2 * Copyright (C) 2009 Wind River Systems Inc
3 * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
5 * based on arch/mips/mm/fault.c which is:
7 * Copyright (C) 1995-2000 Ralf Baechle
9 * This file is subject to the terms and conditions of the GNU General Public
10 * License. See the file "COPYING" in the main directory of this archive
14 #include <linux/signal.h>
15 #include <linux/sched.h>
16 #include <linux/interrupt.h>
17 #include <linux/kernel.h>
18 #include <linux/errno.h>
19 #include <linux/string.h>
20 #include <linux/types.h>
21 #include <linux/ptrace.h>
22 #include <linux/mman.h>
24 #include <linux/module.h>
25 #include <linux/uaccess.h>
26 #include <linux/ptrace.h>
28 #include <asm/mmu_context.h>
29 #include <asm/traps.h>
31 #define EXC_SUPERV_INSN_ACCESS 9 /* Supervisor only instruction address */
32 #define EXC_SUPERV_DATA_ACCESS 11 /* Supervisor only data address */
33 #define EXC_X_PROTECTION_FAULT 13 /* TLB permission violation (x) */
34 #define EXC_R_PROTECTION_FAULT 14 /* TLB permission violation (r) */
35 #define EXC_W_PROTECTION_FAULT 15 /* TLB permission violation (w) */
38 * This routine handles page faults. It determines the address,
39 * and the problem, and then passes it off to one of the appropriate
42 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
43 unsigned long address)
45 struct vm_area_struct *vma = NULL;
46 struct task_struct *tsk = current;
47 struct mm_struct *mm = tsk->mm;
48 int code = SEGV_MAPERR;
50 unsigned int flags = 0;
54 /* Restart the instruction */
58 * We fault-in kernel-space virtual memory on-demand. The
59 * 'reference' page table is init_mm.pgd.
61 * NOTE! We MUST NOT take any locks for this case. We may
62 * be in an interrupt or a critical region, and should
63 * only copy the information from the master page table,
66 if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) {
68 goto bad_area_nosemaphore;
73 if (unlikely(address >= TASK_SIZE))
74 goto bad_area_nosemaphore;
77 * If we're in an interrupt or have no user
78 * context, we must not take the fault..
80 if (in_atomic() || !mm)
81 goto bad_area_nosemaphore;
84 flags |= FAULT_FLAG_USER;
86 if (!down_read_trylock(&mm->mmap_sem)) {
87 if (!user_mode(regs) && !search_exception_tables(regs->ea))
88 goto bad_area_nosemaphore;
89 down_read(&mm->mmap_sem);
92 vma = find_vma(mm, address);
95 if (vma->vm_start <= address)
97 if (!(vma->vm_flags & VM_GROWSDOWN))
99 if (expand_stack(vma, address))
102 * Ok, we have a good vm_area for this memory access, so
109 case EXC_SUPERV_INSN_ACCESS:
111 case EXC_SUPERV_DATA_ACCESS:
113 case EXC_X_PROTECTION_FAULT:
114 if (!(vma->vm_flags & VM_EXEC))
117 case EXC_R_PROTECTION_FAULT:
118 if (!(vma->vm_flags & VM_READ))
121 case EXC_W_PROTECTION_FAULT:
122 if (!(vma->vm_flags & VM_WRITE))
124 flags = FAULT_FLAG_WRITE;
130 * If for any reason at all we couldn't handle the fault,
131 * make sure we exit gracefully rather than endlessly redo
134 fault = handle_mm_fault(mm, vma, address, flags);
135 if (unlikely(fault & VM_FAULT_ERROR)) {
136 if (fault & VM_FAULT_OOM)
138 else if (fault & VM_FAULT_SIGSEGV)
140 else if (fault & VM_FAULT_SIGBUS)
144 if (fault & VM_FAULT_MAJOR)
149 up_read(&mm->mmap_sem);
153 * Something tried to access memory that isn't in our memory map..
154 * Fix it, but check if it's kernel or user first..
157 up_read(&mm->mmap_sem);
159 bad_area_nosemaphore:
160 /* User mode accesses just cause a SIGSEGV */
161 if (user_mode(regs)) {
162 if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) {
163 pr_info("%s: unhandled page fault (%d) at 0x%08lx, "
164 "cause %ld\n", current->comm, SIGSEGV, address, cause);
167 _exception(SIGSEGV, regs, code, address);
172 /* Are we prepared to handle this kernel fault? */
173 if (fixup_exception(regs))
177 * Oops. The kernel tried to access some bad page. We'll have to
178 * terminate things with extreme prejudice.
182 pr_alert("Unable to handle kernel %s at virtual address %08lx",
183 address < PAGE_SIZE ? "NULL pointer dereference" :
184 "paging request", address);
185 pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
191 * We ran out of memory, or some other thing happened to us that made
192 * us unable to handle the page fault gracefully.
195 up_read(&mm->mmap_sem);
196 if (is_global_init(tsk)) {
198 down_read(&mm->mmap_sem);
201 if (!user_mode(regs))
203 pagefault_out_of_memory();
207 up_read(&mm->mmap_sem);
209 /* Kernel mode? Handle exceptions or die */
210 if (!user_mode(regs))
213 _exception(SIGBUS, regs, BUS_ADRERR, address);
219 * Synchronize this task's top level page-table
220 * with the 'reference' page table.
222 * Do _not_ use "tsk" here. We might be inside
223 * an interrupt in the middle of a task switch..
225 int offset = pgd_index(address);
231 pgd = pgd_current + offset;
232 pgd_k = init_mm.pgd + offset;
234 if (!pgd_present(*pgd_k))
236 set_pgd(pgd, *pgd_k);
238 pud = pud_offset(pgd, address);
239 pud_k = pud_offset(pgd_k, address);
240 if (!pud_present(*pud_k))
242 pmd = pmd_offset(pud, address);
243 pmd_k = pmd_offset(pud_k, address);
244 if (!pmd_present(*pmd_k))
246 set_pmd(pmd, *pmd_k);
248 pte_k = pte_offset_kernel(pmd_k, address);
249 if (!pte_present(*pte_k))
252 flush_tlb_one(address);