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 34 *code_out = SEGV_MAPERR; 35 36 /* 37 * If the fault was during atomic operation, don't take the fault, just 38 * fail. 39 */ 40 if (in_atomic()) 41 goto out_nosemaphore; 42 43 down_read(&mm->mmap_sem); 44 vma = find_vma(mm, address); 45 if (!vma) 46 goto out; 47 else if (vma->vm_start <= address) 48 goto good_area; 49 else if (!(vma->vm_flags & VM_GROWSDOWN)) 50 goto out; 51 else if (is_user && !ARCH_IS_STACKGROW(address)) 52 goto out; 53 else if (expand_stack(vma, address)) 54 goto out; 55 56 good_area: 57 *code_out = SEGV_ACCERR; 58 if (is_write && !(vma->vm_flags & VM_WRITE)) 59 goto out; 60 61 /* Don't require VM_READ|VM_EXEC for write faults! */ 62 if (!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC))) 63 goto out; 64 65 do { 66 int fault; 67 68 fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 69 if (unlikely(fault & VM_FAULT_ERROR)) { 70 if (fault & VM_FAULT_OOM) { 71 goto out_of_memory; 72 } else if (fault & VM_FAULT_SIGBUS) { 73 err = -EACCES; 74 goto out; 75 } 76 BUG(); 77 } 78 if (fault & VM_FAULT_MAJOR) 79 current->maj_flt++; 80 else 81 current->min_flt++; 82 83 pgd = pgd_offset(mm, address); 84 pud = pud_offset(pgd, address); 85 pmd = pmd_offset(pud, address); 86 pte = pte_offset_kernel(pmd, address); 87 } while (!pte_present(*pte)); 88 err = 0; 89 /* 90 * The below warning was added in place of 91 * pte_mkyoung(); if (is_write) pte_mkdirty(); 92 * If it's triggered, we'd see normally a hang here (a clean pte is 93 * marked read-only to emulate the dirty bit). 94 * However, the generic code can mark a PTE writable but clean on a 95 * concurrent read fault, triggering this harmlessly. So comment it out. 96 */ 97 #if 0 98 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte))); 99 #endif 100 flush_tlb_page(vma, address); 101 out: 102 up_read(&mm->mmap_sem); 103 out_nosemaphore: 104 return err; 105 106 out_of_memory: 107 /* 108 * We ran out of memory, call the OOM killer, and return the userspace 109 * (which will retry the fault, or kill us if we got oom-killed). 110 */ 111 up_read(&mm->mmap_sem); 112 pagefault_out_of_memory(); 113 return 0; 114 } 115 EXPORT_SYMBOL(handle_page_fault); 116 117 static void show_segv_info(struct uml_pt_regs *regs) 118 { 119 struct task_struct *tsk = current; 120 struct faultinfo *fi = UPT_FAULTINFO(regs); 121 122 if (!unhandled_signal(tsk, SIGSEGV)) 123 return; 124 125 if (!printk_ratelimit()) 126 return; 127 128 printk("%s%s[%d]: segfault at %lx ip %p sp %p error %x", 129 task_pid_nr(tsk) > 1 ? KERN_INFO : KERN_EMERG, 130 tsk->comm, task_pid_nr(tsk), FAULT_ADDRESS(*fi), 131 (void *)UPT_IP(regs), (void *)UPT_SP(regs), 132 fi->error_code); 133 134 print_vma_addr(KERN_CONT " in ", UPT_IP(regs)); 135 printk(KERN_CONT "\n"); 136 } 137 138 static void bad_segv(struct faultinfo fi, unsigned long ip) 139 { 140 struct siginfo si; 141 142 si.si_signo = SIGSEGV; 143 si.si_code = SEGV_ACCERR; 144 si.si_addr = (void __user *) FAULT_ADDRESS(fi); 145 current->thread.arch.faultinfo = fi; 146 force_sig_info(SIGSEGV, &si, current); 147 } 148 149 void fatal_sigsegv(void) 150 { 151 force_sigsegv(SIGSEGV, current); 152 do_signal(); 153 /* 154 * This is to tell gcc that we're not returning - do_signal 155 * can, in general, return, but in this case, it's not, since 156 * we just got a fatal SIGSEGV queued. 157 */ 158 os_dump_core(); 159 } 160 161 void segv_handler(int sig, struct uml_pt_regs *regs) 162 { 163 struct faultinfo * fi = UPT_FAULTINFO(regs); 164 165 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) { 166 show_segv_info(regs); 167 bad_segv(*fi, UPT_IP(regs)); 168 return; 169 } 170 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs); 171 } 172 173 /* 174 * We give a *copy* of the faultinfo in the regs to segv. 175 * This must be done, since nesting SEGVs could overwrite 176 * the info in the regs. A pointer to the info then would 177 * give us bad data! 178 */ 179 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 180 struct uml_pt_regs *regs) 181 { 182 struct siginfo si; 183 jmp_buf *catcher; 184 int err; 185 int is_write = FAULT_WRITE(fi); 186 unsigned long address = FAULT_ADDRESS(fi); 187 188 if (!is_user && (address >= start_vm) && (address < end_vm)) { 189 flush_tlb_kernel_vm(); 190 return 0; 191 } 192 else if (current->mm == NULL) { 193 show_regs(container_of(regs, struct pt_regs, regs)); 194 panic("Segfault with no mm"); 195 } 196 197 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi)) 198 err = handle_page_fault(address, ip, is_write, is_user, 199 &si.si_code); 200 else { 201 err = -EFAULT; 202 /* 203 * A thread accessed NULL, we get a fault, but CR2 is invalid. 204 * This code is used in __do_copy_from_user() of TT mode. 205 * XXX tt mode is gone, so maybe this isn't needed any more 206 */ 207 address = 0; 208 } 209 210 catcher = current->thread.fault_catcher; 211 if (!err) 212 return 0; 213 else if (catcher != NULL) { 214 current->thread.fault_addr = (void *) address; 215 UML_LONGJMP(catcher, 1); 216 } 217 else if (current->thread.fault_addr != NULL) 218 panic("fault_addr set but no fault catcher"); 219 else if (!is_user && arch_fixup(ip, regs)) 220 return 0; 221 222 if (!is_user) { 223 show_regs(container_of(regs, struct pt_regs, regs)); 224 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx", 225 address, ip); 226 } 227 228 show_segv_info(regs); 229 230 if (err == -EACCES) { 231 si.si_signo = SIGBUS; 232 si.si_errno = 0; 233 si.si_code = BUS_ADRERR; 234 si.si_addr = (void __user *)address; 235 current->thread.arch.faultinfo = fi; 236 force_sig_info(SIGBUS, &si, current); 237 } else { 238 BUG_ON(err != -EFAULT); 239 si.si_signo = SIGSEGV; 240 si.si_addr = (void __user *) address; 241 current->thread.arch.faultinfo = fi; 242 force_sig_info(SIGSEGV, &si, current); 243 } 244 return 0; 245 } 246 247 void relay_signal(int sig, struct uml_pt_regs *regs) 248 { 249 if (!UPT_IS_USER(regs)) { 250 if (sig == SIGBUS) 251 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp " 252 "mount likely just ran out of space\n"); 253 panic("Kernel mode signal %d", sig); 254 } 255 256 arch_examine_signal(sig, regs); 257 258 current->thread.arch.faultinfo = *UPT_FAULTINFO(regs); 259 force_sig(sig, current); 260 } 261 262 void bus_handler(int sig, struct uml_pt_regs *regs) 263 { 264 if (current->thread.fault_catcher != NULL) 265 UML_LONGJMP(current->thread.fault_catcher, 1); 266 else relay_signal(sig, regs); 267 } 268 269 void winch(int sig, struct uml_pt_regs *regs) 270 { 271 do_IRQ(WINCH_IRQ, regs); 272 } 273 274 void trap_init(void) 275 { 276 } 277