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 96 regs->ear = address; 97 regs->esr = error_code; 98 99 /* On a kernel SLB miss we can only check for a valid exception entry */ 100 if (unlikely(kernel_mode(regs) && (address >= TASK_SIZE))) { 101 printk(KERN_WARNING "kernel task_size exceed"); 102 _exception(SIGSEGV, regs, code, address); 103 } 104 105 /* for instr TLB miss and instr storage exception ESR_S is undefined */ 106 if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11) 107 is_write = 0; 108 109 if (unlikely(in_atomic() || !mm)) { 110 if (kernel_mode(regs)) 111 goto bad_area_nosemaphore; 112 113 /* in_atomic() in user mode is really bad, 114 as is current->mm == NULL. */ 115 printk(KERN_EMERG "Page fault in user mode with " 116 "in_atomic(), mm = %p\n", mm); 117 printk(KERN_EMERG "r15 = %lx MSR = %lx\n", 118 regs->r15, regs->msr); 119 die("Weird page fault", regs, SIGSEGV); 120 } 121 122 /* When running in the kernel we expect faults to occur only to 123 * addresses in user space. All other faults represent errors in the 124 * kernel and should generate an OOPS. Unfortunately, in the case of an 125 * erroneous fault occurring in a code path which already holds mmap_sem 126 * we will deadlock attempting to validate the fault against the 127 * address space. Luckily the kernel only validly references user 128 * space from well defined areas of code, which are listed in the 129 * exceptions table. 130 * 131 * As the vast majority of faults will be valid we will only perform 132 * the source reference check when there is a possibility of a deadlock. 133 * Attempt to lock the address space, if we cannot we then validate the 134 * source. If this is invalid we can skip the address space check, 135 * thus avoiding the deadlock. 136 */ 137 if (unlikely(!down_read_trylock(&mm->mmap_sem))) { 138 if (kernel_mode(regs) && !search_exception_tables(regs->pc)) 139 goto bad_area_nosemaphore; 140 141 down_read(&mm->mmap_sem); 142 } 143 144 vma = find_vma(mm, address); 145 if (unlikely(!vma)) 146 goto bad_area; 147 148 if (vma->vm_start <= address) 149 goto good_area; 150 151 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN))) 152 goto bad_area; 153 154 if (unlikely(!is_write)) 155 goto bad_area; 156 157 /* 158 * N.B. The ABI allows programs to access up to 159 * a few hundred bytes below the stack pointer (TBD). 160 * The kernel signal delivery code writes up to about 1.5kB 161 * below the stack pointer (r1) before decrementing it. 162 * The exec code can write slightly over 640kB to the stack 163 * before setting the user r1. Thus we allow the stack to 164 * expand to 1MB without further checks. 165 */ 166 if (unlikely(address + 0x100000 < vma->vm_end)) { 167 168 /* get user regs even if this fault is in kernel mode */ 169 struct pt_regs *uregs = current->thread.regs; 170 if (uregs == NULL) 171 goto bad_area; 172 173 /* 174 * A user-mode access to an address a long way below 175 * the stack pointer is only valid if the instruction 176 * is one which would update the stack pointer to the 177 * address accessed if the instruction completed, 178 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb 179 * (or the byte, halfword, float or double forms). 180 * 181 * If we don't check this then any write to the area 182 * between the last mapped region and the stack will 183 * expand the stack rather than segfaulting. 184 */ 185 if (address + 2048 < uregs->r1 186 && (kernel_mode(regs) || !store_updates_sp(regs))) 187 goto bad_area; 188 } 189 if (expand_stack(vma, address)) 190 goto bad_area; 191 192 good_area: 193 code = SEGV_ACCERR; 194 195 /* a write */ 196 if (unlikely(is_write)) { 197 if (unlikely(!(vma->vm_flags & VM_WRITE))) 198 goto bad_area; 199 /* a read */ 200 } else { 201 /* protection fault */ 202 if (unlikely(error_code & 0x08000000)) 203 goto bad_area; 204 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC)))) 205 goto bad_area; 206 } 207 208 /* 209 * If for any reason at all we couldn't handle the fault, 210 * make sure we exit gracefully rather than endlessly redo 211 * the fault. 212 */ 213 fault = handle_mm_fault(mm, vma, address, is_write ? FAULT_FLAG_WRITE : 0); 214 if (unlikely(fault & VM_FAULT_ERROR)) { 215 if (fault & VM_FAULT_OOM) 216 goto out_of_memory; 217 else if (fault & VM_FAULT_SIGBUS) 218 goto do_sigbus; 219 BUG(); 220 } 221 if (unlikely(fault & VM_FAULT_MAJOR)) 222 current->maj_flt++; 223 else 224 current->min_flt++; 225 up_read(&mm->mmap_sem); 226 /* 227 * keep track of tlb+htab misses that are good addrs but 228 * just need pte's created via handle_mm_fault() 229 * -- Cort 230 */ 231 pte_misses++; 232 return; 233 234 bad_area: 235 up_read(&mm->mmap_sem); 236 237 bad_area_nosemaphore: 238 pte_errors++; 239 240 /* User mode accesses cause a SIGSEGV */ 241 if (user_mode(regs)) { 242 _exception(SIGSEGV, regs, code, address); 243 /* info.si_signo = SIGSEGV; 244 info.si_errno = 0; 245 info.si_code = code; 246 info.si_addr = (void *) address; 247 force_sig_info(SIGSEGV, &info, current);*/ 248 return; 249 } 250 251 bad_page_fault(regs, address, SIGSEGV); 252 return; 253 254 /* 255 * We ran out of memory, or some other thing happened to us that made 256 * us unable to handle the page fault gracefully. 257 */ 258 out_of_memory: 259 up_read(&mm->mmap_sem); 260 if (!user_mode(regs)) 261 bad_page_fault(regs, address, SIGKILL); 262 else 263 pagefault_out_of_memory(); 264 return; 265 266 do_sigbus: 267 up_read(&mm->mmap_sem); 268 if (user_mode(regs)) { 269 info.si_signo = SIGBUS; 270 info.si_errno = 0; 271 info.si_code = BUS_ADRERR; 272 info.si_addr = (void __user *)address; 273 force_sig_info(SIGBUS, &info, current); 274 return; 275 } 276 bad_page_fault(regs, address, SIGBUS); 277 } 278