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 <linux/uaccess.h> 11 #include <asm/current.h> 12 #include <asm/pgtable.h> 13 #include <asm/tlbflush.h> 14 #include <arch.h> 15 #include <as-layout.h> 16 #include <kern_util.h> 17 #include <os.h> 18 #include <skas.h> 19 20 /* 21 * Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by 22 * segv(). 23 */ 24 int handle_page_fault(unsigned long address, unsigned long ip, 25 int is_write, int is_user, int *code_out) 26 { 27 struct mm_struct *mm = current->mm; 28 struct vm_area_struct *vma; 29 pgd_t *pgd; 30 pud_t *pud; 31 pmd_t *pmd; 32 pte_t *pte; 33 int err = -EFAULT; 34 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE; 35 36 *code_out = SEGV_MAPERR; 37 38 /* 39 * If the fault was with pagefaults disabled, don't take the fault, just 40 * fail. 41 */ 42 if (faulthandler_disabled()) 43 goto out_nosemaphore; 44 45 if (is_user) 46 flags |= FAULT_FLAG_USER; 47 retry: 48 down_read(&mm->mmap_sem); 49 vma = find_vma(mm, address); 50 if (!vma) 51 goto out; 52 else if (vma->vm_start <= address) 53 goto good_area; 54 else if (!(vma->vm_flags & VM_GROWSDOWN)) 55 goto out; 56 else if (is_user && !ARCH_IS_STACKGROW(address)) 57 goto out; 58 else if (expand_stack(vma, address)) 59 goto out; 60 61 good_area: 62 *code_out = SEGV_ACCERR; 63 if (is_write) { 64 if (!(vma->vm_flags & VM_WRITE)) 65 goto out; 66 flags |= FAULT_FLAG_WRITE; 67 } else { 68 /* Don't require VM_READ|VM_EXEC for write faults! */ 69 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 70 goto out; 71 } 72 73 do { 74 int fault; 75 76 fault = handle_mm_fault(mm, vma, address, flags); 77 78 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 79 goto out_nosemaphore; 80 81 if (unlikely(fault & VM_FAULT_ERROR)) { 82 if (fault & VM_FAULT_OOM) { 83 goto out_of_memory; 84 } else if (fault & VM_FAULT_SIGSEGV) { 85 goto out; 86 } else if (fault & VM_FAULT_SIGBUS) { 87 err = -EACCES; 88 goto out; 89 } 90 BUG(); 91 } 92 if (flags & FAULT_FLAG_ALLOW_RETRY) { 93 if (fault & VM_FAULT_MAJOR) 94 current->maj_flt++; 95 else 96 current->min_flt++; 97 if (fault & VM_FAULT_RETRY) { 98 flags &= ~FAULT_FLAG_ALLOW_RETRY; 99 flags |= FAULT_FLAG_TRIED; 100 101 goto retry; 102 } 103 } 104 105 pgd = pgd_offset(mm, address); 106 pud = pud_offset(pgd, address); 107 pmd = pmd_offset(pud, address); 108 pte = pte_offset_kernel(pmd, address); 109 } while (!pte_present(*pte)); 110 err = 0; 111 /* 112 * The below warning was added in place of 113 * pte_mkyoung(); if (is_write) pte_mkdirty(); 114 * If it's triggered, we'd see normally a hang here (a clean pte is 115 * marked read-only to emulate the dirty bit). 116 * However, the generic code can mark a PTE writable but clean on a 117 * concurrent read fault, triggering this harmlessly. So comment it out. 118 */ 119 #if 0 120 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte))); 121 #endif 122 flush_tlb_page(vma, address); 123 out: 124 up_read(&mm->mmap_sem); 125 out_nosemaphore: 126 return err; 127 128 out_of_memory: 129 /* 130 * We ran out of memory, call the OOM killer, and return the userspace 131 * (which will retry the fault, or kill us if we got oom-killed). 132 */ 133 up_read(&mm->mmap_sem); 134 if (!is_user) 135 goto out_nosemaphore; 136 pagefault_out_of_memory(); 137 return 0; 138 } 139 EXPORT_SYMBOL(handle_page_fault); 140 141 static void show_segv_info(struct uml_pt_regs *regs) 142 { 143 struct task_struct *tsk = current; 144 struct faultinfo *fi = UPT_FAULTINFO(regs); 145 146 if (!unhandled_signal(tsk, SIGSEGV)) 147 return; 148 149 if (!printk_ratelimit()) 150 return; 151 152 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x", 153 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 154 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi), 155 (void *)UPT_IP(regs), (void *)UPT_SP(regs), 156 fi->error_code); 157 158 print_vma_addr(KERN_CONT " in ", UPT_IP(regs)); 159 printk(KERN_CONT "\n"); 160 } 161 162 static void bad_segv(struct faultinfo fi, unsigned long ip) 163 { 164 struct siginfo si; 165 166 si.si_signo = SIGSEGV; 167 si.si_code = SEGV_ACCERR; 168 si.si_addr = (void __user *) FAULT_ADDRESS(fi); 169 current->thread.arch.faultinfo = fi; 170 force_sig_info(SIGSEGV, &si, current); 171 } 172 173 void fatal_sigsegv(void) 174 { 175 force_sigsegv(SIGSEGV, current); 176 do_signal(); 177 /* 178 * This is to tell gcc that we're not returning - do_signal 179 * can, in general, return, but in this case, it's not, since 180 * we just got a fatal SIGSEGV queued. 181 */ 182 os_dump_core(); 183 } 184 185 void segv_handler(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs) 186 { 187 struct faultinfo * fi = UPT_FAULTINFO(regs); 188 189 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) { 190 show_segv_info(regs); 191 bad_segv(*fi, UPT_IP(regs)); 192 return; 193 } 194 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs); 195 } 196 197 /* 198 * We give a *copy* of the faultinfo in the regs to segv. 199 * This must be done, since nesting SEGVs could overwrite 200 * the info in the regs. A pointer to the info then would 201 * give us bad data! 202 */ 203 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 204 struct uml_pt_regs *regs) 205 { 206 struct siginfo si; 207 jmp_buf *catcher; 208 int err; 209 int is_write = FAULT_WRITE(fi); 210 unsigned long address = FAULT_ADDRESS(fi); 211 212 if (!is_user && regs) 213 current->thread.segv_regs = container_of(regs, struct pt_regs, regs); 214 215 if (!is_user && (address >= start_vm) && (address < end_vm)) { 216 flush_tlb_kernel_vm(); 217 goto out; 218 } 219 else if (current->mm == NULL) { 220 show_regs(container_of(regs, struct pt_regs, regs)); 221 panic("Segfault with no mm"); 222 } 223 else if (!is_user && address < TASK_SIZE) { 224 show_regs(container_of(regs, struct pt_regs, regs)); 225 panic("Kernel tried to access user memory at addr 0x%lx, ip 0x%lx", 226 address, ip); 227 } 228 229 if (SEGV_IS_FIXABLE(&fi)) 230 err = handle_page_fault(address, ip, is_write, is_user, 231 &si.si_code); 232 else { 233 err = -EFAULT; 234 /* 235 * A thread accessed NULL, we get a fault, but CR2 is invalid. 236 * This code is used in __do_copy_from_user() of TT mode. 237 * XXX tt mode is gone, so maybe this isn't needed any more 238 */ 239 address = 0; 240 } 241 242 catcher = current->thread.fault_catcher; 243 if (!err) 244 goto out; 245 else if (catcher != NULL) { 246 current->thread.fault_addr = (void *) address; 247 UML_LONGJMP(catcher, 1); 248 } 249 else if (current->thread.fault_addr != NULL) 250 panic("fault_addr set but no fault catcher"); 251 else if (!is_user && arch_fixup(ip, regs)) 252 goto out; 253 254 if (!is_user) { 255 show_regs(container_of(regs, struct pt_regs, regs)); 256 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx", 257 address, ip); 258 } 259 260 show_segv_info(regs); 261 262 if (err == -EACCES) { 263 si.si_signo = SIGBUS; 264 si.si_errno = 0; 265 si.si_code = BUS_ADRERR; 266 si.si_addr = (void __user *)address; 267 current->thread.arch.faultinfo = fi; 268 force_sig_info(SIGBUS, &si, current); 269 } else { 270 BUG_ON(err != -EFAULT); 271 si.si_signo = SIGSEGV; 272 si.si_addr = (void __user *) address; 273 current->thread.arch.faultinfo = fi; 274 force_sig_info(SIGSEGV, &si, current); 275 } 276 277 out: 278 if (regs) 279 current->thread.segv_regs = NULL; 280 281 return 0; 282 } 283 284 void relay_signal(int sig, struct siginfo *si, struct uml_pt_regs *regs) 285 { 286 struct faultinfo *fi; 287 struct siginfo clean_si; 288 289 if (!UPT_IS_USER(regs)) { 290 if (sig == SIGBUS) 291 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp " 292 "mount likely just ran out of space\n"); 293 panic("Kernel mode signal %d", sig); 294 } 295 296 arch_examine_signal(sig, regs); 297 298 memset(&clean_si, 0, sizeof(clean_si)); 299 clean_si.si_signo = si->si_signo; 300 clean_si.si_errno = si->si_errno; 301 clean_si.si_code = si->si_code; 302 switch (sig) { 303 case SIGILL: 304 case SIGFPE: 305 case SIGSEGV: 306 case SIGBUS: 307 case SIGTRAP: 308 fi = UPT_FAULTINFO(regs); 309 clean_si.si_addr = (void __user *) FAULT_ADDRESS(*fi); 310 current->thread.arch.faultinfo = *fi; 311 #ifdef __ARCH_SI_TRAPNO 312 clean_si.si_trapno = si->si_trapno; 313 #endif 314 break; 315 default: 316 printk(KERN_ERR "Attempted to relay unknown signal %d (si_code = %d)\n", 317 sig, si->si_code); 318 } 319 320 force_sig_info(sig, &clean_si, current); 321 } 322 323 void bus_handler(int sig, struct siginfo *si, struct uml_pt_regs *regs) 324 { 325 if (current->thread.fault_catcher != NULL) 326 UML_LONGJMP(current->thread.fault_catcher, 1); 327 else 328 relay_signal(sig, si, regs); 329 } 330 331 void winch(int sig, struct siginfo *unused_si, struct uml_pt_regs *regs) 332 { 333 do_IRQ(WINCH_IRQ, regs); 334 } 335 336 void trap_init(void) 337 { 338 } 339