![Nick Piggin](/assets/img/avatar_default.png)
Rather than have the pagefault handler kill a process directly if it gets a VM_FAULT_OOM, have it call into the OOM killer. With increasingly sophisticated oom behaviour (cpusets, memory cgroups, oom killing throttling, oom priority adjustment or selective disabling, panic on oom, etc), it's silly to unconditionally kill the faulting process at page fault time. Create a hook for pagefault oom path to call into instead. Only converted x86 and uml so far. [akpm@linux-foundation.org: make __out_of_memory() static] [akpm@linux-foundation.org: fix comment] Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: Jeff Dike <jdike@addtoit.com> Acked-by: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
252 lines
5.9 KiB
C
252 lines
5.9 KiB
C
/*
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* Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
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* Licensed under the GPL
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*/
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#include <linux/mm.h>
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#include <linux/sched.h>
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#include <linux/hardirq.h>
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#include <asm/current.h>
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#include <asm/pgtable.h>
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#include <asm/tlbflush.h>
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#include "arch.h"
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#include "as-layout.h"
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#include "kern_util.h"
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#include "os.h"
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#include "skas.h"
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#include "sysdep/sigcontext.h"
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/*
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* Note this is constrained to return 0, -EFAULT, -EACCESS, -ENOMEM by
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* segv().
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*/
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int handle_page_fault(unsigned long address, unsigned long ip,
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int is_write, int is_user, int *code_out)
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{
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struct mm_struct *mm = current->mm;
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struct vm_area_struct *vma;
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pgd_t *pgd;
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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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int err = -EFAULT;
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*code_out = SEGV_MAPERR;
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/*
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* If the fault was during atomic operation, don't take the fault, just
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* fail.
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*/
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if (in_atomic())
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goto out_nosemaphore;
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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 out;
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else if (vma->vm_start <= address)
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goto good_area;
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else if (!(vma->vm_flags & VM_GROWSDOWN))
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goto out;
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else if (is_user && !ARCH_IS_STACKGROW(address))
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goto out;
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else if (expand_stack(vma, address))
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goto out;
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good_area:
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*code_out = SEGV_ACCERR;
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if (is_write && !(vma->vm_flags & VM_WRITE))
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goto out;
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/* Don't require VM_READ|VM_EXEC for write faults! */
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if (!is_write && !(vma->vm_flags & (VM_READ | VM_EXEC)))
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goto out;
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do {
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int fault;
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fault = handle_mm_fault(mm, vma, address, is_write);
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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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err = -EACCES;
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goto out;
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}
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BUG();
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}
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if (fault & VM_FAULT_MAJOR)
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current->maj_flt++;
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else
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current->min_flt++;
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pgd = pgd_offset(mm, address);
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pud = pud_offset(pgd, address);
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pmd = pmd_offset(pud, address);
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pte = pte_offset_kernel(pmd, address);
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} while (!pte_present(*pte));
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err = 0;
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/*
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* The below warning was added in place of
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* pte_mkyoung(); if (is_write) pte_mkdirty();
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* If it's triggered, we'd see normally a hang here (a clean pte is
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* marked read-only to emulate the dirty bit).
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* However, the generic code can mark a PTE writable but clean on a
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* concurrent read fault, triggering this harmlessly. So comment it out.
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*/
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#if 0
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WARN_ON(!pte_young(*pte) || (is_write && !pte_dirty(*pte)));
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#endif
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flush_tlb_page(vma, address);
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out:
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up_read(&mm->mmap_sem);
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out_nosemaphore:
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return err;
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out_of_memory:
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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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up_read(&mm->mmap_sem);
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pagefault_out_of_memory();
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return 0;
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}
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static void bad_segv(struct faultinfo fi, unsigned long ip)
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{
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struct siginfo si;
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si.si_signo = SIGSEGV;
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si.si_code = SEGV_ACCERR;
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si.si_addr = (void __user *) FAULT_ADDRESS(fi);
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current->thread.arch.faultinfo = fi;
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force_sig_info(SIGSEGV, &si, current);
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}
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void fatal_sigsegv(void)
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{
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force_sigsegv(SIGSEGV, current);
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do_signal();
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/*
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* This is to tell gcc that we're not returning - do_signal
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* can, in general, return, but in this case, it's not, since
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* we just got a fatal SIGSEGV queued.
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*/
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os_dump_core();
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}
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void segv_handler(int sig, struct uml_pt_regs *regs)
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{
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struct faultinfo * fi = UPT_FAULTINFO(regs);
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if (UPT_IS_USER(regs) && !SEGV_IS_FIXABLE(fi)) {
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bad_segv(*fi, UPT_IP(regs));
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return;
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}
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segv(*fi, UPT_IP(regs), UPT_IS_USER(regs), regs);
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}
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/*
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* We give a *copy* of the faultinfo in the regs to segv.
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* This must be done, since nesting SEGVs could overwrite
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* the info in the regs. A pointer to the info then would
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* give us bad data!
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*/
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unsigned long segv(struct faultinfo fi, unsigned long ip, int is_user,
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struct uml_pt_regs *regs)
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{
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struct siginfo si;
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jmp_buf *catcher;
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int err;
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int is_write = FAULT_WRITE(fi);
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unsigned long address = FAULT_ADDRESS(fi);
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if (!is_user && (address >= start_vm) && (address < end_vm)) {
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flush_tlb_kernel_vm();
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return 0;
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}
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else if (current->mm == NULL) {
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show_regs(container_of(regs, struct pt_regs, regs));
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panic("Segfault with no mm");
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}
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if (SEGV_IS_FIXABLE(&fi) || SEGV_MAYBE_FIXABLE(&fi))
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err = handle_page_fault(address, ip, is_write, is_user,
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&si.si_code);
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else {
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err = -EFAULT;
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/*
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* A thread accessed NULL, we get a fault, but CR2 is invalid.
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* This code is used in __do_copy_from_user() of TT mode.
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* XXX tt mode is gone, so maybe this isn't needed any more
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*/
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address = 0;
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}
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catcher = current->thread.fault_catcher;
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if (!err)
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return 0;
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else if (catcher != NULL) {
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current->thread.fault_addr = (void *) address;
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UML_LONGJMP(catcher, 1);
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}
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else if (current->thread.fault_addr != NULL)
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panic("fault_addr set but no fault catcher");
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else if (!is_user && arch_fixup(ip, regs))
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return 0;
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if (!is_user) {
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show_regs(container_of(regs, struct pt_regs, regs));
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panic("Kernel mode fault at addr 0x%lx, ip 0x%lx",
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address, ip);
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}
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if (err == -EACCES) {
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si.si_signo = SIGBUS;
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si.si_errno = 0;
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si.si_code = BUS_ADRERR;
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si.si_addr = (void __user *)address;
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current->thread.arch.faultinfo = fi;
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force_sig_info(SIGBUS, &si, current);
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} else {
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BUG_ON(err != -EFAULT);
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si.si_signo = SIGSEGV;
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si.si_addr = (void __user *) address;
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current->thread.arch.faultinfo = fi;
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force_sig_info(SIGSEGV, &si, current);
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}
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return 0;
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}
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void relay_signal(int sig, struct uml_pt_regs *regs)
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{
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if (!UPT_IS_USER(regs)) {
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if (sig == SIGBUS)
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printk(KERN_ERR "Bus error - the host /dev/shm or /tmp "
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"mount likely just ran out of space\n");
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panic("Kernel mode signal %d", sig);
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}
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arch_examine_signal(sig, regs);
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current->thread.arch.faultinfo = *UPT_FAULTINFO(regs);
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force_sig(sig, current);
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}
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void bus_handler(int sig, struct uml_pt_regs *regs)
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{
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if (current->thread.fault_catcher != NULL)
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UML_LONGJMP(current->thread.fault_catcher, 1);
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else relay_signal(sig, regs);
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}
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void winch(int sig, struct uml_pt_regs *regs)
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{
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do_IRQ(WINCH_IRQ, regs);
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}
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void trap_init(void)
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{
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}
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