2 * arch/microblaze/mm/fault.c
4 * Copyright (C) 2007 Xilinx, Inc. All rights reserved.
6 * Derived from "arch/ppc/mm/fault.c"
7 * Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
9 * Derived from "arch/i386/mm/fault.c"
10 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
12 * Modified by Cort Dougan and Paul Mackerras.
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.
20 #include <linux/extable.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>
30 #include <linux/interrupt.h>
34 #include <linux/mmu_context.h>
35 #include <linux/uaccess.h>
36 #include <asm/exceptions.h>
38 static unsigned long pte_misses; /* updated by do_page_fault() */
39 static unsigned long pte_errors; /* updated by do_page_fault() */
42 * Check whether the instruction at regs->pc 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->pc))
51 /* check for 1 in the rD field */
52 if (((inst >> 21) & 0x1f) != 1)
54 /* check for store opcodes */
55 if ((inst & 0xd0000000) == 0xd0000000)
62 * bad_page_fault is called when we have a bad access from the kernel.
63 * It is called from do_page_fault above and from some of the procedures
66 void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
68 const struct exception_table_entry *fixup;
70 /* Are we prepared to handle this fault? */
71 fixup = search_exception_tables(regs->pc);
73 regs->pc = fixup->fixup;
77 /* kernel has accessed a bad area */
78 die("kernel access of bad area", regs, sig);
82 * The error_code parameter is ESR for a data fault,
83 * 0 for an instruction fault.
85 void do_page_fault(struct pt_regs *regs, unsigned long address,
86 unsigned long error_code)
88 struct vm_area_struct *vma;
89 struct mm_struct *mm = current->mm;
90 int code = SEGV_MAPERR;
91 int is_write = error_code & ESR_S;
93 unsigned int flags = FAULT_FLAG_DEFAULT;
96 regs->esr = error_code;
98 /* On a kernel SLB miss we can only check for a valid exception entry */
99 if (unlikely(kernel_mode(regs) && (address >= TASK_SIZE))) {
100 pr_warn("kernel task_size exceed");
101 _exception(SIGSEGV, regs, code, address);
104 /* for instr TLB miss and instr storage exception ESR_S is undefined */
105 if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11)
108 if (unlikely(faulthandler_disabled() || !mm)) {
109 if (kernel_mode(regs))
110 goto bad_area_nosemaphore;
112 /* faulthandler_disabled() in user mode is really bad,
113 as is current->mm == NULL. */
114 pr_emerg("Page fault in user mode with faulthandler_disabled(), mm = %p\n",
116 pr_emerg("r15 = %lx MSR = %lx\n",
117 regs->r15, regs->msr);
118 die("Weird page fault", regs, SIGSEGV);
122 flags |= FAULT_FLAG_USER;
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
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.
139 if (unlikely(!mmap_read_trylock(mm))) {
140 if (kernel_mode(regs) && !search_exception_tables(regs->pc))
141 goto bad_area_nosemaphore;
147 vma = find_vma(mm, address);
151 if (vma->vm_start <= address)
154 if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
157 if (unlikely(!is_write))
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.
169 if (unlikely(address + 0x100000 < vma->vm_end)) {
171 /* get user regs even if this fault is in kernel mode */
172 struct pt_regs *uregs = current->thread.regs;
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).
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.
188 if (address + 2048 < uregs->r1
189 && (kernel_mode(regs) || !store_updates_sp(regs)))
192 if (expand_stack(vma, address))
199 if (unlikely(is_write)) {
200 if (unlikely(!(vma->vm_flags & VM_WRITE)))
202 flags |= FAULT_FLAG_WRITE;
205 /* protection fault */
206 if (unlikely(error_code & 0x08000000))
208 if (unlikely(!(vma->vm_flags & (VM_READ | VM_EXEC))))
213 * If for any reason at all we couldn't handle the fault,
214 * make sure we exit gracefully rather than endlessly redo
217 fault = handle_mm_fault(vma, address, flags);
219 if (fault_signal_pending(fault, regs))
222 if (unlikely(fault & VM_FAULT_ERROR)) {
223 if (fault & VM_FAULT_OOM)
225 else if (fault & VM_FAULT_SIGSEGV)
227 else if (fault & VM_FAULT_SIGBUS)
232 if (flags & FAULT_FLAG_ALLOW_RETRY) {
233 if (unlikely(fault & VM_FAULT_MAJOR))
237 if (fault & VM_FAULT_RETRY) {
238 flags |= FAULT_FLAG_TRIED;
241 * No need to mmap_read_unlock(mm) as we would
242 * have already released it in __lock_page_or_retry
250 mmap_read_unlock(mm);
253 * keep track of tlb+htab misses that are good addrs but
254 * just need pte's created via handle_mm_fault()
261 mmap_read_unlock(mm);
263 bad_area_nosemaphore:
266 /* User mode accesses cause a SIGSEGV */
267 if (user_mode(regs)) {
268 _exception(SIGSEGV, regs, code, address);
272 bad_page_fault(regs, address, SIGSEGV);
276 * We ran out of memory, or some other thing happened to us that made
277 * us unable to handle the page fault gracefully.
280 mmap_read_unlock(mm);
281 if (!user_mode(regs))
282 bad_page_fault(regs, address, SIGKILL);
284 pagefault_out_of_memory();
288 mmap_read_unlock(mm);
289 if (user_mode(regs)) {
290 force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
293 bad_page_fault(regs, address, SIGBUS);