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