- 根目录:
- arch
- cris
- mm
- fault.c
/*
* arch/cris/mm/fault.c
*
* Copyright (C) 2000-2010 Axis Communications AB
*/
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/module.h>
#include <linux/wait.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 void show_registers(struct pt_regs *regs);
/* 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 */
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;
int fault;
D(printk(KERN_DEBUG
"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 "atomic" operation or have no
* user context, we must not take the fault.
*/
if (in_atomic() || !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.
*/
fault = handle_mm_fault(mm, vma, address, (writeaccess & 1) ? FAULT_FLAG_WRITE : 0);
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
goto out_of_memory;
else if (fault & VM_FAULT_SIGBUS)
goto do_sigbus;
BUG();
}
if (fault & VM_FAULT_MAJOR)
tsk->maj_flt++;
else
tsk->min_flt++;
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)) {
printk(KERN_NOTICE "%s (pid %d) segfaults for page "
"address %08lx at pc %08lx\n",
tsk->comm, tsk->pid,
address, instruction_pointer(regs));
/* With DPG on, we've already dumped registers above. */
DPG(if (0))
show_registers(regs);
#ifdef CONFIG_NO_SEGFAULT_TERMINATION
DECLARE_WAIT_QUEUE_HEAD(wq);
wait_event_interruptible(wq, 0 == 1);
#else
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);
#endif
return;
}
no_context:
/* Are we prepared to handle this kernel fault?
*
* (The kernel has valid exception-points in the source
* when it accesses 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 (!oops_in_progress) {
oops_in_progress = 1;
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"
" at virtual address %08lx\n", address);
die_if_kernel("Oops", regs, (writeaccess << 1) | protection);
oops_in_progress = 0;
}
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);
if (!user_mode(regs))
goto no_context;
pagefault_out_of_memory();
return;
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;
/* in case of delay slot fault (v32) */
unsigned long ip = (instruction_pointer(regs) & ~0x1);
fixup = search_exception_tables(ip);
if (fixup != 0) {
/* Adjust the instruction pointer in the stackframe. */
instruction_pointer(regs) = fixup->fixup;
arch_fixup(regs);
return 1;
}
return 0;
}