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/*
* linux/arch/arm/mm/fault-common.c
*
* Copyright (C) 1995 Linus Torvalds
* Modifications for ARM processor (c) 1995-1999 Russell King
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/config.h>
extern void die(const char *msg, struct pt_regs *regs, int err);
/*
* This is useful to dump out the page tables associated with
* 'addr' in mm 'mm'.
*/
void show_pte(struct mm_struct *mm, unsigned long addr)
{
pgd_t *pgd;
if (!mm)
mm = &init_mm;
printk(KERN_ALERT "pgd = %p\n", mm->pgd);
pgd = pgd_offset(mm, addr);
printk(KERN_ALERT "*pgd = %08lx", pgd_val(*pgd));
do {
pmd_t *pmd;
pte_t *pte;
if (pgd_none(*pgd))
break;
if (pgd_bad(*pgd)) {
printk("(bad)");
break;
}
pmd = pmd_offset(pgd, addr);
printk(", *pmd = %08lx", pmd_val(*pmd));
if (pmd_none(*pmd))
break;
if (pmd_bad(*pmd)) {
printk("(bad)");
break;
}
pte = pte_offset(pmd, addr);
printk(", *pte = %08lx", pte_val(*pte));
#ifdef CONFIG_CPU_32
printk(", *ppte = %08lx", pte_val(pte[-PTRS_PER_PTE]));
#endif
} while(0);
printk("\n");
}
static int __do_page_fault(struct mm_struct *mm, unsigned long addr, int mode, struct task_struct *tsk)
{
struct vm_area_struct *vma;
int fault, mask;
vma = find_vma(mm, addr);
fault = -2; /* bad map area */
if (!vma)
goto out;
if (vma->vm_start > addr)
goto check_stack;
/*
* Ok, we have a good vm_area for this
* memory access, so we can handle it.
*/
good_area:
if (READ_FAULT(mode)) /* read? */
mask = VM_READ|VM_EXEC;
else
mask = VM_WRITE;
fault = -1; /* bad access type */
if (!(vma->vm_flags & mask))
goto out;
/*
* If for any reason at all we couldn't handle
* the fault, make sure we exit gracefully rather
* than endlessly redo the fault.
*/
survive:
fault = handle_mm_fault(mm, vma, addr & PAGE_MASK, DO_COW(mode));
/*
* Handle the "normal" cases first - successful and sigbus
*/
switch (fault) {
case 2:
tsk->maj_flt++;
return fault;
case 1:
tsk->min_flt++;
case 0:
return fault;
}
fault = -3; /* out of memory */
if (tsk->pid != 1)
goto out;
/*
* If we are out of memory for pid1,
* sleep for a while and retry
*/
tsk->policy |= SCHED_YIELD;
schedule();
goto survive;
check_stack:
if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
goto good_area;
out:
return fault;
}
static int do_page_fault(unsigned long addr, int mode, struct pt_regs *regs)
{
struct task_struct *tsk;
struct mm_struct *mm;
unsigned long fixup;
int fault;
tsk = current;
mm = tsk->mm;
/*
* 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(&mm->mmap_sem);
fault = __do_page_fault(mm, addr, mode, tsk);
up(&mm->mmap_sem);
/*
* Handle the "normal" case first
*/
if (fault > 0)
return 0;
/*
* We had some memory, but were unable to
* successfully fix up this page fault.
*/
if (fault == 0)
goto do_sigbus;
/*
* If we are in kernel mode at this point, we
* have no context to handle this fault with.
*/
if (!user_mode(regs))
goto no_context;
if (fault == -3) {
/*
* We ran out of memory, or some other thing happened to
* us that made us unable to handle the page fault gracefully.
*/
printk("VM: killing process %s\n", tsk->comm);
do_exit(SIGKILL);
} else {
/*
* Something tried to access memory that isn't in our memory map..
* User mode accesses just cause a SIGSEGV
*/
struct siginfo si;
#ifdef CONFIG_DEBUG_USER
printk(KERN_DEBUG "%s: unhandled page fault at pc=0x%08lx, "
"lr=0x%08lx (bad address=0x%08lx, code %d)\n",
tsk->comm, regs->ARM_pc, regs->ARM_lr, addr, mode);
#endif
tsk->thread.address = addr;
tsk->thread.error_code = mode;
tsk->thread.trap_no = 14;
si.si_signo = SIGSEGV;
si.si_errno = 0;
si.si_code = fault == -1 ? SEGV_ACCERR : SEGV_MAPERR;
si.si_addr = (void *)addr;
force_sig_info(SIGSEGV, &si, tsk);
}
return 0;
/*
* We ran out of memory, or some other thing happened to us that made
* us unable to handle the page fault gracefully.
*/
do_sigbus:
/*
* Send a sigbus, regardless of whether we were in kernel
* or user mode.
*/
tsk->thread.address = addr;
tsk->thread.error_code = mode;
tsk->thread.trap_no = 14;
force_sig(SIGBUS, tsk);
/* Kernel mode? Handle exceptions or die */
if (user_mode(regs))
return 0;
no_context:
/* Are we prepared to handle this kernel fault? */
if ((fixup = search_exception_table(instruction_pointer(regs))) != 0) {
#ifdef DEBUG
printk(KERN_DEBUG "%s: Exception at [<%lx>] addr=%lx (fixup: %lx)\n",
tsk->comm, regs->ARM_pc, addr, fixup);
#endif
regs->ARM_pc = fixup;
return 0;
}
/*
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice.
*/
printk(KERN_ALERT "Unable to handle kernel %s at virtual address %08lx\n",
(addr < PAGE_SIZE) ? "NULL pointer dereference" : "paging request", addr);
show_pte(mm, addr);
die("Oops", regs, mode);
do_exit(SIGKILL);
return 0;
}
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