5 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
7 * Derived from "arch/i386/mm/fault.c"
8 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
10 * Modified by Cort Dougan and Paul Mackerras.
12 * Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
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.
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>
29 #include <linux/interrupt.h>
30 #include <linux/smp_lock.h>
31 #include <linux/module.h>
34 #include <asm/pgtable.h>
36 #include <asm/mmu_context.h>
37 #include <asm/system.h>
38 #include <asm/uaccess.h>
39 #include <asm/kdebug.h>
42 * Check whether the instruction at regs->nip is a store using
43 * an update addressing form which will update r1.
45 static int store_updates_sp(struct pt_regs *regs)
49 if (get_user(inst, (unsigned int __user *)regs->nip))
51 /* check for 1 in the rA field */
52 if (((inst >> 16) & 0x1f) != 1)
54 /* check major opcode */
62 case 62: /* std or stdu */
63 return (inst & 3) == 1;
65 /* check minor opcode */
66 switch ((inst >> 1) & 0x3ff) {
71 case 695: /* stfsux */
72 case 759: /* stfdux */
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
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.
87 int do_page_fault(struct pt_regs *regs, unsigned long address,
88 unsigned long error_code)
90 struct vm_area_struct * vma;
91 struct mm_struct *mm = current->mm;
93 unsigned long code = SEGV_MAPERR;
94 unsigned long is_write = error_code & 0x02000000;
95 unsigned long trap = TRAP(regs);
97 BUG_ON((trap == 0x380) || (trap == 0x480));
99 if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code,
100 11, SIGSEGV) == NOTIFY_STOP)
104 if (debugger_fault_handler(regs))
108 /* On a kernel SLB miss we can only check for a valid exception entry */
109 if (!user_mode(regs) && (address >= TASK_SIZE))
112 if (error_code & 0x00400000) {
113 if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
114 11, SIGSEGV) == NOTIFY_STOP)
116 if (debugger_dabr_match(regs))
120 if (in_atomic() || mm == NULL) {
121 if (!user_mode(regs))
123 /* in_atomic() in user mode is really bad,
124 as is current->mm == NULL. */
125 printk(KERN_EMERG "Page fault in user mode with"
126 "in_atomic() = %d mm = %p\n", in_atomic(), mm);
127 printk(KERN_EMERG "NIP = %lx MSR = %lx\n",
128 regs->nip, regs->msr);
129 die("Weird page fault", regs, SIGSEGV);
132 /* When running in the kernel we expect faults to occur only to
133 * addresses in user space. All other faults represent errors in the
134 * kernel and should generate an OOPS. Unfortunatly, in the case of an
135 * erroneous fault occuring in a code path which already holds mmap_sem
136 * we will deadlock attempting to validate the fault against the
137 * address space. Luckily the kernel only validly references user
138 * space from well defined areas of code, which are listed in the
141 * As the vast majority of faults will be valid we will only perform
142 * the source reference check when there is a possibilty of a deadlock.
143 * Attempt to lock the address space, if we cannot we then validate the
144 * source. If this is invalid we can skip the address space check,
145 * thus avoiding the deadlock.
147 if (!down_read_trylock(&mm->mmap_sem)) {
148 if (!user_mode(regs) && !search_exception_tables(regs->nip))
149 goto bad_area_nosemaphore;
151 down_read(&mm->mmap_sem);
154 vma = find_vma(mm, address);
158 if (vma->vm_start <= address) {
161 if (!(vma->vm_flags & VM_GROWSDOWN))
165 * N.B. The POWER/Open ABI allows programs to access up to
166 * 288 bytes below the stack pointer.
167 * The kernel signal delivery code writes up to about 1.5kB
168 * below the stack pointer (r1) before decrementing it.
169 * The exec code can write slightly over 640kB to the stack
170 * before setting the user r1. Thus we allow the stack to
171 * expand to 1MB without further checks.
173 if (address + 0x100000 < vma->vm_end) {
174 /* get user regs even if this fault is in kernel mode */
175 struct pt_regs *uregs = current->thread.regs;
180 * A user-mode access to an address a long way below
181 * the stack pointer is only valid if the instruction
182 * is one which would update the stack pointer to the
183 * address accessed if the instruction completed,
184 * i.e. either stwu rs,n(r1) or stwux rs,r1,rb
185 * (or the byte, halfword, float or double forms).
187 * If we don't check this then any write to the area
188 * between the last mapped region and the stack will
189 * expand the stack rather than segfaulting.
191 if (address + 2048 < uregs->gpr[1]
192 && (!user_mode(regs) || !store_updates_sp(regs)))
196 if (expand_stack(vma, address))
204 if (!(vma->vm_flags & VM_WRITE))
208 /* protection fault */
209 if (error_code & 0x08000000)
211 if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
217 * If for any reason at all we couldn't handle the fault,
218 * make sure we exit gracefully rather than endlessly redo
221 switch (handle_mm_fault(mm, vma, address, is_write)) {
229 case VM_FAULT_SIGBUS:
237 up_read(&mm->mmap_sem);
241 up_read(&mm->mmap_sem);
243 bad_area_nosemaphore:
244 /* User mode accesses cause a SIGSEGV */
245 if (user_mode(regs)) {
246 info.si_signo = SIGSEGV;
249 info.si_addr = (void __user *) address;
250 force_sig_info(SIGSEGV, &info, current);
257 * We ran out of memory, or some other thing happened to us that made
258 * us unable to handle the page fault gracefully.
261 up_read(&mm->mmap_sem);
262 if (current->pid == 1) {
264 down_read(&mm->mmap_sem);
267 printk("VM: killing process %s\n", current->comm);
273 up_read(&mm->mmap_sem);
274 if (user_mode(regs)) {
275 info.si_signo = SIGBUS;
277 info.si_code = BUS_ADRERR;
278 info.si_addr = (void __user *)address;
279 force_sig_info(SIGBUS, &info, current);
286 * bad_page_fault is called when we have a bad access from the kernel.
287 * It is called from do_page_fault above and from some of the procedures
290 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
292 const struct exception_table_entry *entry;
294 /* Are we prepared to handle this fault? */
295 if ((entry = search_exception_tables(regs->nip)) != NULL) {
296 regs->nip = entry->fixup;
300 /* kernel has accessed a bad area */
301 die("Kernel access of bad area", regs, sig);