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microblaze_mmu_v2: Page fault handling high level - fault.c
Signed-off-by: Michal Simek <monstr@monstr.eu>
This commit is contained in:
Michal Simek
parent
23098649e0
commit
5de9612100
304
arch/microblaze/mm/fault.c
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304
arch/microblaze/mm/fault.c
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/*
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* arch/microblaze/mm/fault.c
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*
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* Copyright (C) 2007 Xilinx, Inc. All rights reserved.
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*
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* Derived from "arch/ppc/mm/fault.c"
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* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
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*
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* Derived from "arch/i386/mm/fault.c"
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* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
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*
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* Modified by Cort Dougan and Paul Mackerras.
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*
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* This file is subject to the terms and conditions of the GNU General
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* Public License. See the file COPYING in the main directory of this
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* archive for more details.
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*
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*/
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#include <linux/module.h>
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#include <linux/signal.h>
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#include <linux/sched.h>
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#include <linux/kernel.h>
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#include <linux/errno.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/ptrace.h>
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#include <linux/mman.h>
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#include <linux/mm.h>
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#include <linux/interrupt.h>
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#include <asm/page.h>
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#include <asm/pgtable.h>
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#include <asm/mmu.h>
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#include <asm/mmu_context.h>
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#include <asm/system.h>
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#include <linux/uaccess.h>
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#include <asm/exceptions.h>
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#if defined(CONFIG_KGDB)
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int debugger_kernel_faults = 1;
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#endif
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static unsigned long pte_misses; /* updated by do_page_fault() */
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static unsigned long pte_errors; /* updated by do_page_fault() */
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/*
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* Check whether the instruction at regs->pc is a store using
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* an update addressing form which will update r1.
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*/
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static int store_updates_sp(struct pt_regs *regs)
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{
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unsigned int inst;
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if (get_user(inst, (unsigned int *)regs->pc))
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return 0;
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/* check for 1 in the rD field */
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if (((inst >> 21) & 0x1f) != 1)
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return 0;
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/* check for store opcodes */
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if ((inst & 0xd0000000) == 0xd0000000)
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return 1;
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return 0;
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}
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/*
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* bad_page_fault is called when we have a bad access from the kernel.
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* It is called from do_page_fault above and from some of the procedures
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* in traps.c.
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*/
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static void bad_page_fault(struct pt_regs *regs, unsigned long address, int sig)
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{
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const struct exception_table_entry *fixup;
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/* MS: no context */
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/* Are we prepared to handle this fault? */
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fixup = search_exception_tables(regs->pc);
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if (fixup) {
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regs->pc = fixup->fixup;
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return;
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}
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/* kernel has accessed a bad area */
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#if defined(CONFIG_KGDB)
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if (debugger_kernel_faults)
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debugger(regs);
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#endif
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die("kernel access of bad area", regs, sig);
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}
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/*
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* The error_code parameter is ESR for a data fault,
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* 0 for an instruction fault.
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*/
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void do_page_fault(struct pt_regs *regs, unsigned long address,
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unsigned long error_code)
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{
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struct vm_area_struct *vma;
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struct mm_struct *mm = current->mm;
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siginfo_t info;
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int code = SEGV_MAPERR;
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int is_write = error_code & ESR_S;
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int fault;
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regs->ear = address;
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regs->esr = error_code;
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/* On a kernel SLB miss we can only check for a valid exception entry */
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if (kernel_mode(regs) && (address >= TASK_SIZE)) {
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printk(KERN_WARNING "kernel task_size exceed");
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_exception(SIGSEGV, regs, code, address);
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}
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/* for instr TLB miss and instr storage exception ESR_S is undefined */
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if ((error_code & 0x13) == 0x13 || (error_code & 0x11) == 0x11)
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is_write = 0;
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#if defined(CONFIG_KGDB)
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if (debugger_fault_handler && regs->trap == 0x300) {
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debugger_fault_handler(regs);
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return;
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}
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#endif /* CONFIG_KGDB */
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if (in_atomic() || mm == NULL) {
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/* FIXME */
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if (kernel_mode(regs)) {
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printk(KERN_EMERG
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"Page fault in kernel mode - Oooou!!! pid %d\n",
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current->pid);
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_exception(SIGSEGV, regs, code, address);
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return;
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}
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/* in_atomic() in user mode is really bad,
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as is current->mm == NULL. */
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printk(KERN_EMERG "Page fault in user mode with "
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"in_atomic(), mm = %p\n", mm);
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printk(KERN_EMERG "r15 = %lx MSR = %lx\n",
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regs->r15, regs->msr);
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die("Weird page fault", regs, SIGSEGV);
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}
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/* When running in the kernel we expect faults to occur only to
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* addresses in user space. All other faults represent errors in the
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* kernel and should generate an OOPS. Unfortunately, in the case of an
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* erroneous fault occurring in a code path which already holds mmap_sem
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* we will deadlock attempting to validate the fault against the
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* address space. Luckily the kernel only validly references user
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* space from well defined areas of code, which are listed in the
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* exceptions table.
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*
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* As the vast majority of faults will be valid we will only perform
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* the source reference check when there is a possibility of a deadlock.
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* Attempt to lock the address space, if we cannot we then validate the
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* source. If this is invalid we can skip the address space check,
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* thus avoiding the deadlock.
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*/
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if (!down_read_trylock(&mm->mmap_sem)) {
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if (kernel_mode(regs) && !search_exception_tables(regs->pc))
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goto bad_area_nosemaphore;
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down_read(&mm->mmap_sem);
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}
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vma = find_vma(mm, address);
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if (!vma)
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goto bad_area;
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if (vma->vm_start <= address)
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goto good_area;
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if (!(vma->vm_flags & VM_GROWSDOWN))
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goto bad_area;
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if (!is_write)
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goto bad_area;
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/*
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* N.B. The ABI allows programs to access up to
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* a few hundred bytes below the stack pointer (TBD).
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* The kernel signal delivery code writes up to about 1.5kB
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* below the stack pointer (r1) before decrementing it.
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* The exec code can write slightly over 640kB to the stack
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* before setting the user r1. Thus we allow the stack to
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* expand to 1MB without further checks.
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*/
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if (address + 0x100000 < vma->vm_end) {
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/* get user regs even if this fault is in kernel mode */
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struct pt_regs *uregs = current->thread.regs;
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if (uregs == NULL)
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goto bad_area;
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/*
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* A user-mode access to an address a long way below
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* the stack pointer is only valid if the instruction
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* is one which would update the stack pointer to the
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* address accessed if the instruction completed,
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* i.e. either stwu rs,n(r1) or stwux rs,r1,rb
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* (or the byte, halfword, float or double forms).
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*
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* If we don't check this then any write to the area
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* between the last mapped region and the stack will
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* expand the stack rather than segfaulting.
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*/
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if (address + 2048 < uregs->r1
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&& (kernel_mode(regs) || !store_updates_sp(regs)))
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goto bad_area;
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}
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if (expand_stack(vma, address))
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goto bad_area;
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good_area:
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code = SEGV_ACCERR;
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/* a write */
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if (is_write) {
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if (!(vma->vm_flags & VM_WRITE))
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goto bad_area;
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/* a read */
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} else {
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/* protection fault */
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if (error_code & 0x08000000)
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goto bad_area;
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if (!(vma->vm_flags & (VM_READ | VM_EXEC)))
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goto bad_area;
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}
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/*
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* If for any reason at all we couldn't handle the fault,
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* make sure we exit gracefully rather than endlessly redo
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* the fault.
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*/
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survive:
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fault = handle_mm_fault(mm, vma, address, is_write);
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if (unlikely(fault & VM_FAULT_ERROR)) {
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if (fault & VM_FAULT_OOM)
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goto out_of_memory;
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else if (fault & VM_FAULT_SIGBUS)
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goto do_sigbus;
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BUG();
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}
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if (fault & VM_FAULT_MAJOR)
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current->maj_flt++;
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else
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current->min_flt++;
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up_read(&mm->mmap_sem);
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/*
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* keep track of tlb+htab misses that are good addrs but
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* just need pte's created via handle_mm_fault()
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* -- Cort
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*/
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pte_misses++;
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return;
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bad_area:
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up_read(&mm->mmap_sem);
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bad_area_nosemaphore:
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pte_errors++;
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/* User mode accesses cause a SIGSEGV */
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if (user_mode(regs)) {
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_exception(SIGSEGV, regs, code, address);
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/* info.si_signo = SIGSEGV;
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info.si_errno = 0;
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info.si_code = code;
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info.si_addr = (void *) address;
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force_sig_info(SIGSEGV, &info, current);*/
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return;
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}
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bad_page_fault(regs, address, SIGSEGV);
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return;
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/*
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* We ran out of memory, or some other thing happened to us that made
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* us unable to handle the page fault gracefully.
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*/
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out_of_memory:
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if (current->pid == 1) {
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yield();
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down_read(&mm->mmap_sem);
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goto survive;
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}
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up_read(&mm->mmap_sem);
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printk(KERN_WARNING "VM: killing process %s\n", current->comm);
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if (user_mode(regs))
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do_exit(SIGKILL);
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bad_page_fault(regs, address, SIGKILL);
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return;
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do_sigbus:
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up_read(&mm->mmap_sem);
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if (user_mode(regs)) {
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info.si_signo = SIGBUS;
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info.si_errno = 0;
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info.si_code = BUS_ADRERR;
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info.si_addr = (void __user *)address;
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force_sig_info(SIGBUS, &info, current);
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return;
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}
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bad_page_fault(regs, address, SIGBUS);
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}
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