271 строка
6.5 KiB
C
271 строка
6.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2009 Sunplus Core Technology Co., Ltd.
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* Lennox Wu <lennox.wu@sunplusct.com>
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* Chen Liqin <liqin.chen@sunplusct.com>
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* Copyright (C) 2012 Regents of the University of California
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*/
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#include <linux/mm.h>
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#include <linux/kernel.h>
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#include <linux/interrupt.h>
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#include <linux/perf_event.h>
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#include <linux/signal.h>
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#include <linux/uaccess.h>
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#include <asm/pgalloc.h>
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#include <asm/ptrace.h>
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/*
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* This routine handles page faults. It determines the address and the
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* problem, and then passes it off to one of the appropriate routines.
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*/
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asmlinkage void do_page_fault(struct pt_regs *regs)
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{
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struct task_struct *tsk;
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struct vm_area_struct *vma;
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struct mm_struct *mm;
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unsigned long addr, cause;
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unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
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int code = SEGV_MAPERR;
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vm_fault_t fault;
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cause = regs->scause;
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addr = regs->sbadaddr;
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tsk = current;
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mm = tsk->mm;
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/*
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* Fault-in kernel-space virtual memory on-demand.
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* The '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 (unlikely((addr >= VMALLOC_START) && (addr <= VMALLOC_END)))
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goto vmalloc_fault;
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/* Enable interrupts if they were enabled in the parent context. */
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if (likely(regs->sstatus & SR_SPIE))
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local_irq_enable();
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/*
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* If we're in an interrupt, have no user context, or are running
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* in an atomic region, then 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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if (user_mode(regs))
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flags |= FAULT_FLAG_USER;
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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
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retry:
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down_read(&mm->mmap_sem);
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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 (likely(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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code = SEGV_ACCERR;
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switch (cause) {
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case EXC_INST_PAGE_FAULT:
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if (!(vma->vm_flags & VM_EXEC))
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goto bad_area;
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break;
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case EXC_LOAD_PAGE_FAULT:
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if (!(vma->vm_flags & VM_READ))
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goto bad_area;
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break;
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case EXC_STORE_PAGE_FAULT:
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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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break;
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default:
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panic("%s: unhandled cause %lu", __func__, cause);
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}
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/*
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* If for any reason at all we could not 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(tsk))
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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_SIGBUS)
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goto do_sigbus;
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BUG();
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}
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/*
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* Major/minor page fault accounting is only done on the
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* initial attempt. If we go through a retry, it is extremely
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* likely that the 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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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ,
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1, regs, addr);
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} else {
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tsk->min_flt++;
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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN,
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1, regs, addr);
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}
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if (fault & VM_FAULT_RETRY) {
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/*
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* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
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* of starvation.
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*/
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flags &= ~(FAULT_FLAG_ALLOW_RETRY);
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flags |= FAULT_FLAG_TRIED;
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/*
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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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/* User mode accesses just cause a SIGSEGV */
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if (user_mode(regs)) {
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do_trap(regs, SIGSEGV, code, 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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if (fixup_exception(regs))
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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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bust_spinlocks(1);
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pr_alert("Unable to handle kernel %s at virtual address " REG_FMT "\n",
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(addr < PAGE_SIZE) ? "NULL pointer dereference" :
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"paging request", addr);
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die(regs, "Oops");
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do_exit(SIGKILL);
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/*
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* We ran out of memory, call the OOM killer, and return the userspace
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* (which will retry the fault, or kill us if we got oom-killed).
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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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do_trap(regs, SIGBUS, BUS_ADRERR, addr, tsk);
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return;
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vmalloc_fault:
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{
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pgd_t *pgd, *pgd_k;
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pud_t *pud, *pud_k;
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p4d_t *p4d, *p4d_k;
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pmd_t *pmd, *pmd_k;
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pte_t *pte_k;
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int index;
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/* User mode accesses just cause a SIGSEGV */
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if (user_mode(regs))
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return do_trap(regs, SIGSEGV, code, addr, tsk);
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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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* Do _not_ use "tsk->active_mm->pgd" here.
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* We might be inside an interrupt in the middle
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* of a task switch.
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*/
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index = pgd_index(addr);
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pgd = (pgd_t *)pfn_to_virt(csr_read(CSR_SATP)) + 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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set_pgd(pgd, *pgd_k);
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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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/*
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* Since the vmalloc area is global, it is unnecessary
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* to copy individual PTEs
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*/
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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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set_pmd(pmd, *pmd_k);
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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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* addresses. 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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