[deliverable/linux.git] / arch / i386 / mm / fault.c

/*
 *  linux/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/interrupt.h>
#include <linux/init.h>
#include <linux/tty.h>
#include <linux/vt_kern.h>		/* For unblank_screen() */
#include <linux/highmem.h>
#include <linux/bootmem.h>		/* for max_low_pfn */
#include <linux/vmalloc.h>
#include <linux/module.h>
#include <linux/kprobes.h>
#include <linux/uaccess.h>
#include <linux/kdebug.h>

#include <asm/system.h>
#include <asm/desc.h>
#include <asm/segment.h>

extern void die(const char *,struct pt_regs *,long);

static ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);

int register_page_fault_notifier(struct notifier_block *nb)
{
	vmalloc_sync_all();
	return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
}
EXPORT_SYMBOL_GPL(register_page_fault_notifier);

int unregister_page_fault_notifier(struct notifier_block *nb)
{
	return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
}
EXPORT_SYMBOL_GPL(unregister_page_fault_notifier);

static inline int notify_page_fault(struct pt_regs *regs, long err)
{
	struct die_args args = {
		.regs = regs,
		.str = "page fault",
		.err = err,
		.trapnr = 14,
		.signr = SIGSEGV
	};
	return atomic_notifier_call_chain(&notify_page_fault_chain,
	                                  DIE_PAGE_FAULT, &args);
}

/*
 * Return EIP plus the CS segment base.  The segment limit is also
 * adjusted, clamped to the kernel/user address space (whichever is
 * appropriate), and returned in *eip_limit.
 *
 * The segment is checked, because it might have been changed by another
 * task between the original faulting instruction and here.
 *
 * If CS is no longer a valid code segment, or if EIP is beyond the
 * limit, or if it is a kernel address when CS is not a kernel segment,
 * then the returned value will be greater than *eip_limit.
 * 
 * This is slow, but is very rarely executed.
 */
static inline unsigned long get_segment_eip(struct pt_regs *regs,
					    unsigned long *eip_limit)
{
	unsigned long eip = regs->eip;
	unsigned seg = regs->xcs & 0xffff;
	u32 seg_ar, seg_limit, base, *desc;

	/* Unlikely, but must come before segment checks. */
	if (unlikely(regs->eflags & VM_MASK)) {
		base = seg << 4;
		*eip_limit = base + 0xffff;
		return base + (eip & 0xffff);
	}

	/* The standard kernel/user address space limit. */
	*eip_limit = user_mode(regs) ? USER_DS.seg : KERNEL_DS.seg;
	
	/* By far the most common cases. */
	if (likely(SEGMENT_IS_FLAT_CODE(seg)))
		return eip;

	/* Check the segment exists, is within the current LDT/GDT size,
	   that kernel/user (ring 0..3) has the appropriate privilege,
	   that it's a code segment, and get the limit. */
	__asm__ ("larl %3,%0; lsll %3,%1"
		 : "=&r" (seg_ar), "=r" (seg_limit) : "0" (0), "rm" (seg));
	if ((~seg_ar & 0x9800) || eip > seg_limit) {
		*eip_limit = 0;
		return 1;	 /* So that returned eip > *eip_limit. */
	}

	/* Get the GDT/LDT descriptor base. 
	   When you look for races in this code remember that
	   LDT and other horrors are only used in user space. */
	if (seg & (1<<2)) {
		/* Must lock the LDT while reading it. */
		down(&current->mm->context.sem);
		desc = current->mm->context.ldt;
		desc = (void *)desc + (seg & ~7);
	} else {
		/* Must disable preemption while reading the GDT. */
 		desc = (u32 *)get_cpu_gdt_table(get_cpu());
		desc = (void *)desc + (seg & ~7);
	}

	/* Decode the code segment base from the descriptor */
	base = get_desc_base((unsigned long *)desc);

	if (seg & (1<<2)) { 
		up(&current->mm->context.sem);
	} else
		put_cpu();

	/* Adjust EIP and segment limit, and clamp at the kernel limit.
	   It's legitimate for segments to wrap at 0xffffffff. */
	seg_limit += base;
	if (seg_limit < *eip_limit && seg_limit >= base)
		*eip_limit = seg_limit;
	return eip + base;
}

/* 
 * Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
 * Check that here and ignore it.
 */
static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
{ 
	unsigned long limit;
	unsigned char *instr = (unsigned char *)get_segment_eip (regs, &limit);
	int scan_more = 1;
	int prefetch = 0; 
	int i;

	for (i = 0; scan_more && i < 15; i++) { 
		unsigned char opcode;
		unsigned char instr_hi;
		unsigned char instr_lo;

		if (instr > (unsigned char *)limit)
			break;
		if (probe_kernel_address(instr, opcode))
			break; 

		instr_hi = opcode & 0xf0; 
		instr_lo = opcode & 0x0f; 
		instr++;

		switch (instr_hi) { 
		case 0x20:
		case 0x30:
			/* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
			scan_more = ((instr_lo & 7) == 0x6);
			break;
			
		case 0x60:
			/* 0x64 thru 0x67 are valid prefixes in all modes. */
			scan_more = (instr_lo & 0xC) == 0x4;
			break;		
		case 0xF0:
			/* 0xF0, 0xF2, and 0xF3 are valid prefixes */
			scan_more = !instr_lo || (instr_lo>>1) == 1;
			break;			
		case 0x00:
			/* Prefetch instruction is 0x0F0D or 0x0F18 */
			scan_more = 0;
			if (instr > (unsigned char *)limit)
				break;
			if (probe_kernel_address(instr, opcode))
				break;
			prefetch = (instr_lo == 0xF) &&
				(opcode == 0x0D || opcode == 0x18);
			break;			
		default:
			scan_more = 0;
			break;
		} 
	}
	return prefetch;
}

static inline int is_prefetch(struct pt_regs *regs, unsigned long addr,
			      unsigned long error_code)
{
	if (unlikely(boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
		     boot_cpu_data.x86 >= 6)) {
		/* Catch an obscure case of prefetch inside an NX page. */
		if (nx_enabled && (error_code & 16))
			return 0;
		return __is_prefetch(regs, addr);
	}
	return 0;
} 

static noinline void force_sig_info_fault(int si_signo, int si_code,
	unsigned long address, struct task_struct *tsk)
{
	siginfo_t info;

	info.si_signo = si_signo;
	info.si_errno = 0;
	info.si_code = si_code;
	info.si_addr = (void __user *)address;
	force_sig_info(si_signo, &info, tsk);
}

fastcall void do_invalid_op(struct pt_regs *, unsigned long);

static inline pmd_t *vmalloc_sync_one(pgd_t *pgd, unsigned long address)
{
	unsigned index = pgd_index(address);
	pgd_t *pgd_k;
	pud_t *pud, *pud_k;
	pmd_t *pmd, *pmd_k;

	pgd += index;
	pgd_k = init_mm.pgd + index;

	if (!pgd_present(*pgd_k))
		return NULL;

	/*
	 * set_pgd(pgd, *pgd_k); here would be useless on PAE
	 * and redundant with the set_pmd() on non-PAE. As would
	 * set_pud.
	 */

	pud = pud_offset(pgd, address);
	pud_k = pud_offset(pgd_k, address);
	if (!pud_present(*pud_k))
		return NULL;

	pmd = pmd_offset(pud, address);
	pmd_k = pmd_offset(pud_k, address);
	if (!pmd_present(*pmd_k))
		return NULL;
	if (!pmd_present(*pmd))
		set_pmd(pmd, *pmd_k);
	else
		BUG_ON(pmd_page(*pmd) != pmd_page(*pmd_k));
	return pmd_k;
}

/*
 * Handle a fault on the vmalloc or module mapping area
 *
 * This assumes no large pages in there.
 */
static inline int vmalloc_fault(unsigned long address)
{
	unsigned long pgd_paddr;
	pmd_t *pmd_k;
	pte_t *pte_k;
	/*
	 * Synchronize this task's top level page-table
	 * with the 'reference' page table.
	 *
	 * Do _not_ use "current" here. We might be inside
	 * an interrupt in the middle of a task switch..
	 */
	pgd_paddr = read_cr3();
	pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
	if (!pmd_k)
		return -1;
	pte_k = pte_offset_kernel(pmd_k, address);
	if (!pte_present(*pte_k))
		return -1;
	return 0;
}

/*
 * 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:
 *	bit 0 == 0 means no page found, 1 means protection fault
 *	bit 1 == 0 means read, 1 means write
 *	bit 2 == 0 means kernel, 1 means user-mode
 *	bit 3 == 1 means use of reserved bit detected
 *	bit 4 == 1 means fault was an instruction fetch
 */
fastcall void __kprobes do_page_fault(struct pt_regs *regs,
				      unsigned long error_code)
{
	struct task_struct *tsk;
	struct mm_struct *mm;
	struct vm_area_struct * vma;
	unsigned long address;
	int write, si_code;

	/* get the address */
        address = read_cr2();

	tsk = current;

	si_code = SEGV_MAPERR;

	/*
	 * We fault-in kernel-space virtual memory on-demand. The
	 * 'reference' page table is init_mm.pgd.
	 *
	 * NOTE! We MUST NOT take any locks for this case. We may
	 * be in an interrupt or a critical region, and should
	 * only copy the information from the master page table,
	 * nothing more.
	 *
	 * This verifies that the fault happens in kernel space
	 * (error_code & 4) == 0, and that the fault was not a
	 * protection error (error_code & 9) == 0.
	 */
	if (unlikely(address >= TASK_SIZE)) {
		if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0)
			return;
		if (notify_page_fault(regs, error_code) == NOTIFY_STOP)
			return;
		/*
		 * Don't take the mm semaphore here. If we fixup a prefetch
		 * fault we could otherwise deadlock.
		 */
		goto bad_area_nosemaphore;
	}

	if (notify_page_fault(regs, error_code) == NOTIFY_STOP)
		return;

	/* It's safe to allow irq's after cr2 has been saved and the vmalloc
	   fault has been handled. */
	if (regs->eflags & (X86_EFLAGS_IF|VM_MASK))
		local_irq_enable();

	mm = tsk->mm;

	/*
	 * If we're in an interrupt, have no user context or are running in an
	 * atomic region then we must not take the fault..
	 */
	if (in_atomic() || !mm)
		goto bad_area_nosemaphore;

	/* 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 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 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 ((error_code & 4) == 0 &&
		    !search_exception_tables(regs->eip))
			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;
	if (error_code & 4) {
		/*
		 * Accessing the stack below %esp is always a bug.
		 * The large cushion allows instructions like enter
		 * and pusha to work.  ("enter $65535,$31" pushes
		 * 32 pointers and then decrements %esp by 65535.)
		 */
		if (address + 65536 + 32 * sizeof(unsigned long) < regs->esp)
			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;
	write = 0;
	switch (error_code & 3) {
		default:	/* 3: write, present */
				/* fall through */
		case 2:		/* write, not present */
			if (!(vma->vm_flags & VM_WRITE))
				goto bad_area;
			write++;
			break;
		case 1:		/* read, present */
			goto bad_area;
		case 0:		/* read, not present */
			if (!(vma->vm_flags & (VM_READ | VM_EXEC | 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, write)) {
		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();
	}

	/*
	 * Did it hit the DOS screen memory VA from vm86 mode?
	 */
	if (regs->eflags & VM_MASK) {
		unsigned long bit = (address - 0xA0000) >> PAGE_SHIFT;
		if (bit < 32)
			tsk->thread.screen_bitmap |= 1 << bit;
	}
	up_read(&mm->mmap_sem);
	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);

bad_area_nosemaphore:
	/* User mode accesses just cause a SIGSEGV */
	if (error_code & 4) {
		/* 
		 * Valid to do another page fault here because this one came 
		 * from user space.
		 */
		if (is_prefetch(regs, address, error_code))
			return;

		tsk->thread.cr2 = address;
		/* Kernel addresses are always protection faults */
		tsk->thread.error_code = error_code | (address >= TASK_SIZE);
		tsk->thread.trap_no = 14;
		force_sig_info_fault(SIGSEGV, si_code, address, tsk);
		return;
	}

#ifdef CONFIG_X86_F00F_BUG
	/*
	 * Pentium F0 0F C7 C8 bug workaround.
	 */
	if (boot_cpu_data.f00f_bug) {
		unsigned long nr;
		
		nr = (address - idt_descr.address) >> 3;

		if (nr == 6) {
			do_invalid_op(regs, 0);
			return;
		}
	}
#endif

no_context:
	/* Are we prepared to handle this kernel fault?  */
	if (fixup_exception(regs))
		return;

	/* 
	 * Valid to do another page fault here, because if this fault
	 * had been triggered by is_prefetch fixup_exception would have 
	 * handled it.
	 */
 	if (is_prefetch(regs, address, error_code))
 		return;

/*
 * Oops. The kernel tried to access some bad page. We'll have to
 * terminate things with extreme prejudice.
 */

	bust_spinlocks(1);

	if (oops_may_print()) {
		__typeof__(pte_val(__pte(0))) page;

#ifdef CONFIG_X86_PAE
		if (error_code & 16) {
			pte_t *pte = lookup_address(address);

			if (pte && pte_present(*pte) && !pte_exec_kernel(*pte))
				printk(KERN_CRIT "kernel tried to execute "
					"NX-protected page - exploit attempt? "
					"(uid: %d)\n", current->uid);
		}
#endif
		if (address < PAGE_SIZE)
			printk(KERN_ALERT "BUG: unable to handle kernel NULL "
					"pointer dereference");
		else
			printk(KERN_ALERT "BUG: unable to handle kernel paging"
					" request");
		printk(" at virtual address %08lx\n",address);
		printk(KERN_ALERT " printing eip:\n");
		printk("%08lx\n", regs->eip);

		page = read_cr3();
		page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
#ifdef CONFIG_X86_PAE
		printk(KERN_ALERT "*pdpt = %016Lx\n", page);
		if ((page >> PAGE_SHIFT) < max_low_pfn
		    && page & _PAGE_PRESENT) {
			page &= PAGE_MASK;
			page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT)
			                                         & (PTRS_PER_PMD - 1)];
			printk(KERN_ALERT "*pde = %016Lx\n", page);
			page &= ~_PAGE_NX;
		}
#else
		printk(KERN_ALERT "*pde = %08lx\n", page);
#endif

		/*
		 * We must not directly access the pte in the highpte
		 * case if the page table is located in highmem.
		 * And let's rather not kmap-atomic the pte, just in case
		 * it's allocated already.
		 */
		if ((page >> PAGE_SHIFT) < max_low_pfn
		    && (page & _PAGE_PRESENT)) {
			page &= PAGE_MASK;
			page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
			                                         & (PTRS_PER_PTE - 1)];
			printk(KERN_ALERT "*pte = %0*Lx\n", sizeof(page)*2, (u64)page);
		}
	}

	tsk->thread.cr2 = address;
	tsk->thread.trap_no = 14;
	tsk->thread.error_code = error_code;
	die("Oops", regs, error_code);
	bust_spinlocks(0);
	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 (error_code & 4)
		do_exit(SIGKILL);
	goto no_context;

do_sigbus:
	up_read(&mm->mmap_sem);

	/* Kernel mode? Handle exceptions or die */
	if (!(error_code & 4))
		goto no_context;

	/* User space => ok to do another page fault */
	if (is_prefetch(regs, address, error_code))
		return;

	tsk->thread.cr2 = address;
	tsk->thread.error_code = error_code;
	tsk->thread.trap_no = 14;
	force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
}

void vmalloc_sync_all(void)
{
	/*
	 * Note that races in the updates of insync and start aren't
	 * problematic: insync can only get set bits added, and updates to
	 * start are only improving performance (without affecting correctness
	 * if undone).
	 */
	static DECLARE_BITMAP(insync, PTRS_PER_PGD);
	static unsigned long start = TASK_SIZE;
	unsigned long address;

	if (SHARED_KERNEL_PMD)
		return;

	BUILD_BUG_ON(TASK_SIZE & ~PGDIR_MASK);
	for (address = start; address >= TASK_SIZE; address += PGDIR_SIZE) {
		if (!test_bit(pgd_index(address), insync)) {
			unsigned long flags;
			struct page *page;

			spin_lock_irqsave(&pgd_lock, flags);
			for (page = pgd_list; page; page =
					(struct page *)page->index)
				if (!vmalloc_sync_one(page_address(page),
								address)) {
					BUG_ON(page != pgd_list);
					break;
				}
			spin_unlock_irqrestore(&pgd_lock, flags);
			if (!page)
				set_bit(pgd_index(address), insync);
		}
		if (address == start && test_bit(pgd_index(address), insync))
			start = address + PGDIR_SIZE;
	}
}
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/arch/i386/mm/fault.c
	3	*
	4	* Copyright (C) 1995 Linus Torvalds
	5	*/
	6
	7	#include <linux/signal.h>
	8	#include <linux/sched.h>
	9	#include <linux/kernel.h>
	10	#include <linux/errno.h>
	11	#include <linux/string.h>
	12	#include <linux/types.h>
	13	#include <linux/ptrace.h>
	14	#include <linux/mman.h>
	15	#include <linux/mm.h>
	16	#include <linux/smp.h>
1da177e4 LT	17	#include <linux/interrupt.h>
	18	#include <linux/init.h>
	19	#include <linux/tty.h>
	20	#include <linux/vt_kern.h> /* For unblank_screen() */
	21	#include <linux/highmem.h>
28609f6e	22	#include <linux/bootmem.h> /* for max_low_pfn */
1eeb66a1	23	#include <linux/vmalloc.h>
1da177e4	24	#include <linux/module.h>
3d97ae5b	25	#include <linux/kprobes.h>
11a4180c	26	#include <linux/uaccess.h>
1eeb66a1	27	#include <linux/kdebug.h>
1da177e4 LT	28
1da177e4 LT	29	#include <asm/system.h>
1da177e4	30	#include <asm/desc.h>
78be3706	31	#include <asm/segment.h>
1da177e4 LT	32
	33	extern void die(const char ,struct pt_regs ,long);
	34
474c2568 AK	35	static ATOMIC_NOTIFIER_HEAD(notify_page_fault_chain);
474c2568 AK	36
b71b5b65 AK	37	int register_page_fault_notifier(struct notifier_block *nb)
	38	{
	39	vmalloc_sync_all();
	40	return atomic_notifier_chain_register(&notify_page_fault_chain, nb);
	41	}
474c2568	42	EXPORT_SYMBOL_GPL(register_page_fault_notifier);
b71b5b65 AK	43
	44	int unregister_page_fault_notifier(struct notifier_block *nb)
	45	{
	46	return atomic_notifier_chain_unregister(&notify_page_fault_chain, nb);
	47	}
474c2568	48	EXPORT_SYMBOL_GPL(unregister_page_fault_notifier);
b71b5b65	49
9b355897	50	static inline int notify_page_fault(struct pt_regs *regs, long err)
b71b5b65 AK	51	{
	52	struct die_args args = {
	53	.regs = regs,
9b355897	54	.str = "page fault",
b71b5b65	55	.err = err,
9b355897 JB	56	.trapnr = 14,
9b355897 JB	57	.signr = SIGSEGV
b71b5b65	58	};
9b355897 JB	59	return atomic_notifier_call_chain(&notify_page_fault_chain,
9b355897 JB	60	DIE_PAGE_FAULT, &args);
b71b5b65	61	}
b71b5b65	62
1da177e4 LT	63	/*
	64	* Return EIP plus the CS segment base. The segment limit is also
	65	* adjusted, clamped to the kernel/user address space (whichever is
	66	* appropriate), and returned in *eip_limit.
	67	*
	68	* The segment is checked, because it might have been changed by another
	69	* task between the original faulting instruction and here.
	70	*
	71	* If CS is no longer a valid code segment, or if EIP is beyond the
	72	* limit, or if it is a kernel address when CS is not a kernel segment,
	73	* then the returned value will be greater than *eip_limit.
	74	*
	75	* This is slow, but is very rarely executed.
	76	*/
	77	static inline unsigned long get_segment_eip(struct pt_regs *regs,
	78	unsigned long *eip_limit)
	79	{
	80	unsigned long eip = regs->eip;
	81	unsigned seg = regs->xcs & 0xffff;
	82	u32 seg_ar, seg_limit, base, *desc;
	83
19964fec CE	84	/* Unlikely, but must come before segment checks. */
	85	if (unlikely(regs->eflags & VM_MASK)) {
	86	base = seg << 4;
	87	*eip_limit = base + 0xffff;
	88	return base + (eip & 0xffff);
	89	}
	90
1da177e4	91	/* The standard kernel/user address space limit. */
78be3706	92	*eip_limit = user_mode(regs) ? USER_DS.seg : KERNEL_DS.seg;
1da177e4 LT	93
1da177e4 LT	94	/* By far the most common cases. */
78be3706	95	if (likely(SEGMENT_IS_FLAT_CODE(seg)))
1da177e4 LT	96	return eip;
	97
	98	/* Check the segment exists, is within the current LDT/GDT size,
	99	that kernel/user (ring 0..3) has the appropriate privilege,
	100	that it's a code segment, and get the limit. */
	101	__asm__ ("larl %3,%0; lsll %3,%1"
	102	: "=&r" (seg_ar), "=r" (seg_limit) : "0" (0), "rm" (seg));
	103	if ((~seg_ar & 0x9800) \|\| eip > seg_limit) {
	104	*eip_limit = 0;
	105	return 1; /* So that returned eip > eip_limit. /
	106	}
	107
	108	/* Get the GDT/LDT descriptor base.
	109	When you look for races in this code remember that
	110	LDT and other horrors are only used in user space. */
	111	if (seg & (1<<2)) {
	112	/* Must lock the LDT while reading it. */
	113	down(&current->mm->context.sem);
	114	desc = current->mm->context.ldt;
	115	desc = (void *)desc + (seg & ~7);
	116	} else {
	117	/* Must disable preemption while reading the GDT. */
251e6912	118	desc = (u32 *)get_cpu_gdt_table(get_cpu());
1da177e4 LT	119	desc = (void *)desc + (seg & ~7);
	120	}
	121
	122	/* Decode the code segment base from the descriptor */
	123	base = get_desc_base((unsigned long *)desc);
	124
	125	if (seg & (1<<2)) {
	126	up(&current->mm->context.sem);
	127	} else
	128	put_cpu();
	129
	130	/* Adjust EIP and segment limit, and clamp at the kernel limit.
	131	It's legitimate for segments to wrap at 0xffffffff. */
	132	seg_limit += base;
	133	if (seg_limit < *eip_limit && seg_limit >= base)
	134	*eip_limit = seg_limit;
	135	return eip + base;
	136	}
	137
	138	/*
	139	* Sometimes AMD Athlon/Opteron CPUs report invalid exceptions on prefetch.
	140	* Check that here and ignore it.
	141	*/
	142	static int __is_prefetch(struct pt_regs *regs, unsigned long addr)
	143	{
	144	unsigned long limit;
11a4180c	145	unsigned char instr = (unsigned char )get_segment_eip (regs, &limit);
1da177e4 LT	146	int scan_more = 1;
	147	int prefetch = 0;
	148	int i;
	149
	150	for (i = 0; scan_more && i < 15; i++) {
	151	unsigned char opcode;
	152	unsigned char instr_hi;
	153	unsigned char instr_lo;
	154
11a4180c	155	if (instr > (unsigned char *)limit)
1da177e4	156	break;
11a4180c	157	if (probe_kernel_address(instr, opcode))
1da177e4 LT	158	break;
	159
	160	instr_hi = opcode & 0xf0;
	161	instr_lo = opcode & 0x0f;
	162	instr++;
	163
	164	switch (instr_hi) {
	165	case 0x20:
	166	case 0x30:
	167	/* Values 0x26,0x2E,0x36,0x3E are valid x86 prefixes. */
	168	scan_more = ((instr_lo & 7) == 0x6);
	169	break;
	170
	171	case 0x60:
	172	/* 0x64 thru 0x67 are valid prefixes in all modes. */
	173	scan_more = (instr_lo & 0xC) == 0x4;
	174	break;
	175	case 0xF0:
	176	/* 0xF0, 0xF2, and 0xF3 are valid prefixes */
	177	scan_more = !instr_lo \|\| (instr_lo>>1) == 1;
	178	break;
	179	case 0x00:
	180	/* Prefetch instruction is 0x0F0D or 0x0F18 */
	181	scan_more = 0;
11a4180c	182	if (instr > (unsigned char *)limit)
1da177e4	183	break;
11a4180c	184	if (probe_kernel_address(instr, opcode))
1da177e4 LT	185	break;
	186	prefetch = (instr_lo == 0xF) &&
	187	(opcode == 0x0D \|\| opcode == 0x18);
	188	break;
	189	default:
	190	scan_more = 0;
	191	break;
	192	}
	193	}
	194	return prefetch;
	195	}
	196
	197	static inline int is_prefetch(struct pt_regs *regs, unsigned long addr,
	198	unsigned long error_code)
	199	{
	200	if (unlikely(boot_cpu_data.x86_vendor == X86_VENDOR_AMD &&
	201	boot_cpu_data.x86 >= 6)) {
	202	/* Catch an obscure case of prefetch inside an NX page. */
	203	if (nx_enabled && (error_code & 16))
	204	return 0;
	205	return __is_prefetch(regs, addr);
	206	}
	207	return 0;
	208	}
	209
869f96a0 IM	210	static noinline void force_sig_info_fault(int si_signo, int si_code,
	211	unsigned long address, struct task_struct *tsk)
	212	{
	213	siginfo_t info;
	214
	215	info.si_signo = si_signo;
	216	info.si_errno = 0;
	217	info.si_code = si_code;
	218	info.si_addr = (void __user *)address;
	219	force_sig_info(si_signo, &info, tsk);
	220	}
	221
1da177e4 LT	222	fastcall void do_invalid_op(struct pt_regs *, unsigned long);
1da177e4 LT	223
101f12af JB	224	static inline pmd_t vmalloc_sync_one(pgd_t pgd, unsigned long address)
	225	{
	226	unsigned index = pgd_index(address);
	227	pgd_t *pgd_k;
	228	pud_t pud, pud_k;
	229	pmd_t pmd, pmd_k;
	230
	231	pgd += index;
	232	pgd_k = init_mm.pgd + index;
	233
	234	if (!pgd_present(*pgd_k))
	235	return NULL;
	236
	237	/*
	238	* set_pgd(pgd, *pgd_k); here would be useless on PAE
	239	* and redundant with the set_pmd() on non-PAE. As would
	240	* set_pud.
	241	*/
	242
	243	pud = pud_offset(pgd, address);
	244	pud_k = pud_offset(pgd_k, address);
	245	if (!pud_present(*pud_k))
	246	return NULL;
	247
	248	pmd = pmd_offset(pud, address);
	249	pmd_k = pmd_offset(pud_k, address);
	250	if (!pmd_present(*pmd_k))
	251	return NULL;
	252	if (!pmd_present(*pmd))
	253	set_pmd(pmd, *pmd_k);
	254	else
	255	BUG_ON(pmd_page(pmd) != pmd_page(pmd_k));
	256	return pmd_k;
	257	}
	258
	259	/*
	260	* Handle a fault on the vmalloc or module mapping area
	261	*
	262	* This assumes no large pages in there.
	263	*/
	264	static inline int vmalloc_fault(unsigned long address)
	265	{
	266	unsigned long pgd_paddr;
	267	pmd_t *pmd_k;
	268	pte_t *pte_k;
	269	/*
	270	* Synchronize this task's top level page-table
	271	* with the 'reference' page table.
	272	*
	273	* Do _not_ use "current" here. We might be inside
	274	* an interrupt in the middle of a task switch..
	275	*/
	276	pgd_paddr = read_cr3();
	277	pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
	278	if (!pmd_k)
	279	return -1;
	280	pte_k = pte_offset_kernel(pmd_k, address);
	281	if (!pte_present(*pte_k))
	282	return -1;
	283	return 0;
	284	}
	285
1da177e4 LT	286	/*
	287	* This routine handles page faults. It determines the address,
	288	* and the problem, and then passes it off to one of the appropriate
	289	* routines.
	290	*
	291	* error_code:
	292	* bit 0 == 0 means no page found, 1 means protection fault
	293	* bit 1 == 0 means read, 1 means write
	294	* bit 2 == 0 means kernel, 1 means user-mode
101f12af JB	295	* bit 3 == 1 means use of reserved bit detected
101f12af JB	296	* bit 4 == 1 means fault was an instruction fetch
1da177e4	297	*/
3d97ae5b PP	298	fastcall void __kprobes do_page_fault(struct pt_regs *regs,
3d97ae5b PP	299	unsigned long error_code)
1da177e4 LT	300	{
	301	struct task_struct *tsk;
	302	struct mm_struct *mm;
	303	struct vm_area_struct * vma;
	304	unsigned long address;
869f96a0	305	int write, si_code;
1da177e4 LT	306
1da177e4 LT	307	/* get the address */
4bb0d3ec	308	address = read_cr2();
1da177e4	309
1da177e4 LT	310	tsk = current;
1da177e4 LT	311
869f96a0	312	si_code = SEGV_MAPERR;
1da177e4 LT	313
	314	/*
	315	* We fault-in kernel-space virtual memory on-demand. The
	316	* 'reference' page table is init_mm.pgd.
	317	*
	318	* NOTE! We MUST NOT take any locks for this case. We may
	319	* be in an interrupt or a critical region, and should
	320	* only copy the information from the master page table,
	321	* nothing more.
	322	*
	323	* This verifies that the fault happens in kernel space
	324	* (error_code & 4) == 0, and that the fault was not a
101f12af	325	* protection error (error_code & 9) == 0.
1da177e4	326	*/
101f12af JB	327	if (unlikely(address >= TASK_SIZE)) {
	328	if (!(error_code & 0x0000000d) && vmalloc_fault(address) >= 0)
	329	return;
9b355897	330	if (notify_page_fault(regs, error_code) == NOTIFY_STOP)
101f12af JB	331	return;
101f12af JB	332	/*
1da177e4 LT	333	* Don't take the mm semaphore here. If we fixup a prefetch
	334	* fault we could otherwise deadlock.
	335	*/
	336	goto bad_area_nosemaphore;
101f12af JB	337	}
101f12af JB	338
9b355897	339	if (notify_page_fault(regs, error_code) == NOTIFY_STOP)
101f12af JB	340	return;
	341
	342	/* It's safe to allow irq's after cr2 has been saved and the vmalloc
	343	fault has been handled. */
	344	if (regs->eflags & (X86_EFLAGS_IF\|VM_MASK))
	345	local_irq_enable();
1da177e4 LT	346
	347	mm = tsk->mm;
	348
	349	/*
	350	* If we're in an interrupt, have no user context or are running in an
	351	* atomic region then we must not take the fault..
	352	*/
	353	if (in_atomic() \|\| !mm)
	354	goto bad_area_nosemaphore;
	355
	356	/* When running in the kernel we expect faults to occur only to
	357	* addresses in user space. All other faults represent errors in the
	358	* kernel and should generate an OOPS. Unfortunatly, in the case of an
80f7228b	359	* erroneous fault occurring in a code path which already holds mmap_sem
1da177e4 LT	360	* we will deadlock attempting to validate the fault against the
	361	* address space. Luckily the kernel only validly references user
	362	* space from well defined areas of code, which are listed in the
	363	* exceptions table.
	364	*
	365	* As the vast majority of faults will be valid we will only perform
	366	* the source reference check when there is a possibilty of a deadlock.
	367	* Attempt to lock the address space, if we cannot we then validate the
	368	* source. If this is invalid we can skip the address space check,
	369	* thus avoiding the deadlock.
	370	*/
	371	if (!down_read_trylock(&mm->mmap_sem)) {
	372	if ((error_code & 4) == 0 &&
	373	!search_exception_tables(regs->eip))
	374	goto bad_area_nosemaphore;
	375	down_read(&mm->mmap_sem);
	376	}
	377
	378	vma = find_vma(mm, address);
	379	if (!vma)
	380	goto bad_area;
	381	if (vma->vm_start <= address)
	382	goto good_area;
	383	if (!(vma->vm_flags & VM_GROWSDOWN))
	384	goto bad_area;
	385	if (error_code & 4) {
	386	/*
21528454 CE	387	* Accessing the stack below %esp is always a bug.
	388	* The large cushion allows instructions like enter
	389	* and pusha to work. ("enter $65535,$31" pushes
	390	* 32 pointers and then decrements %esp by 65535.)
1da177e4	391	*/
21528454	392	if (address + 65536 + 32 * sizeof(unsigned long) < regs->esp)
1da177e4 LT	393	goto bad_area;
	394	}
	395	if (expand_stack(vma, address))
	396	goto bad_area;
	397	/*
	398	* Ok, we have a good vm_area for this memory access, so
	399	* we can handle it..
	400	*/
	401	good_area:
869f96a0	402	si_code = SEGV_ACCERR;
1da177e4 LT	403	write = 0;
	404	switch (error_code & 3) {
	405	default: /* 3: write, present */
78be3706	406	/* fall through */
1da177e4 LT	407	case 2: /* write, not present */
	408	if (!(vma->vm_flags & VM_WRITE))
	409	goto bad_area;
	410	write++;
	411	break;
	412	case 1: /* read, present */
	413	goto bad_area;
	414	case 0: /* read, not present */
df67b3da	415	if (!(vma->vm_flags & (VM_READ \| VM_EXEC \| VM_WRITE)))
1da177e4 LT	416	goto bad_area;
	417	}
	418
	419	survive:
	420	/*
	421	* If for any reason at all we couldn't handle the fault,
	422	* make sure we exit gracefully rather than endlessly redo
	423	* the fault.
	424	*/
	425	switch (handle_mm_fault(mm, vma, address, write)) {
	426	case VM_FAULT_MINOR:
	427	tsk->min_flt++;
	428	break;
	429	case VM_FAULT_MAJOR:
	430	tsk->maj_flt++;
	431	break;
	432	case VM_FAULT_SIGBUS:
	433	goto do_sigbus;
	434	case VM_FAULT_OOM:
	435	goto out_of_memory;
	436	default:
	437	BUG();
	438	}
	439
	440	/*
	441	* Did it hit the DOS screen memory VA from vm86 mode?
	442	*/
	443	if (regs->eflags & VM_MASK) {
	444	unsigned long bit = (address - 0xA0000) >> PAGE_SHIFT;
	445	if (bit < 32)
	446	tsk->thread.screen_bitmap \|= 1 << bit;
	447	}
	448	up_read(&mm->mmap_sem);
	449	return;
	450
	451	/*
	452	* Something tried to access memory that isn't in our memory map..
	453	* Fix it, but check if it's kernel or user first..
	454	*/
	455	bad_area:
	456	up_read(&mm->mmap_sem);
	457
	458	bad_area_nosemaphore:
	459	/* User mode accesses just cause a SIGSEGV */
	460	if (error_code & 4) {
	461	/*
	462	* Valid to do another page fault here because this one came
	463	* from user space.
	464	*/
	465	if (is_prefetch(regs, address, error_code))
	466	return;
	467
	468	tsk->thread.cr2 = address;
	469	/* Kernel addresses are always protection faults */
	470	tsk->thread.error_code = error_code \| (address >= TASK_SIZE);
	471	tsk->thread.trap_no = 14;
869f96a0	472	force_sig_info_fault(SIGSEGV, si_code, address, tsk);
1da177e4 LT	473	return;
	474	}
	475
	476	#ifdef CONFIG_X86_F00F_BUG
	477	/*
	478	* Pentium F0 0F C7 C8 bug workaround.
	479	*/
	480	if (boot_cpu_data.f00f_bug) {
	481	unsigned long nr;
	482
	483	nr = (address - idt_descr.address) >> 3;
	484
	485	if (nr == 6) {
	486	do_invalid_op(regs, 0);
	487	return;
	488	}
	489	}
	490	#endif
	491
	492	no_context:
	493	/* Are we prepared to handle this kernel fault? */
	494	if (fixup_exception(regs))
	495	return;
	496
	497	/*
	498	* Valid to do another page fault here, because if this fault
	499	* had been triggered by is_prefetch fixup_exception would have
	500	* handled it.
	501	*/
	502	if (is_prefetch(regs, address, error_code))
	503	return;
	504
	505	/*
	506	* Oops. The kernel tried to access some bad page. We'll have to
	507	* terminate things with extreme prejudice.
	508	*/
	509
	510	bust_spinlocks(1);
	511
dd287796	512	if (oops_may_print()) {
28609f6e JB	513	__typeof__(pte_val(__pte(0))) page;
	514
	515	#ifdef CONFIG_X86_PAE
dd287796 AM	516	if (error_code & 16) {
	517	pte_t *pte = lookup_address(address);
	518
	519	if (pte && pte_present(pte) && !pte_exec_kernel(pte))
	520	printk(KERN_CRIT "kernel tried to execute "
	521	"NX-protected page - exploit attempt? "
	522	"(uid: %d)\n", current->uid);
	523	}
28609f6e	524	#endif
dd287796 AM	525	if (address < PAGE_SIZE)
	526	printk(KERN_ALERT "BUG: unable to handle kernel NULL "
	527	"pointer dereference");
	528	else
	529	printk(KERN_ALERT "BUG: unable to handle kernel paging"
	530	" request");
	531	printk(" at virtual address %08lx\n",address);
	532	printk(KERN_ALERT " printing eip:\n");
	533	printk("%08lx\n", regs->eip);
28609f6e JB	534
	535	page = read_cr3();
	536	page = ((__typeof__(page) *) __va(page))[address >> PGDIR_SHIFT];
	537	#ifdef CONFIG_X86_PAE
	538	printk(KERN_ALERT "*pdpt = %016Lx\n", page);
	539	if ((page >> PAGE_SHIFT) < max_low_pfn
	540	&& page & _PAGE_PRESENT) {
	541	page &= PAGE_MASK;
	542	page = ((__typeof__(page) *) __va(page))[(address >> PMD_SHIFT)
	543	& (PTRS_PER_PMD - 1)];
	544	printk(KERN_ALERT "*pde = %016Lx\n", page);
	545	page &= ~_PAGE_NX;
	546	}
	547	#else
dd287796	548	printk(KERN_ALERT "*pde = %08lx\n", page);
1da177e4	549	#endif
28609f6e JB	550
	551	/*
	552	* We must not directly access the pte in the highpte
	553	* case if the page table is located in highmem.
	554	* And let's rather not kmap-atomic the pte, just in case
	555	* it's allocated already.
	556	*/
	557	if ((page >> PAGE_SHIFT) < max_low_pfn
	558	&& (page & _PAGE_PRESENT)) {
	559	page &= PAGE_MASK;
	560	page = ((__typeof__(page) *) __va(page))[(address >> PAGE_SHIFT)
	561	& (PTRS_PER_PTE - 1)];
	562	printk(KERN_ALERT "pte = %0Lx\n", sizeof(page)*2, (u64)page);
	563	}
	564	}
	565
4f339ecb AN	566	tsk->thread.cr2 = address;
	567	tsk->thread.trap_no = 14;
	568	tsk->thread.error_code = error_code;
1da177e4 LT	569	die("Oops", regs, error_code);
	570	bust_spinlocks(0);
	571	do_exit(SIGKILL);
	572
	573	/*
	574	* We ran out of memory, or some other thing happened to us that made
	575	* us unable to handle the page fault gracefully.
	576	*/
	577	out_of_memory:
	578	up_read(&mm->mmap_sem);
f400e198	579	if (is_init(tsk)) {
1da177e4 LT	580	yield();
	581	down_read(&mm->mmap_sem);
	582	goto survive;
	583	}
	584	printk("VM: killing process %s\n", tsk->comm);
	585	if (error_code & 4)
	586	do_exit(SIGKILL);
	587	goto no_context;
	588
	589	do_sigbus:
	590	up_read(&mm->mmap_sem);
	591
	592	/* Kernel mode? Handle exceptions or die */
	593	if (!(error_code & 4))
	594	goto no_context;
	595
	596	/* User space => ok to do another page fault */
	597	if (is_prefetch(regs, address, error_code))
	598	return;
	599
	600	tsk->thread.cr2 = address;
	601	tsk->thread.error_code = error_code;
	602	tsk->thread.trap_no = 14;
869f96a0	603	force_sig_info_fault(SIGBUS, BUS_ADRERR, address, tsk);
101f12af	604	}
1da177e4	605
101f12af JB	606	void vmalloc_sync_all(void)
	607	{
	608	/*
	609	* Note that races in the updates of insync and start aren't
	610	* problematic: insync can only get set bits added, and updates to
	611	* start are only improving performance (without affecting correctness
	612	* if undone).
	613	*/
	614	static DECLARE_BITMAP(insync, PTRS_PER_PGD);
	615	static unsigned long start = TASK_SIZE;
	616	unsigned long address;
1da177e4	617
5311ab62 JF	618	if (SHARED_KERNEL_PMD)
	619	return;
	620
101f12af JB	621	BUILD_BUG_ON(TASK_SIZE & ~PGDIR_MASK);
	622	for (address = start; address >= TASK_SIZE; address += PGDIR_SIZE) {
	623	if (!test_bit(pgd_index(address), insync)) {
	624	unsigned long flags;
	625	struct page *page;
	626
	627	spin_lock_irqsave(&pgd_lock, flags);
	628	for (page = pgd_list; page; page =
	629	(struct page *)page->index)
	630	if (!vmalloc_sync_one(page_address(page),
	631	address)) {
	632	BUG_ON(page != pgd_list);
	633	break;
	634	}
	635	spin_unlock_irqrestore(&pgd_lock, flags);
	636	if (!page)
	637	set_bit(pgd_index(address), insync);
	638	}
	639	if (address == start && test_bit(pgd_index(address), insync))
	640	start = address + PGDIR_SIZE;
1da177e4 LT	641	}
1da177e4 LT	642	}