blob: 5c40c3ebe52f770522b7e98b3c3ca327aec1d94b [file] [log] [blame]
* arch/microblaze/mm/fault.c
* Copyright (C) 2007 Xilinx, Inc. All rights reserved.
* Derived from "arch/ppc/mm/fault.c"
* Copyright (C) 1995-1996 Gary Thomas (
* Derived from "arch/i386/mm/fault.c"
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
* Modified by Cort Dougan and Paul Mackerras.
* This file is subject to the terms and conditions of the GNU General
* Public License. See the file COPYING in the main directory of this
* archive for more details.
#include <linux/extable.h>
#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/perf_event.h>
#include <asm/page.h>
#include <asm/mmu.h>
#include <linux/mmu_context.h>
#include <linux/uaccess.h>
#include <asm/exceptions.h>
static unsigned long pte_misses; /* updated by do_page_fault() */
static unsigned long pte_errors; /* updated by do_page_fault() */
* Check whether the instruction at regs->pc is a store using
* an update addressing form which will update r1.
static int store_updates_sp(struct pt_regs *regs)
unsigned int inst;
if (get_user(inst, (unsigned int __user *)regs->pc))
return 0;
/* check for 1 in the rD field */
if (((inst >> 21) & 0x1f) != 1)
return 0;
/* check for store opcodes */
if ((inst & 0xd0000000) == 0xd0000000)
return 1;
return 0;
* bad_page_fault is called when we have a bad access from the kernel.
* It is called from do_page_fault above and from some of the procedures
* in traps.c.
void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
const struct exception_table_entry *fixup;
/* MS: no context */
/* Are we prepared to handle this fault? */
fixup = search_exception_tables(regs->pc);
if (fixup) {
regs->pc = fixup->fixup;
/* kernel has accessed a bad area */
die("kernel access of bad area", regs, sig);
* The error_code parameter is ESR for a data fault,
* 0 for an instruction fault.
void do_page_fault(struct pt_regs *regs, unsigned long address,
unsigned long error_code)
struct vm_area_struct *vma;
struct mm_struct *mm = current->mm;
int code = SEGV_MAPERR;
int is_write = error_code & ESR_S;
vm_fault_t fault;
unsigned int flags = FAULT_FLAG_DEFAULT;
regs->ear = address;
regs->esr = error_code;
/* On a kernel SLB miss we can only check for a valid exception entry */
if (unlikely(kernel_mode(regs) && (address >= TASK_SIZE))) {
pr_warn("kernel task_size exceed");
_exception(SIGSEGV, regs, code, address);
/* for instr TLB miss and instr storage exception ESR_S is undefined */
if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11)
is_write = 0;
if (unlikely(faulthandler_disabled() || !mm)) {
if (kernel_mode(regs))
goto bad_area_nosemaphore;
/* faulthandler_disabled() in user mode is really bad,
as is current->mm == NULL. */
pr_emerg("Page fault in user mode with faulthandler_disabled(), mm = %p\n",
pr_emerg("r15 = %lx MSR = %lx\n",
regs->r15, regs->msr);
die("Weird page fault", regs, SIGSEGV);
if (user_mode(regs))
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS, 1, regs, address);
/* When running in the kernel we expect faults to occur only to
* addresses in user space. All other faults represent errors in the
* kernel and should generate an OOPS. Unfortunately, in the case of an
* erroneous fault occurring in a code path which already holds mmap_lock
* we will deadlock attempting to validate the fault against the
* address space. Luckily the kernel only validly references user
* space from well defined areas of code, which are listed in the
* exceptions table.
* As the vast majority of faults will be valid we will only perform
* the source reference check when there is a possibility of a deadlock.
* Attempt to lock the address space, if we cannot we then validate the
* source. If this is invalid we can skip the address space check,
* thus avoiding the deadlock.
if (unlikely(!mmap_read_trylock(mm))) {
if (kernel_mode(regs) && !search_exception_tables(regs->pc))
goto bad_area_nosemaphore;
vma = find_vma(mm, address);
if (unlikely(!vma))
goto bad_area;
if (vma->vm_start <= address)
goto good_area;
if (unlikely(!(vma->vm_flags & VM_GROWSDOWN)))
goto bad_area;
if (unlikely(!is_write))
goto bad_area;
* N.B. The ABI allows programs to access up to
* a few hundred bytes below the stack pointer (TBD).
* The kernel signal delivery code writes up to about 1.5kB
* below the stack pointer (r1) before decrementing it.
* The exec code can write slightly over 640kB to the stack
* before setting the user r1. Thus we allow the stack to
* expand to 1MB without further checks.
if (unlikely(address + 0x100000 < vma->vm_end)) {
/* get user regs even if this fault is in kernel mode */
struct pt_regs *uregs = current->thread.regs;
if (uregs == NULL)
goto bad_area;
* A user-mode access to an address a long way below
* the stack pointer is only valid if the instruction
* is one which would update the stack pointer to the
* address accessed if the instruction completed,
* i.e. either stwu rs,n(r1) or stwux rs,r1,rb
* (or the byte, halfword, float or double forms).
* If we don't check this then any write to the area
* between the last mapped region and the stack will
* expand the stack rather than segfaulting.
if (address + 2048 < uregs->r1
&& (kernel_mode(regs) || !store_updates_sp(regs)))
goto bad_area;
if (expand_stack(vma, address))
goto bad_area;
/* a write */
if (unlikely(is_write)) {
if (unlikely(!(vma->vm_flags & VM_WRITE)))
goto bad_area;
/* a read */
} else {
/* protection fault */
if (unlikely(error_code & 0x08000000))
goto bad_area;
if (unlikely(!(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(vma, address, flags, regs);
if (fault_signal_pending(fault, regs))
/* The fault is fully completed (including releasing mmap lock) */
if (unlikely(fault & VM_FAULT_ERROR)) {
if (fault & VM_FAULT_OOM)
goto out_of_memory;
else if (fault & VM_FAULT_SIGSEGV)
goto bad_area;
else if (fault & VM_FAULT_SIGBUS)
goto do_sigbus;
if (fault & VM_FAULT_RETRY) {
* No need to mmap_read_unlock(mm) as we would
* have already released it in __lock_page_or_retry
* in mm/filemap.c.
goto retry;
* keep track of tlb+htab misses that are good addrs but
* just need pte's created via handle_mm_fault()
* -- Cort
/* User mode accesses cause a SIGSEGV */
if (user_mode(regs)) {
_exception(SIGSEGV, regs, code, address);
bad_page_fault(regs, address, SIGSEGV);
* We ran out of memory, or some other thing happened to us that made
* us unable to handle the page fault gracefully.
if (!user_mode(regs))
bad_page_fault(regs, address, SIGKILL);
if (user_mode(regs)) {
force_sig_fault(SIGBUS, BUS_ADRERR, (void __user *)address);
bad_page_fault(regs, address, SIGBUS);