1 // TODO VM_EXEC flag work-around, cache aliasing
3 * arch/xtensa/mm/fault.c
5 * This file is subject to the terms and conditions of the GNU General Public
6 * License. See the file "COPYING" in the main directory of this archive
9 * Copyright (C) 2001 - 2010 Tensilica Inc.
11 * Chris Zankel <chris@zankel.net>
12 * Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
16 #include <linux/module.h>
17 #include <linux/hardirq.h>
18 #include <linux/uaccess.h>
19 #include <asm/mmu_context.h>
20 #include <asm/cacheflush.h>
21 #include <asm/hardirq.h>
22 #include <asm/pgalloc.h>
24 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
25 void bad_page_fault(struct pt_regs*, unsigned long, int);
27 #undef DEBUG_PAGE_FAULT
30 * This routine handles page faults. It determines the address,
31 * and the problem, and then passes it off to one of the appropriate
34 * Note: does not handle Miss and MultiHit.
37 void do_page_fault(struct pt_regs *regs)
39 struct vm_area_struct * vma;
40 struct mm_struct *mm = current->mm;
41 unsigned int exccause = regs->exccause;
42 unsigned int address = regs->excvaddr;
45 int is_write, is_exec;
47 unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
49 info.si_code = SEGV_MAPERR;
51 /* We fault-in kernel-space virtual memory on-demand. The
52 * 'reference' page table is init_mm.pgd.
54 if (address >= TASK_SIZE && !user_mode(regs))
57 /* If we're in an interrupt or have no user
58 * context, we must not take the fault..
60 if (faulthandler_disabled() || !mm) {
61 bad_page_fault(regs, address, SIGSEGV);
65 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
66 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
67 exccause == EXCCAUSE_ITLB_MISS ||
68 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
70 #ifdef DEBUG_PAGE_FAULT
71 printk("[%s:%d:%08x:%d:%08x:%s%s]\n", current->comm, current->pid,
72 address, exccause, regs->pc, is_write? "w":"", is_exec? "x":"");
76 flags |= FAULT_FLAG_USER;
78 down_read(&mm->mmap_sem);
79 vma = find_vma(mm, address);
83 if (vma->vm_start <= address)
85 if (!(vma->vm_flags & VM_GROWSDOWN))
87 if (expand_stack(vma, address))
90 /* Ok, we have a good vm_area for this memory access, so
95 info.si_code = SEGV_ACCERR;
98 if (!(vma->vm_flags & VM_WRITE))
100 flags |= FAULT_FLAG_WRITE;
101 } else if (is_exec) {
102 if (!(vma->vm_flags & VM_EXEC))
104 } else /* Allow read even from write-only pages. */
105 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
108 /* If for any reason at all we couldn't handle the fault,
109 * make sure we exit gracefully rather than endlessly redo
112 fault = handle_mm_fault(mm, vma, address, flags);
114 if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
117 if (unlikely(fault & VM_FAULT_ERROR)) {
118 if (fault & VM_FAULT_OOM)
120 else if (fault & VM_FAULT_SIGSEGV)
122 else if (fault & VM_FAULT_SIGBUS)
126 if (flags & FAULT_FLAG_ALLOW_RETRY) {
127 if (fault & VM_FAULT_MAJOR)
131 if (fault & VM_FAULT_RETRY) {
132 flags &= ~FAULT_FLAG_ALLOW_RETRY;
133 flags |= FAULT_FLAG_TRIED;
135 /* No need to up_read(&mm->mmap_sem) as we would
136 * have already released it in __lock_page_or_retry
144 up_read(&mm->mmap_sem);
147 /* Something tried to access memory that isn't in our memory map..
148 * Fix it, but check if it's kernel or user first..
151 up_read(&mm->mmap_sem);
152 if (user_mode(regs)) {
153 current->thread.bad_vaddr = address;
154 current->thread.error_code = is_write;
155 info.si_signo = SIGSEGV;
157 /* info.si_code has been set above */
158 info.si_addr = (void *) address;
159 force_sig_info(SIGSEGV, &info, current);
162 bad_page_fault(regs, address, SIGSEGV);
166 /* We ran out of memory, or some other thing happened to us that made
167 * us unable to handle the page fault gracefully.
170 up_read(&mm->mmap_sem);
171 if (!user_mode(regs))
172 bad_page_fault(regs, address, SIGKILL);
174 pagefault_out_of_memory();
178 up_read(&mm->mmap_sem);
180 /* Send a sigbus, regardless of whether we were in kernel
183 current->thread.bad_vaddr = address;
184 info.si_code = SIGBUS;
186 info.si_code = BUS_ADRERR;
187 info.si_addr = (void *) address;
188 force_sig_info(SIGBUS, &info, current);
190 /* Kernel mode? Handle exceptions or die */
191 if (!user_mode(regs))
192 bad_page_fault(regs, address, SIGBUS);
197 /* Synchronize this task's top level page-table
198 * with the 'reference' page table.
200 struct mm_struct *act_mm = current->active_mm;
201 int index = pgd_index(address);
209 pgd = act_mm->pgd + index;
210 pgd_k = init_mm.pgd + index;
212 if (!pgd_present(*pgd_k))
215 pgd_val(*pgd) = pgd_val(*pgd_k);
217 pmd = pmd_offset(pgd, address);
218 pmd_k = pmd_offset(pgd_k, address);
219 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
222 pmd_val(*pmd) = pmd_val(*pmd_k);
223 pte_k = pte_offset_kernel(pmd_k, address);
225 if (!pte_present(*pte_k))
230 bad_page_fault(regs, address, SIGKILL);
236 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
238 extern void die(const char*, struct pt_regs*, long);
239 const struct exception_table_entry *entry;
241 /* Are we prepared to handle this kernel fault? */
242 if ((entry = search_exception_tables(regs->pc)) != NULL) {
243 #ifdef DEBUG_PAGE_FAULT
244 printk(KERN_DEBUG "%s: Exception at pc=%#010lx (%lx)\n",
245 current->comm, regs->pc, entry->fixup);
247 current->thread.bad_uaddr = address;
248 regs->pc = entry->fixup;
252 /* Oops. The kernel tried to access some bad page. We'll have to
253 * terminate things with extreme prejudice.
255 printk(KERN_ALERT "Unable to handle kernel paging request at virtual "
256 "address %08lx\n pc = %08lx, ra = %08lx\n",
257 address, regs->pc, regs->areg[0]);
258 die("Oops", regs, sig);