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