256 lines
6.3 KiB
C
256 lines
6.3 KiB
C
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// TODO VM_EXEC flag work-around, cache aliasing
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/*
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* arch/xtensa/mm/fault.c
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*
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* Copyright (C) 2001 - 2010 Tensilica Inc.
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*
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* Chris Zankel <chris@zankel.net>
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* Joe Taylor <joe@tensilica.com, joetylr@yahoo.com>
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*/
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#include <linux/mm.h>
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#include <linux/extable.h>
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#include <linux/hardirq.h>
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#include <linux/perf_event.h>
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#include <linux/uaccess.h>
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#include <asm/mmu_context.h>
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#include <asm/cacheflush.h>
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#include <asm/hardirq.h>
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#include <asm/pgalloc.h>
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DEFINE_PER_CPU(unsigned long, asid_cache) = ASID_USER_FIRST;
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void bad_page_fault(struct pt_regs*, unsigned long, int);
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/*
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* This routine handles page faults. It determines the address,
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* and the problem, and then passes it off to one of the appropriate
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* routines.
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*
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* Note: does not handle Miss and MultiHit.
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*/
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void do_page_fault(struct pt_regs *regs)
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{
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struct vm_area_struct * vma;
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struct mm_struct *mm = current->mm;
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unsigned int exccause = regs->exccause;
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unsigned int address = regs->excvaddr;
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int code;
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int is_write, is_exec;
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vm_fault_t fault;
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unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
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code = SEGV_MAPERR;
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/* We fault-in kernel-space virtual memory on-demand. The
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* 'reference' page table is init_mm.pgd.
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*/
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if (address >= TASK_SIZE && !user_mode(regs))
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goto vmalloc_fault;
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/* If we're in an interrupt or have no user
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* context, we must not take the fault..
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*/
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if (faulthandler_disabled() || !mm) {
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bad_page_fault(regs, address, SIGSEGV);
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return;
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}
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is_write = (exccause == EXCCAUSE_STORE_CACHE_ATTRIBUTE) ? 1 : 0;
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is_exec = (exccause == EXCCAUSE_ITLB_PRIVILEGE ||
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exccause == EXCCAUSE_ITLB_MISS ||
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exccause == EXCCAUSE_FETCH_CACHE_ATTRIBUTE) ? 1 : 0;
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pr_debug("[%s:%d:%08x:%d:%08lx:%s%s]\n",
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current->comm, current->pid,
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address, exccause, regs->pc,
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is_write ? "w" : "", is_exec ? "x" : "");
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if (user_mode(regs))
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flags |= FAULT_FLAG_USER;
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retry:
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down_read(&mm->mmap_sem);
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vma = find_vma(mm, address);
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if (!vma)
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goto bad_area;
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if (vma->vm_start <= address)
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goto good_area;
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if (!(vma->vm_flags & VM_GROWSDOWN))
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goto bad_area;
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if (expand_stack(vma, address))
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goto bad_area;
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/* Ok, we have a good vm_area for this memory access, so
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* we can handle it..
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*/
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good_area:
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code = SEGV_ACCERR;
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if (is_write) {
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if (!(vma->vm_flags & VM_WRITE))
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goto bad_area;
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flags |= FAULT_FLAG_WRITE;
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} else if (is_exec) {
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if (!(vma->vm_flags & VM_EXEC))
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goto bad_area;
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} else /* Allow read even from write-only pages. */
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if (!(vma->vm_flags & (VM_READ | VM_WRITE)))
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goto bad_area;
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/* If for any reason at all we couldn't handle the fault,
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* make sure we exit gracefully rather than endlessly redo
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* the fault.
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*/
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fault = handle_mm_fault(vma, address, flags);
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if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
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return;
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if (unlikely(fault & VM_FAULT_ERROR)) {
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if (fault & VM_FAULT_OOM)
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goto out_of_memory;
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else if (fault & VM_FAULT_SIGSEGV)
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goto bad_area;
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else if (fault & VM_FAULT_SIGBUS)
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goto do_sigbus;
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BUG();
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}
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if (flags & FAULT_FLAG_ALLOW_RETRY) {
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if (fault & VM_FAULT_MAJOR)
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current->maj_flt++;
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else
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current->min_flt++;
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if (fault & VM_FAULT_RETRY) {
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flags &= ~FAULT_FLAG_ALLOW_RETRY;
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flags |= FAULT_FLAG_TRIED;
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/* No need to up_read(&mm->mmap_sem) as we would
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* have already released it in __lock_page_or_retry
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* in mm/filemap.c.
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*/
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goto retry;
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}
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}
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up_read(&mm->mmap_sem);
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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
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if (flags & VM_FAULT_MAJOR)
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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1, regs, address);
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else
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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1, regs, address);
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return;
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/* Something tried to access memory that isn't in our memory map..
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* Fix it, but check if it's kernel or user first..
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*/
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bad_area:
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up_read(&mm->mmap_sem);
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if (user_mode(regs)) {
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current->thread.bad_vaddr = address;
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current->thread.error_code = is_write;
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force_sig_fault(SIGSEGV, code, (void *) address, current);
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return;
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}
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bad_page_fault(regs, address, SIGSEGV);
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return;
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/* We ran out of memory, or some other thing happened to us that made
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* us unable to handle the page fault gracefully.
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*/
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out_of_memory:
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up_read(&mm->mmap_sem);
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if (!user_mode(regs))
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bad_page_fault(regs, address, SIGKILL);
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else
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pagefault_out_of_memory();
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return;
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do_sigbus:
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up_read(&mm->mmap_sem);
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/* Send a sigbus, regardless of whether we were in kernel
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* or user mode.
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*/
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current->thread.bad_vaddr = address;
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force_sig_fault(SIGBUS, BUS_ADRERR, (void *) address, current);
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/* Kernel mode? Handle exceptions or die */
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if (!user_mode(regs))
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bad_page_fault(regs, address, SIGBUS);
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return;
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vmalloc_fault:
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{
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/* Synchronize this task's top level page-table
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* with the 'reference' page table.
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*/
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struct mm_struct *act_mm = current->active_mm;
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int index = pgd_index(address);
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pgd_t *pgd, *pgd_k;
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pmd_t *pmd, *pmd_k;
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pte_t *pte_k;
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if (act_mm == NULL)
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goto bad_page_fault;
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pgd = act_mm->pgd + index;
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pgd_k = init_mm.pgd + index;
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if (!pgd_present(*pgd_k))
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goto bad_page_fault;
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pgd_val(*pgd) = pgd_val(*pgd_k);
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pmd = pmd_offset(pgd, address);
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pmd_k = pmd_offset(pgd_k, address);
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if (!pmd_present(*pmd) || !pmd_present(*pmd_k))
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goto bad_page_fault;
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pmd_val(*pmd) = pmd_val(*pmd_k);
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pte_k = pte_offset_kernel(pmd_k, address);
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if (!pte_present(*pte_k))
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goto bad_page_fault;
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return;
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}
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bad_page_fault:
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bad_page_fault(regs, address, SIGKILL);
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return;
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}
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void
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bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
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{
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extern void die(const char*, struct pt_regs*, long);
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const struct exception_table_entry *entry;
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/* Are we prepared to handle this kernel fault? */
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if ((entry = search_exception_tables(regs->pc)) != NULL) {
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pr_debug("%s: Exception at pc=%#010lx (%lx)\n",
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current->comm, regs->pc, entry->fixup);
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current->thread.bad_uaddr = address;
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regs->pc = entry->fixup;
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return;
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}
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/* Oops. The kernel tried to access some bad page. We'll have to
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* terminate things with extreme prejudice.
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*/
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pr_alert("Unable to handle kernel paging request at virtual "
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"address %08lx\n pc = %08lx, ra = %08lx\n",
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address, regs->pc, regs->areg[0]);
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die("Oops", regs, sig);
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do_exit(sig);
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}
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