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acrn-kernel/arch/s390/mm/fault.c

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/*
* arch/s390/mm/fault.c
*
* S390 version
* Copyright (C) 1999 IBM Deutschland Entwicklung GmbH, IBM Corporation
* Author(s): Hartmut Penner (hp@de.ibm.com)
* Ulrich Weigand (uweigand@de.ibm.com)
*
* Derived from "arch/i386/mm/fault.c"
* Copyright (C) 1995 Linus Torvalds
*/
#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/smp.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/console.h>
#include <linux/module.h>
#include <linux/hardirq.h>
#include <linux/kprobes.h>
#include <asm/system.h>
#include <asm/uaccess.h>
#include <asm/pgtable.h>
#include <asm/kdebug.h>
#ifndef CONFIG_64BIT
#define __FAIL_ADDR_MASK 0x7ffff000
#define __FIXUP_MASK 0x7fffffff
#define __SUBCODE_MASK 0x0200
#define __PF_RES_FIELD 0ULL
#else /* CONFIG_64BIT */
#define __FAIL_ADDR_MASK -4096L
#define __FIXUP_MASK ~0L
#define __SUBCODE_MASK 0x0600
#define __PF_RES_FIELD 0x8000000000000000ULL
#endif /* CONFIG_64BIT */
#ifdef CONFIG_SYSCTL
extern int sysctl_userprocess_debug;
#endif
extern void die(const char *,struct pt_regs *,long);
#ifdef CONFIG_KPROBES
ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
int register_page_fault_notifier(struct notifier_block *nb)
{
return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
}
int unregister_page_fault_notifier(struct notifier_block *nb)
{
return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
}
static inline int notify_page_fault(enum die_val val, const char *str,
struct pt_regs *regs, long err, int trap, int sig)
{
struct die_args args = {
.regs = regs,
.str = str,
.err = err,
.trapnr = trap,
.signr = sig
};
return atomic_notifier_call_chain(&notify_page_fault_chain, val, &args);
}
#else
static inline int notify_page_fault(enum die_val val, const char *str,
struct pt_regs *regs, long err, int trap, int sig)
{
return NOTIFY_DONE;
}
#endif
extern spinlock_t timerlist_lock;
/*
* Unlock any spinlocks which will prevent us from getting the
* message out (timerlist_lock is acquired through the
* console unblank code)
*/
void bust_spinlocks(int yes)
{
if (yes) {
oops_in_progress = 1;
} else {
int loglevel_save = console_loglevel;
console_unblank();
oops_in_progress = 0;
/*
* OK, the message is on the console. Now we call printk()
* without oops_in_progress set so that printk will give klogd
* a poke. Hold onto your hats...
*/
console_loglevel = 15;
printk(" ");
console_loglevel = loglevel_save;
}
}
/*
* Check which address space is addressed by the access
* register in S390_lowcore.exc_access_id.
* Returns 1 for user space and 0 for kernel space.
*/
static int __check_access_register(struct pt_regs *regs, int error_code)
{
int areg = S390_lowcore.exc_access_id;
if (areg == 0)
/* Access via access register 0 -> kernel address */
return 0;
save_access_regs(current->thread.acrs);
if (regs && areg < NUM_ACRS && current->thread.acrs[areg] <= 1)
/*
* access register contains 0 -> kernel address,
* access register contains 1 -> user space address
*/
return current->thread.acrs[areg];
/* Something unhealthy was done with the access registers... */
die("page fault via unknown access register", regs, error_code);
do_exit(SIGKILL);
return 0;
}
/*
* Check which address space the address belongs to.
* Returns 1 for user space and 0 for kernel space.
*/
static inline int check_user_space(struct pt_regs *regs, int error_code)
{
/*
* The lowest two bits of S390_lowcore.trans_exc_code indicate
* which paging table was used:
* 0: Primary Segment Table Descriptor
* 1: STD determined via access register
* 2: Secondary Segment Table Descriptor
* 3: Home Segment Table Descriptor
*/
int descriptor = S390_lowcore.trans_exc_code & 3;
if (unlikely(descriptor == 1))
return __check_access_register(regs, error_code);
if (descriptor == 2)
return current->thread.mm_segment.ar4;
return descriptor != 0;
}
/*
* Send SIGSEGV to task. This is an external routine
* to keep the stack usage of do_page_fault small.
*/
static void do_sigsegv(struct pt_regs *regs, unsigned long error_code,
int si_code, unsigned long address)
{
struct siginfo si;
#if defined(CONFIG_SYSCTL) || defined(CONFIG_PROCESS_DEBUG)
#if defined(CONFIG_SYSCTL)
if (sysctl_userprocess_debug)
#endif
{
printk("User process fault: interruption code 0x%lX\n",
error_code);
printk("failing address: %lX\n", address);
show_regs(regs);
}
#endif
si.si_signo = SIGSEGV;
si.si_code = si_code;
si.si_addr = (void __user *) address;
force_sig_info(SIGSEGV, &si, current);
}
/*
* This routine handles page faults. It determines the address,
* and the problem, and then passes it off to one of the appropriate
* routines.
*
* error_code:
* 04 Protection -> Write-Protection (suprression)
* 10 Segment translation -> Not present (nullification)
* 11 Page translation -> Not present (nullification)
* 3b Region third trans. -> Not present (nullification)
*/
static inline void __kprobes
do_exception(struct pt_regs *regs, unsigned long error_code, int is_protection)
{
struct task_struct *tsk;
struct mm_struct *mm;
struct vm_area_struct * vma;
unsigned long address;
int user_address;
const struct exception_table_entry *fixup;
int si_code = SEGV_MAPERR;
tsk = current;
mm = tsk->mm;
if (notify_page_fault(DIE_PAGE_FAULT, "page fault", regs, error_code, 14,
SIGSEGV) == NOTIFY_STOP)
return;
/*
* Check for low-address protection. This needs to be treated
* as a special case because the translation exception code
* field is not guaranteed to contain valid data in this case.
*/
if (is_protection && !(S390_lowcore.trans_exc_code & 4)) {
/* Low-address protection hit in kernel mode means
NULL pointer write access in kernel mode. */
if (!(regs->psw.mask & PSW_MASK_PSTATE)) {
address = 0;
user_address = 0;
goto no_context;
}
/* Low-address protection hit in user mode 'cannot happen'. */
die ("Low-address protection", regs, error_code);
do_exit(SIGKILL);
}
/*
* get the failing address
* more specific the segment and page table portion of
* the address
*/
address = S390_lowcore.trans_exc_code & __FAIL_ADDR_MASK;
user_address = check_user_space(regs, error_code);
/*
* Verify that the fault happened in user space, that
* we are not in an interrupt and that there is a
* user context.
*/
if (user_address == 0 || in_atomic() || !mm)
goto no_context;
/*
* When we get here, the fault happened in the current
* task's user address space, so we can switch on the
* interrupts again and then search the VMAs
*/
local_irq_enable();
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;
if (expand_stack(vma, address))
goto bad_area;
/*
* Ok, we have a good vm_area for this memory access, so
* we can handle it..
*/
good_area:
si_code = SEGV_ACCERR;
if (!is_protection) {
/* page not present, check vm flags */
if (!(vma->vm_flags & (VM_READ | VM_EXEC | VM_WRITE)))
goto bad_area;
} else {
if (!(vma->vm_flags & VM_WRITE))
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_protection)) {
case VM_FAULT_MINOR:
tsk->min_flt++;
break;
case VM_FAULT_MAJOR:
tsk->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);
/*
* The instruction that caused the program check will
* be repeated. Don't signal single step via SIGTRAP.
*/
clear_tsk_thread_flag(current, TIF_SINGLE_STEP);
return;
/*
* Something tried to access memory that isn't in our memory map..
* Fix it, but check if it's kernel or user first..
*/
bad_area:
up_read(&mm->mmap_sem);
/* User mode accesses just cause a SIGSEGV */
if (regs->psw.mask & PSW_MASK_PSTATE) {
tsk->thread.prot_addr = address;
tsk->thread.trap_no = error_code;
do_sigsegv(regs, error_code, si_code, address);
return;
}
no_context:
/* Are we prepared to handle this kernel fault? */
fixup = search_exception_tables(regs->psw.addr & __FIXUP_MASK);
if (fixup) {
regs->psw.addr = fixup->fixup | PSW_ADDR_AMODE;
return;
}
/*
* Oops. The kernel tried to access some bad page. We'll have to
* terminate things with extreme prejudice.
*/
if (user_address == 0)
printk(KERN_ALERT "Unable to handle kernel pointer dereference"
" at virtual kernel address %p\n", (void *)address);
else
printk(KERN_ALERT "Unable to handle kernel paging request"
" at virtual user address %p\n", (void *)address);
die("Oops", regs, error_code);
do_exit(SIGKILL);
/*
* 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 (is_init(tsk)) {
yield();
down_read(&mm->mmap_sem);
goto survive;
}
printk("VM: killing process %s\n", tsk->comm);
if (regs->psw.mask & PSW_MASK_PSTATE)
do_exit(SIGKILL);
goto no_context;
do_sigbus:
up_read(&mm->mmap_sem);
/*
* Send a sigbus, regardless of whether we were in kernel
* or user mode.
*/
tsk->thread.prot_addr = address;
tsk->thread.trap_no = error_code;
force_sig(SIGBUS, tsk);
/* Kernel mode? Handle exceptions or die */
if (!(regs->psw.mask & PSW_MASK_PSTATE))
goto no_context;
}
void do_protection_exception(struct pt_regs *regs, unsigned long error_code)
{
regs->psw.addr -= (error_code >> 16);
do_exception(regs, 4, 1);
}
void do_dat_exception(struct pt_regs *regs, unsigned long error_code)
{
do_exception(regs, error_code & 0xff, 0);
}
#ifdef CONFIG_PFAULT
/*
* 'pfault' pseudo page faults routines.
*/
static int pfault_disable = 0;
static int __init nopfault(char *str)
{
pfault_disable = 1;
return 1;
}
__setup("nopfault", nopfault);
typedef struct {
__u16 refdiagc;
__u16 reffcode;
__u16 refdwlen;
__u16 refversn;
__u64 refgaddr;
__u64 refselmk;
__u64 refcmpmk;
__u64 reserved;
} __attribute__ ((packed)) pfault_refbk_t;
int pfault_init(void)
{
pfault_refbk_t refbk =
{ 0x258, 0, 5, 2, __LC_CURRENT, 1ULL << 48, 1ULL << 48,
__PF_RES_FIELD };
int rc;
if (pfault_disable)
return -1;
asm volatile(
" diag %1,%0,0x258\n"
"0: j 2f\n"
"1: la %0,8\n"
"2:\n"
EX_TABLE(0b,1b)
: "=d" (rc) : "a" (&refbk), "m" (refbk) : "cc");
__ctl_set_bit(0, 9);
return rc;
}
void pfault_fini(void)
{
pfault_refbk_t refbk =
{ 0x258, 1, 5, 2, 0ULL, 0ULL, 0ULL, 0ULL };
if (pfault_disable)
return;
__ctl_clear_bit(0,9);
asm volatile(
" diag %0,0,0x258\n"
"0:\n"
EX_TABLE(0b,0b)
: : "a" (&refbk), "m" (refbk) : "cc");
}
asmlinkage void
pfault_interrupt(__u16 error_code)
{
struct task_struct *tsk;
__u16 subcode;
/*
* Get the external interruption subcode & pfault
* initial/completion signal bit. VM stores this
* in the 'cpu address' field associated with the
* external interrupt.
*/
subcode = S390_lowcore.cpu_addr;
if ((subcode & 0xff00) != __SUBCODE_MASK)
return;
/*
* Get the token (= address of the task structure of the affected task).
*/
tsk = *(struct task_struct **) __LC_PFAULT_INTPARM;
if (subcode & 0x0080) {
/* signal bit is set -> a page has been swapped in by VM */
if (xchg(&tsk->thread.pfault_wait, -1) != 0) {
/* Initial interrupt was faster than the completion
* interrupt. pfault_wait is valid. Set pfault_wait
* back to zero and wake up the process. This can
* safely be done because the task is still sleeping
* and can't produce new pfaults. */
tsk->thread.pfault_wait = 0;
wake_up_process(tsk);
put_task_struct(tsk);
}
} else {
/* signal bit not set -> a real page is missing. */
get_task_struct(tsk);
set_task_state(tsk, TASK_UNINTERRUPTIBLE);
if (xchg(&tsk->thread.pfault_wait, 1) != 0) {
/* Completion interrupt was faster than the initial
* interrupt (swapped in a -1 for pfault_wait). Set
* pfault_wait back to zero and exit. This can be
* done safely because tsk is running in kernel
* mode and can't produce new pfaults. */
tsk->thread.pfault_wait = 0;
set_task_state(tsk, TASK_RUNNING);
put_task_struct(tsk);
} else
set_tsk_need_resched(tsk);
}
}
#endif
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