403 lines
9 KiB
C
403 lines
9 KiB
C
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// SPDX-License-Identifier: GPL-2.0
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// Copyright (C) 2005-2017 Andes Technology Corporation
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#include <linux/extable.h>
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#include <linux/module.h>
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#include <linux/signal.h>
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#include <linux/ptrace.h>
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#include <linux/mm.h>
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#include <linux/init.h>
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#include <linux/hardirq.h>
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#include <linux/uaccess.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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extern void die(const char *str, struct pt_regs *regs, long err);
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/*
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* This is useful to dump out the page tables associated with
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* 'addr' in mm 'mm'.
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*/
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void show_pte(struct mm_struct *mm, unsigned long addr)
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{
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pgd_t *pgd;
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if (!mm)
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mm = &init_mm;
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pr_alert("pgd = %p\n", mm->pgd);
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pgd = pgd_offset(mm, addr);
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pr_alert("[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
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do {
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pmd_t *pmd;
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if (pgd_none(*pgd))
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break;
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if (pgd_bad(*pgd)) {
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pr_alert("(bad)");
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break;
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}
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pmd = pmd_offset(pgd, addr);
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#if PTRS_PER_PMD != 1
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pr_alert(", *pmd=%08lx", pmd_val(*pmd));
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#endif
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if (pmd_none(*pmd))
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break;
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if (pmd_bad(*pmd)) {
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pr_alert("(bad)");
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break;
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}
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if (IS_ENABLED(CONFIG_HIGHMEM))
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{
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pte_t *pte;
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/* We must not map this if we have highmem enabled */
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pte = pte_offset_map(pmd, addr);
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pr_alert(", *pte=%08lx", pte_val(*pte));
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pte_unmap(pte);
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}
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} while (0);
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pr_alert("\n");
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}
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void do_page_fault(unsigned long entry, unsigned long addr,
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unsigned int error_code, struct pt_regs *regs)
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{
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struct task_struct *tsk;
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struct mm_struct *mm;
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struct vm_area_struct *vma;
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int si_code;
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vm_fault_t fault;
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unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
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unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
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error_code = error_code & (ITYPE_mskINST | ITYPE_mskETYPE);
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tsk = current;
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mm = tsk->mm;
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si_code = SEGV_MAPERR;
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/*
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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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* NOTE! We MUST NOT take any locks for this case. We may
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* be in an interrupt or a critical region, and should
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* only copy the information from the master page table,
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* nothing more.
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*/
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if (addr >= TASK_SIZE) {
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if (user_mode(regs))
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goto bad_area_nosemaphore;
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if (addr >= TASK_SIZE && addr < VMALLOC_END
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&& (entry == ENTRY_PTE_NOT_PRESENT))
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goto vmalloc_fault;
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else
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goto no_context;
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}
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/* Send a signal to the task for handling the unalignment access. */
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if (entry == ENTRY_GENERAL_EXCPETION
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&& error_code == ETYPE_ALIGNMENT_CHECK) {
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if (user_mode(regs))
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goto bad_area_nosemaphore;
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else
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goto no_context;
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}
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/*
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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 (unlikely(faulthandler_disabled() || !mm))
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goto no_context;
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/*
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* As per x86, we may deadlock here. However, since the kernel only
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* validly references user space from well defined areas of the code,
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* we can bug out early if this is from code which shouldn't.
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*/
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if (unlikely(!down_read_trylock(&mm->mmap_sem))) {
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if (!user_mode(regs) &&
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!search_exception_tables(instruction_pointer(regs)))
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goto no_context;
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retry:
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down_read(&mm->mmap_sem);
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} else {
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/*
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* The above down_read_trylock() might have succeeded in which
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* case, we'll have missed the might_sleep() from down_read().
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*/
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might_sleep();
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if (IS_ENABLED(CONFIG_DEBUG_VM)) {
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if (!user_mode(regs) &&
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!search_exception_tables(instruction_pointer(regs)))
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goto no_context;
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}
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}
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vma = find_vma(mm, addr);
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if (unlikely(!vma))
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goto bad_area;
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if (vma->vm_start <= addr)
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goto good_area;
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if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
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goto bad_area;
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if (unlikely(expand_stack(vma, addr)))
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goto bad_area;
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/*
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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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si_code = SEGV_ACCERR;
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/* first do some preliminary protection checks */
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if (entry == ENTRY_PTE_NOT_PRESENT) {
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if (error_code & ITYPE_mskINST)
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mask = VM_EXEC;
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else {
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mask = VM_READ | VM_WRITE;
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if (vma->vm_flags & VM_WRITE)
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flags |= FAULT_FLAG_WRITE;
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}
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} else if (entry == ENTRY_TLB_MISC) {
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switch (error_code & ITYPE_mskETYPE) {
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case RD_PROT:
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mask = VM_READ;
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break;
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case WRT_PROT:
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mask = VM_WRITE;
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flags |= FAULT_FLAG_WRITE;
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break;
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case NOEXEC:
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mask = VM_EXEC;
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break;
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case PAGE_MODIFY:
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mask = VM_WRITE;
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flags |= FAULT_FLAG_WRITE;
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break;
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case ACC_BIT:
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BUG();
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default:
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break;
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}
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}
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if (!(vma->vm_flags & mask))
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goto bad_area;
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/*
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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, addr, flags);
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/*
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* If we need to retry but a fatal signal is pending, handle the
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* signal first. We do not need to release the mmap_sem because it
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* would already be released in __lock_page_or_retry in mm/filemap.c.
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*/
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if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current)) {
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if (!user_mode(regs))
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goto no_context;
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return;
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}
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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_SIGBUS)
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goto do_sigbus;
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else
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goto bad_area;
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}
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/*
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* Major/minor page fault accounting is only done on the initial
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* attempt. If we go through a retry, it is extremely likely that the
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* page will be found in page cache at that point.
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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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tsk->maj_flt++;
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else
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tsk->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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return;
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/*
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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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bad_area_nosemaphore:
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/* User mode accesses just cause a SIGSEGV */
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if (user_mode(regs)) {
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tsk->thread.address = addr;
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tsk->thread.error_code = error_code;
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tsk->thread.trap_no = entry;
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force_sig_fault(SIGSEGV, si_code, (void __user *)addr, tsk);
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return;
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}
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no_context:
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/* Are we prepared to handle this kernel fault?
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*
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* (The kernel has valid exception-points in the source
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* when it acesses user-memory. When it fails in one
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* of those points, we find it in a table and do a jump
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* to some fixup code that loads an appropriate error
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* code)
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*/
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{
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const struct exception_table_entry *entry;
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if ((entry =
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search_exception_tables(instruction_pointer(regs))) !=
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NULL) {
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/* Adjust the instruction pointer in the stackframe */
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instruction_pointer(regs) = entry->fixup;
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return;
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}
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}
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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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bust_spinlocks(1);
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pr_alert("Unable to handle kernel %s at virtual address %08lx\n",
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(addr < PAGE_SIZE) ? "NULL pointer dereference" :
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"paging request", addr);
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show_pte(mm, addr);
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die("Oops", regs, error_code);
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bust_spinlocks(0);
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do_exit(SIGKILL);
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return;
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/*
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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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goto no_context;
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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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/* Kernel mode? Handle exceptions or die */
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if (!user_mode(regs))
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goto no_context;
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/*
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* Send a sigbus
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*/
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tsk->thread.address = addr;
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tsk->thread.error_code = error_code;
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tsk->thread.trap_no = entry;
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force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)addr, tsk);
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return;
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vmalloc_fault:
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{
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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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* Use current_pgd instead of tsk->active_mm->pgd
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* since the latter might be unavailable if this
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* code is executed in a misfortunately run irq
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* (like inside schedule() between switch_mm and
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* switch_to...).
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*/
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unsigned int index = pgd_index(addr);
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pgd_t *pgd, *pgd_k;
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pud_t *pud, *pud_k;
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pmd_t *pmd, *pmd_k;
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pte_t *pte_k;
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pgd = (pgd_t *) __va(__nds32__mfsr(NDS32_SR_L1_PPTB)) + 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 no_context;
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pud = pud_offset(pgd, addr);
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pud_k = pud_offset(pgd_k, addr);
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if (!pud_present(*pud_k))
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goto no_context;
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pmd = pmd_offset(pud, addr);
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pmd_k = pmd_offset(pud_k, addr);
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if (!pmd_present(*pmd_k))
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goto no_context;
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if (!pmd_present(*pmd))
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set_pmd(pmd, *pmd_k);
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else
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BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
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/*
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* Since the vmalloc area is global, we don't
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* need to copy individual PTE's, it is enough to
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* copy the pgd pointer into the pte page of the
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* root task. If that is there, we'll find our pte if
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* it exists.
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*/
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/* Make sure the actual PTE exists as well to
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* catch kernel vmalloc-area accesses to non-mapped
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* addres. If we don't do this, this will just
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* silently loop forever.
|
||
|
|
*/
|
||
|
|
|
||
|
|
pte_k = pte_offset_kernel(pmd_k, addr);
|
||
|
|
if (!pte_present(*pte_k))
|
||
|
|
goto no_context;
|
||
|
|
|
||
|
|
return;
|
||
|
|
}
|
||
|
|
}
|