Viewing file:  fault.c (12.98 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
/*
* linux/arch/cris/mm/fault.c
*
* Copyright (C) 2000, 2001 Axis Communications AB
*
* Authors: Bjorn Wesen
*
* $Log: fault.c,v $
* 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/signal.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/string.h>
#include <linux/types.h>
#include <linux/ptrace.h>
#include <linux/mman.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <asm/system.h>
#include <asm/segment.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h>
#include <asm/svinto.h>
extern void die_if_kernel(const char *,struct pt_regs *,long);
asmlinkage void do_invalid_op (struct pt_regs *, unsigned long);
asmlinkage void do_page_fault(unsigned long address, struct pt_regs *regs,
int error_code);
/* 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 pgd_t *current_pgd;
/* fast TLB-fill fault handler
* this is called from entry.S with interrupts disabled
*/
void
handle_mmu_bus_fault(struct pt_regs *regs)
{
int cause, select;
#ifdef DEBUG
int index;
int page_id;
int acc, inv;
#endif
int miss, we, writeac;
pmd_t *pmd;
pte_t pte;
int errcode;
unsigned long address;
cause = *R_MMU_CAUSE;
select = *R_TLB_SELECT;
address = cause & PAGE_MASK; /* get faulting address */
#ifdef DEBUG
page_id = IO_EXTRACT(R_MMU_CAUSE, page_id, cause);
acc = IO_EXTRACT(R_MMU_CAUSE, acc_excp, cause);
inv = IO_EXTRACT(R_MMU_CAUSE, inv_excp, cause);
index = IO_EXTRACT(R_TLB_SELECT, index, select);
#endif
miss = IO_EXTRACT(R_MMU_CAUSE, miss_excp, cause);
we = IO_EXTRACT(R_MMU_CAUSE, we_excp, cause);
writeac = IO_EXTRACT(R_MMU_CAUSE, wr_rd, cause);
/* ETRAX 100LX TR89 bugfix: if the second half of an unaligned
* write causes a MMU-fault, it will not be restarted correctly.
* This could happen if a write crosses a page-boundary and the
* second page is not yet COW'ed or even loaded. The workaround
* is to clear the unaligned bit in the CPU status record, so
* that the CPU will rerun both the first and second halves of
* the instruction. This will not have any sideeffects unless
* the first half goes to any device or memory that can't be
* written twice, and which is mapped through the MMU.
*
* We only need to do this for writes.
*/
if(writeac)
regs->csrinstr &= ~(1 << 5);
/* Set errcode's R/W flag according to the mode which caused the
* fault
*/
errcode = writeac << 1;
D(printk("bus_fault from IRP 0x%lx: addr 0x%lx, miss %d, inv %d, we %d, acc %d, dx %d pid %d\n",
regs->irp, address, miss, inv, we, acc, index, page_id));
/* for a miss, we need to reload the TLB entry */
if (miss) {
/* see if the pte exists at all
* refer through current_pgd, dont use mm->pgd
*/
pmd = (pmd_t *)(current_pgd + pgd_index(address));
if (pmd_none(*pmd))
goto dofault;
if (pmd_bad(*pmd)) {
printk("bad pgdir entry 0x%lx at 0x%p\n", *(unsigned long*)pmd, pmd);
pmd_clear(pmd);
return;
}
pte = *pte_offset(pmd, address);
if (!pte_present(pte))
goto dofault;
#ifdef DEBUG
printk(" found pte %lx pg %p ", pte_val(pte), pte_page(pte));
if (pte_val(pte) & _PAGE_SILENT_WRITE)
printk("Silent-W ");
if (pte_val(pte) & _PAGE_KERNEL)
printk("Kernel ");
if (pte_val(pte) & _PAGE_SILENT_READ)
printk("Silent-R ");
if (pte_val(pte) & _PAGE_GLOBAL)
printk("Global ");
if (pte_val(pte) & _PAGE_PRESENT)
printk("Present ");
if (pte_val(pte) & _PAGE_ACCESSED)
printk("Accessed ");
if (pte_val(pte) & _PAGE_MODIFIED)
printk("Modified ");
if (pte_val(pte) & _PAGE_READ)
printk("Readable ");
if (pte_val(pte) & _PAGE_WRITE)
printk("Writeable ");
printk("\n");
#endif
/* load up the chosen TLB entry
* this assumes the pte format is the same as the TLB_LO layout.
*
* the write to R_TLB_LO also writes the vpn and page_id fields from
* R_MMU_CAUSE, which we in this case obviously want to keep
*/
*R_TLB_LO = pte_val(pte);
return;
}
errcode = 1 | (we << 1);
dofault:
/* leave it to the MM system fault handler below */
D(printk("do_page_fault %lx errcode %d\n", address, errcode));
do_page_fault(address, regs, errcode);
}
/*
* 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 error_code)
{
struct task_struct *tsk;
struct mm_struct *mm;
struct vm_area_struct * vma;
int writeaccess;
unsigned long fixup;
siginfo_t info;
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 &&
!(error_code & 1) &&
!user_mode(regs))
goto vmalloc_fault;
/* we can and should enable interrupts at this point */
sti();
mm = tsk->mm;
writeaccess = error_code & 2;
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) {
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)) {
case 1:
tsk->min_flt++;
break;
case 2:
tsk->maj_flt++;
break;
case 0:
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 ((fixup = search_exception_table(regs->irp)) != 0) {
/* Adjust the instruction pointer in the stackframe */
regs->irp = fixup;
/* We do not want to return by restoring the CPU-state
* anymore, so switch frame-types (see ptrace.h)
*/
regs->frametype = CRIS_FRAME_NORMAL;
D(printk("doing fixup to 0x%lx\n", fixup));
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)
printk(KERN_ALERT "Unable to handle kernel NULL pointer dereference");
else
printk(KERN_ALERT "Unable to handle kernel access");
printk(" at virtual address %08lx\n",address);
die_if_kernel("Oops", regs, error_code);
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_code = 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;
pmd_t *pmd, *pmd_k;
pte_t *pte_k;
pgd = (pgd_t *)current_pgd + 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.
*/
pmd = pmd_offset(pgd, address);
pmd_k = pmd_offset(pgd_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(pmd_k, address);
if (!pte_present(*pte_k))
goto no_context;
return;
}
}
|