/*
* linux/arch/arm26/mm/fault.c
*
* Copyright (C) 1995 Linus Torvalds
* Modifications for ARM processor (c) 1995-2001 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/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 <linux/proc_fs.h>
#include <linux/init.h>
#include <asm/system.h>
#include <asm/pgtable.h>
#include <asm/uaccess.h> //FIXME this header may be bogusly included
#include "fault.h"
#define FAULT_CODE_LDRSTRPOST 0x80
#define FAULT_CODE_LDRSTRPRE 0x40
#define FAULT_CODE_LDRSTRREG 0x20
#define FAULT_CODE_LDMSTM 0x10
#define FAULT_CODE_LDCSTC 0x08
#define FAULT_CODE_PREFETCH 0x04
#define FAULT_CODE_WRITE 0x02
#define FAULT_CODE_FORCECOW 0x01
#define DO_COW(m) ((m) & (FAULT_CODE_WRITE|FAULT_CODE_FORCECOW))
#define READ_FAULT(m) (!((m) & FAULT_CODE_WRITE))
#define DEBUG
/*
* 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 "[%08lx] *pgd=%08lx", addr, pgd_val(*pgd));
do {
pmd_t *pmd;
pte_t *pte;
pmd = pmd_offset(pgd, addr);
if (pmd_none(*pmd))
break;
if (pmd_bad(*pmd)) {
printk("(bad)");
break;
}
/* We must not map this if we have highmem enabled */
/* FIXME */
pte = pte_offset_map(pmd, addr);
printk(", *pte=%08lx", pte_val(*pte));
pte_unmap(pte);
} while(0);
printk("\n");
}
/*
* Oops. The kernel tried to access some page that wasn't present.
*/
static void
__do_kernel_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
struct pt_regs *regs)
{
/*
* Are we prepared to handle this kernel fault?
*/
if (fixup_exception(regs))
return;
/*
* No handler, we'll have to terminate things with extreme prejudice.
*/
bust_spinlocks(1);
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, fsr);
bust_spinlocks(0);
do_exit(SIGKILL);
}
/*
* Something tried to access memory that isn't in our memory map..
* User mode accesses just cause a SIGSEGV
*/
static void
__do_user_fault(struct task_struct *tsk, unsigned long addr,
unsigned int fsr, int code, struct pt_regs *regs)
{
struct siginfo si;
#ifdef CONFIG_DEBUG_USER
printk("%s: unhandled page fault at 0x%08lx, code 0x%03x\n",
tsk->comm, addr, fsr);
show_pte(tsk->mm, addr);
show_regs(regs);
//dump_backtrace(regs, tsk); // FIXME ARM32 dropped this - why?
while(1); //FIXME - hack to stop debug going nutso
#endif
tsk->thread.address = addr;
tsk->thread.error_code = fsr;
tsk->thread.trap_no = 14;
si.si_signo = SIGSEGV;
si.si_errno = 0;
si.si_code = code;
si.si_addr = (void *)addr;
force_sig_info(SIGSEGV, &si, tsk);
}
static int
__do_page_fault(struct mm_struct *mm, unsigned long addr, unsigned int fsr,
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(fsr)) /* 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(fsr));
/*
* Handle the "normal" cases first - successful and sigbus
*/
switch (fault) {
case VM_FAULT_MAJOR:
tsk->maj_flt++;
return fault;
case VM_FAULT_MINOR:
tsk->min_flt++;
case VM_FAULT_SIGBUS:
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
*/
yield();
goto survive;
check_stack:
if (vma->vm_flags & VM_GROWSDOWN && !expand_stack(vma, addr))
goto good_area;
out:
return fault;
}
int do_page_fault(unsigned long addr, unsigned int fsr, struct pt_regs *regs)
{
struct task_struct *tsk;
struct mm_struct *mm;
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_read(&mm->mmap_sem);
fault = __do_page_fault(mm, addr, fsr, tsk);
up_read(&mm->mmap_sem);
/*
* Handle the "normal" case first
*/
switch (fault) {
case VM_FAULT_MINOR:
case VM_FAULT_MAJOR:
return 0;
case VM_FAULT_SIGBUS:
goto do_sigbus;
}
/*
* If we are in kernel mode at this point, we
* have no context to handle this fault with.
* FIXME - is this test right?
*/
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{
__do_user_fault(tsk, addr, fsr, fault == -1 ? SEGV_ACCERR : SEGV_MAPERR, regs);
}
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; //FIXME - need other bits setting?
tsk->thread.error_code = fsr;
tsk->thread.trap_no = 14;
force_sig(SIGBUS, tsk);
#ifdef CONFIG_DEBUG_USER
printk(KERN_DEBUG "%s: sigbus at 0x%08lx, pc=0x%08lx\n",
current->comm, addr, instruction_pointer(regs));
#endif
/* Kernel mode? Handle exceptions or die */
if (user_mode(regs))
return 0;
no_context:
__do_kernel_fault(mm, addr, fsr, regs);
return 0;
}
/*
* Handle a data abort. Note that we have to handle a range of addresses
* on ARM2/3 for ldm. If both pages are zero-mapped, then we have to force
* a copy-on-write. However, on the second page, we always force COW.
*/
asmlinkage void
do_DataAbort(unsigned long min_addr, unsigned long max_addr, int mode, struct pt_regs *regs)
{
do_page_fault(min_addr, mode, regs);
if ((min_addr ^ max_addr) >> PAGE_SHIFT){
do_page_fault(max_addr, mode | FAULT_CODE_FORCECOW, regs);
}
}
asmlinkage int
do_PrefetchAbort(unsigned long addr, struct pt_regs *regs)
{
#if 0
if (the memc mapping for this page exists) {
printk ("Page in, but got abort (undefined instruction?)\n");
return 0;
}
#endif
do_page_fault(addr, FAULT_CODE_PREFETCH, regs);
return 1;
}
