Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame^] | 1 | /* |
| 2 | * arch/ppc/mm/fault.c |
| 3 | * |
| 4 | * PowerPC version |
| 5 | * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org) |
| 6 | * |
| 7 | * Derived from "arch/i386/mm/fault.c" |
| 8 | * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds |
| 9 | * |
| 10 | * Modified by Cort Dougan and Paul Mackerras. |
| 11 | * |
| 12 | * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com) |
| 13 | * |
| 14 | * This program is free software; you can redistribute it and/or |
| 15 | * modify it under the terms of the GNU General Public License |
| 16 | * as published by the Free Software Foundation; either version |
| 17 | * 2 of the License, or (at your option) any later version. |
| 18 | */ |
| 19 | |
| 20 | #include <linux/config.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/mman.h> |
| 28 | #include <linux/mm.h> |
| 29 | #include <linux/interrupt.h> |
| 30 | #include <linux/smp_lock.h> |
| 31 | #include <linux/module.h> |
| 32 | |
| 33 | #include <asm/page.h> |
| 34 | #include <asm/pgtable.h> |
| 35 | #include <asm/mmu.h> |
| 36 | #include <asm/mmu_context.h> |
| 37 | #include <asm/system.h> |
| 38 | #include <asm/uaccess.h> |
| 39 | #include <asm/kdebug.h> |
| 40 | |
| 41 | /* |
| 42 | * Check whether the instruction at regs->nip is a store using |
| 43 | * an update addressing form which will update r1. |
| 44 | */ |
| 45 | static int store_updates_sp(struct pt_regs *regs) |
| 46 | { |
| 47 | unsigned int inst; |
| 48 | |
| 49 | if (get_user(inst, (unsigned int __user *)regs->nip)) |
| 50 | return 0; |
| 51 | /* check for 1 in the rA field */ |
| 52 | if (((inst >> 16) & 0x1f) != 1) |
| 53 | return 0; |
| 54 | /* check major opcode */ |
| 55 | switch (inst >> 26) { |
| 56 | case 37: /* stwu */ |
| 57 | case 39: /* stbu */ |
| 58 | case 45: /* sthu */ |
| 59 | case 53: /* stfsu */ |
| 60 | case 55: /* stfdu */ |
| 61 | return 1; |
| 62 | case 62: /* std or stdu */ |
| 63 | return (inst & 3) == 1; |
| 64 | case 31: |
| 65 | /* check minor opcode */ |
| 66 | switch ((inst >> 1) & 0x3ff) { |
| 67 | case 181: /* stdux */ |
| 68 | case 183: /* stwux */ |
| 69 | case 247: /* stbux */ |
| 70 | case 439: /* sthux */ |
| 71 | case 695: /* stfsux */ |
| 72 | case 759: /* stfdux */ |
| 73 | return 1; |
| 74 | } |
| 75 | } |
| 76 | return 0; |
| 77 | } |
| 78 | |
| 79 | /* |
| 80 | * The error_code parameter is |
| 81 | * - DSISR for a non-SLB data access fault, |
| 82 | * - SRR1 & 0x08000000 for a non-SLB instruction access fault |
| 83 | * - 0 any SLB fault. |
| 84 | * The return value is 0 if the fault was handled, or the signal |
| 85 | * number if this is a kernel fault that can't be handled here. |
| 86 | */ |
| 87 | int 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 | unsigned long code = SEGV_MAPERR; |
| 94 | unsigned long is_write = error_code & DSISR_ISSTORE; |
| 95 | unsigned long trap = TRAP(regs); |
| 96 | unsigned long is_exec = trap == 0x400; |
| 97 | |
| 98 | BUG_ON((trap == 0x380) || (trap == 0x480)); |
| 99 | |
| 100 | if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code, |
| 101 | 11, SIGSEGV) == NOTIFY_STOP) |
| 102 | return 0; |
| 103 | |
| 104 | if (trap == 0x300) { |
| 105 | if (debugger_fault_handler(regs)) |
| 106 | return 0; |
| 107 | } |
| 108 | |
| 109 | /* On a kernel SLB miss we can only check for a valid exception entry */ |
| 110 | if (!user_mode(regs) && (address >= TASK_SIZE)) |
| 111 | return SIGSEGV; |
| 112 | |
| 113 | if (error_code & DSISR_DABRMATCH) { |
| 114 | if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code, |
| 115 | 11, SIGSEGV) == NOTIFY_STOP) |
| 116 | return 0; |
| 117 | if (debugger_dabr_match(regs)) |
| 118 | return 0; |
| 119 | } |
| 120 | |
| 121 | if (in_atomic() || mm == NULL) { |
| 122 | if (!user_mode(regs)) |
| 123 | return SIGSEGV; |
| 124 | /* in_atomic() in user mode is really bad, |
| 125 | as is current->mm == NULL. */ |
| 126 | printk(KERN_EMERG "Page fault in user mode with" |
| 127 | "in_atomic() = %d mm = %p\n", in_atomic(), mm); |
| 128 | printk(KERN_EMERG "NIP = %lx MSR = %lx\n", |
| 129 | regs->nip, regs->msr); |
| 130 | die("Weird page fault", regs, SIGSEGV); |
| 131 | } |
| 132 | |
| 133 | /* When running in the kernel we expect faults to occur only to |
| 134 | * addresses in user space. All other faults represent errors in the |
| 135 | * kernel and should generate an OOPS. Unfortunatly, in the case of an |
| 136 | * erroneous fault occuring in a code path which already holds mmap_sem |
| 137 | * we will deadlock attempting to validate the fault against the |
| 138 | * address space. Luckily the kernel only validly references user |
| 139 | * space from well defined areas of code, which are listed in the |
| 140 | * exceptions table. |
| 141 | * |
| 142 | * As the vast majority of faults will be valid we will only perform |
| 143 | * the source reference check when there is a possibilty of a deadlock. |
| 144 | * Attempt to lock the address space, if we cannot we then validate the |
| 145 | * source. If this is invalid we can skip the address space check, |
| 146 | * thus avoiding the deadlock. |
| 147 | */ |
| 148 | if (!down_read_trylock(&mm->mmap_sem)) { |
| 149 | if (!user_mode(regs) && !search_exception_tables(regs->nip)) |
| 150 | goto bad_area_nosemaphore; |
| 151 | |
| 152 | down_read(&mm->mmap_sem); |
| 153 | } |
| 154 | |
| 155 | vma = find_vma(mm, address); |
| 156 | if (!vma) |
| 157 | goto bad_area; |
| 158 | |
| 159 | if (vma->vm_start <= address) { |
| 160 | goto good_area; |
| 161 | } |
| 162 | if (!(vma->vm_flags & VM_GROWSDOWN)) |
| 163 | goto bad_area; |
| 164 | |
| 165 | /* |
| 166 | * N.B. The POWER/Open ABI allows programs to access up to |
| 167 | * 288 bytes below the stack pointer. |
| 168 | * The kernel signal delivery code writes up to about 1.5kB |
| 169 | * below the stack pointer (r1) before decrementing it. |
| 170 | * The exec code can write slightly over 640kB to the stack |
| 171 | * before setting the user r1. Thus we allow the stack to |
| 172 | * expand to 1MB without further checks. |
| 173 | */ |
| 174 | if (address + 0x100000 < vma->vm_end) { |
| 175 | /* get user regs even if this fault is in kernel mode */ |
| 176 | struct pt_regs *uregs = current->thread.regs; |
| 177 | if (uregs == NULL) |
| 178 | goto bad_area; |
| 179 | |
| 180 | /* |
| 181 | * A user-mode access to an address a long way below |
| 182 | * the stack pointer is only valid if the instruction |
| 183 | * is one which would update the stack pointer to the |
| 184 | * address accessed if the instruction completed, |
| 185 | * i.e. either stwu rs,n(r1) or stwux rs,r1,rb |
| 186 | * (or the byte, halfword, float or double forms). |
| 187 | * |
| 188 | * If we don't check this then any write to the area |
| 189 | * between the last mapped region and the stack will |
| 190 | * expand the stack rather than segfaulting. |
| 191 | */ |
| 192 | if (address + 2048 < uregs->gpr[1] |
| 193 | && (!user_mode(regs) || !store_updates_sp(regs))) |
| 194 | goto bad_area; |
| 195 | } |
| 196 | |
| 197 | if (expand_stack(vma, address)) |
| 198 | goto bad_area; |
| 199 | |
| 200 | good_area: |
| 201 | code = SEGV_ACCERR; |
| 202 | |
| 203 | if (is_exec) { |
| 204 | /* protection fault */ |
| 205 | if (error_code & DSISR_PROTFAULT) |
| 206 | goto bad_area; |
| 207 | if (!(vma->vm_flags & VM_EXEC)) |
| 208 | goto bad_area; |
| 209 | /* a write */ |
| 210 | } else if (is_write) { |
| 211 | if (!(vma->vm_flags & VM_WRITE)) |
| 212 | goto bad_area; |
| 213 | /* a read */ |
| 214 | } else { |
| 215 | if (!(vma->vm_flags & VM_READ)) |
| 216 | goto bad_area; |
| 217 | } |
| 218 | |
| 219 | survive: |
| 220 | /* |
| 221 | * If for any reason at all we couldn't handle the fault, |
| 222 | * make sure we exit gracefully rather than endlessly redo |
| 223 | * the fault. |
| 224 | */ |
| 225 | switch (handle_mm_fault(mm, vma, address, is_write)) { |
| 226 | |
| 227 | case VM_FAULT_MINOR: |
| 228 | current->min_flt++; |
| 229 | break; |
| 230 | case VM_FAULT_MAJOR: |
| 231 | current->maj_flt++; |
| 232 | break; |
| 233 | case VM_FAULT_SIGBUS: |
| 234 | goto do_sigbus; |
| 235 | case VM_FAULT_OOM: |
| 236 | goto out_of_memory; |
| 237 | default: |
| 238 | BUG(); |
| 239 | } |
| 240 | |
| 241 | up_read(&mm->mmap_sem); |
| 242 | return 0; |
| 243 | |
| 244 | bad_area: |
| 245 | up_read(&mm->mmap_sem); |
| 246 | |
| 247 | bad_area_nosemaphore: |
| 248 | /* User mode accesses cause a SIGSEGV */ |
| 249 | if (user_mode(regs)) { |
| 250 | info.si_signo = SIGSEGV; |
| 251 | info.si_errno = 0; |
| 252 | info.si_code = code; |
| 253 | info.si_addr = (void __user *) address; |
| 254 | force_sig_info(SIGSEGV, &info, current); |
| 255 | return 0; |
| 256 | } |
| 257 | |
| 258 | if (trap == 0x400 && (error_code & DSISR_PROTFAULT) |
| 259 | && printk_ratelimit()) |
| 260 | printk(KERN_CRIT "kernel tried to execute NX-protected" |
| 261 | " page (%lx) - exploit attempt? (uid: %d)\n", |
| 262 | address, current->uid); |
| 263 | |
| 264 | return SIGSEGV; |
| 265 | |
| 266 | /* |
| 267 | * We ran out of memory, or some other thing happened to us that made |
| 268 | * us unable to handle the page fault gracefully. |
| 269 | */ |
| 270 | out_of_memory: |
| 271 | up_read(&mm->mmap_sem); |
| 272 | if (current->pid == 1) { |
| 273 | yield(); |
| 274 | down_read(&mm->mmap_sem); |
| 275 | goto survive; |
| 276 | } |
| 277 | printk("VM: killing process %s\n", current->comm); |
| 278 | if (user_mode(regs)) |
| 279 | do_exit(SIGKILL); |
| 280 | return SIGKILL; |
| 281 | |
| 282 | do_sigbus: |
| 283 | up_read(&mm->mmap_sem); |
| 284 | if (user_mode(regs)) { |
| 285 | info.si_signo = SIGBUS; |
| 286 | info.si_errno = 0; |
| 287 | info.si_code = BUS_ADRERR; |
| 288 | info.si_addr = (void __user *)address; |
| 289 | force_sig_info(SIGBUS, &info, current); |
| 290 | return 0; |
| 291 | } |
| 292 | return SIGBUS; |
| 293 | } |
| 294 | |
| 295 | /* |
| 296 | * bad_page_fault is called when we have a bad access from the kernel. |
| 297 | * It is called from do_page_fault above and from some of the procedures |
| 298 | * in traps.c. |
| 299 | */ |
| 300 | void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig) |
| 301 | { |
| 302 | const struct exception_table_entry *entry; |
| 303 | |
| 304 | /* Are we prepared to handle this fault? */ |
| 305 | if ((entry = search_exception_tables(regs->nip)) != NULL) { |
| 306 | regs->nip = entry->fixup; |
| 307 | return; |
| 308 | } |
| 309 | |
| 310 | /* kernel has accessed a bad area */ |
| 311 | die("Kernel access of bad area", regs, sig); |
| 312 | } |