linux/arch/powerpc/mm/fault.c
Li Zhong ba12eedee3 powerpc: Exception hooks for context tracking subsystem
This is the exception hooks for context tracking subsystem, including
data access, program check, single step, instruction breakpoint, machine check,
alignment, fp unavailable, altivec assist, unknown exception, whose handlers
might use RCU.

This patch corresponds to
[PATCH] x86: Exception hooks for userspace RCU extended QS
  commit 6ba3c97a38

But after the exception handling moved to generic code, and some changes in
following two commits:
56dd9470d7
  context_tracking: Move exception handling to generic code
6c1e0256fa
  context_tracking: Restore correct previous context state on exception exit

it is able for exception hooks to use the generic code above instead of a
redundant arch implementation.

Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
2013-05-14 16:00:19 +10:00

534 lines
14 KiB
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/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/highmem.h>
#include <linux/module.h>
#include <linux/kprobes.h>
#include <linux/kdebug.h>
#include <linux/perf_event.h>
#include <linux/magic.h>
#include <linux/ratelimit.h>
#include <linux/context_tracking.h>
#include <asm/firmware.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/uaccess.h>
#include <asm/tlbflush.h>
#include <asm/siginfo.h>
#include <asm/debug.h>
#include <mm/mmu_decl.h>
#include "icswx.h"
#ifdef CONFIG_KPROBES
static inline int notify_page_fault(struct pt_regs *regs)
{
int ret = 0;
/* kprobe_running() needs smp_processor_id() */
if (!user_mode(regs)) {
preempt_disable();
if (kprobe_running() && kprobe_fault_handler(regs, 11))
ret = 1;
preempt_enable();
}
return ret;
}
#else
static inline int notify_page_fault(struct pt_regs *regs)
{
return 0;
}
#endif
/*
* 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;
}
/*
* do_page_fault error handling helpers
*/
#define MM_FAULT_RETURN 0
#define MM_FAULT_CONTINUE -1
#define MM_FAULT_ERR(sig) (sig)
static int do_sigbus(struct pt_regs *regs, unsigned long address)
{
siginfo_t info;
up_read(&current->mm->mmap_sem);
if (user_mode(regs)) {
current->thread.trap_nr = BUS_ADRERR;
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 MM_FAULT_RETURN;
}
return MM_FAULT_ERR(SIGBUS);
}
static int mm_fault_error(struct pt_regs *regs, unsigned long addr, int fault)
{
/*
* Pagefault was interrupted by SIGKILL. We have no reason to
* continue the pagefault.
*/
if (fatal_signal_pending(current)) {
/*
* If we have retry set, the mmap semaphore will have
* alrady been released in __lock_page_or_retry(). Else
* we release it now.
*/
if (!(fault & VM_FAULT_RETRY))
up_read(&current->mm->mmap_sem);
/* Coming from kernel, we need to deal with uaccess fixups */
if (user_mode(regs))
return MM_FAULT_RETURN;
return MM_FAULT_ERR(SIGKILL);
}
/* No fault: be happy */
if (!(fault & VM_FAULT_ERROR))
return MM_FAULT_CONTINUE;
/* Out of memory */
if (fault & VM_FAULT_OOM) {
up_read(&current->mm->mmap_sem);
/*
* 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))
return MM_FAULT_ERR(SIGKILL);
pagefault_out_of_memory();
return MM_FAULT_RETURN;
}
/* Bus error. x86 handles HWPOISON here, we'll add this if/when
* we support the feature in HW
*/
if (fault & VM_FAULT_SIGBUS)
return do_sigbus(regs, addr);
/* We don't understand the fault code, this is fatal */
BUG();
return MM_FAULT_CONTINUE;
}
/*
* For 600- and 800-family processors, the error_code parameter is DSISR
* for a data fault, SRR1 for an instruction fault. For 400-family processors
* the error_code parameter is ESR for a data fault, 0 for an instruction
* fault.
* For 64-bit processors, 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)
{
enum ctx_state prev_state = exception_enter();
struct vm_area_struct * vma;
struct mm_struct *mm = current->mm;
unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_KILLABLE;
int code = SEGV_MAPERR;
int is_write = 0;
int trap = TRAP(regs);
int is_exec = trap == 0x400;
int fault;
int rc = 0;
#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE))
/*
* Fortunately the bit assignments in SRR1 for an instruction
* fault and DSISR for a data fault are mostly the same for the
* bits we are interested in. But there are some bits which
* indicate errors in DSISR but can validly be set in SRR1.
*/
if (trap == 0x400)
error_code &= 0x48200000;
else
is_write = error_code & DSISR_ISSTORE;
#else
is_write = error_code & ESR_DST;
#endif /* CONFIG_4xx || CONFIG_BOOKE */
if (is_write)
flags |= FAULT_FLAG_WRITE;
#ifdef CONFIG_PPC_ICSWX
/*
* we need to do this early because this "data storage
* interrupt" does not update the DAR/DEAR so we don't want to
* look at it
*/
if (error_code & ICSWX_DSI_UCT) {
rc = acop_handle_fault(regs, address, error_code);
if (rc)
goto bail;
}
#endif /* CONFIG_PPC_ICSWX */
if (notify_page_fault(regs))
goto bail;
if (unlikely(debugger_fault_handler(regs)))
goto bail;
/* On a kernel SLB miss we can only check for a valid exception entry */
if (!user_mode(regs) && (address >= TASK_SIZE)) {
rc = SIGSEGV;
goto bail;
}
#if !(defined(CONFIG_4xx) || defined(CONFIG_BOOKE) || \
defined(CONFIG_PPC_BOOK3S_64))
if (error_code & DSISR_DABRMATCH) {
/* breakpoint match */
do_break(regs, address, error_code);
goto bail;
}
#endif
/* We restore the interrupt state now */
if (!arch_irq_disabled_regs(regs))
local_irq_enable();
if (in_atomic() || mm == NULL) {
if (!user_mode(regs)) {
rc = SIGSEGV;
goto bail;
}
/* 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);
}
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_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 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 (!down_read_trylock(&mm->mmap_sem)) {
if (!user_mode(regs) && !search_exception_tables(regs->nip))
goto bad_area_nosemaphore;
retry:
down_read(&mm->mmap_sem);
} else {
/*
* The above down_read_trylock() might have succeeded in
* which case we'll have missed the might_sleep() from
* down_read():
*/
might_sleep();
}
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 defined(CONFIG_6xx)
if (error_code & 0x95700000)
/* an error such as lwarx to I/O controller space,
address matching DABR, eciwx, etc. */
goto bad_area;
#endif /* CONFIG_6xx */
#if defined(CONFIG_8xx)
/* 8xx sometimes need to load a invalid/non-present TLBs.
* These must be invalidated separately as linux mm don't.
*/
if (error_code & 0x40000000) /* no translation? */
_tlbil_va(address, 0, 0, 0);
/* The MPC8xx seems to always set 0x80000000, which is
* "undefined". Of those that can be set, this is the only
* one which seems bad.
*/
if (error_code & 0x10000000)
/* Guarded storage error. */
goto bad_area;
#endif /* CONFIG_8xx */
if (is_exec) {
#ifdef CONFIG_PPC_STD_MMU
/* Protection fault on exec go straight to failure on
* Hash based MMUs as they either don't support per-page
* execute permission, or if they do, it's handled already
* at the hash level. This test would probably have to
* be removed if we change the way this works to make hash
* processors use the same I/D cache coherency mechanism
* as embedded.
*/
if (error_code & DSISR_PROTFAULT)
goto bad_area;
#endif /* CONFIG_PPC_STD_MMU */
/*
* Allow execution from readable areas if the MMU does not
* provide separate controls over reading and executing.
*
* Note: That code used to not be enabled for 4xx/BookE.
* It is now as I/D cache coherency for these is done at
* set_pte_at() time and I see no reason why the test
* below wouldn't be valid on those processors. This -may-
* break programs compiled with a really old ABI though.
*/
if (!(vma->vm_flags & VM_EXEC) &&
(cpu_has_feature(CPU_FTR_NOEXECUTE) ||
!(vma->vm_flags & (VM_READ | VM_WRITE))))
goto bad_area;
/* a write */
} else if (is_write) {
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
/* a read */
} else {
/* protection fault */
if (error_code & 0x08000000)
goto bad_area;
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
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(mm, vma, address, flags);
if (unlikely(fault & (VM_FAULT_RETRY|VM_FAULT_ERROR))) {
rc = mm_fault_error(regs, address, fault);
if (rc >= MM_FAULT_RETURN)
goto bail;
else
rc = 0;
}
/*
* Major/minor page fault accounting is only done on the
* initial attempt. If we go through a retry, it is extremely
* likely that the page will be found in page cache at that point.
*/
if (flags & FAULT_FLAG_ALLOW_RETRY) {
if (fault & VM_FAULT_MAJOR) {
current->maj_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MAJ, 1,
regs, address);
#ifdef CONFIG_PPC_SMLPAR
if (firmware_has_feature(FW_FEATURE_CMO)) {
preempt_disable();
get_lppaca()->page_ins += (1 << PAGE_FACTOR);
preempt_enable();
}
#endif /* CONFIG_PPC_SMLPAR */
} else {
current->min_flt++;
perf_sw_event(PERF_COUNT_SW_PAGE_FAULTS_MIN, 1,
regs, address);
}
if (fault & VM_FAULT_RETRY) {
/* Clear FAULT_FLAG_ALLOW_RETRY to avoid any risk
* of starvation. */
flags &= ~FAULT_FLAG_ALLOW_RETRY;
flags |= FAULT_FLAG_TRIED;
goto retry;
}
}
up_read(&mm->mmap_sem);
goto bail;
bad_area:
up_read(&mm->mmap_sem);
bad_area_nosemaphore:
/* User mode accesses cause a SIGSEGV */
if (user_mode(regs)) {
_exception(SIGSEGV, regs, code, address);
goto bail;
}
if (is_exec && (error_code & DSISR_PROTFAULT))
printk_ratelimited(KERN_CRIT "kernel tried to execute NX-protected"
" page (%lx) - exploit attempt? (uid: %d)\n",
address, from_kuid(&init_user_ns, current_uid()));
rc = SIGSEGV;
bail:
exception_exit(prev_state);
return rc;
}
/*
* bad_page_fault is called when we have a bad access from the kernel.
* It is called from the DSI and ISI handlers in head.S 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;
unsigned long *stackend;
/* 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 */
switch (regs->trap) {
case 0x300:
case 0x380:
printk(KERN_ALERT "Unable to handle kernel paging request for "
"data at address 0x%08lx\n", regs->dar);
break;
case 0x400:
case 0x480:
printk(KERN_ALERT "Unable to handle kernel paging request for "
"instruction fetch\n");
break;
default:
printk(KERN_ALERT "Unable to handle kernel paging request for "
"unknown fault\n");
break;
}
printk(KERN_ALERT "Faulting instruction address: 0x%08lx\n",
regs->nip);
stackend = end_of_stack(current);
if (current != &init_task && *stackend != STACK_END_MAGIC)
printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
die("Kernel access of bad area", regs, sig);
}