269 lines
6.3 KiB
C
269 lines
6.3 KiB
C
/*
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* Copyright (C) 2004-2006 Atmel Corporation
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*
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* Based on linux/arch/sh/mm/fault.c:
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* Copyright (C) 1999 Niibe Yutaka
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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/mm.h>
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#include <linux/module.h>
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#include <linux/pagemap.h>
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#include <linux/kdebug.h>
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#include <linux/kprobes.h>
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#include <asm/mmu_context.h>
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#include <asm/sysreg.h>
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#include <asm/tlb.h>
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#include <asm/uaccess.h>
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#ifdef CONFIG_KPROBES
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static inline int notify_page_fault(struct pt_regs *regs, int trap)
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{
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int ret = 0;
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if (!user_mode(regs)) {
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if (kprobe_running() && kprobe_fault_handler(regs, trap))
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ret = 1;
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}
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return ret;
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}
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#else
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static inline int notify_page_fault(struct pt_regs *regs, int trap)
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{
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return 0;
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}
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#endif
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int exception_trace = 1;
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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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* ecr is the Exception Cause Register. Possible values are:
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* 6: Protection fault (instruction access)
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* 15: Protection fault (read access)
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* 16: Protection fault (write access)
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* 20: Page not found (instruction access)
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* 24: Page not found (read access)
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* 28: Page not found (write access)
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*/
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asmlinkage void do_page_fault(unsigned long ecr, 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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const struct exception_table_entry *fixup;
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unsigned long address;
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unsigned long page;
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int writeaccess;
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long signr;
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int code;
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int fault;
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if (notify_page_fault(regs, ecr))
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return;
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address = sysreg_read(TLBEAR);
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tsk = current;
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mm = tsk->mm;
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signr = SIGSEGV;
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code = SEGV_MAPERR;
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/*
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* If we're in an interrupt or have no user context, we must
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* not take the fault...
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*/
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if (in_atomic() || !mm || regs->sr & SYSREG_BIT(GM))
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goto no_context;
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local_irq_enable();
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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 we
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* can handle it...
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*/
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good_area:
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code = SEGV_ACCERR;
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writeaccess = 0;
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switch (ecr) {
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case ECR_PROTECTION_X:
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case ECR_TLB_MISS_X:
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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 ECR_PROTECTION_R:
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case ECR_TLB_MISS_R:
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if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC)))
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goto bad_area;
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break;
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case ECR_PROTECTION_W:
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case ECR_TLB_MISS_W:
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if (!(vma->vm_flags & VM_WRITE))
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goto bad_area;
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writeaccess = 1;
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break;
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default:
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panic("Unhandled case %lu in do_page_fault!", ecr);
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}
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/*
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* If for any reason at all we couldn't handle the fault, make
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* sure we exit gracefully rather than endlessly redo the
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* fault.
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*/
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survive:
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fault = handle_mm_fault(mm, vma, address, writeaccess);
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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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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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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
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* map. 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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if (exception_trace && printk_ratelimit())
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printk("%s%s[%d]: segfault at %08lx pc %08lx "
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"sp %08lx ecr %lu\n",
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is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
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tsk->comm, tsk->pid, address, regs->pc,
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regs->sp, ecr);
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_exception(SIGSEGV, regs, code, address);
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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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fixup = search_exception_tables(regs->pc);
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if (fixup) {
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regs->pc = fixup->fixup;
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return;
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}
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/*
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* Oops. The kernel tried to access some bad page. We'll have
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* to terminate things with extreme prejudice.
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*/
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if (address < PAGE_SIZE)
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printk(KERN_ALERT
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"Unable to handle kernel NULL pointer dereference");
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else
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printk(KERN_ALERT
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"Unable to handle kernel paging request");
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printk(" at virtual address %08lx\n", address);
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page = sysreg_read(PTBR);
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printk(KERN_ALERT "ptbr = %08lx", page);
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if (page) {
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page = ((unsigned long *)page)[address >> 22];
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printk(" pgd = %08lx", page);
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if (page & _PAGE_PRESENT) {
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page &= PAGE_MASK;
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address &= 0x003ff000;
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page = ((unsigned long *)__va(page))[address >> PAGE_SHIFT];
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printk(" pte = %08lx", page);
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}
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}
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printk("\n");
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die("Kernel access of bad area", regs, signr);
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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
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* that made 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 (is_global_init(current)) {
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yield();
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down_read(&mm->mmap_sem);
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goto survive;
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}
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printk("VM: Killing process %s\n", tsk->comm);
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if (user_mode(regs))
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do_group_exit(SIGKILL);
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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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/* Kernel mode? Handle exceptions or die */
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signr = SIGBUS;
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code = BUS_ADRERR;
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if (!user_mode(regs))
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goto no_context;
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if (exception_trace)
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printk("%s%s[%d]: bus error at %08lx pc %08lx "
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"sp %08lx ecr %lu\n",
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is_global_init(tsk) ? KERN_EMERG : KERN_INFO,
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tsk->comm, tsk->pid, address, regs->pc,
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regs->sp, ecr);
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_exception(SIGBUS, regs, BUS_ADRERR, address);
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}
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asmlinkage void do_bus_error(unsigned long addr, int write_access,
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struct pt_regs *regs)
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{
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printk(KERN_ALERT
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"Bus error at physical address 0x%08lx (%s access)\n",
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addr, write_access ? "write" : "read");
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printk(KERN_INFO "DTLB dump:\n");
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dump_dtlb();
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die("Bus Error", regs, SIGKILL);
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}
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/*
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* This functionality is currently not possible to implement because
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* we're using segmentation to ensure a fixed mapping of the kernel
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* virtual address space.
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*
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* It would be possible to implement this, but it would require us to
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* disable segmentation at startup and load the kernel mappings into
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* the TLB like any other pages. There will be lots of trickery to
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* avoid recursive invocation of the TLB miss handler, though...
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*/
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#ifdef CONFIG_DEBUG_PAGEALLOC
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void kernel_map_pages(struct page *page, int numpages, int enable)
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{
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}
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EXPORT_SYMBOL(kernel_map_pages);
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#endif
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