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 <linux/uaccess.h> 37 #include <asm/exceptions.h> 38 39 static unsigned long pte_misses; /* updated by do_page_fault() */ 40 static unsigned long pte_errors; /* updated by do_page_fault() */ 41 42 /* 43 * Check whether the instruction at regs->pc is a store using 44 * an update addressing form which will update r1. 45 */ 46 static int store_updates_sp(struct pt_regs *regs) 47 { 48 unsigned int inst; 49 50 if (get_user(inst, (unsigned int __user *)regs->pc)) 51 return 0; 52 /* check for 1 in the rD field */ 53 if (((inst >> 21) & 0x1f) != 1) 54 return 0; 55 /* check for store opcodes */ 56 if ((inst & 0xd0000000) == 0xd0000000) 57 return 1; 58 return 0; 59 } 60 61 62 /* 63 * bad_page_fault is called when we have a bad access from the kernel. 64 * It is called from do_page_fault above and from some of the procedures 65 * in traps.c. 66 */ 67 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) 68 { 69 const struct exception_table_entry *fixup; 70 /* MS: no context */ 71 /* Are we prepared to handle this fault? */ 72 fixup = search_exception_tables(regs->pc); 73 if (fixup) { 74 regs->pc = fixup->fixup; 75 return; 76 } 77 78 /* kernel has accessed a bad area */ 79 die("kernel access of bad area", regs, sig); 80 } 81 82 /* 83 * The error_code parameter is ESR for a data fault, 84 * 0 for an instruction fault. 85 */ 86 void do_page_fault(struct pt_regs *regs, unsigned long address, 87 unsigned long error_code) 88 { 89 struct vm_area_struct *vma; 90 struct mm_struct *mm = current->mm; 91 siginfo_t info; 92 int code = SEGV_MAPERR; 93 int is_write = error_code & ESR_S; 94 int fault; 95 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE | 96 (is_write ? FAULT_FLAG_WRITE : 0); 97 98 regs->ear = address; 99 regs->esr = error_code; 100 101 /* On a kernel SLB miss we can only check for a valid exception entry */ 102 if (unlikely(kernel_mode(regs) && (address >= TASK_SIZE))) { 103 printk(KERN_WARNING "kernel task_size exceed"); 104 _exception(SIGSEGV, regs, code, address); 105 } 106 107 /* for instr TLB miss and instr storage exception ESR_S is undefined */ 108 if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11) 109 is_write = 0; 110 111 if (unlikely(in_atomic() || !mm)) { 112 if (kernel_mode(regs)) 113 goto bad_area_nosemaphore; 114 115 /* in_atomic() in user mode is really bad, 116 as is current->mm == NULL. */ 117 printk(KERN_EMERG "Page fault in user mode with " 118 "in_atomic(), mm = %p\n", mm); 119 printk(KERN_EMERG "r15 = %lx MSR = %lx\n", 120 regs->r15, regs->msr); 121 die("Weird page fault", regs, SIGSEGV); 122 } 123 124 /* When running in the kernel we expect faults to occur only to 125 * addresses in user space. All other faults represent errors in the 126 * kernel and should generate an OOPS. Unfortunately, in the case of an 127 * erroneous fault occurring in a code path which already holds mmap_sem 128 * we will deadlock attempting to validate the fault against the 129 * address space. Luckily the kernel only validly references user 130 * space from well defined areas of code, which are listed in the 131 * exceptions table. 132 * 133 * As the vast majority of faults will be valid we will only perform 134 * the source reference check when there is a possibility of a deadlock. 135 * Attempt to lock the address space, if we cannot we then validate the 136 * source. If this is invalid we can skip the address space check, 137 * thus avoiding the deadlock. 138 */ 139 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 140 if (kernel_mode(regs) && !search_exception_tables(regs->pc)) 141 goto bad_area_nosemaphore; 142 143 retry: 144 down_read(&mm->mmap_sem); 145 } 146 147 vma = find_vma(mm, address); 148 if (unlikely(!vma)) 149 goto bad_area; 150 151 if (vma->vm_start <= address) 152 goto good_area; 153 154 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 155 goto bad_area; 156 157 if (unlikely(!is_write)) 158 goto bad_area; 159 160 /* 161 * N.B. The ABI allows programs to access up to 162 * a few hundred bytes below the stack pointer (TBD). 163 * The kernel signal delivery code writes up to about 1.5kB 164 * below the stack pointer (r1) before decrementing it. 165 * The exec code can write slightly over 640kB to the stack 166 * before setting the user r1. Thus we allow the stack to 167 * expand to 1MB without further checks. 168 */ 169 if (unlikely(address + 0x100000 < vma->vm_end)) { 170 171 /* get user regs even if this fault is in kernel mode */ 172 struct pt_regs *uregs = current->thread.regs; 173 if (uregs == NULL) 174 goto bad_area; 175 176 /* 177 * A user-mode access to an address a long way below 178 * the stack pointer is only valid if the instruction 179 * is one which would update the stack pointer to the 180 * address accessed if the instruction completed, 181 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 182 * (or the byte, halfword, float or double forms). 183 * 184 * If we don't check this then any write to the area 185 * between the last mapped region and the stack will 186 * expand the stack rather than segfaulting. 187 */ 188 if (address + 2048 < uregs->r1 189 && (kernel_mode(regs) || !store_updates_sp(regs))) 190 goto bad_area; 191 } 192 if (expand_stack(vma, address)) 193 goto bad_area; 194 195 good_area: 196 code = SEGV_ACCERR; 197 198 /* a write */ 199 if (unlikely(is_write)) { 200 if (unlikely(!(vma->vm_flags & VM_WRITE))) 201 goto bad_area; 202 /* a read */ 203 } else { 204 /* protection fault */ 205 if (unlikely(error_code & 0x08000000)) 206 goto bad_area; 207 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC)))) 208 goto bad_area; 209 } 210 211 /* 212 * If for any reason at all we couldn't handle the fault, 213 * make sure we exit gracefully rather than endlessly redo 214 * the fault. 215 */ 216 fault = handle_mm_fault(mm, vma, address, flags); 217 218 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) 219 return; 220 221 if (unlikely(fault & VM_FAULT_ERROR)) { 222 if (fault & VM_FAULT_OOM) 223 goto out_of_memory; 224 else if (fault & VM_FAULT_SIGBUS) 225 goto do_sigbus; 226 BUG(); 227 } 228 229 if (flags & FAULT_FLAG_ALLOW_RETRY) { 230 if (unlikely(fault & VM_FAULT_MAJOR)) 231 current->maj_flt++; 232 else 233 current->min_flt++; 234 if (fault & VM_FAULT_RETRY) { 235 flags &= ~FAULT_FLAG_ALLOW_RETRY; 236 flags |= FAULT_FLAG_TRIED; 237 238 /* 239 * No need to up_read(&mm->mmap_sem) as we would 240 * have already released it in __lock_page_or_retry 241 * in mm/filemap.c. 242 */ 243 244 goto retry; 245 } 246 } 247 248 up_read(&mm->mmap_sem); 249 250 /* 251 * keep track of tlb+htab misses that are good addrs but 252 * just need pte's created via handle_mm_fault() 253 * -- Cort 254 */ 255 pte_misses++; 256 return; 257 258 bad_area: 259 up_read(&mm->mmap_sem); 260 261 bad_area_nosemaphore: 262 pte_errors++; 263 264 /* User mode accesses cause a SIGSEGV */ 265 if (user_mode(regs)) { 266 _exception(SIGSEGV, regs, code, address); 267 /* info.si_signo = SIGSEGV; 268 info.si_errno = 0; 269 info.si_code = code; 270 info.si_addr = (void *) address; 271 force_sig_info(SIGSEGV, &info, current);*/ 272 return; 273 } 274 275 bad_page_fault(regs, address, SIGSEGV); 276 return; 277 278 /* 279 * We ran out of memory, or some other thing happened to us that made 280 * us unable to handle the page fault gracefully. 281 */ 282 out_of_memory: 283 up_read(&mm->mmap_sem); 284 if (!user_mode(regs)) 285 bad_page_fault(regs, address, SIGKILL); 286 else 287 pagefault_out_of_memory(); 288 return; 289 290 do_sigbus: 291 up_read(&mm->mmap_sem); 292 if (user_mode(regs)) { 293 info.si_signo = SIGBUS; 294 info.si_errno = 0; 295 info.si_code = BUS_ADRERR; 296 info.si_addr = (void __user *)address; 297 force_sig_info(SIGBUS, &info, current); 298 return; 299 } 300 bad_page_fault(regs, address, SIGBUS); 301 } 302