1 /* 2 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com) 3 * Licensed under the GPL 4 */ 5 6 #include <linux/mm.h> 7 #include <linux/sched.h> 8 #include <linux/hardirq.h> 9 #include <linux/module.h> 10 #include <asm/current.h> 11 #include <asm/pgtable.h> 12 #include <asm/tlbflush.h> 13 #include <arch.h> 14 #include <as-layout.h> 15 #include <kern_util.h> 16 #include <os.h> 17 #include <skas.h> 18 19 /* 20 * Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by 21 * segv(). 22 */ 23 int handle_page_fault(unsigned long address, unsigned long ip, 24 int is_write, int is_user, int *code_out) 25 { 26 struct mm_struct *mm = current->mm; 27 struct vm_area_struct *vma; 28 pgd_t *pgd; 29 pud_t *pud; 30 pmd_t *pmd; 31 pte_t *pte; 32 int err = -EFAULT; 33 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 34 35 *code_out = SEGV_MAPERR; 36 37 /* 38 * If the fault was during atomic operation, don't take the fault, just 39 * fail. 40 */ 41 if (in_atomic()) 42 goto out_nosemaphore; 43 44 if (is_user) 45 flags |= FAULT_FLAG_USER; 46 retry: 47 down_read(&mm->mmap_sem); 48 vma = find_vma(mm, address); 49 if (!vma) 50 goto out; 51 else if (vma->vm_start <= address) 52 goto good_area; 53 else if (!(vma->vm_flags & VM_GROWSDOWN)) 54 goto out; 55 else if (is_user && !ARCH_IS_STACKGROW(address)) 56 goto out; 57 else if (expand_stack(vma, address)) 58 goto out; 59 60 good_area: 61 *code_out = SEGV_ACCERR; 62 if (is_write) { 63 if (!(vma->vm_flags & VM_WRITE)) 64 goto out; 65 flags |= FAULT_FLAG_WRITE; 66 } else { 67 /* Don't require VM_READ|VM_EXEC for write faults! */ 68 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 69 goto out; 70 } 71 72 do { 73 int fault; 74 75 fault = handle_mm_fault(mm, vma, address, flags); 76 77 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 78 goto out_nosemaphore; 79 80 if (unlikely(fault & VM_FAULT_ERROR)) { 81 if (fault & VM_FAULT_OOM) { 82 goto out_of_memory; 83 } else if (fault & VM_FAULT_SIGBUS) { 84 err = -EACCES; 85 goto out; 86 } 87 BUG(); 88 } 89 if (flags & FAULT_FLAG_ALLOW_RETRY) { 90 if (fault & VM_FAULT_MAJOR) 91 current->maj_flt++; 92 else 93 current->min_flt++; 94 if (fault & VM_FAULT_RETRY) { 95 flags &= ~FAULT_FLAG_ALLOW_RETRY; 96 flags |= FAULT_FLAG_TRIED; 97 98 goto retry; 99 } 100 } 101 102 pgd = pgd_offset(mm, address); 103 pud = pud_offset(pgd, address); 104 pmd = pmd_offset(pud, address); 105 pte = pte_offset_kernel(pmd, address); 106 } while (!pte_present(*pte)); 107 err = 0; 108 /* 109 * The below warning was added in place of 110 * pte_mkyoung(); if (is_write) pte_mkdirty(); 111 * If it's triggered, we'd see normally a hang here (a clean pte is 112 * marked read-only to emulate the dirty bit). 113 * However, the generic code can mark a PTE writable but clean on a 114 * concurrent read fault, triggering this harmlessly. So comment it out. 115 */ 116 #if 0 117 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte))); 118 #endif 119 flush_tlb_page(vma, address); 120 out: 121 up_read(&mm->mmap_sem); 122 out_nosemaphore: 123 return err; 124 125 out_of_memory: 126 /* 127 * We ran out of memory, call the OOM killer, and return the userspace 128 * (which will retry the fault, or kill us if we got oom-killed). 129 */ 130 up_read(&mm->mmap_sem); 131 if (!is_user) 132 goto out_nosemaphore; 133 pagefault_out_of_memory(); 134 return 0; 135 } 136 EXPORT_SYMBOL(handle_page_fault); 137 138 static void show_segv_info(struct uml_pt_regs *regs) 139 { 140 struct task_struct *tsk = current; 141 struct faultinfo *fi = UPT_FAULTINFO(regs); 142 143 if (!unhandled_signal(tsk, SIGSEGV)) 144 return; 145 146 if (!printk_ratelimit()) 147 return; 148 149 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x", 150 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 151 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi), 152 (void *)UPT_IP(regs), (void *)UPT_SP(regs), 153 fi->error_code); 154 155 print_vma_addr(KERN_CONT " in ", UPT_IP(regs)); 156 printk(KERN_CONT "\n"); 157 } 158 159 static void bad_segv(struct faultinfo fi, unsigned long ip) 160 { 161 struct siginfo si; 162 163 si.si_signo = SIGSEGV; 164 si.si_code = SEGV_ACCERR; 165 si.si_addr = (void __user *) FAULT_ADDRESS(fi); 166 current->thread.arch.faultinfo = fi; 167 force_sig_info(SIGSEGV, &si, current); 168 } 169 170 void fatal_sigsegv(void) 171 { 172 force_sigsegv(SIGSEGV, current); 173 do_signal(); 174 /* 175 * This is to tell gcc that we're not returning - do_signal 176 * can, in general, return, but in this case, it's not, since 177 * we just got a fatal SIGSEGV queued. 178 */ 179 os_dump_core(); 180 } 181 182 void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs) 183 { 184 struct faultinfo * fi = UPT_FAULTINFO(regs); 185 186 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) { 187 show_segv_info(regs); 188 bad_segv(*fi, UPT_IP(regs)); 189 return; 190 } 191 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs); 192 } 193 194 /* 195 * We give a *copy* of the faultinfo in the regs to segv. 196 * This must be done, since nesting SEGVs could overwrite 197 * the info in the regs. A pointer to the info then would 198 * give us bad data! 199 */ 200 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 201 struct uml_pt_regs *regs) 202 { 203 struct siginfo si; 204 jmp_buf *catcher; 205 int err; 206 int is_write = FAULT_WRITE(fi); 207 unsigned long address = FAULT_ADDRESS(fi); 208 209 if (!is_user && (address >= start_vm) && (address < end_vm)) { 210 flush_tlb_kernel_vm(); 211 return 0; 212 } 213 else if (current->mm == NULL) { 214 show_regs(container_of(regs, struct pt_regs, regs)); 215 panic("Segfault with no mm"); 216 } 217 218 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi)) 219 err = handle_page_fault(address, ip, is_write, is_user, 220 &si.si_code); 221 else { 222 err = -EFAULT; 223 /* 224 * A thread accessed NULL, we get a fault, but CR2 is invalid. 225 * This code is used in __do_copy_from_user() of TT mode. 226 * XXX tt mode is gone, so maybe this isn't needed any more 227 */ 228 address = 0; 229 } 230 231 catcher = current->thread.fault_catcher; 232 if (!err) 233 return 0; 234 else if (catcher != NULL) { 235 current->thread.fault_addr = (void *) address; 236 UML_LONGJMP(catcher, 1); 237 } 238 else if (current->thread.fault_addr != NULL) 239 panic("fault_addr set but no fault catcher"); 240 else if (!is_user && arch_fixup(ip, regs)) 241 return 0; 242 243 if (!is_user) { 244 show_regs(container_of(regs, struct pt_regs, regs)); 245 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx", 246 address, ip); 247 } 248 249 show_segv_info(regs); 250 251 if (err == -EACCES) { 252 si.si_signo = SIGBUS; 253 si.si_errno = 0; 254 si.si_code = BUS_ADRERR; 255 si.si_addr = (void __user *)address; 256 current->thread.arch.faultinfo = fi; 257 force_sig_info(SIGBUS, &si, current); 258 } else { 259 BUG_ON(err != -EFAULT); 260 si.si_signo = SIGSEGV; 261 si.si_addr = (void __user *) address; 262 current->thread.arch.faultinfo = fi; 263 force_sig_info(SIGSEGV, &si, current); 264 } 265 return 0; 266 } 267 268 void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs) 269 { 270 struct faultinfo *fi; 271 struct siginfo clean_si; 272 273 if (!UPT_IS_USER(regs)) { 274 if (sig == SIGBUS) 275 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp " 276 "mount likely just ran out of space\n"); 277 panic("Kernel mode signal %d", sig); 278 } 279 280 arch_examine_signal(sig, regs); 281 282 memset(&clean_si, 0, sizeof(clean_si)); 283 clean_si.si_signo = si->si_signo; 284 clean_si.si_errno = si->si_errno; 285 clean_si.si_code = si->si_code; 286 switch (sig) { 287 case SIGILL: 288 case SIGFPE: 289 case SIGSEGV: 290 case SIGBUS: 291 case SIGTRAP: 292 fi = UPT_FAULTINFO(regs); 293 clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi); 294 current->thread.arch.faultinfo = *fi; 295 #ifdef __ARCH_SI_TRAPNO 296 clean_si.si_trapno = si->si_trapno; 297 #endif 298 break; 299 default: 300 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n", 301 sig, si->si_code); 302 } 303 304 force_sig_info(sig, &clean_si, current); 305 } 306 307 void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs) 308 { 309 if (current->thread.fault_catcher != NULL) 310 UML_LONGJMP(current->thread.fault_catcher, 1); 311 else 312 relay_signal(sig, si, regs); 313 } 314 315 void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs) 316 { 317 do_IRQ(WINCH_IRQ, regs); 318 } 319 320 void trap_init(void) 321 { 322 } 323