1 /* 2 * arch/microblaze/mm/fault.c 3 * 4 * Copyright (C) 2007 Xilinx, Inc. All rights reserved. 5 * 6 * Derived from "arch/ppc/mm/fault.c" 7 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) 8 * 9 * Derived from "arch/i386/mm/fault.c" 10 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds 11 * 12 * Modified by Cort Dougan and Paul Mackerras. 13 * 14 * This file is subject to the terms and conditions of the GNU General 15 * Public License. See the file COPYING in the main directory of this 16 * archive for more details. 17 * 18 */ 19 20 #include <linux/module.h> 21 #include <linux/signal.h> 22 #include <linux/sched.h> 23 #include <linux/kernel.h> 24 #include <linux/errno.h> 25 #include <linux/string.h> 26 #include <linux/types.h> 27 #include <linux/ptrace.h> 28 #include <linux/mman.h> 29 #include <linux/mm.h> 30 #include <linux/interrupt.h> 31 32 #include <asm/page.h> 33 #include <asm/pgtable.h> 34 #include <asm/mmu.h> 35 #include <asm/mmu_context.h> 36 #include <asm/system.h> 37 #include <linux/uaccess.h> 38 #include <asm/exceptions.h> 39 40 #if defined(CONFIG_KGDB) 41 int debugger_kernel_faults = 1; 42 #endif 43 44 static unsigned long pte_misses; /* updated by do_page_fault() */ 45 static unsigned long pte_errors; /* updated by do_page_fault() */ 46 47 /* 48 * Check whether the instruction at regs->pc is a store using 49 * an update addressing form which will update r1. 50 */ 51 static int store_updates_sp(struct pt_regs *regs) 52 { 53 unsigned int inst; 54 55 if (get_user(inst, (unsigned int *)regs->pc)) 56 return 0; 57 /* check for 1 in the rD field */ 58 if (((inst >> 21) & 0x1f) != 1) 59 return 0; 60 /* check for store opcodes */ 61 if ((inst & 0xd0000000) == 0xd0000000) 62 return 1; 63 return 0; 64 } 65 66 67 /* 68 * bad_page_fault is called when we have a bad access from the kernel. 69 * It is called from do_page_fault above and from some of the procedures 70 * in traps.c. 71 */ 72 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 73 { 74 const struct exception_table_entry *fixup; 75 /* MS: no context */ 76 /* Are we prepared to handle this fault? */ 77 fixup = search_exception_tables(regs->pc); 78 if (fixup) { 79 regs->pc = fixup->fixup; 80 return; 81 } 82 83 /* kernel has accessed a bad area */ 84 #if defined(CONFIG_KGDB) 85 if (debugger_kernel_faults) 86 debugger(regs); 87 #endif 88 die("kernel access of bad area", regs, sig); 89 } 90 91 /* 92 * The error_code parameter is ESR for a data fault, 93 * 0 for an instruction fault. 94 */ 95 void do_page_fault(struct pt_regs *regs, unsigned long address, 96 unsigned long error_code) 97 { 98 struct vm_area_struct *vma; 99 struct mm_struct *mm = current->mm; 100 siginfo_t info; 101 int code = SEGV_MAPERR; 102 int is_write = error_code & ESR_S; 103 int fault; 104 105 regs->ear = address; 106 regs->esr = error_code; 107 108 /* On a kernel SLB miss we can only check for a valid exception entry */ 109 if (kernel_mode(regs) && (address >= TASK_SIZE)) { 110 printk(KERN_WARNING "kernel task_size exceed"); 111 _exception(SIGSEGV, regs, code, address); 112 } 113 114 /* for instr TLB miss and instr storage exception ESR_S is undefined */ 115 if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11) 116 is_write = 0; 117 118 #if defined(CONFIG_KGDB) 119 if (debugger_fault_handler && regs->trap == 0x300) { 120 debugger_fault_handler(regs); 121 return; 122 } 123 #endif /* CONFIG_KGDB */ 124 125 if (in_atomic() || !mm) { 126 if (kernel_mode(regs)) 127 goto bad_area_nosemaphore; 128 129 /* in_atomic() in user mode is really bad, 130 as is current->mm == NULL. */ 131 printk(KERN_EMERG "Page fault in user mode with " 132 "in_atomic(), mm = %p\n", mm); 133 printk(KERN_EMERG "r15 = %lx MSR = %lx\n", 134 regs->r15, regs->msr); 135 die("Weird page fault", regs, SIGSEGV); 136 } 137 138 /* When running in the kernel we expect faults to occur only to 139 * addresses in user space. All other faults represent errors in the 140 * kernel and should generate an OOPS. Unfortunately, in the case of an 141 * erroneous fault occurring in a code path which already holds mmap_sem 142 * we will deadlock attempting to validate the fault against the 143 * address space. Luckily the kernel only validly references user 144 * space from well defined areas of code, which are listed in the 145 * exceptions table. 146 * 147 * As the vast majority of faults will be valid we will only perform 148 * the source reference check when there is a possibility of a deadlock. 149 * Attempt to lock the address space, if we cannot we then validate the 150 * source. If this is invalid we can skip the address space check, 151 * thus avoiding the deadlock. 152 */ 153 if (!down_read_trylock(&mm->mmap_sem)) { 154 if (kernel_mode(regs) && !search_exception_tables(regs->pc)) 155 goto bad_area_nosemaphore; 156 157 down_read(&mm->mmap_sem); 158 } 159 160 vma = find_vma(mm, address); 161 if (!vma) 162 goto bad_area; 163 164 if (vma->vm_start <= address) 165 goto good_area; 166 167 if (!(vma->vm_flags & VM_GROWSDOWN)) 168 goto bad_area; 169 170 if (!is_write) 171 goto bad_area; 172 173 /* 174 * N.B. The ABI allows programs to access up to 175 * a few hundred bytes below the stack pointer (TBD). 176 * The kernel signal delivery code writes up to about 1.5kB 177 * below the stack pointer (r1) before decrementing it. 178 * The exec code can write slightly over 640kB to the stack 179 * before setting the user r1. Thus we allow the stack to 180 * expand to 1MB without further checks. 181 */ 182 if (address + 0x100000 < vma->vm_end) { 183 184 /* get user regs even if this fault is in kernel mode */ 185 struct pt_regs *uregs = current->thread.regs; 186 if (uregs == NULL) 187 goto bad_area; 188 189 /* 190 * A user-mode access to an address a long way below 191 * the stack pointer is only valid if the instruction 192 * is one which would update the stack pointer to the 193 * address accessed if the instruction completed, 194 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 195 * (or the byte, halfword, float or double forms). 196 * 197 * If we don't check this then any write to the area 198 * between the last mapped region and the stack will 199 * expand the stack rather than segfaulting. 200 */ 201 if (address + 2048 < uregs->r1 202 && (kernel_mode(regs) || !store_updates_sp(regs))) 203 goto bad_area; 204 } 205 if (expand_stack(vma, address)) 206 goto bad_area; 207 208 good_area: 209 code = SEGV_ACCERR; 210 211 /* a write */ 212 if (is_write) { 213 if (!(vma->vm_flags & VM_WRITE)) 214 goto bad_area; 215 /* a read */ 216 } else { 217 /* protection fault */ 218 if (error_code & 0x08000000) 219 goto bad_area; 220 if (!(vma->vm_flags & (VM_READ | VM_EXEC))) 221 goto bad_area; 222 } 223 224 /* 225 * If for any reason at all we couldn't handle the fault, 226 * make sure we exit gracefully rather than endlessly redo 227 * the fault. 228 */ 229 survive: 230 fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 231 if (unlikely(fault & VM_FAULT_ERROR)) { 232 if (fault & VM_FAULT_OOM) 233 goto out_of_memory; 234 else if (fault & VM_FAULT_SIGBUS) 235 goto do_sigbus; 236 BUG(); 237 } 238 if (fault & VM_FAULT_MAJOR) 239 current->maj_flt++; 240 else 241 current->min_flt++; 242 up_read(&mm->mmap_sem); 243 /* 244 * keep track of tlb+htab misses that are good addrs but 245 * just need pte's created via handle_mm_fault() 246 * -- Cort 247 */ 248 pte_misses++; 249 return; 250 251 bad_area: 252 up_read(&mm->mmap_sem); 253 254 bad_area_nosemaphore: 255 pte_errors++; 256 257 /* User mode accesses cause a SIGSEGV */ 258 if (user_mode(regs)) { 259 _exception(SIGSEGV, regs, code, address); 260 /* info.si_signo = SIGSEGV; 261 info.si_errno = 0; 262 info.si_code = code; 263 info.si_addr = (void *) address; 264 force_sig_info(SIGSEGV, &info, current);*/ 265 return; 266 } 267 268 bad_page_fault(regs, address, SIGSEGV); 269 return; 270 271 /* 272 * We ran out of memory, or some other thing happened to us that made 273 * us unable to handle the page fault gracefully. 274 */ 275 out_of_memory: 276 if (current->pid == 1) { 277 yield(); 278 down_read(&mm->mmap_sem); 279 goto survive; 280 } 281 up_read(&mm->mmap_sem); 282 printk(KERN_WARNING "VM: killing process %s\n", current->comm); 283 if (user_mode(regs)) 284 do_exit(SIGKILL); 285 bad_page_fault(regs, address, SIGKILL); 286 return; 287 288 do_sigbus: 289 up_read(&mm->mmap_sem); 290 if (user_mode(regs)) { 291 info.si_signo = SIGBUS; 292 info.si_errno = 0; 293 info.si_code = BUS_ADRERR; 294 info.si_addr = (void __user *)address; 295 force_sig_info(SIGBUS, &info, current); 296 return; 297 } 298 bad_page_fault(regs, address, SIGBUS); 299 } 300