UPT_IP(regs)); 149 return; 150 } 151 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs); 152 } 153 154 /* 155 * We give a *copy* of the faultinfo in the regs to segv. 156 * This must be done, since nesting SEGVs could overwrite 157 * the info in the regs. A pointer to the info then would 158 * give us bad data! 159 */ 160 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 161 union uml_pt_regs *regs) 162 { 163 struct siginfo si; 164 void *catcher; 165 int err; 166 int is_write = FAULT_WRITE(fi); 167 unsigned long address = FAULT_ADDRESS(fi); 168 169 if(!is_user && (address >= start_vm) && (address < end_vm)){ 170 flush_tlb_kernel_vm(); 171 return 0; 172 } 173 else if(current->mm == NULL) { 174 show_regs(container_of(regs, struct pt_regs, regs)); 175 panic("Segfault with no mm"); 176 } 177 178 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi)) 179 err = handle_page_fault(address, ip, is_write, is_user, &si.si_code); 180 else { 181 err = -EFAULT; 182 /* A thread accessed NULL, we get a fault, but CR2 is invalid. 183 * This code is used in __do_copy_from_user() of TT mode. */ 184 address = 0; 185 } 186 187 catcher = current->thread.fault_catcher; 188 if(!err) 189 return 0; 190 else if(catcher != NULL){ 191 current->thread.fault_addr = (void *) address; 192 do_longjmp(catcher, 1); 193 } 194 else if(current->thread.fault_addr != NULL) 195 panic("fault_addr set but no fault catcher"); 196 else if(!is_user && arch_fixup(ip, regs)) 197 return 0; 198 199 if(!is_user) { 200 show_regs(container_of(regs, struct pt_regs, regs)); 201 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx", 202 address, ip); 203 } 204 205 if (err == -EACCES) { 206 si.si_signo = SIGBUS; 207 si.si_errno = 0; 208 si.si_code = BUS_ADRERR; 209 si.si_addr = (void __user *)address; 210 current->thread.arch.faultinfo = fi; 211 force_sig_info(SIGBUS, &si, current); 212 } else if (err == -ENOMEM) { 213 printk("VM: killing process %s\n", current->comm); 214 do_exit(SIGKILL); 215 } else { 216 BUG_ON(err != -EFAULT); 217 si.si_signo = SIGSEGV; 218 si.si_addr = (void __user *) address; 219 current->thread.arch.faultinfo = fi; 220 force_sig_info(SIGSEGV, &si, current); 221 } 222 return 0; 223 } 224 225 void relay_signal(int sig, union uml_pt_regs *regs) 226 { 227 if(arch_handle_signal(sig, regs)) 228 return; 229 230 if(!UPT_IS_USER(regs)){ 231 if(sig == SIGBUS) 232 printk("Bus error - the host /dev/shm or /tmp mount " 233 "likely just ran out of space\n"); 234 panic("Kernel mode signal %d", sig); 235 } 236 237 current->thread.arch.faultinfo = *UPT_FAULTINFO(regs); 238 force_sig(sig, current); 239 } 240 241 static void bus_handler(int sig, union uml_pt_regs *regs) 242 { 243 if(current->thread.fault_catcher != NULL) 244 do_longjmp(current->thread.fault_catcher, 1); 245 else relay_signal(sig, regs); 246 } 247 248 static void winch(int sig, union uml_pt_regs *regs) 249 { 250 do_IRQ(WINCH_IRQ, regs); 251 } 252 253 const struct kern_handlers handlinfo_kern = { 254 .relay_signal = relay_signal, 255 .winch = winch, 256 .bus_handler = bus_handler, 257 .page_fault = segv_handler, 258 .sigio_handler = sigio_handler, 259 .timer_handler = timer_handler 260 }; 261 262 void trap_init(void) 263 { 264 } 265