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