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 <asm/current.h> 10 #include <asm/pgtable.h> 11 #include <asm/tlbflush.h> 12 #include "arch.h" 13 #include "as-layout.h" 14 #include "kern_util.h" 15 #include "os.h" 16 #include "skas.h" 17 #include "sysdep/sigcontext.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 survive: 68 fault = handle_mm_fault(mm, vma, address, is_write); 69 if (unlikely(fault & VM_FAULT_ERROR)) { 70 if (fault & VM_FAULT_OOM) { 71 err = -ENOMEM; 72 goto out_of_memory; 73 } else if (fault & VM_FAULT_SIGBUS) { 74 err = -EACCES; 75 goto out; 76 } 77 BUG(); 78 } 79 if (fault & VM_FAULT_MAJOR) 80 current->maj_flt++; 81 else 82 current->min_flt++; 83 84 pgd = pgd_offset(mm, address); 85 pud = pud_offset(pgd, address); 86 pmd = pmd_offset(pud, address); 87 pte = pte_offset_kernel(pmd, address); 88 } while (!pte_present(*pte)); 89 err = 0; 90 /* 91 * The below warning was added in place of 92 * pte_mkyoung(); if (is_write) pte_mkdirty(); 93 * If it's triggered, we'd see normally a hang here (a clean pte is 94 * marked read-only to emulate the dirty bit). 95 * However, the generic code can mark a PTE writable but clean on a 96 * concurrent read fault, triggering this harmlessly. So comment it out. 97 */ 98 #if 0 99 WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte))); 100 #endif 101 flush_tlb_page(vma, address); 102 out: 103 up_read(&mm->mmap_sem); 104 out_nosemaphore: 105 return err; 106 107 /* 108 * We ran out of memory, or some other thing happened to us that made 109 * us unable to handle the page fault gracefully. 110 */ 111 out_of_memory: 112 if (is_global_init(current)) { 113 up_read(&mm->mmap_sem); 114 yield(); 115 down_read(&mm->mmap_sem); 116 goto survive; 117 } 118 goto out; 119 } 120 121 static void bad_segv(struct faultinfo fi, unsigned long ip) 122 { 123 struct siginfo si; 124 125 si.si_signo = SIGSEGV; 126 si.si_code = SEGV_ACCERR; 127 si.si_addr = (void __user *) FAULT_ADDRESS(fi); 128 current->thread.arch.faultinfo = fi; 129 force_sig_info(SIGSEGV, &si, current); 130 } 131 132 void fatal_sigsegv(void) 133 { 134 force_sigsegv(SIGSEGV, current); 135 do_signal(); 136 /* 137 * This is to tell gcc that we're not returning - do_signal 138 * can, in general, return, but in this case, it's not, since 139 * we just got a fatal SIGSEGV queued. 140 */ 141 os_dump_core(); 142 } 143 144 void segv_handler(int sig, struct uml_pt_regs *regs) 145 { 146 struct faultinfo * fi = UPT_FAULTINFO(regs); 147 148 if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) { 149 bad_segv(*fi, UPT_IP(regs)); 150 return; 151 } 152 segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs); 153 } 154 155 /* 156 * We give a *copy* of the faultinfo in the regs to segv. 157 * This must be done, since nesting SEGVs could overwrite 158 * the info in the regs. A pointer to the info then would 159 * give us bad data! 160 */ 161 unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user, 162 struct uml_pt_regs *regs) 163 { 164 struct siginfo si; 165 jmp_buf *catcher; 166 int err; 167 int is_write = FAULT_WRITE(fi); 168 unsigned long address = FAULT_ADDRESS(fi); 169 170 if (!is_user && (address >= start_vm) && (address < end_vm)) { 171 flush_tlb_kernel_vm(); 172 return 0; 173 } 174 else if (current->mm == NULL) { 175 show_regs(container_of(regs, struct pt_regs, regs)); 176 panic("Segfault with no mm"); 177 } 178 179 if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi)) 180 err = handle_page_fault(address, ip, is_write, is_user, 181 &si.si_code); 182 else { 183 err = -EFAULT; 184 /* 185 * A thread accessed NULL, we get a fault, but CR2 is invalid. 186 * This code is used in __do_copy_from_user() of TT mode. 187 * XXX tt mode is gone, so maybe this isn't needed any more 188 */ 189 address = 0; 190 } 191 192 catcher = current->thread.fault_catcher; 193 if (!err) 194 return 0; 195 else if (catcher != NULL) { 196 current->thread.fault_addr = (void *) address; 197 UML_LONGJMP(catcher, 1); 198 } 199 else if (current->thread.fault_addr != NULL) 200 panic("fault_addr set but no fault catcher"); 201 else if (!is_user && arch_fixup(ip, regs)) 202 return 0; 203 204 if (!is_user) { 205 show_regs(container_of(regs, struct pt_regs, regs)); 206 panic("Kernel mode fault at addr 0x%lx, ip 0x%lx", 207 address, ip); 208 } 209 210 if (err == -EACCES) { 211 si.si_signo = SIGBUS; 212 si.si_errno = 0; 213 si.si_code = BUS_ADRERR; 214 si.si_addr = (void __user *)address; 215 current->thread.arch.faultinfo = fi; 216 force_sig_info(SIGBUS, &si, current); 217 } else if (err == -ENOMEM) { 218 printk(KERN_INFO "VM: killing process %s\n", current->comm); 219 do_exit(SIGKILL); 220 } else { 221 BUG_ON(err != -EFAULT); 222 si.si_signo = SIGSEGV; 223 si.si_addr = (void __user *) address; 224 current->thread.arch.faultinfo = fi; 225 force_sig_info(SIGSEGV, &si, current); 226 } 227 return 0; 228 } 229 230 void relay_signal(int sig, struct uml_pt_regs *regs) 231 { 232 if (!UPT_IS_USER(regs)) { 233 if (sig == SIGBUS) 234 printk(KERN_ERR "Bus error - the host /dev/shm or /tmp " 235 "mount likely just ran out of space\n"); 236 panic("Kernel mode signal %d", sig); 237 } 238 239 arch_examine_signal(sig, regs); 240 241 current->thread.arch.faultinfo = *UPT_FAULTINFO(regs); 242 force_sig(sig, current); 243 } 244 245 void bus_handler(int sig, struct uml_pt_regs *regs) 246 { 247 if (current->thread.fault_catcher != NULL) 248 UML_LONGJMP(current->thread.fault_catcher, 1); 249 else relay_signal(sig, regs); 250 } 251 252 void winch(int sig, struct uml_pt_regs *regs) 253 { 254 do_IRQ(WINCH_IRQ, regs); 255 } 256 257 void trap_init(void) 258 { 259 } 260