334 lines
8.6 KiB
C
334 lines
8.6 KiB
C
/*
|
|
* arch/ppc/mm/fault.c
|
|
*
|
|
* PowerPC version
|
|
* Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
|
|
*
|
|
* Derived from "arch/i386/mm/fault.c"
|
|
* Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
|
|
*
|
|
* Modified by Cort Dougan and Paul Mackerras.
|
|
*
|
|
* Modified for PPC64 by Dave Engebretsen (engebret@ibm.com)
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License
|
|
* as published by the Free Software Foundation; either version
|
|
* 2 of the License, or (at your option) any later version.
|
|
*/
|
|
|
|
#include <linux/config.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/mman.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/interrupt.h>
|
|
#include <linux/smp_lock.h>
|
|
#include <linux/module.h>
|
|
#include <linux/kprobes.h>
|
|
|
|
#include <asm/page.h>
|
|
#include <asm/pgtable.h>
|
|
#include <asm/mmu.h>
|
|
#include <asm/mmu_context.h>
|
|
#include <asm/system.h>
|
|
#include <asm/uaccess.h>
|
|
#include <asm/kdebug.h>
|
|
#include <asm/siginfo.h>
|
|
|
|
/*
|
|
* Check whether the instruction at regs->nip 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->nip))
|
|
return 0;
|
|
/* check for 1 in the rA field */
|
|
if (((inst >> 16) & 0x1f) != 1)
|
|
return 0;
|
|
/* check major opcode */
|
|
switch (inst >> 26) {
|
|
case 37: /* stwu */
|
|
case 39: /* stbu */
|
|
case 45: /* sthu */
|
|
case 53: /* stfsu */
|
|
case 55: /* stfdu */
|
|
return 1;
|
|
case 62: /* std or stdu */
|
|
return (inst & 3) == 1;
|
|
case 31:
|
|
/* check minor opcode */
|
|
switch ((inst >> 1) & 0x3ff) {
|
|
case 181: /* stdux */
|
|
case 183: /* stwux */
|
|
case 247: /* stbux */
|
|
case 439: /* sthux */
|
|
case 695: /* stfsux */
|
|
case 759: /* stfdux */
|
|
return 1;
|
|
}
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void do_dabr(struct pt_regs *regs, unsigned long error_code)
|
|
{
|
|
siginfo_t info;
|
|
|
|
if (notify_die(DIE_DABR_MATCH, "dabr_match", regs, error_code,
|
|
11, SIGSEGV) == NOTIFY_STOP)
|
|
return;
|
|
|
|
if (debugger_dabr_match(regs))
|
|
return;
|
|
|
|
/* Clear the DABR */
|
|
set_dabr(0);
|
|
|
|
/* Deliver the signal to userspace */
|
|
info.si_signo = SIGTRAP;
|
|
info.si_errno = 0;
|
|
info.si_code = TRAP_HWBKPT;
|
|
info.si_addr = (void __user *)regs->nip;
|
|
force_sig_info(SIGTRAP, &info, current);
|
|
}
|
|
|
|
/*
|
|
* The error_code parameter is
|
|
* - DSISR for a non-SLB data access fault,
|
|
* - SRR1 & 0x08000000 for a non-SLB instruction access fault
|
|
* - 0 any SLB fault.
|
|
* The return value is 0 if the fault was handled, or the signal
|
|
* number if this is a kernel fault that can't be handled here.
|
|
*/
|
|
int __kprobes 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;
|
|
siginfo_t info;
|
|
unsigned long code = SEGV_MAPERR;
|
|
unsigned long is_write = error_code & DSISR_ISSTORE;
|
|
unsigned long trap = TRAP(regs);
|
|
unsigned long is_exec = trap == 0x400;
|
|
|
|
BUG_ON((trap == 0x380) || (trap == 0x480));
|
|
|
|
if (notify_die(DIE_PAGE_FAULT, "page_fault", regs, error_code,
|
|
11, SIGSEGV) == NOTIFY_STOP)
|
|
return 0;
|
|
|
|
if (trap == 0x300) {
|
|
if (debugger_fault_handler(regs))
|
|
return 0;
|
|
}
|
|
|
|
/* On a kernel SLB miss we can only check for a valid exception entry */
|
|
if (!user_mode(regs) && (address >= TASK_SIZE))
|
|
return SIGSEGV;
|
|
|
|
if (error_code & DSISR_DABRMATCH) {
|
|
do_dabr(regs, error_code);
|
|
return 0;
|
|
}
|
|
|
|
if (in_atomic() || mm == NULL) {
|
|
if (!user_mode(regs))
|
|
return SIGSEGV;
|
|
/* in_atomic() in user mode is really bad,
|
|
as is current->mm == NULL. */
|
|
printk(KERN_EMERG "Page fault in user mode with"
|
|
"in_atomic() = %d mm = %p\n", in_atomic(), mm);
|
|
printk(KERN_EMERG "NIP = %lx MSR = %lx\n",
|
|
regs->nip, regs->msr);
|
|
die("Weird page fault", regs, SIGSEGV);
|
|
}
|
|
|
|
/* 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. Unfortunatly, in the case of an
|
|
* erroneous fault occuring in a code path which already holds mmap_sem
|
|
* 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 possibilty 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 (!down_read_trylock(&mm->mmap_sem)) {
|
|
if (!user_mode(regs) && !search_exception_tables(regs->nip))
|
|
goto bad_area_nosemaphore;
|
|
|
|
down_read(&mm->mmap_sem);
|
|
}
|
|
|
|
vma = find_vma(mm, address);
|
|
if (!vma)
|
|
goto bad_area;
|
|
|
|
if (vma->vm_start <= address) {
|
|
goto good_area;
|
|
}
|
|
if (!(vma->vm_flags & VM_GROWSDOWN))
|
|
goto bad_area;
|
|
|
|
/*
|
|
* N.B. The POWER/Open ABI allows programs to access up to
|
|
* 288 bytes below the stack pointer.
|
|
* 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 (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->gpr[1]
|
|
&& (!user_mode(regs) || !store_updates_sp(regs)))
|
|
goto bad_area;
|
|
}
|
|
|
|
if (expand_stack(vma, address))
|
|
goto bad_area;
|
|
|
|
good_area:
|
|
code = SEGV_ACCERR;
|
|
|
|
if (is_exec) {
|
|
/* protection fault */
|
|
if (error_code & DSISR_PROTFAULT)
|
|
goto bad_area;
|
|
if (!(vma->vm_flags & VM_EXEC))
|
|
goto bad_area;
|
|
/* a write */
|
|
} else if (is_write) {
|
|
if (!(vma->vm_flags & VM_WRITE))
|
|
goto bad_area;
|
|
/* a read */
|
|
} else {
|
|
if (!(vma->vm_flags & VM_READ))
|
|
goto bad_area;
|
|
}
|
|
|
|
survive:
|
|
/*
|
|
* If for any reason at all we couldn't handle the fault,
|
|
* make sure we exit gracefully rather than endlessly redo
|
|
* the fault.
|
|
*/
|
|
switch (handle_mm_fault(mm, vma, address, is_write)) {
|
|
|
|
case VM_FAULT_MINOR:
|
|
current->min_flt++;
|
|
break;
|
|
case VM_FAULT_MAJOR:
|
|
current->maj_flt++;
|
|
break;
|
|
case VM_FAULT_SIGBUS:
|
|
goto do_sigbus;
|
|
case VM_FAULT_OOM:
|
|
goto out_of_memory;
|
|
default:
|
|
BUG();
|
|
}
|
|
|
|
up_read(&mm->mmap_sem);
|
|
return 0;
|
|
|
|
bad_area:
|
|
up_read(&mm->mmap_sem);
|
|
|
|
bad_area_nosemaphore:
|
|
/* User mode accesses cause a SIGSEGV */
|
|
if (user_mode(regs)) {
|
|
info.si_signo = SIGSEGV;
|
|
info.si_errno = 0;
|
|
info.si_code = code;
|
|
info.si_addr = (void __user *) address;
|
|
force_sig_info(SIGSEGV, &info, current);
|
|
return 0;
|
|
}
|
|
|
|
if (trap == 0x400 && (error_code & DSISR_PROTFAULT)
|
|
&& printk_ratelimit())
|
|
printk(KERN_CRIT "kernel tried to execute NX-protected"
|
|
" page (%lx) - exploit attempt? (uid: %d)\n",
|
|
address, current->uid);
|
|
|
|
return SIGSEGV;
|
|
|
|
/*
|
|
* We ran out of memory, or some other thing happened to us that made
|
|
* us unable to handle the page fault gracefully.
|
|
*/
|
|
out_of_memory:
|
|
up_read(&mm->mmap_sem);
|
|
if (current->pid == 1) {
|
|
yield();
|
|
down_read(&mm->mmap_sem);
|
|
goto survive;
|
|
}
|
|
printk("VM: killing process %s\n", current->comm);
|
|
if (user_mode(regs))
|
|
do_exit(SIGKILL);
|
|
return SIGKILL;
|
|
|
|
do_sigbus:
|
|
up_read(&mm->mmap_sem);
|
|
if (user_mode(regs)) {
|
|
info.si_signo = SIGBUS;
|
|
info.si_errno = 0;
|
|
info.si_code = BUS_ADRERR;
|
|
info.si_addr = (void __user *)address;
|
|
force_sig_info(SIGBUS, &info, current);
|
|
return 0;
|
|
}
|
|
return SIGBUS;
|
|
}
|
|
|
|
/*
|
|
* 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 *entry;
|
|
|
|
/* Are we prepared to handle this fault? */
|
|
if ((entry = search_exception_tables(regs->nip)) != NULL) {
|
|
regs->nip = entry->fixup;
|
|
return;
|
|
}
|
|
|
|
/* kernel has accessed a bad area */
|
|
die("Kernel access of bad area", regs, sig);
|
|
}
|