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6347e2a10f
Follow commit 871341023c.
Kernel faults are expected to handle OOM conditions gracefully (gup,
uaccess etc.), so they should never invoke the OOM killer. Reserve
this for faults triggered in user context when it is the only option.
Signed-off-by: Ley Foon Tan <lftan@altera.com>
276 lines
6.7 KiB
C
276 lines
6.7 KiB
C
/*
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* Copyright (C) 2009 Wind River Systems Inc
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* Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
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*
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* based on arch/mips/mm/fault.c which is:
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*
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* Copyright (C) 1995-2000 Ralf Baechle
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*
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* This file is subject to the terms and conditions of the GNU General Public
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* License. See the file "COPYING" in the main directory of this archive
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* for more details.
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*/
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#include <linux/signal.h>
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#include <linux/sched.h>
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#include <linux/interrupt.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/ptrace.h>
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#include <linux/mman.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/uaccess.h>
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#include <linux/ptrace.h>
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#include <asm/mmu_context.h>
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#include <asm/traps.h>
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#define EXC_SUPERV_INSN_ACCESS 9 /* Supervisor only instruction address */
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#define EXC_SUPERV_DATA_ACCESS 11 /* Supervisor only data address */
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#define EXC_X_PROTECTION_FAULT 13 /* TLB permission violation (x) */
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#define EXC_R_PROTECTION_FAULT 14 /* TLB permission violation (r) */
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#define EXC_W_PROTECTION_FAULT 15 /* TLB permission violation (w) */
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/*
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* This routine handles page faults. It determines the address,
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* and the problem, and then passes it off to one of the appropriate
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* routines.
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*/
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asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long cause,
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unsigned long address)
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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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int code = SEGV_MAPERR;
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int fault;
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unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
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cause >>= 2;
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/* Restart the instruction */
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regs->ea -= 4;
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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 (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) {
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if (user_mode(regs))
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goto bad_area_nosemaphore;
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else
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goto vmalloc_fault;
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}
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if (unlikely(address >= TASK_SIZE))
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goto bad_area_nosemaphore;
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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 bad_area_nosemaphore;
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if (user_mode(regs))
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flags |= FAULT_FLAG_USER;
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if (!down_read_trylock(&mm->mmap_sem)) {
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if (!user_mode(regs) && !search_exception_tables(regs->ea))
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goto bad_area_nosemaphore;
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retry:
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down_read(&mm->mmap_sem);
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}
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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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code = SEGV_ACCERR;
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switch (cause) {
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case EXC_SUPERV_INSN_ACCESS:
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goto bad_area;
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case EXC_SUPERV_DATA_ACCESS:
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goto bad_area;
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case EXC_X_PROTECTION_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_R_PROTECTION_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_W_PROTECTION_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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}
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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 ((fault & VM_FAULT_RETRY) && fatal_signal_pending(current))
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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_SIGSEGV)
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goto bad_area;
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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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current->maj_flt++;
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else
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current->min_flt++;
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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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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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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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if (unhandled_signal(current, SIGSEGV) && printk_ratelimit()) {
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pr_info("%s: unhandled page fault (%d) at 0x%08lx, "
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"cause %ld\n", current->comm, SIGSEGV, address, cause);
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show_regs(regs);
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}
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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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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 %08lx",
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address < PAGE_SIZE ? "NULL pointer dereference" :
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"paging request", address);
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pr_alert("ea = %08lx, ra = %08lx, cause = %ld\n", regs->ea, regs->ra,
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cause);
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panic("Oops");
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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 that made
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* 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 (!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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_exception(SIGBUS, regs, BUS_ADRERR, address);
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return;
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vmalloc_fault:
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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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* Do _not_ use "tsk" here. We might be inside
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* an interrupt in the middle of a task switch..
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*/
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int offset = pgd_index(address);
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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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pte_t *pte_k;
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pgd = pgd_current + offset;
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pgd_k = init_mm.pgd + offset;
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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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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 no_context;
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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 no_context;
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set_pmd(pmd, *pmd_k);
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pte_k = pte_offset_kernel(pmd_k, address);
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if (!pte_present(*pte_k))
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goto no_context;
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flush_tlb_one(address);
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return;
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}
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}
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