460 lines
12 KiB
C
460 lines
12 KiB
C
/*
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* linux/arch/cris/mm/fault.c
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*
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* Copyright (C) 2000, 2001 Axis Communications AB
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*
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* Authors: Bjorn Wesen
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*
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* $Log: fault.c,v $
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* Revision 1.20 2005/03/04 08:16:18 starvik
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* Merge of Linux 2.6.11.
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*
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* Revision 1.19 2005/01/14 10:07:59 starvik
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* Fixed warning.
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*
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* Revision 1.18 2005/01/12 08:10:14 starvik
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* Re-added the change of frametype when handling kernel page fault fixup
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* for v10. This is necessary to avoid that the CPU remakes the faulting
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* access.
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*
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* Revision 1.17 2005/01/11 13:53:05 starvik
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* Use raw_printk.
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*
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* Revision 1.16 2004/12/17 11:39:41 starvik
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* SMP support.
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*
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* Revision 1.15 2004/11/23 18:36:18 starvik
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* Stack is now non-executable.
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* Signal handler trampolines are placed in a reserved page mapped into all
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* processes.
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*
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* Revision 1.14 2004/11/23 07:10:21 starvik
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* Moved find_fixup_code to generic code.
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*
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* Revision 1.13 2004/11/23 07:00:54 starvik
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* Actually use the execute permission bit in the MMU. This makes it possible
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* to prevent e.g. attacks where executable code is put on the stack.
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*
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* Revision 1.12 2004/09/29 06:16:04 starvik
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* Use instruction_pointer
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*
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* Revision 1.11 2004/05/14 07:58:05 starvik
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* Merge of changes from 2.4
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*
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* Revision 1.10 2003/10/27 14:51:24 starvik
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* Removed debugcode
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*
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* Revision 1.9 2003/10/27 14:50:42 starvik
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* Changed do_page_fault signature
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*
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* Revision 1.8 2003/07/04 13:02:48 tobiasa
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* Moved code snippet from arch/cris/mm/fault.c that searches for fixup code
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* to separate function in arch-specific files.
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*
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* Revision 1.7 2003/01/22 06:48:38 starvik
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* Fixed warnings issued by GCC 3.2.1
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*
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* Revision 1.6 2003/01/09 14:42:52 starvik
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* Merge of Linux 2.5.55
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*
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* Revision 1.5 2002/12/11 14:44:48 starvik
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* Extracted v10 (ETRAX 100LX) specific stuff to arch/cris/arch-v10/mm
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*
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* Revision 1.4 2002/11/13 15:10:28 starvik
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* pte_offset has been renamed to pte_offset_kernel
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*
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* Revision 1.3 2002/11/05 06:45:13 starvik
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* Merge of Linux 2.5.45
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*
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* Revision 1.2 2001/12/18 13:35:22 bjornw
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* Applied the 2.4.13->2.4.16 CRIS patch to 2.5.1 (is a copy of 2.4.15).
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*
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* Revision 1.20 2001/11/22 13:34:06 bjornw
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* * Bug workaround (LX TR89): force a rerun of the whole of an interrupted
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* unaligned write, because the second half of the write will be corrupted
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* otherwise. Affected unaligned writes spanning not-yet mapped pages.
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* * Optimization: use the wr_rd bit in R_MMU_CAUSE to know whether a miss
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* was due to a read or a write (before we didn't know this until the next
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* restart of the interrupted instruction, thus wasting one fault-irq)
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*
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* Revision 1.19 2001/11/12 19:02:10 pkj
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* Fixed compiler warnings.
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*
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* Revision 1.18 2001/07/18 22:14:32 bjornw
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* Enable interrupts in the bulk of do_page_fault
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*
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* Revision 1.17 2001/07/18 13:07:23 bjornw
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* * Detect non-existant PTE's in vmalloc pmd synchronization
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* * Remove comment about fast-paths for VMALLOC_START etc, because all that
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* was totally bogus anyway it turned out :)
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* * Fix detection of vmalloc-area synchronization
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* * Add some comments
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*
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* Revision 1.16 2001/06/13 00:06:08 bjornw
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* current_pgd should be volatile
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*
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* Revision 1.15 2001/06/13 00:02:23 bjornw
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* Use a separate variable to store the current pgd to avoid races in schedule
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*
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* Revision 1.14 2001/05/16 17:41:07 hp
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* Last comment tweak further tweaked.
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*
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* Revision 1.13 2001/05/15 00:58:44 hp
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* Expand a bit on the comment why we compare address >= TASK_SIZE rather
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* than >= VMALLOC_START.
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*
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* Revision 1.12 2001/04/04 10:51:14 bjornw
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* mmap_sem is grabbed for reading
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*
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* Revision 1.11 2001/03/23 07:36:07 starvik
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* Corrected according to review remarks
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*
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* Revision 1.10 2001/03/21 16:10:11 bjornw
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* CRIS_FRAME_FIXUP not needed anymore, use FRAME_NORMAL
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*
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* Revision 1.9 2001/03/05 13:22:20 bjornw
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* Spell-fix and fix in vmalloc_fault handling
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*
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* Revision 1.8 2000/11/22 14:45:31 bjornw
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* * 2.4.0-test10 removed the set_pgdir instantaneous kernel global mapping
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* into all processes. Instead we fill in the missing PTE entries on demand.
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*
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* Revision 1.7 2000/11/21 16:39:09 bjornw
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* fixup switches frametype
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*
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* Revision 1.6 2000/11/17 16:54:08 bjornw
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* More detailed siginfo reporting
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*
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*
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*/
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#include <linux/mm.h>
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#include <linux/interrupt.h>
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#include <linux/module.h>
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#include <asm/uaccess.h>
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extern int find_fixup_code(struct pt_regs *);
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extern void die_if_kernel(const char *, struct pt_regs *, long);
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extern int raw_printk(const char *fmt, ...);
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/* debug of low-level TLB reload */
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#undef DEBUG
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#ifdef DEBUG
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#define D(x) x
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#else
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#define D(x)
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#endif
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/* debug of higher-level faults */
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#define DPG(x)
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/* current active page directory */
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volatile DEFINE_PER_CPU(pgd_t *,current_pgd);
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unsigned long cris_signal_return_page;
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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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* Notice that the address we're given is aligned to the page the fault
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* occurred in, since we only get the PFN in R_MMU_CAUSE not the complete
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* address.
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*
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* error_code:
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* bit 0 == 0 means no page found, 1 means protection fault
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* bit 1 == 0 means read, 1 means write
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*
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* If this routine detects a bad access, it returns 1, otherwise it
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* returns 0.
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*/
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asmlinkage void
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do_page_fault(unsigned long address, struct pt_regs *regs,
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int protection, int writeaccess)
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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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siginfo_t info;
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int fault;
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D(printk("Page fault for %lX on %X at %lX, prot %d write %d\n",
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address, smp_processor_id(), instruction_pointer(regs),
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protection, writeaccess));
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tsk = current;
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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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* NOTE2: This is done so that, when updating the vmalloc
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* mappings we don't have to walk all processes pgdirs and
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* add the high mappings all at once. Instead we do it as they
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* are used. However vmalloc'ed page entries have the PAGE_GLOBAL
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* bit set so sometimes the TLB can use a lingering entry.
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*
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* This verifies that the fault happens in kernel space
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* and that the fault was not a protection error (error_code & 1).
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*/
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if (address >= VMALLOC_START &&
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!protection &&
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!user_mode(regs))
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goto vmalloc_fault;
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/* When stack execution is not allowed we store the signal
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* trampolines in the reserved cris_signal_return_page.
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* Handle this in the exact same way as vmalloc (we know
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* that the mapping is there and is valid so no need to
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* call handle_mm_fault).
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*/
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if (cris_signal_return_page &&
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address == cris_signal_return_page &&
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!protection && user_mode(regs))
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goto vmalloc_fault;
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/* we can and should enable interrupts at this point */
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local_irq_enable();
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mm = tsk->mm;
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info.si_code = SEGV_MAPERR;
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/*
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* If we're in an interrupt or have no user
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* context, we must not take the fault..
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*/
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if (in_atomic() || !mm)
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goto no_context;
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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 (user_mode(regs)) {
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/*
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* accessing the stack below usp is always a bug.
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* we get page-aligned addresses so we can only check
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* if we're within a page from usp, but that might be
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* enough to catch brutal errors at least.
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*/
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if (address + PAGE_SIZE < rdusp())
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goto bad_area;
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}
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if (expand_stack(vma, address))
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goto bad_area;
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/*
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* Ok, we have a good vm_area for this memory access, so
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* we can handle it..
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*/
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good_area:
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info.si_code = SEGV_ACCERR;
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/* first do some preliminary protection checks */
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if (writeaccess == 2){
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if (!(vma->vm_flags & VM_EXEC))
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goto bad_area;
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} else if (writeaccess == 1) {
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if (!(vma->vm_flags & VM_WRITE))
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goto bad_area;
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} else {
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if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
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goto bad_area;
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}
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/*
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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, writeaccess & 1);
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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 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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DPG(show_registers(regs));
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/* User mode accesses just cause a SIGSEGV */
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if (user_mode(regs)) {
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info.si_signo = SIGSEGV;
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info.si_errno = 0;
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/* info.si_code has been set above */
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info.si_addr = (void *)address;
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force_sig_info(SIGSEGV, &info, tsk);
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return;
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}
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no_context:
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/* Are we prepared to handle this kernel fault?
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*
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* (The kernel has valid exception-points in the source
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* when it acesses user-memory. When it fails in one
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* of those points, we find it in a table and do a jump
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* to some fixup code that loads an appropriate error
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* code)
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*/
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if (find_fixup_code(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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if ((unsigned long) (address) < PAGE_SIZE)
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raw_printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
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else
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raw_printk(KERN_ALERT "Unable to handle kernel access");
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raw_printk(" at virtual address %08lx\n",address);
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die_if_kernel("Oops", regs, (writeaccess << 1) | protection);
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do_exit(SIGKILL);
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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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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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/*
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* Send a sigbus, regardless of whether we were in kernel
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* or user mode.
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*/
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info.si_signo = SIGBUS;
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info.si_errno = 0;
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info.si_code = BUS_ADRERR;
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info.si_addr = (void *)address;
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force_sig_info(SIGBUS, &info, tsk);
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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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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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* Use current_pgd instead of tsk->active_mm->pgd
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* since the latter might be unavailable if this
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* code is executed in a misfortunately run irq
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* (like inside schedule() between switch_mm and
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* switch_to...).
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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_t *)per_cpu(current_pgd, smp_processor_id()) + offset;
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pgd_k = init_mm.pgd + offset;
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/* Since we're two-level, we don't need to do both
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* set_pgd and set_pmd (they do the same thing). If
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* we go three-level at some point, do the right thing
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* with pgd_present and set_pgd here.
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*
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* Also, since the vmalloc area is global, we don't
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* need to copy individual PTE's, it is enough to
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* copy the pgd pointer into the pte page of the
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* root task. If that is there, we'll find our pte if
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* it exists.
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*/
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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 bad_area_nosemaphore;
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set_pmd(pmd, *pmd_k);
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/* Make sure the actual PTE exists as well to
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* catch kernel vmalloc-area accesses to non-mapped
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* addresses. If we don't do this, this will just
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* silently loop forever.
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*/
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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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return;
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}
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}
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/* Find fixup code. */
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int
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find_fixup_code(struct pt_regs *regs)
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{
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const struct exception_table_entry *fixup;
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if ((fixup = search_exception_tables(instruction_pointer(regs))) != 0) {
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/* Adjust the instruction pointer in the stackframe. */
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instruction_pointer(regs) = fixup->fixup;
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arch_fixup(regs);
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return 1;
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}
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return 0;
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}
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