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/extable.h>
17 #include <linux/hardirq.h>
18 #include <linux/perf_event.h>
19 #include <linux/uaccess.h>
20 #include <asm/mmu_context.h>
21 #include <asm/cacheflush.h>
22 #include <asm/hardirq.h>
23 #include <asm/pgalloc.h>
25 DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
26 void bad_page_fault(struct pt_regs*, unsigned long, int);
29 * This routine handles page faults. It determines the address,
30 * and the problem, and then passes it off to one of the appropriate
33 * Note: does not handle Miss and MultiHit.
36 void do_page_fault(struct pt_regs *regs)
38 struct vm_area_struct * vma;
39 struct mm_struct *mm = current->mm;
40 unsigned int exccause = regs->exccause;
41 unsigned int address = regs->excvaddr;
44 int is_write, is_exec;
46 unsigned int flags = FAULT_FLAG_DEFAULT;
50 /* We fault-in kernel-space virtual memory on-demand. The
51 * 'reference' page table is init_mm.pgd.
53 if (address >= TASK_SIZE && !user_mode(regs))
56 /* If we're in an interrupt or have no user
57 * context, we must not take the fault..
59 if (faulthandler_disabled() || !mm) {
60 bad_page_fault(regs, address, SIGSEGV);
64 is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
65 is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
66 exccause == EXCCAUSE_ITLB_MISS ||
67 exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
69 pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
70 current->comm, current->pid,
71 address, exccause, regs->pc,
72 is_write ? "w" : "", is_exec ? "x" : "");
75 flags |= FAULT_FLAG_USER;
77 down_read(&mm->mmap_sem);
78 vma = find_vma(mm, address);
82 if (vma->vm_start <= address)
84 if (!(vma->vm_flags & VM_GROWSDOWN))
86 if (expand_stack(vma, address))
89 /* Ok, we have a good vm_area for this memory access, so
97 if (!(vma->vm_flags & VM_WRITE))
99 flags |= FAULT_FLAG_WRITE;
100 } else if (is_exec) {
101 if (!(vma->vm_flags & VM_EXEC))
103 } else /* Allow read even from write-only pages. */
104 if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
107 /* If for any reason at all we couldn't handle the fault,
108 * make sure we exit gracefully rather than endlessly redo
111 fault = handle_mm_fault(vma, address, flags);
113 if (fault_signal_pending(fault, regs))
116 if (unlikely(fault & VM_FAULT_ERROR)) {
117 if (fault & VM_FAULT_OOM)
119 else if (fault & VM_FAULT_SIGSEGV)
121 else if (fault & VM_FAULT_SIGBUS)
125 if (flags & FAULT_FLAG_ALLOW_RETRY) {
126 if (fault & VM_FAULT_MAJOR)
130 if (fault & VM_FAULT_RETRY) {
131 flags |= FAULT_FLAG_TRIED;
133 /* No need to up_read(&mm->mmap_sem) as we would
134 * have already released it in __lock_page_or_retry
142 up_read(&mm->mmap_sem);
143 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
144 if (flags & VM_FAULT_MAJOR)
145 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
147 perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
151 /* Something tried to access memory that isn't in our memory map..
152 * Fix it, but check if it's kernel or user first..
155 up_read(&mm->mmap_sem);
156 if (user_mode(regs)) {
157 current->thread.bad_vaddr = address;
158 current->thread.error_code = is_write;
159 force_sig_fault(SIGSEGV, code, (void *) address);
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 force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address);
186 /* Kernel mode? Handle exceptions or die */
187 if (!user_mode(regs))
188 bad_page_fault(regs, address, SIGBUS);
193 /* Synchronize this task's top level page-table
194 * with the 'reference' page table.
196 struct mm_struct *act_mm = current->active_mm;
197 int index = pgd_index(address);
207 pgd = act_mm->pgd + index;
208 pgd_k = init_mm.pgd + index;
210 if (!pgd_present(*pgd_k))
213 pgd_val(*pgd) = pgd_val(*pgd_k);
215 p4d = p4d_offset(pgd, address);
216 p4d_k = p4d_offset(pgd_k, address);
217 if (!p4d_present(*p4d) || !p4d_present(*p4d_k))
220 pud = pud_offset(p4d, address);
221 pud_k = pud_offset(p4d_k, address);
222 if (!pud_present(*pud) || !pud_present(*pud_k))
225 pmd = pmd_offset(pud, address);
226 pmd_k = pmd_offset(pud_k, address);
227 if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
230 pmd_val(*pmd) = pmd_val(*pmd_k);
231 pte_k = pte_offset_kernel(pmd_k, address);
233 if (!pte_present(*pte_k))
238 bad_page_fault(regs, address, SIGKILL);
244 bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
246 extern void die(const char*, struct pt_regs*, long);
247 const struct exception_table_entry *entry;
249 /* Are we prepared to handle this kernel fault? */
250 if ((entry = search_exception_tables(regs->pc)) != NULL) {
251 pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
252 current->comm, regs->pc, entry->fixup);
253 current->thread.bad_uaddr = address;
254 regs->pc = entry->fixup;
258 /* Oops. The kernel tried to access some bad page. We'll have to
259 * terminate things with extreme prejudice.
261 pr_alert("Unable to handle kernel paging request at virtual "
262 "address %08lx\n pc = %08lx, ra = %08lx\n",
263 address, regs->pc, regs->areg[0]);
264 die("Oops", regs, sig);