![Kautuk Consul](/assets/img/avatar_default.png)
commit 8878a539ff
was done by me
to make the page fault handler retryable as well as interruptible.
Due to this commit, there is a mistake in the way in which
tsk->[maj|min]_flt counter gets incremented for VM_FAULT_ERROR:
If VM_FAULT_ERROR is returned in the fault flags by handle_mm_fault,
then either maj_flt or min_flt will get incremented. This is wrong
as in the case of a VM_FAULT_ERROR we need to be skip ahead to the
error handling code in do_page_fault.
Added a check after the call to __do_page_fault() to check for
(fault & VM_FAULT_ERROR).
Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
615 lines
14 KiB
C
615 lines
14 KiB
C
/*
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* linux/arch/arm/mm/fault.c
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*
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* Copyright (C) 1995 Linus Torvalds
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* Modifications for ARM processor (c) 1995-2004 Russell King
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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/module.h>
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#include <linux/signal.h>
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#include <linux/mm.h>
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#include <linux/hardirq.h>
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#include <linux/init.h>
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#include <linux/kprobes.h>
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#include <linux/uaccess.h>
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#include <linux/page-flags.h>
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#include <linux/sched.h>
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#include <linux/highmem.h>
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#include <linux/perf_event.h>
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#include <asm/exception.h>
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#include <asm/pgtable.h>
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#include <asm/system_misc.h>
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#include <asm/system_info.h>
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#include <asm/tlbflush.h>
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#include "fault.h"
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#ifdef CONFIG_MMU
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#ifdef CONFIG_KPROBES
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static inline int notify_page_fault(struct pt_regs *regs, unsigned int fsr)
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{
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int ret = 0;
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if (!user_mode(regs)) {
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/* kprobe_running() needs smp_processor_id() */
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preempt_disable();
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if (kprobe_running() && kprobe_fault_handler(regs, fsr))
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ret = 1;
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preempt_enable();
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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, unsigned int fsr)
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{
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return 0;
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}
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#endif
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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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printk(KERN_ALERT "pgd = %p\n", mm->pgd);
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pgd = pgd_offset(mm, addr);
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printk(KERN_ALERT "[%08lx] *pgd=%08llx",
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addr, (long long)pgd_val(*pgd));
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do {
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pud_t *pud;
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pmd_t *pmd;
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pte_t *pte;
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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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printk("(bad)");
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break;
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}
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pud = pud_offset(pgd, addr);
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if (PTRS_PER_PUD != 1)
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printk(", *pud=%08llx", (long long)pud_val(*pud));
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if (pud_none(*pud))
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break;
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if (pud_bad(*pud)) {
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printk("(bad)");
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break;
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}
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pmd = pmd_offset(pud, addr);
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if (PTRS_PER_PMD != 1)
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printk(", *pmd=%08llx", (long long)pmd_val(*pmd));
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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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printk("(bad)");
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break;
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}
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/* We must not map this if we have highmem enabled */
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if (PageHighMem(pfn_to_page(pmd_val(*pmd) >> PAGE_SHIFT)))
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break;
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pte = pte_offset_map(pmd, addr);
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printk(", *pte=%08llx", (long long)pte_val(*pte));
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#ifndef CONFIG_ARM_LPAE
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printk(", *ppte=%08llx",
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(long long)pte_val(pte[PTE_HWTABLE_PTRS]));
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#endif
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pte_unmap(pte);
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} while(0);
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printk("\n");
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}
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#else /* CONFIG_MMU */
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void show_pte(struct mm_struct *mm, unsigned long addr)
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{ }
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#endif /* CONFIG_MMU */
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/*
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* Oops. The kernel tried to access some page that wasn't present.
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*/
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static void
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__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
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struct pt_regs *regs)
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{
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/*
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* Are we prepared to handle this kernel fault?
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*/
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if (fixup_exception(regs))
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return;
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/*
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* No handler, we'll have to terminate things with extreme prejudice.
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*/
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bust_spinlocks(1);
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printk(KERN_ALERT
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"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, fsr);
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bust_spinlocks(0);
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do_exit(SIGKILL);
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}
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/*
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* Something tried to access memory that isn't in our memory map..
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* User mode accesses just cause a SIGSEGV
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*/
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static void
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__do_user_fault(struct task_struct *tsk, unsigned long addr,
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unsigned int fsr, unsigned int sig, int code,
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struct pt_regs *regs)
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{
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struct siginfo si;
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#ifdef CONFIG_DEBUG_USER
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if (((user_debug & UDBG_SEGV) && (sig == SIGSEGV)) ||
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((user_debug & UDBG_BUS) && (sig == SIGBUS))) {
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printk(KERN_DEBUG "%s: unhandled page fault (%d) at 0x%08lx, code 0x%03x\n",
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tsk->comm, sig, addr, fsr);
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show_pte(tsk->mm, addr);
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show_regs(regs);
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}
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#endif
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tsk->thread.address = addr;
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tsk->thread.error_code = fsr;
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tsk->thread.trap_no = 14;
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si.si_signo = sig;
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si.si_errno = 0;
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si.si_code = code;
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si.si_addr = (void __user *)addr;
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force_sig_info(sig, &si, tsk);
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}
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void do_bad_area(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
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{
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struct task_struct *tsk = current;
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struct mm_struct *mm = tsk->active_mm;
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/*
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* If we are in kernel mode at this point, we
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* have no context to handle this fault with.
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*/
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if (user_mode(regs))
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__do_user_fault(tsk, addr, fsr, SIGSEGV, SEGV_MAPERR, regs);
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else
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__do_kernel_fault(mm, addr, fsr, regs);
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}
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#ifdef CONFIG_MMU
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#define VM_FAULT_BADMAP 0x010000
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#define VM_FAULT_BADACCESS 0x020000
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/*
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* Check that the permissions on the VMA allow for the fault which occurred.
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* If we encountered a write fault, we must have write permission, otherwise
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* we allow any permission.
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*/
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static inline bool access_error(unsigned int fsr, struct vm_area_struct *vma)
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{
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unsigned int mask = VM_READ | VM_WRITE | VM_EXEC;
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if (fsr & FSR_WRITE)
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mask = VM_WRITE;
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if (fsr & FSR_LNX_PF)
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mask = VM_EXEC;
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return vma->vm_flags & mask ? false : true;
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}
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static int __kprobes
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__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
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unsigned int flags, struct task_struct *tsk)
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{
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struct vm_area_struct *vma;
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int fault;
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vma = find_vma(mm, addr);
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fault = VM_FAULT_BADMAP;
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if (unlikely(!vma))
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goto out;
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if (unlikely(vma->vm_start > addr))
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goto check_stack;
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/*
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* Ok, we have a good vm_area for this
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* memory access, so we can handle it.
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*/
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good_area:
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if (access_error(fsr, vma)) {
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fault = VM_FAULT_BADACCESS;
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goto out;
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}
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return handle_mm_fault(mm, vma, addr & PAGE_MASK, flags);
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check_stack:
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if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
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goto good_area;
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out:
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return fault;
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}
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static int __kprobes
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do_page_fault(unsigned long addr, unsigned int fsr, 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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int fault, sig, code;
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int write = fsr & FSR_WRITE;
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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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if (notify_page_fault(regs, fsr))
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return 0;
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tsk = current;
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mm = tsk->mm;
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/* Enable interrupts if they were enabled in the parent context. */
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if (interrupts_enabled(regs))
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local_irq_enable();
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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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/*
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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 (!down_read_trylock(&mm->mmap_sem)) {
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if (!user_mode(regs) && !search_exception_tables(regs->ARM_pc))
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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
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* which case, we'll have missed the might_sleep() from
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* down_read()
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*/
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might_sleep();
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#ifdef CONFIG_DEBUG_VM
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if (!user_mode(regs) &&
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!search_exception_tables(regs->ARM_pc))
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goto no_context;
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#endif
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}
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fault = __do_page_fault(mm, addr, fsr, flags, tsk);
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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
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* it would already be released in __lock_page_or_retry in
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* mm/filemap.c. */
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if ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
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return 0;
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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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perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, addr);
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if (!(fault & VM_FAULT_ERROR) && 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, 1,
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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, 1,
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regs, addr);
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}
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if (fault & VM_FAULT_RETRY) {
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/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
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* of starvation. */
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flags &= ~FAULT_FLAG_ALLOW_RETRY;
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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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/*
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* Handle the "normal" case first - VM_FAULT_MAJOR / VM_FAULT_MINOR
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*/
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if (likely(!(fault & (VM_FAULT_ERROR | VM_FAULT_BADMAP | VM_FAULT_BADACCESS))))
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return 0;
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if (fault & VM_FAULT_OOM) {
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/*
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* We ran out of memory, call the OOM killer, and return to
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* userspace (which will retry the fault, or kill us if we
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* got oom-killed)
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*/
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pagefault_out_of_memory();
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return 0;
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}
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/*
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* If we are in kernel mode at this point, we
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* have no context to handle this fault with.
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*/
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if (!user_mode(regs))
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goto no_context;
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if (fault & VM_FAULT_SIGBUS) {
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/*
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* We had some memory, but were unable to
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* successfully fix up this page fault.
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*/
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sig = SIGBUS;
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code = BUS_ADRERR;
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} else {
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/*
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* Something tried to access memory that
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* isn't in our memory map..
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*/
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sig = SIGSEGV;
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code = fault == VM_FAULT_BADACCESS ?
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SEGV_ACCERR : SEGV_MAPERR;
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}
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__do_user_fault(tsk, addr, fsr, sig, code, regs);
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return 0;
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no_context:
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__do_kernel_fault(mm, addr, fsr, regs);
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return 0;
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}
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#else /* CONFIG_MMU */
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static int
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do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
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{
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return 0;
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}
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#endif /* CONFIG_MMU */
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/*
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* First Level Translation Fault Handler
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*
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* We enter here because the first level page table doesn't contain
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* a valid entry for the address.
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*
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* If the address is in kernel space (>= TASK_SIZE), then we are
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* probably faulting in the vmalloc() area.
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*
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* If the init_task's first level page tables contains the relevant
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* entry, we copy the it to this task. If not, we send the process
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* a signal, fixup the exception, or oops the kernel.
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*
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* NOTE! We MUST NOT take any locks for this case. We may be in an
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* interrupt or a critical region, and should only copy the information
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* from the master page table, nothing more.
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*/
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#ifdef CONFIG_MMU
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static int __kprobes
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do_translation_fault(unsigned long addr, unsigned int fsr,
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struct pt_regs *regs)
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{
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unsigned int index;
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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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if (addr < TASK_SIZE)
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return do_page_fault(addr, fsr, regs);
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if (user_mode(regs))
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goto bad_area;
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index = pgd_index(addr);
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/*
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* FIXME: CP15 C1 is write only on ARMv3 architectures.
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*/
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pgd = cpu_get_pgd() + index;
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pgd_k = init_mm.pgd + index;
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if (pgd_none(*pgd_k))
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goto bad_area;
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if (!pgd_present(*pgd))
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set_pgd(pgd, *pgd_k);
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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_none(*pud_k))
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goto bad_area;
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if (!pud_present(*pud))
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set_pud(pud, *pud_k);
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pmd = pmd_offset(pud, addr);
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pmd_k = pmd_offset(pud_k, addr);
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#ifdef CONFIG_ARM_LPAE
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/*
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* Only one hardware entry per PMD with LPAE.
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*/
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index = 0;
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#else
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/*
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* On ARM one Linux PGD entry contains two hardware entries (see page
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* tables layout in pgtable.h). We normally guarantee that we always
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* fill both L1 entries. But create_mapping() doesn't follow the rule.
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* It can create inidividual L1 entries, so here we have to call
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* pmd_none() check for the entry really corresponded to address, not
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* for the first of pair.
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*/
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index = (addr >> SECTION_SHIFT) & 1;
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#endif
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if (pmd_none(pmd_k[index]))
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goto bad_area;
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copy_pmd(pmd, pmd_k);
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return 0;
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bad_area:
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do_bad_area(addr, fsr, regs);
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return 0;
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}
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#else /* CONFIG_MMU */
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static int
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do_translation_fault(unsigned long addr, unsigned int fsr,
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struct pt_regs *regs)
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{
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return 0;
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}
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#endif /* CONFIG_MMU */
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/*
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* Some section permission faults need to be handled gracefully.
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* They can happen due to a __{get,put}_user during an oops.
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*/
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static int
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do_sect_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
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{
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do_bad_area(addr, fsr, regs);
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return 0;
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}
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/*
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* This abort handler always returns "fault".
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*/
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static int
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do_bad(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
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{
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return 1;
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}
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struct fsr_info {
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int (*fn)(unsigned long addr, unsigned int fsr, struct pt_regs *regs);
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int sig;
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int code;
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const char *name;
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};
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/* FSR definition */
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#ifdef CONFIG_ARM_LPAE
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#include "fsr-3level.c"
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#else
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#include "fsr-2level.c"
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#endif
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void __init
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hook_fault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
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int sig, int code, const char *name)
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{
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if (nr < 0 || nr >= ARRAY_SIZE(fsr_info))
|
|
BUG();
|
|
|
|
fsr_info[nr].fn = fn;
|
|
fsr_info[nr].sig = sig;
|
|
fsr_info[nr].code = code;
|
|
fsr_info[nr].name = name;
|
|
}
|
|
|
|
/*
|
|
* Dispatch a data abort to the relevant handler.
|
|
*/
|
|
asmlinkage void __exception
|
|
do_DataAbort(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
|
|
{
|
|
const struct fsr_info *inf = fsr_info + fsr_fs(fsr);
|
|
struct siginfo info;
|
|
|
|
if (!inf->fn(addr, fsr & ~FSR_LNX_PF, regs))
|
|
return;
|
|
|
|
printk(KERN_ALERT "Unhandled fault: %s (0x%03x) at 0x%08lx\n",
|
|
inf->name, fsr, addr);
|
|
|
|
info.si_signo = inf->sig;
|
|
info.si_errno = 0;
|
|
info.si_code = inf->code;
|
|
info.si_addr = (void __user *)addr;
|
|
arm_notify_die("", regs, &info, fsr, 0);
|
|
}
|
|
|
|
void __init
|
|
hook_ifault_code(int nr, int (*fn)(unsigned long, unsigned int, struct pt_regs *),
|
|
int sig, int code, const char *name)
|
|
{
|
|
if (nr < 0 || nr >= ARRAY_SIZE(ifsr_info))
|
|
BUG();
|
|
|
|
ifsr_info[nr].fn = fn;
|
|
ifsr_info[nr].sig = sig;
|
|
ifsr_info[nr].code = code;
|
|
ifsr_info[nr].name = name;
|
|
}
|
|
|
|
asmlinkage void __exception
|
|
do_PrefetchAbort(unsigned long addr, unsigned int ifsr, struct pt_regs *regs)
|
|
{
|
|
const struct fsr_info *inf = ifsr_info + fsr_fs(ifsr);
|
|
struct siginfo info;
|
|
|
|
if (!inf->fn(addr, ifsr | FSR_LNX_PF, regs))
|
|
return;
|
|
|
|
printk(KERN_ALERT "Unhandled prefetch abort: %s (0x%03x) at 0x%08lx\n",
|
|
inf->name, ifsr, addr);
|
|
|
|
info.si_signo = inf->sig;
|
|
info.si_errno = 0;
|
|
info.si_code = inf->code;
|
|
info.si_addr = (void __user *)addr;
|
|
arm_notify_die("", regs, &info, ifsr, 0);
|
|
}
|
|
|
|
#ifndef CONFIG_ARM_LPAE
|
|
static int __init exceptions_init(void)
|
|
{
|
|
if (cpu_architecture() >= CPU_ARCH_ARMv6) {
|
|
hook_fault_code(4, do_translation_fault, SIGSEGV, SEGV_MAPERR,
|
|
"I-cache maintenance fault");
|
|
}
|
|
|
|
if (cpu_architecture() >= CPU_ARCH_ARMv7) {
|
|
/*
|
|
* TODO: Access flag faults introduced in ARMv6K.
|
|
* Runtime check for 'K' extension is needed
|
|
*/
|
|
hook_fault_code(3, do_bad, SIGSEGV, SEGV_MAPERR,
|
|
"section access flag fault");
|
|
hook_fault_code(6, do_bad, SIGSEGV, SEGV_MAPERR,
|
|
"section access flag fault");
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
arch_initcall(exceptions_init);
|
|
#endif
|