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402 lines
8.8 KiB
402 lines
8.8 KiB
// 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 <linux/perf_event.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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p4d_t *p4d; |
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pud_t *pud; |
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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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p4d = p4d_offset(pgd, addr); |
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pud = pud_offset(p4d, addr); |
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pmd = pmd_offset(pud, 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_ACCESS_FLAGS; |
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unsigned int flags = FAULT_FLAG_DEFAULT; |
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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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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr); |
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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(!mmap_read_trylock(mm))) { |
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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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mmap_read_lock(mm); |
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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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} |
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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, regs); |
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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_lock 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_signal_pending(fault, regs)) { |
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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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if (flags & FAULT_FLAG_ALLOW_RETRY) { |
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if (fault & VM_FAULT_RETRY) { |
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flags |= FAULT_FLAG_TRIED; |
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/* No need to mmap_read_unlock(mm) 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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mmap_read_unlock(mm); |
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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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mmap_read_unlock(mm); |
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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); |
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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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mmap_read_unlock(mm); |
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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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mmap_read_unlock(mm); |
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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); |
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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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p4d_t *p4d, *p4d_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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p4d = p4d_offset(pgd, addr); |
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p4d_k = p4d_offset(pgd_k, addr); |
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if (!p4d_present(*p4d_k)) |
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goto no_context; |
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pud = pud_offset(p4d, addr); |
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pud_k = pud_offset(p4d_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. |
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*/ |
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pte_k = pte_offset_kernel(pmd_k, addr); |
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if (!pte_present(*pte_k)) |
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goto no_context; |
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return; |
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} |
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}
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