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linux/arch/powerpc/mm/fault.c

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/*
* 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/ratelimit.h>
#include <linux/context_tracking.h>
#include <linux/hugetlb.h>
#include <linux/uaccess.h>
#include <asm/firmware.h>
#include <asm/page.h>
#include <asm/pgtable.h>
#include <asm/mmu.h>
#include <asm/mmu_context.h>
#include <asm/tlbflush.h>
#include <asm/siginfo.h>
#include <asm/debug.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,
unsigned int fault)
{
siginfo_t info;
unsigned int lsb = 0;
up_read(&current->mm->mmap_sem);
if (!user_mode(regs))
return MM_FAULT_ERR(SIGBUS);
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;
#ifdef CONFIG_MEMORY_FAILURE
if (fault & (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE)) {
pr_err("MCE: Killing %s:%d due to hardware memory corruption fault at %lx\n",
current->comm, current->pid, address);
info.si_code = BUS_MCEERR_AR;
}
if (fault & VM_FAULT_HWPOISON_LARGE)
lsb = hstate_index_to_shift(VM_FAULT_GET_HINDEX(fault));
if (fault & VM_FAULT_HWPOISON)
lsb = PAGE_SHIFT;
#endif
info.si_addr_lsb = lsb;
force_sig_info(SIGBUS, &info, current);
return MM_FAULT_RETURN;
}
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;
}
if (fault & (VM_FAULT_SIGBUS|VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE))
return do_sigbus(regs, addr, fault);
/* 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, store_update_sp = 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 */
#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 (faulthandler_disabled() || mm == NULL) {
if (!user_mode(regs)) {
rc = SIGSEGV;
goto bail;
}
/* faulthandler_disabled() in user mode is really bad,
as is current->mm == NULL. */
printk(KERN_EMERG "Page fault in user mode with "
"faulthandler_disabled() = %d mm = %p\n",
faulthandler_disabled(), 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);
/*
* We want to do this outside mmap_sem, because reading code around nip
* can result in fault, which will cause a deadlock when called with
* mmap_sem held
*/
if (user_mode(regs))
store_update_sp = store_updates_sp(regs);
if (user_mode(regs))
flags |= FAULT_FLAG_USER;
/* 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] && !store_update_sp)
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)
/* 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) {
/*
* 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;
#ifdef CONFIG_PPC_STD_MMU
/*
* protfault should only happen due to us
* mapping a region readonly temporarily. PROT_NONE
* is also covered by the VMA check above.
*/
WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
#endif /* CONFIG_PPC_STD_MMU */
/* a write */
} else if (is_write) {
if (!(vma->vm_flags & VM_WRITE))
goto bad_area;
flags |= FAULT_FLAG_WRITE;
/* a read */
} else {
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
goto bad_area;
WARN_ON_ONCE(error_code & DSISR_PROTFAULT);
}
/*
* 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))) {
if (fault & VM_FAULT_SIGSEGV)
goto bad_area;
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)) {
u32 page_ins;
preempt_disable();
page_ins = be32_to_cpu(get_lppaca()->page_ins);
page_ins += 1 << PAGE_FACTOR;
get_lppaca()->page_ins = cpu_to_be32(page_ins);
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;
/* 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);
if (task_stack_end_corrupted(current))
printk(KERN_ALERT "Thread overran stack, or stack corrupted\n");
die("Kernel access of bad area", regs, sig);
}
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