ARC: Page Fault handling
This includes recent changes to make handler "retry" and/or "killable" The killable (early exit) logic is loosely based on how SH implements it return if SIGKILL + either of VM_FAULT_OOM or VM_FAULT_RETRY which is different from Hexagon implementation which would NOT early exit for SIGKILL + VM_FAULT_OOM + !VM_FAULT_RETRY credits: Non executable stack support from Simon Spooner Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
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Vineet Gupta
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d79e678d74
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/* Page Fault Handling for ARC (TLB Miss / ProtV)
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*
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* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*/
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#include <linux/signal.h>
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#include <linux/errno.h>
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#include <linux/ptrace.h>
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#include <linux/version.h>
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#include <linux/uaccess.h>
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#include <linux/kdebug.h>
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#include <asm/pgalloc.h>
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static int handle_vmalloc_fault(struct mm_struct *mm, unsigned long address)
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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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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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pgd = pgd_offset_fast(mm, address);
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pgd_k = pgd_offset_k(address);
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if (!pgd_present(*pgd_k))
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goto bad_area;
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pud = pud_offset(pgd, address);
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pud_k = pud_offset(pgd_k, address);
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if (!pud_present(*pud_k))
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goto bad_area;
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pmd = pmd_offset(pud, address);
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pmd_k = pmd_offset(pud_k, address);
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if (!pmd_present(*pmd_k))
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goto bad_area;
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set_pmd(pmd, *pmd_k);
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/* XXX: create the TLB entry here */
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return 0;
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bad_area:
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return 1;
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}
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void do_page_fault(struct pt_regs *regs, int write, unsigned long address,
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unsigned long cause_code)
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{
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struct vm_area_struct *vma = NULL;
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struct task_struct *tsk = current;
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struct mm_struct *mm = tsk->mm;
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siginfo_t info;
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int fault, ret;
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unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE |
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(write ? FAULT_FLAG_WRITE : 0);
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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 (address >= VMALLOC_START && address <= VMALLOC_END) {
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ret = handle_vmalloc_fault(mm, address);
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if (unlikely(ret))
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goto bad_area_nosemaphore;
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else
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return;
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}
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info.si_code = SEGV_MAPERR;
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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 (in_atomic() || !mm)
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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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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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/*
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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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info.si_code = SEGV_ACCERR;
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/* Handle protection violation, execute on heap or stack */
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if (cause_code == ((ECR_V_PROTV << 16) | ECR_C_PROTV_INST_FETCH))
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goto bad_area;
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if (write) {
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if (!(vma->vm_flags & VM_WRITE))
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goto bad_area;
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} else {
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if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
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goto bad_area;
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}
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survive:
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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(mm, vma, address, flags);
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/* If Pagefault was interrupted by SIGKILL, exit page fault "early" */
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if (unlikely(fatal_signal_pending(current))) {
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if ((fault & VM_FAULT_ERROR) && !(fault & VM_FAULT_RETRY))
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up_read(&mm->mmap_sem);
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if (user_mode(regs))
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return;
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}
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if (likely(!(fault & VM_FAULT_ERROR))) {
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if (flags & FAULT_FLAG_ALLOW_RETRY) {
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/* To avoid updating stats twice for retry case */
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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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goto retry;
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}
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}
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/* Fault Handled Gracefully */
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up_read(&mm->mmap_sem);
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return;
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}
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/* TBD: switch to pagefault_out_of_memory() */
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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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/* no man's land */
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BUG();
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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.fault_address = address;
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tsk->thread.cause_code = cause_code;
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info.si_signo = SIGSEGV;
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info.si_errno = 0;
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/* info.si_code has been set above */
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info.si_addr = (void __user *)address;
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force_sig_info(SIGSEGV, &info, 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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if (fixup_exception(regs))
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return;
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die("Oops", regs, address, cause_code);
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out_of_memory:
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if (is_global_init(tsk)) {
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yield();
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goto survive;
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}
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up_read(&mm->mmap_sem);
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if (user_mode(regs))
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do_group_exit(SIGKILL); /* This will never return */
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goto no_context;
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do_sigbus:
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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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tsk->thread.fault_address = address;
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tsk->thread.cause_code = cause_code;
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info.si_signo = SIGBUS;
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info.si_errno = 0;
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info.si_code = BUS_ADRERR;
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info.si_addr = (void __user *)address;
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force_sig_info(SIGBUS, &info, tsk);
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}
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