411 lines
11 KiB
C
411 lines
11 KiB
C
/*
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* arch/ppc/mm/fault.c
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*
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* PowerPC version
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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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* Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*/
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#include <linux/config.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 <linux/highmem.h>
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#include <linux/module.h>
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#include <linux/kprobes.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 <asm/uaccess.h>
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#include <asm/tlbflush.h>
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#include <asm/kdebug.h>
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#include <asm/siginfo.h>
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/*
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* Check whether the instruction at regs->nip 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 __user *)regs->nip))
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return 0;
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/* check for 1 in the rA field */
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if (((inst >> 16) & 0x1f) != 1)
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return 0;
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/* check major opcode */
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switch (inst >> 26) {
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case 37: /* stwu */
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case 39: /* stbu */
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case 45: /* sthu */
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case 53: /* stfsu */
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case 55: /* stfdu */
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return 1;
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case 62: /* std or stdu */
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return (inst & 3) == 1;
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case 31:
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/* check minor opcode */
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switch ((inst >> 1) & 0x3ff) {
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case 181: /* stdux */
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case 183: /* stwux */
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case 247: /* stbux */
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case 439: /* sthux */
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case 695: /* stfsux */
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case 759: /* stfdux */
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return 1;
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}
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}
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return 0;
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}
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#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
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static void do_dabr(struct pt_regs *regs, unsigned long error_code)
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{
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siginfo_t info;
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if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
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11, SIGSEGV) == NOTIFY_STOP)
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return;
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if (debugger_dabr_match(regs))
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return;
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/* Clear the DABR */
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set_dabr(0);
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/* Deliver the signal to userspace */
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info.si_signo = SIGTRAP;
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info.si_errno = 0;
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info.si_code = TRAP_HWBKPT;
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info.si_addr = (void __user *)regs->nip;
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force_sig_info(SIGTRAP, &info, current);
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}
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#endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/
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/*
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* For 600- and 800-family processors, the error_code parameter is DSISR
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* for a data fault, SRR1 for an instruction fault. For 400-family processors
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* the error_code parameter is ESR for a data fault, 0 for an instruction
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* fault.
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* For 64-bit processors, the error_code parameter is
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* - DSISR for a non-SLB data access fault,
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* - SRR1 & 0x08000000 for a non-SLB instruction access fault
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* - 0 any SLB fault.
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*
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* The return value is 0 if the fault was handled, or the signal
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* number if this is a kernel fault that can't be handled here.
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*/
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int __kprobes 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 = 0;
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int trap = TRAP(regs);
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int is_exec = trap == 0x400;
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#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
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/*
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* Fortunately the bit assignments in SRR1 for an instruction
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* fault and DSISR for a data fault are mostly the same for the
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* bits we are interested in. But there are some bits which
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* indicate errors in DSISR but can validly be set in SRR1.
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*/
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if (trap == 0x400)
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error_code &= 0x48200000;
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else
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is_write = error_code & DSISR_ISSTORE;
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#else
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is_write = error_code & ESR_DST;
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#endif /* CONFIG_4xx || CONFIG_BOOKE */
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if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code,
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11, SIGSEGV) == NOTIFY_STOP)
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return 0;
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if (trap == 0x300) {
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if (debugger_fault_handler(regs))
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return 0;
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}
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/* On a kernel SLB miss we can only check for a valid exception entry */
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if (!user_mode(regs) && (address >= TASK_SIZE))
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return SIGSEGV;
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#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
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if (error_code & DSISR_DABRMATCH) {
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/* DABR match */
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do_dabr(regs, error_code);
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return 0;
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}
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#endif /* !(CONFIG_4xx || CONFIG_BOOKE)*/
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if (in_atomic() || mm == NULL) {
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if (!user_mode(regs))
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return SIGSEGV;
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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() = %d mm = %p\n", in_atomic(), mm);
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printk(KERN_EMERG "NIP = %lx MSR = %lx\n",
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regs->nip, 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. Unfortunatly, in the case of an
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* erroneous fault occuring 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 possibilty 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 (!user_mode(regs) && !search_exception_tables(regs->nip))
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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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/*
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* N.B. The POWER/Open ABI allows programs to access up to
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* 288 bytes below the stack pointer.
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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->gpr[1]
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&& (!user_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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#if defined(CONFIG_6xx)
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if (error_code & 0x95700000)
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/* an error such as lwarx to I/O controller space,
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address matching DABR, eciwx, etc. */
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goto bad_area;
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#endif /* CONFIG_6xx */
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#if defined(CONFIG_8xx)
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/* The MPC8xx seems to always set 0x80000000, which is
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* "undefined". Of those that can be set, this is the only
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* one which seems bad.
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*/
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if (error_code & 0x10000000)
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/* Guarded storage error. */
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goto bad_area;
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#endif /* CONFIG_8xx */
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if (is_exec) {
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#ifdef CONFIG_PPC64
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/* protection fault */
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if (error_code & DSISR_PROTFAULT)
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goto bad_area;
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if (!(vma->vm_flags & VM_EXEC))
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goto bad_area;
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#endif
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#if defined(CONFIG_4xx) || defined(CONFIG_BOOKE)
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pte_t *ptep;
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/* Since 4xx/Book-E supports per-page execute permission,
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* we lazily flush dcache to icache. */
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ptep = NULL;
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if (get_pteptr(mm, address, &ptep) && pte_present(*ptep)) {
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struct page *page = pte_page(*ptep);
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if (! test_bit(PG_arch_1, &page->flags)) {
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flush_dcache_icache_page(page);
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set_bit(PG_arch_1, &page->flags);
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}
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pte_update(ptep, 0, _PAGE_HWEXEC);
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_tlbie(address);
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pte_unmap(ptep);
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up_read(&mm->mmap_sem);
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return 0;
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}
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if (ptep != NULL)
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pte_unmap(ptep);
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#endif
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/* a write */
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} else 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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switch (handle_mm_fault(mm, vma, address, is_write)) {
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case VM_FAULT_MINOR:
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current->min_flt++;
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break;
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case VM_FAULT_MAJOR:
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current->maj_flt++;
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break;
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case VM_FAULT_SIGBUS:
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goto do_sigbus;
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case VM_FAULT_OOM:
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goto out_of_memory;
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default:
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BUG();
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}
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up_read(&mm->mmap_sem);
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return 0;
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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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/* 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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return 0;
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}
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if (is_exec && (error_code & DSISR_PROTFAULT)
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&& printk_ratelimit())
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printk(KERN_CRIT "kernel tried to execute NX-protected"
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" page (%lx) - exploit attempt? (uid: %d)\n",
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address, current->uid);
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return SIGSEGV;
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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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up_read(&mm->mmap_sem);
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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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printk("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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return SIGKILL;
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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 0;
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}
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return SIGBUS;
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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 the DSI and ISI handlers in head.S and from some
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* of the procedures in traps.c.
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*/
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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 *entry;
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/* Are we prepared to handle this fault? */
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if ((entry = search_exception_tables(regs->nip)) != NULL) {
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regs->nip = entry->fixup;
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return;
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}
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/* kernel has accessed a bad area */
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printk(KERN_ALERT "Unable to handle kernel paging request for ");
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switch (regs->trap) {
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case 0x300:
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case 0x380:
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printk("data at address 0x%08lx\n", regs->dar);
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break;
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case 0x400:
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case 0x480:
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printk("instruction fetch\n");
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break;
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default:
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printk("unknown fault\n");
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}
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printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
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regs->nip);
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die("Kernel access of bad area", regs, sig);
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}
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