xref: /linux/tools/testing/vma/include/dup.h (revision eeccf287a2a517954b57cf9d733b3cf5d47afa34)

/* SPDX-License-Identifier: GPL-2.0+ */

#pragma once

/* Forward declarations to avoid header cycle. */
struct vm_area_struct;
static inline void vma_start_write(struct vm_area_struct *vma);

extern const struct vm_operations_struct vma_dummy_vm_ops;
extern unsigned long stack_guard_gap;
extern const struct vm_operations_struct vma_dummy_vm_ops;
extern unsigned long rlimit(unsigned int limit);
struct task_struct *get_current(void);

#define MMF_HAS_MDWE	28
#define current get_current()

/*
 * Define the task command name length as enum, then it can be visible to
 * BPF programs.
 */
enum {
	TASK_COMM_LEN = 16,
};

/* PARTIALLY implemented types. */
struct mm_struct {
	struct maple_tree mm_mt;
	int map_count;			/* number of VMAs */
	unsigned long total_vm;	   /* Total pages mapped */
	unsigned long locked_vm;   /* Pages that have PG_mlocked set */
	unsigned long data_vm;	   /* VM_WRITE & ~VM_SHARED & ~VM_STACK */
	unsigned long exec_vm;	   /* VM_EXEC & ~VM_WRITE & ~VM_STACK */
	unsigned long stack_vm;	   /* VM_STACK */

	unsigned long def_flags;

	mm_flags_t flags; /* Must use mm_flags_* helpers to access */
};
struct address_space {
	struct rb_root_cached	i_mmap;
	unsigned long		flags;
	atomic_t		i_mmap_writable;
};
struct file_operations {
	int (*mmap)(struct file *, struct vm_area_struct *);
	int (*mmap_prepare)(struct vm_area_desc *);
};
struct file {
	struct address_space	*f_mapping;
	const struct file_operations	*f_op;
};
struct anon_vma_chain {
	struct anon_vma *anon_vma;
	struct list_head same_vma;
};
struct task_struct {
	char comm[TASK_COMM_LEN];
	pid_t pid;
	struct mm_struct *mm;

	/* Used for emulating ABI behavior of previous Linux versions: */
	unsigned int			personality;
};

struct kref {
	refcount_t refcount;
};

struct anon_vma_name {
	struct kref kref;
	/* The name needs to be at the end because it is dynamically sized. */
	char name[];
};

/*
 * Contains declarations that are DUPLICATED from kernel source in order to
 * faciliate userland VMA testing.
 *
 * These must be kept in sync with kernel source.
 */

#define VMA_LOCK_OFFSET	0x40000000

typedef struct { unsigned long v; } freeptr_t;

#define VM_NONE		0x00000000

typedef int __bitwise vma_flag_t;

#define ACCESS_PRIVATE(p, member) ((p)->member)

#define DECLARE_VMA_BIT(name, bitnum) \
	VMA_ ## name ## _BIT = ((__force vma_flag_t)bitnum)
#define DECLARE_VMA_BIT_ALIAS(name, aliased) \
	VMA_ ## name ## _BIT = VMA_ ## aliased ## _BIT
enum {
	DECLARE_VMA_BIT(READ, 0),
	DECLARE_VMA_BIT(WRITE, 1),
	DECLARE_VMA_BIT(EXEC, 2),
	DECLARE_VMA_BIT(SHARED, 3),
	/* mprotect() hardcodes VM_MAYREAD >> 4 == VM_READ, and so for r/w/x bits. */
	DECLARE_VMA_BIT(MAYREAD, 4),	/* limits for mprotect() etc. */
	DECLARE_VMA_BIT(MAYWRITE, 5),
	DECLARE_VMA_BIT(MAYEXEC, 6),
	DECLARE_VMA_BIT(MAYSHARE, 7),
	DECLARE_VMA_BIT(GROWSDOWN, 8),	/* general info on the segment */
#ifdef CONFIG_MMU
	DECLARE_VMA_BIT(UFFD_MISSING, 9),/* missing pages tracking */
#else
	/* nommu: R/O MAP_PRIVATE mapping that might overlay a file mapping */
	DECLARE_VMA_BIT(MAYOVERLAY, 9),
#endif /* CONFIG_MMU */
	/* Page-ranges managed without "struct page", just pure PFN */
	DECLARE_VMA_BIT(PFNMAP, 10),
	DECLARE_VMA_BIT(MAYBE_GUARD, 11),
	DECLARE_VMA_BIT(UFFD_WP, 12),	/* wrprotect pages tracking */
	DECLARE_VMA_BIT(LOCKED, 13),
	DECLARE_VMA_BIT(IO, 14),	/* Memory mapped I/O or similar */
	DECLARE_VMA_BIT(SEQ_READ, 15),	/* App will access data sequentially */
	DECLARE_VMA_BIT(RAND_READ, 16),	/* App will not benefit from clustered reads */
	DECLARE_VMA_BIT(DONTCOPY, 17),	/* Do not copy this vma on fork */
	DECLARE_VMA_BIT(DONTEXPAND, 18),/* Cannot expand with mremap() */
	DECLARE_VMA_BIT(LOCKONFAULT, 19),/* Lock pages covered when faulted in */
	DECLARE_VMA_BIT(ACCOUNT, 20),	/* Is a VM accounted object */
	DECLARE_VMA_BIT(NORESERVE, 21),	/* should the VM suppress accounting */
	DECLARE_VMA_BIT(HUGETLB, 22),	/* Huge TLB Page VM */
	DECLARE_VMA_BIT(SYNC, 23),	/* Synchronous page faults */
	DECLARE_VMA_BIT(ARCH_1, 24),	/* Architecture-specific flag */
	DECLARE_VMA_BIT(WIPEONFORK, 25),/* Wipe VMA contents in child. */
	DECLARE_VMA_BIT(DONTDUMP, 26),	/* Do not include in the core dump */
	DECLARE_VMA_BIT(SOFTDIRTY, 27),	/* NOT soft dirty clean area */
	DECLARE_VMA_BIT(MIXEDMAP, 28),	/* Can contain struct page and pure PFN pages */
	DECLARE_VMA_BIT(HUGEPAGE, 29),	/* MADV_HUGEPAGE marked this vma */
	DECLARE_VMA_BIT(NOHUGEPAGE, 30),/* MADV_NOHUGEPAGE marked this vma */
	DECLARE_VMA_BIT(MERGEABLE, 31),	/* KSM may merge identical pages */
	/* These bits are reused, we define specific uses below. */
	DECLARE_VMA_BIT(HIGH_ARCH_0, 32),
	DECLARE_VMA_BIT(HIGH_ARCH_1, 33),
	DECLARE_VMA_BIT(HIGH_ARCH_2, 34),
	DECLARE_VMA_BIT(HIGH_ARCH_3, 35),
	DECLARE_VMA_BIT(HIGH_ARCH_4, 36),
	DECLARE_VMA_BIT(HIGH_ARCH_5, 37),
	DECLARE_VMA_BIT(HIGH_ARCH_6, 38),
	/*
	 * This flag is used to connect VFIO to arch specific KVM code. It
	 * indicates that the memory under this VMA is safe for use with any
	 * non-cachable memory type inside KVM. Some VFIO devices, on some
	 * platforms, are thought to be unsafe and can cause machine crashes
	 * if KVM does not lock down the memory type.
	 */
	DECLARE_VMA_BIT(ALLOW_ANY_UNCACHED, 39),
#ifdef CONFIG_PPC32
	DECLARE_VMA_BIT_ALIAS(DROPPABLE, ARCH_1),
#else
	DECLARE_VMA_BIT(DROPPABLE, 40),
#endif
	DECLARE_VMA_BIT(UFFD_MINOR, 41),
	DECLARE_VMA_BIT(SEALED, 42),
	/* Flags that reuse flags above. */
	DECLARE_VMA_BIT_ALIAS(PKEY_BIT0, HIGH_ARCH_0),
	DECLARE_VMA_BIT_ALIAS(PKEY_BIT1, HIGH_ARCH_1),
	DECLARE_VMA_BIT_ALIAS(PKEY_BIT2, HIGH_ARCH_2),
	DECLARE_VMA_BIT_ALIAS(PKEY_BIT3, HIGH_ARCH_3),
	DECLARE_VMA_BIT_ALIAS(PKEY_BIT4, HIGH_ARCH_4),
#if defined(CONFIG_X86_USER_SHADOW_STACK)
	/*
	 * VM_SHADOW_STACK should not be set with VM_SHARED because of lack of
	 * support core mm.
	 *
	 * These VMAs will get a single end guard page. This helps userspace
	 * protect itself from attacks. A single page is enough for current
	 * shadow stack archs (x86). See the comments near alloc_shstk() in
	 * arch/x86/kernel/shstk.c for more details on the guard size.
	 */
	DECLARE_VMA_BIT_ALIAS(SHADOW_STACK, HIGH_ARCH_5),
#elif defined(CONFIG_ARM64_GCS)
	/*
	 * arm64's Guarded Control Stack implements similar functionality and
	 * has similar constraints to shadow stacks.
	 */
	DECLARE_VMA_BIT_ALIAS(SHADOW_STACK, HIGH_ARCH_6),
#endif
	DECLARE_VMA_BIT_ALIAS(SAO, ARCH_1),		/* Strong Access Ordering (powerpc) */
	DECLARE_VMA_BIT_ALIAS(GROWSUP, ARCH_1),		/* parisc */
	DECLARE_VMA_BIT_ALIAS(SPARC_ADI, ARCH_1),	/* sparc64 */
	DECLARE_VMA_BIT_ALIAS(ARM64_BTI, ARCH_1),	/* arm64 */
	DECLARE_VMA_BIT_ALIAS(ARCH_CLEAR, ARCH_1),	/* sparc64, arm64 */
	DECLARE_VMA_BIT_ALIAS(MAPPED_COPY, ARCH_1),	/* !CONFIG_MMU */
	DECLARE_VMA_BIT_ALIAS(MTE, HIGH_ARCH_4),	/* arm64 */
	DECLARE_VMA_BIT_ALIAS(MTE_ALLOWED, HIGH_ARCH_5),/* arm64 */
#ifdef CONFIG_STACK_GROWSUP
	DECLARE_VMA_BIT_ALIAS(STACK, GROWSUP),
	DECLARE_VMA_BIT_ALIAS(STACK_EARLY, GROWSDOWN),
#else
	DECLARE_VMA_BIT_ALIAS(STACK, GROWSDOWN),
#endif
};

#define INIT_VM_FLAG(name) BIT((__force int) VMA_ ## name ## _BIT)
#define VM_READ		INIT_VM_FLAG(READ)
#define VM_WRITE	INIT_VM_FLAG(WRITE)
#define VM_EXEC		INIT_VM_FLAG(EXEC)
#define VM_SHARED	INIT_VM_FLAG(SHARED)
#define VM_MAYREAD	INIT_VM_FLAG(MAYREAD)
#define VM_MAYWRITE	INIT_VM_FLAG(MAYWRITE)
#define VM_MAYEXEC	INIT_VM_FLAG(MAYEXEC)
#define VM_MAYSHARE	INIT_VM_FLAG(MAYSHARE)
#define VM_GROWSDOWN	INIT_VM_FLAG(GROWSDOWN)
#ifdef CONFIG_MMU
#define VM_UFFD_MISSING	INIT_VM_FLAG(UFFD_MISSING)
#else
#define VM_UFFD_MISSING	VM_NONE
#define VM_MAYOVERLAY	INIT_VM_FLAG(MAYOVERLAY)
#endif
#define VM_PFNMAP	INIT_VM_FLAG(PFNMAP)
#define VM_MAYBE_GUARD	INIT_VM_FLAG(MAYBE_GUARD)
#define VM_UFFD_WP	INIT_VM_FLAG(UFFD_WP)
#define VM_LOCKED	INIT_VM_FLAG(LOCKED)
#define VM_IO		INIT_VM_FLAG(IO)
#define VM_SEQ_READ	INIT_VM_FLAG(SEQ_READ)
#define VM_RAND_READ	INIT_VM_FLAG(RAND_READ)
#define VM_DONTCOPY	INIT_VM_FLAG(DONTCOPY)
#define VM_DONTEXPAND	INIT_VM_FLAG(DONTEXPAND)
#define VM_LOCKONFAULT	INIT_VM_FLAG(LOCKONFAULT)
#define VM_ACCOUNT	INIT_VM_FLAG(ACCOUNT)
#define VM_NORESERVE	INIT_VM_FLAG(NORESERVE)
#define VM_HUGETLB	INIT_VM_FLAG(HUGETLB)
#define VM_SYNC		INIT_VM_FLAG(SYNC)
#define VM_ARCH_1	INIT_VM_FLAG(ARCH_1)
#define VM_WIPEONFORK	INIT_VM_FLAG(WIPEONFORK)
#define VM_DONTDUMP	INIT_VM_FLAG(DONTDUMP)
#ifdef CONFIG_MEM_SOFT_DIRTY
#define VM_SOFTDIRTY	INIT_VM_FLAG(SOFTDIRTY)
#else
#define VM_SOFTDIRTY	VM_NONE
#endif
#define VM_MIXEDMAP	INIT_VM_FLAG(MIXEDMAP)
#define VM_HUGEPAGE	INIT_VM_FLAG(HUGEPAGE)
#define VM_NOHUGEPAGE	INIT_VM_FLAG(NOHUGEPAGE)
#define VM_MERGEABLE	INIT_VM_FLAG(MERGEABLE)
#define VM_STACK	INIT_VM_FLAG(STACK)
#ifdef CONFIG_STACK_GROWS_UP
#define VM_STACK_EARLY	INIT_VM_FLAG(STACK_EARLY)
#else
#define VM_STACK_EARLY	VM_NONE
#endif
#ifdef CONFIG_ARCH_HAS_PKEYS
#define VM_PKEY_SHIFT ((__force int)VMA_HIGH_ARCH_0_BIT)
/* Despite the naming, these are FLAGS not bits. */
#define VM_PKEY_BIT0 INIT_VM_FLAG(PKEY_BIT0)
#define VM_PKEY_BIT1 INIT_VM_FLAG(PKEY_BIT1)
#define VM_PKEY_BIT2 INIT_VM_FLAG(PKEY_BIT2)
#if CONFIG_ARCH_PKEY_BITS > 3
#define VM_PKEY_BIT3 INIT_VM_FLAG(PKEY_BIT3)
#else
#define VM_PKEY_BIT3  VM_NONE
#endif /* CONFIG_ARCH_PKEY_BITS > 3 */
#if CONFIG_ARCH_PKEY_BITS > 4
#define VM_PKEY_BIT4 INIT_VM_FLAG(PKEY_BIT4)
#else
#define VM_PKEY_BIT4  VM_NONE
#endif /* CONFIG_ARCH_PKEY_BITS > 4 */
#endif /* CONFIG_ARCH_HAS_PKEYS */
#if defined(CONFIG_X86_USER_SHADOW_STACK) || defined(CONFIG_ARM64_GCS)
#define VM_SHADOW_STACK	INIT_VM_FLAG(SHADOW_STACK)
#else
#define VM_SHADOW_STACK	VM_NONE
#endif
#if defined(CONFIG_PPC64)
#define VM_SAO		INIT_VM_FLAG(SAO)
#elif defined(CONFIG_PARISC)
#define VM_GROWSUP	INIT_VM_FLAG(GROWSUP)
#elif defined(CONFIG_SPARC64)
#define VM_SPARC_ADI	INIT_VM_FLAG(SPARC_ADI)
#define VM_ARCH_CLEAR	INIT_VM_FLAG(ARCH_CLEAR)
#elif defined(CONFIG_ARM64)
#define VM_ARM64_BTI	INIT_VM_FLAG(ARM64_BTI)
#define VM_ARCH_CLEAR	INIT_VM_FLAG(ARCH_CLEAR)
#elif !defined(CONFIG_MMU)
#define VM_MAPPED_COPY	INIT_VM_FLAG(MAPPED_COPY)
#endif
#ifndef VM_GROWSUP
#define VM_GROWSUP	VM_NONE
#endif
#ifdef CONFIG_ARM64_MTE
#define VM_MTE		INIT_VM_FLAG(MTE)
#define VM_MTE_ALLOWED	INIT_VM_FLAG(MTE_ALLOWED)
#else
#define VM_MTE		VM_NONE
#define VM_MTE_ALLOWED	VM_NONE
#endif
#ifdef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR
#define VM_UFFD_MINOR	INIT_VM_FLAG(UFFD_MINOR)
#else
#define VM_UFFD_MINOR	VM_NONE
#endif
#ifdef CONFIG_64BIT
#define VM_ALLOW_ANY_UNCACHED	INIT_VM_FLAG(ALLOW_ANY_UNCACHED)
#define VM_SEALED		INIT_VM_FLAG(SEALED)
#else
#define VM_ALLOW_ANY_UNCACHED	VM_NONE
#define VM_SEALED		VM_NONE
#endif
#if defined(CONFIG_64BIT) || defined(CONFIG_PPC32)
#define VM_DROPPABLE		INIT_VM_FLAG(DROPPABLE)
#else
#define VM_DROPPABLE		VM_NONE
#endif

/* Bits set in the VMA until the stack is in its final location */
#define VM_STACK_INCOMPLETE_SETUP (VM_RAND_READ | VM_SEQ_READ | VM_STACK_EARLY)

#define TASK_EXEC ((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0)

/* Common data flag combinations */
#define VM_DATA_FLAGS_TSK_EXEC	(VM_READ | VM_WRITE | TASK_EXEC | \
				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)
#define VM_DATA_FLAGS_NON_EXEC	(VM_READ | VM_WRITE | VM_MAYREAD | \
				 VM_MAYWRITE | VM_MAYEXEC)
#define VM_DATA_FLAGS_EXEC	(VM_READ | VM_WRITE | VM_EXEC | \
				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)

#ifndef VM_DATA_DEFAULT_FLAGS		/* arch can override this */
#define VM_DATA_DEFAULT_FLAGS  VM_DATA_FLAGS_EXEC
#endif

#ifndef VM_STACK_DEFAULT_FLAGS		/* arch can override this */
#define VM_STACK_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS
#endif

#define VM_STARTGAP_FLAGS (VM_GROWSDOWN | VM_SHADOW_STACK)

#define VM_STACK_FLAGS	(VM_STACK | VM_STACK_DEFAULT_FLAGS | VM_ACCOUNT)

/* VMA basic access permission flags */
#define VM_ACCESS_FLAGS (VM_READ | VM_WRITE | VM_EXEC)

/*
 * Special vmas that are non-mergable, non-mlock()able.
 */
#define VM_SPECIAL (VM_IO | VM_DONTEXPAND | VM_PFNMAP | VM_MIXEDMAP)

#define DEFAULT_MAP_WINDOW	((1UL << 47) - PAGE_SIZE)
#define TASK_SIZE_LOW		DEFAULT_MAP_WINDOW
#define TASK_SIZE_MAX		DEFAULT_MAP_WINDOW
#define STACK_TOP		TASK_SIZE_LOW
#define STACK_TOP_MAX		TASK_SIZE_MAX

/* This mask represents all the VMA flag bits used by mlock */
#define VM_LOCKED_MASK	(VM_LOCKED | VM_LOCKONFAULT)

#define TASK_EXEC ((current->personality & READ_IMPLIES_EXEC) ? VM_EXEC : 0)

#define VM_DATA_FLAGS_TSK_EXEC	(VM_READ | VM_WRITE | TASK_EXEC | \
				 VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC)

#define RLIMIT_STACK		3	/* max stack size */
#define RLIMIT_MEMLOCK		8	/* max locked-in-memory address space */

#define CAP_IPC_LOCK         14

#define VM_STICKY (VM_SOFTDIRTY | VM_MAYBE_GUARD)

#define VM_IGNORE_MERGE VM_STICKY

#define VM_COPY_ON_FORK (VM_PFNMAP | VM_MIXEDMAP | VM_UFFD_WP | VM_MAYBE_GUARD)

#define pgprot_val(x)		((x).pgprot)
#define __pgprot(x)		((pgprot_t) { (x) } )

#define for_each_vma(__vmi, __vma)					\
	while (((__vma) = vma_next(&(__vmi))) != NULL)

/* The MM code likes to work with exclusive end addresses */
#define for_each_vma_range(__vmi, __vma, __end)				\
	while (((__vma) = vma_find(&(__vmi), (__end))) != NULL)

#define offset_in_page(p)	((unsigned long)(p) & ~PAGE_MASK)

#define PHYS_PFN(x)	((unsigned long)((x) >> PAGE_SHIFT))

#define test_and_set_bit(nr, addr) __test_and_set_bit(nr, addr)
#define test_and_clear_bit(nr, addr) __test_and_clear_bit(nr, addr)

#define AS_MM_ALL_LOCKS 2

#define swap(a, b) \
	do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)

/*
 * Flags for bug emulation.
 *
 * These occupy the top three bytes.
 */
enum {
	READ_IMPLIES_EXEC =	0x0400000,
};

struct vma_iterator {
	struct ma_state mas;
};

#define VMA_ITERATOR(name, __mm, __addr)				\
	struct vma_iterator name = {					\
		.mas = {						\
			.tree = &(__mm)->mm_mt,				\
			.index = __addr,				\
			.node = NULL,					\
			.status = ma_start,				\
		},							\
	}

#define DEFINE_MUTEX(mutexname) \
	struct mutex mutexname = {}

#define DECLARE_BITMAP(name, bits) \
	unsigned long name[BITS_TO_LONGS(bits)]

#define EMPTY_VMA_FLAGS ((vma_flags_t){ })

/* What action should be taken after an .mmap_prepare call is complete? */
enum mmap_action_type {
	MMAP_NOTHING,		/* Mapping is complete, no further action. */
	MMAP_REMAP_PFN,		/* Remap PFN range. */
	MMAP_IO_REMAP_PFN,	/* I/O remap PFN range. */
};

/*
 * Describes an action an mmap_prepare hook can instruct to be taken to complete
 * the mapping of a VMA. Specified in vm_area_desc.
 */
struct mmap_action {
	union {
		/* Remap range. */
		struct {
			unsigned long start;
			unsigned long start_pfn;
			unsigned long size;
			pgprot_t pgprot;
		} remap;
	};
	enum mmap_action_type type;

	/*
	 * If specified, this hook is invoked after the selected action has been
	 * successfully completed. Note that the VMA write lock still held.
	 *
	 * The absolute minimum ought to be done here.
	 *
	 * Returns 0 on success, or an error code.
	 */
	int (*success_hook)(const struct vm_area_struct *vma);

	/*
	 * If specified, this hook is invoked when an error occurred when
	 * attempting the selection action.
	 *
	 * The hook can return an error code in order to filter the error, but
	 * it is not valid to clear the error here.
	 */
	int (*error_hook)(int err);

	/*
	 * This should be set in rare instances where the operation required
	 * that the rmap should not be able to access the VMA until
	 * completely set up.
	 */
	bool hide_from_rmap_until_complete :1;
};

/* Operations which modify VMAs. */
enum vma_operation {
	VMA_OP_SPLIT,
	VMA_OP_MERGE_UNFAULTED,
	VMA_OP_REMAP,
	VMA_OP_FORK,
};

/*
 * Describes a VMA that is about to be mmap()'ed. Drivers may choose to
 * manipulate mutable fields which will cause those fields to be updated in the
 * resultant VMA.
 *
 * Helper functions are not required for manipulating any field.
 */
struct vm_area_desc {
	/* Immutable state. */
	const struct mm_struct *const mm;
	struct file *const file; /* May vary from vm_file in stacked callers. */
	unsigned long start;
	unsigned long end;

	/* Mutable fields. Populated with initial state. */
	pgoff_t pgoff;
	struct file *vm_file;
	union {
		vm_flags_t vm_flags;
		vma_flags_t vma_flags;
	};
	pgprot_t page_prot;

	/* Write-only fields. */
	const struct vm_operations_struct *vm_ops;
	void *private_data;

	/* Take further action? */
	struct mmap_action action;
};

struct vm_area_struct {
	/* The first cache line has the info for VMA tree walking. */

	union {
		struct {
			/* VMA covers [vm_start; vm_end) addresses within mm */
			unsigned long vm_start;
			unsigned long vm_end;
		};
		freeptr_t vm_freeptr; /* Pointer used by SLAB_TYPESAFE_BY_RCU */
	};

	struct mm_struct *vm_mm;	/* The address space we belong to. */
	pgprot_t vm_page_prot;          /* Access permissions of this VMA. */

	/*
	 * Flags, see mm.h.
	 * To modify use vm_flags_{init|reset|set|clear|mod} functions.
	 */
	union {
		const vm_flags_t vm_flags;
		vma_flags_t flags;
	};

#ifdef CONFIG_PER_VMA_LOCK
	/*
	 * Can only be written (using WRITE_ONCE()) while holding both:
	 *  - mmap_lock (in write mode)
	 *  - vm_refcnt bit at VMA_LOCK_OFFSET is set
	 * Can be read reliably while holding one of:
	 *  - mmap_lock (in read or write mode)
	 *  - vm_refcnt bit at VMA_LOCK_OFFSET is set or vm_refcnt > 1
	 * Can be read unreliably (using READ_ONCE()) for pessimistic bailout
	 * while holding nothing (except RCU to keep the VMA struct allocated).
	 *
	 * This sequence counter is explicitly allowed to overflow; sequence
	 * counter reuse can only lead to occasional unnecessary use of the
	 * slowpath.
	 */
	unsigned int vm_lock_seq;
#endif

	/*
	 * A file's MAP_PRIVATE vma can be in both i_mmap tree and anon_vma
	 * list, after a COW of one of the file pages.	A MAP_SHARED vma
	 * can only be in the i_mmap tree.  An anonymous MAP_PRIVATE, stack
	 * or brk vma (with NULL file) can only be in an anon_vma list.
	 */
	struct list_head anon_vma_chain; /* Serialized by mmap_lock &
					  * page_table_lock */
	struct anon_vma *anon_vma;	/* Serialized by page_table_lock */

	/* Function pointers to deal with this struct. */
	const struct vm_operations_struct *vm_ops;

	/* Information about our backing store: */
	unsigned long vm_pgoff;		/* Offset (within vm_file) in PAGE_SIZE
					   units */
	struct file * vm_file;		/* File we map to (can be NULL). */
	void * vm_private_data;		/* was vm_pte (shared mem) */

#ifdef CONFIG_SWAP
	atomic_long_t swap_readahead_info;
#endif
#ifndef CONFIG_MMU
	struct vm_region *vm_region;	/* NOMMU mapping region */
#endif
#ifdef CONFIG_NUMA
	struct mempolicy *vm_policy;	/* NUMA policy for the VMA */
#endif
#ifdef CONFIG_NUMA_BALANCING
	struct vma_numab_state *numab_state;	/* NUMA Balancing state */
#endif
#ifdef CONFIG_PER_VMA_LOCK
	/* Unstable RCU readers are allowed to read this. */
	refcount_t vm_refcnt;
#endif
	/*
	 * For areas with an address space and backing store,
	 * linkage into the address_space->i_mmap interval tree.
	 *
	 */
	struct {
		struct rb_node rb;
		unsigned long rb_subtree_last;
	} shared;
#ifdef CONFIG_ANON_VMA_NAME
	/*
	 * For private and shared anonymous mappings, a pointer to a null
	 * terminated string containing the name given to the vma, or NULL if
	 * unnamed. Serialized by mmap_lock. Use anon_vma_name to access.
	 */
	struct anon_vma_name *anon_name;
#endif
	struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
} __randomize_layout;

struct vm_operations_struct {
	void (*open)(struct vm_area_struct * area);
	/**
	 * @close: Called when the VMA is being removed from the MM.
	 * Context: User context.  May sleep.  Caller holds mmap_lock.
	 */
	void (*close)(struct vm_area_struct * area);
	/* Called any time before splitting to check if it's allowed */
	int (*may_split)(struct vm_area_struct *area, unsigned long addr);
	int (*mremap)(struct vm_area_struct *area);
	/*
	 * Called by mprotect() to make driver-specific permission
	 * checks before mprotect() is finalised.   The VMA must not
	 * be modified.  Returns 0 if mprotect() can proceed.
	 */
	int (*mprotect)(struct vm_area_struct *vma, unsigned long start,
			unsigned long end, unsigned long newflags);
	vm_fault_t (*fault)(struct vm_fault *vmf);
	vm_fault_t (*huge_fault)(struct vm_fault *vmf, unsigned int order);
	vm_fault_t (*map_pages)(struct vm_fault *vmf,
			pgoff_t start_pgoff, pgoff_t end_pgoff);
	unsigned long (*pagesize)(struct vm_area_struct * area);

	/* notification that a previously read-only page is about to become
	 * writable, if an error is returned it will cause a SIGBUS */
	vm_fault_t (*page_mkwrite)(struct vm_fault *vmf);

	/* same as page_mkwrite when using VM_PFNMAP|VM_MIXEDMAP */
	vm_fault_t (*pfn_mkwrite)(struct vm_fault *vmf);

	/* called by access_process_vm when get_user_pages() fails, typically
	 * for use by special VMAs. See also generic_access_phys() for a generic
	 * implementation useful for any iomem mapping.
	 */
	int (*access)(struct vm_area_struct *vma, unsigned long addr,
		      void *buf, int len, int write);

	/* Called by the /proc/PID/maps code to ask the vma whether it
	 * has a special name.  Returning non-NULL will also cause this
	 * vma to be dumped unconditionally. */
	const char *(*name)(struct vm_area_struct *vma);

#ifdef CONFIG_NUMA
	/*
	 * set_policy() op must add a reference to any non-NULL @new mempolicy
	 * to hold the policy upon return.  Caller should pass NULL @new to
	 * remove a policy and fall back to surrounding context--i.e. do not
	 * install a MPOL_DEFAULT policy, nor the task or system default
	 * mempolicy.
	 */
	int (*set_policy)(struct vm_area_struct *vma, struct mempolicy *new);

	/*
	 * get_policy() op must add reference [mpol_get()] to any policy at
	 * (vma,addr) marked as MPOL_SHARED.  The shared policy infrastructure
	 * in mm/mempolicy.c will do this automatically.
	 * get_policy() must NOT add a ref if the policy at (vma,addr) is not
	 * marked as MPOL_SHARED. vma policies are protected by the mmap_lock.
	 * If no [shared/vma] mempolicy exists at the addr, get_policy() op
	 * must return NULL--i.e., do not "fallback" to task or system default
	 * policy.
	 */
	struct mempolicy *(*get_policy)(struct vm_area_struct *vma,
					unsigned long addr, pgoff_t *ilx);
#endif
#ifdef CONFIG_FIND_NORMAL_PAGE
	/*
	 * Called by vm_normal_page() for special PTEs in @vma at @addr. This
	 * allows for returning a "normal" page from vm_normal_page() even
	 * though the PTE indicates that the "struct page" either does not exist
	 * or should not be touched: "special".
	 *
	 * Do not add new users: this really only works when a "normal" page
	 * was mapped, but then the PTE got changed to something weird (+
	 * marked special) that would not make pte_pfn() identify the originally
	 * inserted page.
	 */
	struct page *(*find_normal_page)(struct vm_area_struct *vma,
					 unsigned long addr);
#endif /* CONFIG_FIND_NORMAL_PAGE */
};

struct vm_unmapped_area_info {
#define VM_UNMAPPED_AREA_TOPDOWN 1
	unsigned long flags;
	unsigned long length;
	unsigned long low_limit;
	unsigned long high_limit;
	unsigned long align_mask;
	unsigned long align_offset;
	unsigned long start_gap;
};

struct pagetable_move_control {
	struct vm_area_struct *old; /* Source VMA. */
	struct vm_area_struct *new; /* Destination VMA. */
	unsigned long old_addr; /* Address from which the move begins. */
	unsigned long old_end; /* Exclusive address at which old range ends. */
	unsigned long new_addr; /* Address to move page tables to. */
	unsigned long len_in; /* Bytes to remap specified by user. */

	bool need_rmap_locks; /* Do rmap locks need to be taken? */
	bool for_stack; /* Is this an early temp stack being moved? */
};

#define PAGETABLE_MOVE(name, old_, new_, old_addr_, new_addr_, len_)	\
	struct pagetable_move_control name = {				\
		.old = old_,						\
		.new = new_,						\
		.old_addr = old_addr_,					\
		.old_end = (old_addr_) + (len_),			\
		.new_addr = new_addr_,					\
		.len_in = len_,						\
	}

static inline void vma_iter_invalidate(struct vma_iterator *vmi)
{
	mas_pause(&vmi->mas);
}

static inline pgprot_t pgprot_modify(pgprot_t oldprot, pgprot_t newprot)
{
	return __pgprot(pgprot_val(oldprot) | pgprot_val(newprot));
}

static inline pgprot_t vm_get_page_prot(vm_flags_t vm_flags)
{
	return __pgprot(vm_flags);
}

static inline bool mm_flags_test(int flag, const struct mm_struct *mm)
{
	return test_bit(flag, ACCESS_PRIVATE(&mm->flags, __mm_flags));
}

/*
 * Copy value to the first system word of VMA flags, non-atomically.
 *
 * IMPORTANT: This does not overwrite bytes past the first system word. The
 * caller must account for this.
 */
static inline void vma_flags_overwrite_word(vma_flags_t *flags, unsigned long value)
{
	*ACCESS_PRIVATE(flags, __vma_flags) = value;
}

/*
 * Copy value to the first system word of VMA flags ONCE, non-atomically.
 *
 * IMPORTANT: This does not overwrite bytes past the first system word. The
 * caller must account for this.
 */
static inline void vma_flags_overwrite_word_once(vma_flags_t *flags, unsigned long value)
{
	unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);

	WRITE_ONCE(*bitmap, value);
}

/* Update the first system word of VMA flags setting bits, non-atomically. */
static inline void vma_flags_set_word(vma_flags_t *flags, unsigned long value)
{
	unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);

	*bitmap |= value;
}

/* Update the first system word of VMA flags clearing bits, non-atomically. */
static inline void vma_flags_clear_word(vma_flags_t *flags, unsigned long value)
{
	unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);

	*bitmap &= ~value;
}

static inline void vma_flags_clear_all(vma_flags_t *flags)
{
	bitmap_zero(ACCESS_PRIVATE(flags, __vma_flags), NUM_VMA_FLAG_BITS);
}

static inline void vma_flag_set(vma_flags_t *flags, vma_flag_t bit)
{
	unsigned long *bitmap = ACCESS_PRIVATE(flags, __vma_flags);

	__set_bit((__force int)bit, bitmap);
}

/* Use when VMA is not part of the VMA tree and needs no locking */
static inline void vm_flags_init(struct vm_area_struct *vma,
				 vm_flags_t flags)
{
	vma_flags_clear_all(&vma->flags);
	vma_flags_overwrite_word(&vma->flags, flags);
}

/*
 * Use when VMA is part of the VMA tree and modifications need coordination
 * Note: vm_flags_reset and vm_flags_reset_once do not lock the vma and
 * it should be locked explicitly beforehand.
 */
static inline void vm_flags_reset(struct vm_area_struct *vma,
				  vm_flags_t flags)
{
	vma_assert_write_locked(vma);
	vm_flags_init(vma, flags);
}

static inline void vm_flags_reset_once(struct vm_area_struct *vma,
				       vm_flags_t flags)
{
	vma_assert_write_locked(vma);
	/*
	 * The user should only be interested in avoiding reordering of
	 * assignment to the first word.
	 */
	vma_flags_clear_all(&vma->flags);
	vma_flags_overwrite_word_once(&vma->flags, flags);
}

static inline void vm_flags_set(struct vm_area_struct *vma,
				vm_flags_t flags)
{
	vma_start_write(vma);
	vma_flags_set_word(&vma->flags, flags);
}

static inline void vm_flags_clear(struct vm_area_struct *vma,
				  vm_flags_t flags)
{
	vma_start_write(vma);
	vma_flags_clear_word(&vma->flags, flags);
}

static inline vma_flags_t __mk_vma_flags(size_t count, const vma_flag_t *bits);

#define mk_vma_flags(...) __mk_vma_flags(COUNT_ARGS(__VA_ARGS__), \
					 (const vma_flag_t []){__VA_ARGS__})

static __always_inline bool vma_flags_test_mask(const vma_flags_t *flags,
		vma_flags_t to_test)
{
	const unsigned long *bitmap = flags->__vma_flags;
	const unsigned long *bitmap_to_test = to_test.__vma_flags;

	return bitmap_intersects(bitmap_to_test, bitmap, NUM_VMA_FLAG_BITS);
}

#define vma_flags_test(flags, ...) \
	vma_flags_test_mask(flags, mk_vma_flags(__VA_ARGS__))

static __always_inline bool vma_flags_test_all_mask(const vma_flags_t *flags,
		vma_flags_t to_test)
{
	const unsigned long *bitmap = flags->__vma_flags;
	const unsigned long *bitmap_to_test = to_test.__vma_flags;

	return bitmap_subset(bitmap_to_test, bitmap, NUM_VMA_FLAG_BITS);
}

#define vma_flags_test_all(flags, ...) \
	vma_flags_test_all_mask(flags, mk_vma_flags(__VA_ARGS__))

static __always_inline void vma_flags_set_mask(vma_flags_t *flags, vma_flags_t to_set)
{
	unsigned long *bitmap = flags->__vma_flags;
	const unsigned long *bitmap_to_set = to_set.__vma_flags;

	bitmap_or(bitmap, bitmap, bitmap_to_set, NUM_VMA_FLAG_BITS);
}

#define vma_flags_set(flags, ...) \
	vma_flags_set_mask(flags, mk_vma_flags(__VA_ARGS__))

static __always_inline void vma_flags_clear_mask(vma_flags_t *flags, vma_flags_t to_clear)
{
	unsigned long *bitmap = flags->__vma_flags;
	const unsigned long *bitmap_to_clear = to_clear.__vma_flags;

	bitmap_andnot(bitmap, bitmap, bitmap_to_clear, NUM_VMA_FLAG_BITS);
}

#define vma_flags_clear(flags, ...) \
	vma_flags_clear_mask(flags, mk_vma_flags(__VA_ARGS__))

static inline bool vma_test_all_flags_mask(const struct vm_area_struct *vma,
					   vma_flags_t flags)
{
	return vma_flags_test_all_mask(&vma->flags, flags);
}

#define vma_test_all_flags(vma, ...) \
	vma_test_all_flags_mask(vma, mk_vma_flags(__VA_ARGS__))

static inline bool is_shared_maywrite_vm_flags(vm_flags_t vm_flags)
{
	return (vm_flags & (VM_SHARED | VM_MAYWRITE)) ==
		(VM_SHARED | VM_MAYWRITE);
}

static inline void vma_set_flags_mask(struct vm_area_struct *vma,
				      vma_flags_t flags)
{
	vma_flags_set_mask(&vma->flags, flags);
}

#define vma_set_flags(vma, ...) \
	vma_set_flags_mask(vma, mk_vma_flags(__VA_ARGS__))

static inline bool vma_desc_test_flags_mask(const struct vm_area_desc *desc,
					    vma_flags_t flags)
{
	return vma_flags_test_mask(&desc->vma_flags, flags);
}

#define vma_desc_test_flags(desc, ...) \
	vma_desc_test_flags_mask(desc, mk_vma_flags(__VA_ARGS__))

static inline void vma_desc_set_flags_mask(struct vm_area_desc *desc,
					   vma_flags_t flags)
{
	vma_flags_set_mask(&desc->vma_flags, flags);
}

#define vma_desc_set_flags(desc, ...) \
	vma_desc_set_flags_mask(desc, mk_vma_flags(__VA_ARGS__))

static inline void vma_desc_clear_flags_mask(struct vm_area_desc *desc,
					     vma_flags_t flags)
{
	vma_flags_clear_mask(&desc->vma_flags, flags);
}

#define vma_desc_clear_flags(desc, ...) \
	vma_desc_clear_flags_mask(desc, mk_vma_flags(__VA_ARGS__))

static inline bool is_shared_maywrite(const vma_flags_t *flags)
{
	return vma_flags_test_all(flags, VMA_SHARED_BIT, VMA_MAYWRITE_BIT);
}

static inline bool vma_is_shared_maywrite(struct vm_area_struct *vma)
{
	return is_shared_maywrite(&vma->flags);
}

static inline struct vm_area_struct *vma_next(struct vma_iterator *vmi)
{
	/*
	 * Uses mas_find() to get the first VMA when the iterator starts.
	 * Calling mas_next() could skip the first entry.
	 */
	return mas_find(&vmi->mas, ULONG_MAX);
}

/*
 * WARNING: to avoid racing with vma_mark_attached()/vma_mark_detached(), these
 * assertions should be made either under mmap_write_lock or when the object
 * has been isolated under mmap_write_lock, ensuring no competing writers.
 */
static inline void vma_assert_attached(struct vm_area_struct *vma)
{
	WARN_ON_ONCE(!refcount_read(&vma->vm_refcnt));
}

static inline void vma_assert_detached(struct vm_area_struct *vma)
{
	WARN_ON_ONCE(refcount_read(&vma->vm_refcnt));
}

static inline void vma_assert_write_locked(struct vm_area_struct *);
static inline void vma_mark_attached(struct vm_area_struct *vma)
{
	vma_assert_write_locked(vma);
	vma_assert_detached(vma);
	refcount_set_release(&vma->vm_refcnt, 1);
}

static inline void vma_mark_detached(struct vm_area_struct *vma)
{
	vma_assert_write_locked(vma);
	vma_assert_attached(vma);
	/* We are the only writer, so no need to use vma_refcount_put(). */
	if (unlikely(!refcount_dec_and_test(&vma->vm_refcnt))) {
		/*
		 * Reader must have temporarily raised vm_refcnt but it will
		 * drop it without using the vma since vma is write-locked.
		 */
	}
}

static inline void vma_init(struct vm_area_struct *vma, struct mm_struct *mm)
{
	memset(vma, 0, sizeof(*vma));
	vma->vm_mm = mm;
	vma->vm_ops = &vma_dummy_vm_ops;
	INIT_LIST_HEAD(&vma->anon_vma_chain);
	vma->vm_lock_seq = UINT_MAX;
}

/*
 * These are defined in vma.h, but sadly vm_stat_account() is referenced by
 * kernel/fork.c, so we have to these broadly available there, and temporarily
 * define them here to resolve the dependency cycle.
 */
#define is_exec_mapping(flags) \
	((flags & (VM_EXEC | VM_WRITE | VM_STACK)) == VM_EXEC)

#define is_stack_mapping(flags) \
	(((flags & VM_STACK) == VM_STACK) || (flags & VM_SHADOW_STACK))

#define is_data_mapping(flags) \
	((flags & (VM_WRITE | VM_SHARED | VM_STACK)) == VM_WRITE)

static inline void vm_stat_account(struct mm_struct *mm, vm_flags_t flags,
				   long npages)
{
	WRITE_ONCE(mm->total_vm, READ_ONCE(mm->total_vm)+npages);

	if (is_exec_mapping(flags))
		mm->exec_vm += npages;
	else if (is_stack_mapping(flags))
		mm->stack_vm += npages;
	else if (is_data_mapping(flags))
		mm->data_vm += npages;
}

#undef is_exec_mapping
#undef is_stack_mapping
#undef is_data_mapping

static inline void vm_unacct_memory(long pages)
{
	vm_acct_memory(-pages);
}

static inline void mapping_allow_writable(struct address_space *mapping)
{
	atomic_inc(&mapping->i_mmap_writable);
}

static inline
struct vm_area_struct *vma_find(struct vma_iterator *vmi, unsigned long max)
{
	return mas_find(&vmi->mas, max - 1);
}

static inline int vma_iter_clear_gfp(struct vma_iterator *vmi,
			unsigned long start, unsigned long end, gfp_t gfp)
{
	__mas_set_range(&vmi->mas, start, end - 1);
	mas_store_gfp(&vmi->mas, NULL, gfp);
	if (unlikely(mas_is_err(&vmi->mas)))
		return -ENOMEM;

	return 0;
}

static inline void vma_set_anonymous(struct vm_area_struct *vma)
{
	vma->vm_ops = NULL;
}

/* Declared in vma.h. */
static inline void set_vma_from_desc(struct vm_area_struct *vma,
		struct vm_area_desc *desc);

static inline int __compat_vma_mmap(const struct file_operations *f_op,
		struct file *file, struct vm_area_struct *vma)
{
	struct vm_area_desc desc = {
		.mm = vma->vm_mm,
		.file = file,
		.start = vma->vm_start,
		.end = vma->vm_end,

		.pgoff = vma->vm_pgoff,
		.vm_file = vma->vm_file,
		.vm_flags = vma->vm_flags,
		.page_prot = vma->vm_page_prot,

		.action.type = MMAP_NOTHING, /* Default */
	};
	int err;

	err = f_op->mmap_prepare(&desc);
	if (err)
		return err;

	mmap_action_prepare(&desc.action, &desc);
	set_vma_from_desc(vma, &desc);
	return mmap_action_complete(&desc.action, vma);
}

static inline int compat_vma_mmap(struct file *file,
		struct vm_area_struct *vma)
{
	return __compat_vma_mmap(file->f_op, file, vma);
}


static inline void vma_iter_init(struct vma_iterator *vmi,
		struct mm_struct *mm, unsigned long addr)
{
	mas_init(&vmi->mas, &mm->mm_mt, addr);
}

static inline unsigned long vma_pages(struct vm_area_struct *vma)
{
	return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
}

static inline void mmap_assert_locked(struct mm_struct *);
static inline struct vm_area_struct *find_vma_intersection(struct mm_struct *mm,
						unsigned long start_addr,
						unsigned long end_addr)
{
	unsigned long index = start_addr;

	mmap_assert_locked(mm);
	return mt_find(&mm->mm_mt, &index, end_addr - 1);
}

static inline
struct vm_area_struct *vma_lookup(struct mm_struct *mm, unsigned long addr)
{
	return mtree_load(&mm->mm_mt, addr);
}

static inline struct vm_area_struct *vma_prev(struct vma_iterator *vmi)
{
	return mas_prev(&vmi->mas, 0);
}

static inline void vma_iter_set(struct vma_iterator *vmi, unsigned long addr)
{
	mas_set(&vmi->mas, addr);
}

static inline bool vma_is_anonymous(struct vm_area_struct *vma)
{
	return !vma->vm_ops;
}

/* Defined in vma.h, so temporarily define here to avoid circular dependency. */
#define vma_iter_load(vmi) \
	mas_walk(&(vmi)->mas)

static inline struct vm_area_struct *
find_vma_prev(struct mm_struct *mm, unsigned long addr,
			struct vm_area_struct **pprev)
{
	struct vm_area_struct *vma;
	VMA_ITERATOR(vmi, mm, addr);

	vma = vma_iter_load(&vmi);
	*pprev = vma_prev(&vmi);
	if (!vma)
		vma = vma_next(&vmi);
	return vma;
}

#undef vma_iter_load

static inline void vma_iter_free(struct vma_iterator *vmi)
{
	mas_destroy(&vmi->mas);
}

static inline
struct vm_area_struct *vma_iter_next_range(struct vma_iterator *vmi)
{
	return mas_next_range(&vmi->mas, ULONG_MAX);
}

bool vma_wants_writenotify(struct vm_area_struct *vma, pgprot_t vm_page_prot);

/* Update vma->vm_page_prot to reflect vma->vm_flags. */
static inline void vma_set_page_prot(struct vm_area_struct *vma)
{
	vm_flags_t vm_flags = vma->vm_flags;
	pgprot_t vm_page_prot;

	/* testing: we inline vm_pgprot_modify() to avoid clash with vma.h. */
	vm_page_prot = pgprot_modify(vma->vm_page_prot, vm_get_page_prot(vm_flags));

	if (vma_wants_writenotify(vma, vm_page_prot)) {
		vm_flags &= ~VM_SHARED;
		/* testing: we inline vm_pgprot_modify() to avoid clash with vma.h. */
		vm_page_prot = pgprot_modify(vm_page_prot, vm_get_page_prot(vm_flags));
	}
	/* remove_protection_ptes reads vma->vm_page_prot without mmap_lock */
	WRITE_ONCE(vma->vm_page_prot, vm_page_prot);
}

static inline unsigned long stack_guard_start_gap(struct vm_area_struct *vma)
{
	if (vma->vm_flags & VM_GROWSDOWN)
		return stack_guard_gap;

	/* See reasoning around the VM_SHADOW_STACK definition */
	if (vma->vm_flags & VM_SHADOW_STACK)
		return PAGE_SIZE;

	return 0;
}

static inline unsigned long vm_start_gap(struct vm_area_struct *vma)
{
	unsigned long gap = stack_guard_start_gap(vma);
	unsigned long vm_start = vma->vm_start;

	vm_start -= gap;
	if (vm_start > vma->vm_start)
		vm_start = 0;
	return vm_start;
}

static inline unsigned long vm_end_gap(struct vm_area_struct *vma)
{
	unsigned long vm_end = vma->vm_end;

	if (vma->vm_flags & VM_GROWSUP) {
		vm_end += stack_guard_gap;
		if (vm_end < vma->vm_end)
			vm_end = -PAGE_SIZE;
	}
	return vm_end;
}

static inline bool vma_is_accessible(struct vm_area_struct *vma)
{
	return vma->vm_flags & VM_ACCESS_FLAGS;
}

static inline bool mlock_future_ok(const struct mm_struct *mm,
		vm_flags_t vm_flags, unsigned long bytes)
{
	unsigned long locked_pages, limit_pages;

	if (!(vm_flags & VM_LOCKED) || capable(CAP_IPC_LOCK))
		return true;

	locked_pages = bytes >> PAGE_SHIFT;
	locked_pages += mm->locked_vm;

	limit_pages = rlimit(RLIMIT_MEMLOCK);
	limit_pages >>= PAGE_SHIFT;

	return locked_pages <= limit_pages;
}

static inline bool map_deny_write_exec(unsigned long old, unsigned long new)
{
	/* If MDWE is disabled, we have nothing to deny. */
	if (mm_flags_test(MMF_HAS_MDWE, current->mm))
		return false;

	/* If the new VMA is not executable, we have nothing to deny. */
	if (!(new & VM_EXEC))
		return false;

	/* Under MDWE we do not accept newly writably executable VMAs... */
	if (new & VM_WRITE)
		return true;

	/* ...nor previously non-executable VMAs becoming executable. */
	if (!(old & VM_EXEC))
		return true;

	return false;
}

static inline int mapping_map_writable(struct address_space *mapping)
{
	return atomic_inc_unless_negative(&mapping->i_mmap_writable) ?
		0 : -EPERM;
}

/* Did the driver provide valid mmap hook configuration? */
static inline bool can_mmap_file(struct file *file)
{
	bool has_mmap = file->f_op->mmap;
	bool has_mmap_prepare = file->f_op->mmap_prepare;

	/* Hooks are mutually exclusive. */
	if (WARN_ON_ONCE(has_mmap && has_mmap_prepare))
		return false;
	if (!has_mmap && !has_mmap_prepare)
		return false;

	return true;
}

static inline int vfs_mmap(struct file *file, struct vm_area_struct *vma)
{
	if (file->f_op->mmap_prepare)
		return compat_vma_mmap(file, vma);

	return file->f_op->mmap(file, vma);
}

static inline int vfs_mmap_prepare(struct file *file, struct vm_area_desc *desc)
{
	return file->f_op->mmap_prepare(desc);
}

static inline void vma_set_file(struct vm_area_struct *vma, struct file *file)
{
	/* Changing an anonymous vma with this is illegal */
	get_file(file);
	swap(vma->vm_file, file);
	fput(file);
}