btf.c

/* SPDX-License-Identifier: GPL-2.0 */
/* Copyright (c) 2018 Facebook */

#include <uapi/linux/btf.h>
#include <uapi/linux/types.h>
#include <linux/seq_file.h>
#include <linux/compiler.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/anon_inodes.h>
#include <linux/file.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <linux/idr.h>
#include <linux/sort.h>
#include <linux/bpf_verifier.h>
#include <linux/btf.h>

/* BTF (BPF Type Format) is the meta data format which describes
 * the data types of BPF program/map.  Hence, it basically focus
 * on the C programming language which the modern BPF is primary
 * using.
 *
 * ELF Section:
 * ~~~~~~~~~~~
 * The BTF data is stored under the ".BTF" ELF section
 *
 * struct btf_type:
 * ~~~~~~~~~~~~~~~
 * Each 'struct btf_type' object describes a C data type.
 * Depending on the type it is describing, a 'struct btf_type'
 * object may be followed by more data.  F.e.
 * To describe an array, 'struct btf_type' is followed by
 * 'struct btf_array'.
 *
 * 'struct btf_type' and any extra data following it are
 * 4 bytes aligned.
 *
 * Type section:
 * ~~~~~~~~~~~~~
 * The BTF type section contains a list of 'struct btf_type' objects.
 * Each one describes a C type.  Recall from the above section
 * that a 'struct btf_type' object could be immediately followed by extra
 * data in order to desribe some particular C types.
 *
 * type_id:
 * ~~~~~~~
 * Each btf_type object is identified by a type_id.  The type_id
 * is implicitly implied by the location of the btf_type object in
 * the BTF type section.  The first one has type_id 1.  The second
 * one has type_id 2...etc.  Hence, an earlier btf_type has
 * a smaller type_id.
 *
 * A btf_type object may refer to another btf_type object by using
 * type_id (i.e. the "type" in the "struct btf_type").
 *
 * NOTE that we cannot assume any reference-order.
 * A btf_type object can refer to an earlier btf_type object
 * but it can also refer to a later btf_type object.
 *
 * For example, to describe "const void *".  A btf_type
 * object describing "const" may refer to another btf_type
 * object describing "void *".  This type-reference is done
 * by specifying type_id:
 *
 * [1] CONST (anon) type_id=2
 * [2] PTR (anon) type_id=0
 *
 * The above is the btf_verifier debug log:
 *   - Each line started with "[?]" is a btf_type object
 *   - [?] is the type_id of the btf_type object.
 *   - CONST/PTR is the BTF_KIND_XXX
 *   - "(anon)" is the name of the type.  It just
 *     happens that CONST and PTR has no name.
 *   - type_id=XXX is the 'u32 type' in btf_type
 *
 * NOTE: "void" has type_id 0
 *
 * String section:
 * ~~~~~~~~~~~~~~
 * The BTF string section contains the names used by the type section.
 * Each string is referred by an "offset" from the beginning of the
 * string section.
 *
 * Each string is '\0' terminated.
 *
 * The first character in the string section must be '\0'
 * which is used to mean 'anonymous'. Some btf_type may not
 * have a name.
 */

/* BTF verification:
 *
 * To verify BTF data, two passes are needed.
 *
 * Pass #1
 * ~~~~~~~
 * The first pass is to collect all btf_type objects to
 * an array: "btf->types".
 *
 * Depending on the C type that a btf_type is describing,
 * a btf_type may be followed by extra data.  We don't know
 * how many btf_type is there, and more importantly we don't
 * know where each btf_type is located in the type section.
 *
 * Without knowing the location of each type_id, most verifications
 * cannot be done.  e.g. an earlier btf_type may refer to a later
 * btf_type (recall the "const void *" above), so we cannot
 * check this type-reference in the first pass.
 *
 * In the first pass, it still does some verifications (e.g.
 * checking the name is a valid offset to the string section).
 *
 * Pass #2
 * ~~~~~~~
 * The main focus is to resolve a btf_type that is referring
 * to another type.
 *
 * We have to ensure the referring type:
 * 1) does exist in the BTF (i.e. in btf->types[])
 * 2) does not cause a loop:
 *	struct A {
 *		struct B b;
 *	};
 *
 *	struct B {
 *		struct A a;
 *	};
 *
 * btf_type_needs_resolve() decides if a btf_type needs
 * to be resolved.
 *
 * The needs_resolve type implements the "resolve()" ops which
 * essentially does a DFS and detects backedge.
 *
 * During resolve (or DFS), different C types have different
 * "RESOLVED" conditions.
 *
 * When resolving a BTF_KIND_STRUCT, we need to resolve all its
 * members because a member is always referring to another
 * type.  A struct's member can be treated as "RESOLVED" if
 * it is referring to a BTF_KIND_PTR.  Otherwise, the
 * following valid C struct would be rejected:
 *
 *	struct A {
 *		int m;
 *		struct A *a;
 *	};
 *
 * When resolving a BTF_KIND_PTR, it needs to keep resolving if
 * it is referring to another BTF_KIND_PTR.  Otherwise, we cannot
 * detect a pointer loop, e.g.:
 * BTF_KIND_CONST -> BTF_KIND_PTR -> BTF_KIND_CONST -> BTF_KIND_PTR +
 *                        ^                                         |
 *                        +-----------------------------------------+
 *
 */

#define BITS_PER_U64 (sizeof(u64) * BITS_PER_BYTE)
#define BITS_PER_BYTE_MASK (BITS_PER_BYTE - 1)
#define BITS_PER_BYTE_MASKED(bits) ((bits) & BITS_PER_BYTE_MASK)
#define BITS_ROUNDDOWN_BYTES(bits) ((bits) >> 3)
#define BITS_ROUNDUP_BYTES(bits) \
	(BITS_ROUNDDOWN_BYTES(bits) + !!BITS_PER_BYTE_MASKED(bits))

#define BTF_INFO_MASK 0x0f00ffff
#define BTF_INT_MASK 0x0fffffff
#define BTF_TYPE_ID_VALID(type_id) ((type_id) <= BTF_MAX_TYPE)
#define BTF_STR_OFFSET_VALID(name_off) ((name_off) <= BTF_MAX_NAME_OFFSET)

/* 16MB for 64k structs and each has 16 members and
 * a few MB spaces for the string section.
 * The hard limit is S32_MAX.
 */
#define BTF_MAX_SIZE (16 * 1024 * 1024)

#define for_each_member(i, struct_type, member)			\
	for (i = 0, member = btf_type_member(struct_type);	\
	     i < btf_type_vlen(struct_type);			\
	     i++, member++)

#define for_each_member_from(i, from, struct_type, member)		\
	for (i = from, member = btf_type_member(struct_type) + from;	\
	     i < btf_type_vlen(struct_type);				\
	     i++, member++)

static DEFINE_IDR(btf_idr);
static DEFINE_SPINLOCK(btf_idr_lock);

struct btf {
	void *data;
	struct btf_type **types;
	u32 *resolved_ids;
	u32 *resolved_sizes;
	const char *strings;
	void *nohdr_data;
	struct btf_header hdr;
	u32 nr_types;
	u32 types_size;
	u32 data_size;
	refcount_t refcnt;
	u32 id;
	struct rcu_head rcu;
};

enum verifier_phase {
	CHECK_META,
	CHECK_TYPE,
};

struct resolve_vertex {
	const struct btf_type *t;
	u32 type_id;
	u16 next_member;
};

enum visit_state {
	NOT_VISITED,
	VISITED,
	RESOLVED,
};

enum resolve_mode {
	RESOLVE_TBD,	/* To Be Determined */
	RESOLVE_PTR,	/* Resolving for Pointer */
	RESOLVE_STRUCT_OR_ARRAY,	/* Resolving for struct/union
					 * or array
					 */
};

#define MAX_RESOLVE_DEPTH 32

struct btf_sec_info {
	u32 off;
	u32 len;
};

struct btf_verifier_env {
	struct btf *btf;
	u8 *visit_states;
	struct resolve_vertex stack[MAX_RESOLVE_DEPTH];
	struct bpf_verifier_log log;
	u32 log_type_id;
	u32 top_stack;
	enum verifier_phase phase;
	enum resolve_mode resolve_mode;
};

static const char * const btf_kind_str[NR_BTF_KINDS] = {
	[BTF_KIND_UNKN]		= "UNKNOWN",
	[BTF_KIND_INT]		= "INT",
	[BTF_KIND_PTR]		= "PTR",
	[BTF_KIND_ARRAY]	= "ARRAY",
	[BTF_KIND_STRUCT]	= "STRUCT",
	[BTF_KIND_UNION]	= "UNION",
	[BTF_KIND_ENUM]		= "ENUM",
	[BTF_KIND_FWD]		= "FWD",
	[BTF_KIND_TYPEDEF]	= "TYPEDEF",
	[BTF_KIND_VOLATILE]	= "VOLATILE",
	[BTF_KIND_CONST]	= "CONST",
	[BTF_KIND_RESTRICT]	= "RESTRICT",
};

struct btf_kind_operations {
	s32 (*check_meta)(struct btf_verifier_env *env,
			  const struct btf_type *t,
			  u32 meta_left);
	int (*resolve)(struct btf_verifier_env *env,
		       const struct resolve_vertex *v);
	int (*check_member)(struct btf_verifier_env *env,
			    const struct btf_type *struct_type,
			    const struct btf_member *member,
			    const struct btf_type *member_type);
	void (*log_details)(struct btf_verifier_env *env,
			    const struct btf_type *t);
	void (*seq_show)(const struct btf *btf, const struct btf_type *t,
			 u32 type_id, void *data, u8 bits_offsets,
			 struct seq_file *m);
};

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS];
static struct btf_type btf_void;

static bool btf_type_is_modifier(const struct btf_type *t)
{
	/* Some of them is not strictly a C modifier
	 * but they are grouped into the same bucket
	 * for BTF concern:
	 *   A type (t) that refers to another
	 *   type through t->type AND its size cannot
	 *   be determined without following the t->type.
	 *
	 * ptr does not fall into this bucket
	 * because its size is always sizeof(void *).
	 */
	switch (BTF_INFO_KIND(t->info)) {
	case BTF_KIND_TYPEDEF:
	case BTF_KIND_VOLATILE:
	case BTF_KIND_CONST:
	case BTF_KIND_RESTRICT:
		return true;
	}

	return false;
}

static bool btf_type_is_void(const struct btf_type *t)
{
	/* void => no type and size info.
	 * Hence, FWD is also treated as void.
	 */
	return t == &btf_void || BTF_INFO_KIND(t->info) == BTF_KIND_FWD;
}

static bool btf_type_is_void_or_null(const struct btf_type *t)
{
	return !t || btf_type_is_void(t);
}

/* union is only a special case of struct:
 * all its offsetof(member) == 0
 */
static bool btf_type_is_struct(const struct btf_type *t)
{
	u8 kind = BTF_INFO_KIND(t->info);

	return kind == BTF_KIND_STRUCT || kind == BTF_KIND_UNION;
}

static bool btf_type_is_array(const struct btf_type *t)
{
	return BTF_INFO_KIND(t->info) == BTF_KIND_ARRAY;
}

static bool btf_type_is_ptr(const struct btf_type *t)
{
	return BTF_INFO_KIND(t->info) == BTF_KIND_PTR;
}

static bool btf_type_is_int(const struct btf_type *t)
{
	return BTF_INFO_KIND(t->info) == BTF_KIND_INT;
}

/* What types need to be resolved?
 *
 * btf_type_is_modifier() is an obvious one.
 *
 * btf_type_is_struct() because its member refers to
 * another type (through member->type).

 * btf_type_is_array() because its element (array->type)
 * refers to another type.  Array can be thought of a
 * special case of struct while array just has the same
 * member-type repeated by array->nelems of times.
 */
static bool btf_type_needs_resolve(const struct btf_type *t)
{
	return btf_type_is_modifier(t) ||
		btf_type_is_ptr(t) ||
		btf_type_is_struct(t) ||
		btf_type_is_array(t);
}

/* t->size can be used */
static bool btf_type_has_size(const struct btf_type *t)
{
	switch (BTF_INFO_KIND(t->info)) {
	case BTF_KIND_INT:
	case BTF_KIND_STRUCT:
	case BTF_KIND_UNION:
	case BTF_KIND_ENUM:
		return true;
	}

	return false;
}

static const char *btf_int_encoding_str(u8 encoding)
{
	if (encoding == 0)
		return "(none)";
	else if (encoding == BTF_INT_SIGNED)
		return "SIGNED";
	else if (encoding == BTF_INT_CHAR)
		return "CHAR";
	else if (encoding == BTF_INT_BOOL)
		return "BOOL";
	else
		return "UNKN";
}

static u16 btf_type_vlen(const struct btf_type *t)
{
	return BTF_INFO_VLEN(t->info);
}

static u32 btf_type_int(const struct btf_type *t)
{
	return *(u32 *)(t + 1);
}

static const struct btf_array *btf_type_array(const struct btf_type *t)
{
	return (const struct btf_array *)(t + 1);
}

static const struct btf_member *btf_type_member(const struct btf_type *t)
{
	return (const struct btf_member *)(t + 1);
}

static const struct btf_enum *btf_type_enum(const struct btf_type *t)
{
	return (const struct btf_enum *)(t + 1);
}

static const struct btf_kind_operations *btf_type_ops(const struct btf_type *t)
{
	return kind_ops[BTF_INFO_KIND(t->info)];
}

static bool btf_name_offset_valid(const struct btf *btf, u32 offset)
{
	return BTF_STR_OFFSET_VALID(offset) &&
		offset < btf->hdr.str_len;
}

/* Only C-style identifier is permitted. This can be relaxed if
 * necessary.
 */
static bool btf_name_valid_identifier(const struct btf *btf, u32 offset)
{
	/* offset must be valid */
	const char *src = &btf->strings[offset];
	const char *src_limit;

	if (!isalpha(*src) && *src != '_')
		return false;

	/* set a limit on identifier length */
	src_limit = src + KSYM_NAME_LEN;
	src++;
	while (*src && src < src_limit) {
		if (!isalnum(*src) && *src != '_')
			return false;
		src++;
	}

	return !*src;
}

static const char *btf_name_by_offset(const struct btf *btf, u32 offset)
{
	if (!offset)
		return "(anon)";
	else if (offset < btf->hdr.str_len)
		return &btf->strings[offset];
	else
		return "(invalid-name-offset)";
}

static const struct btf_type *btf_type_by_id(const struct btf *btf, u32 type_id)
{
	if (type_id > btf->nr_types)
		return NULL;

	return btf->types[type_id];
}

/*
 * Regular int is not a bit field and it must be either
 * u8/u16/u32/u64.
 */
static bool btf_type_int_is_regular(const struct btf_type *t)
{
	u8 nr_bits, nr_bytes;
	u32 int_data;

	int_data = btf_type_int(t);
	nr_bits = BTF_INT_BITS(int_data);
	nr_bytes = BITS_ROUNDUP_BYTES(nr_bits);
	if (BITS_PER_BYTE_MASKED(nr_bits) ||
	    BTF_INT_OFFSET(int_data) ||
	    (nr_bytes != sizeof(u8) && nr_bytes != sizeof(u16) &&
	     nr_bytes != sizeof(u32) && nr_bytes != sizeof(u64))) {
		return false;
	}

	return true;
}

__printf(2, 3) static void __btf_verifier_log(struct bpf_verifier_log *log,
					      const char *fmt, ...)
{
	va_list args;

	va_start(args, fmt);
	bpf_verifier_vlog(log, fmt, args);
	va_end(args);
}

__printf(2, 3) static void btf_verifier_log(struct btf_verifier_env *env,
					    const char *fmt, ...)
{
	struct bpf_verifier_log *log = &env->log;
	va_list args;

	if (!bpf_verifier_log_needed(log))
		return;

	va_start(args, fmt);
	bpf_verifier_vlog(log, fmt, args);
	va_end(args);
}

__printf(4, 5) static void __btf_verifier_log_type(struct btf_verifier_env *env,
						   const struct btf_type *t,
						   bool log_details,
						   const char *fmt, ...)
{
	struct bpf_verifier_log *log = &env->log;
	u8 kind = BTF_INFO_KIND(t->info);
	struct btf *btf = env->btf;
	va_list args;

	if (!bpf_verifier_log_needed(log))
		return;

	__btf_verifier_log(log, "[%u] %s %s%s",
			   env->log_type_id,
			   btf_kind_str[kind],
			   btf_name_by_offset(btf, t->name_off),
			   log_details ? " " : "");

	if (log_details)
		btf_type_ops(t)->log_details(env, t);

	if (fmt && *fmt) {
		__btf_verifier_log(log, " ");
		va_start(args, fmt);
		bpf_verifier_vlog(log, fmt, args);
		va_end(args);
	}

	__btf_verifier_log(log, "\n");
}

#define btf_verifier_log_type(env, t, ...) \
	__btf_verifier_log_type((env), (t), true, __VA_ARGS__)
#define btf_verifier_log_basic(env, t, ...) \
	__btf_verifier_log_type((env), (t), false, __VA_ARGS__)

__printf(4, 5)
static void btf_verifier_log_member(struct btf_verifier_env *env,
				    const struct btf_type *struct_type,
				    const struct btf_member *member,
				    const char *fmt, ...)
{
	struct bpf_verifier_log *log = &env->log;
	struct btf *btf = env->btf;
	va_list args;

	if (!bpf_verifier_log_needed(log))
		return;

	/* The CHECK_META phase already did a btf dump.
	 *
	 * If member is logged again, it must hit an error in
	 * parsing this member.  It is useful to print out which
	 * struct this member belongs to.
	 */
	if (env->phase != CHECK_META)
		btf_verifier_log_type(env, struct_type, NULL);

	__btf_verifier_log(log, "\t%s type_id=%u bits_offset=%u",
			   btf_name_by_offset(btf, member->name_off),
			   member->type, member->offset);

	if (fmt && *fmt) {
		__btf_verifier_log(log, " ");
		va_start(args, fmt);
		bpf_verifier_vlog(log, fmt, args);
		va_end(args);
	}

	__btf_verifier_log(log, "\n");
}

static void btf_verifier_log_hdr(struct btf_verifier_env *env,
				 u32 btf_data_size)
{
	struct bpf_verifier_log *log = &env->log;
	const struct btf *btf = env->btf;
	const struct btf_header *hdr;

	if (!bpf_verifier_log_needed(log))
		return;

	hdr = &btf->hdr;
	__btf_verifier_log(log, "magic: 0x%x\n", hdr->magic);
	__btf_verifier_log(log, "version: %u\n", hdr->version);
	__btf_verifier_log(log, "flags: 0x%x\n", hdr->flags);
	__btf_verifier_log(log, "hdr_len: %u\n", hdr->hdr_len);
	__btf_verifier_log(log, "type_off: %u\n", hdr->type_off);
	__btf_verifier_log(log, "type_len: %u\n", hdr->type_len);
	__btf_verifier_log(log, "str_off: %u\n", hdr->str_off);
	__btf_verifier_log(log, "str_len: %u\n", hdr->str_len);
	__btf_verifier_log(log, "btf_total_size: %u\n", btf_data_size);
}

static int btf_add_type(struct btf_verifier_env *env, struct btf_type *t)
{
	struct btf *btf = env->btf;

	/* < 2 because +1 for btf_void which is always in btf->types[0].
	 * btf_void is not accounted in btf->nr_types because btf_void
	 * does not come from the BTF file.
	 */
	if (btf->types_size - btf->nr_types < 2) {
		/* Expand 'types' array */

		struct btf_type **new_types;
		u32 expand_by, new_size;

		if (btf->types_size == BTF_MAX_TYPE) {
			btf_verifier_log(env, "Exceeded max num of types");
			return -E2BIG;
		}

		expand_by = max_t(u32, btf->types_size >> 2, 16);
		new_size = min_t(u32, BTF_MAX_TYPE,
				 btf->types_size + expand_by);

		new_types = kvcalloc(new_size, sizeof(*new_types),
				     GFP_KERNEL | __GFP_NOWARN);
		if (!new_types)
			return -ENOMEM;

		if (btf->nr_types == 0)
			new_types[0] = &btf_void;
		else
			memcpy(new_types, btf->types,
			       sizeof(*btf->types) * (btf->nr_types + 1));

		kvfree(btf->types);
		btf->types = new_types;
		btf->types_size = new_size;
	}

	btf->types[++(btf->nr_types)] = t;

	return 0;
}

static int btf_alloc_id(struct btf *btf)
{
	int id;

	idr_preload(GFP_KERNEL);
	spin_lock_bh(&btf_idr_lock);
	id = idr_alloc_cyclic(&btf_idr, btf, 1, INT_MAX, GFP_ATOMIC);
	if (id > 0)
		btf->id = id;
	spin_unlock_bh(&btf_idr_lock);
	idr_preload_end();

	if (WARN_ON_ONCE(!id))
		return -ENOSPC;

	return id > 0 ? 0 : id;
}

static void btf_free_id(struct btf *btf)
{
	unsigned long flags;

	/*
	 * In map-in-map, calling map_delete_elem() on outer
	 * map will call bpf_map_put on the inner map.
	 * It will then eventually call btf_free_id()
	 * on the inner map.  Some of the map_delete_elem()
	 * implementation may have irq disabled, so
	 * we need to use the _irqsave() version instead
	 * of the _bh() version.
	 */
	spin_lock_irqsave(&btf_idr_lock, flags);
	idr_remove(&btf_idr, btf->id);
	spin_unlock_irqrestore(&btf_idr_lock, flags);
}

static void btf_free(struct btf *btf)
{
	kvfree(btf->types);
	kvfree(btf->resolved_sizes);
	kvfree(btf->resolved_ids);
	kvfree(btf->data);
	kfree(btf);
}

static void btf_free_rcu(struct rcu_head *rcu)
{
	struct btf *btf = container_of(rcu, struct btf, rcu);

	btf_free(btf);
}

void btf_put(struct btf *btf)
{
	if (btf && refcount_dec_and_test(&btf->refcnt)) {
		btf_free_id(btf);
		call_rcu(&btf->rcu, btf_free_rcu);
	}
}

static int env_resolve_init(struct btf_verifier_env *env)
{
	struct btf *btf = env->btf;
	u32 nr_types = btf->nr_types;
	u32 *resolved_sizes = NULL;
	u32 *resolved_ids = NULL;
	u8 *visit_states = NULL;

	/* +1 for btf_void */
	resolved_sizes = kvcalloc(nr_types + 1, sizeof(*resolved_sizes),
				  GFP_KERNEL | __GFP_NOWARN);
	if (!resolved_sizes)
		goto nomem;

	resolved_ids = kvcalloc(nr_types + 1, sizeof(*resolved_ids),
				GFP_KERNEL | __GFP_NOWARN);
	if (!resolved_ids)
		goto nomem;

	visit_states = kvcalloc(nr_types + 1, sizeof(*visit_states),
				GFP_KERNEL | __GFP_NOWARN);
	if (!visit_states)
		goto nomem;

	btf->resolved_sizes = resolved_sizes;
	btf->resolved_ids = resolved_ids;
	env->visit_states = visit_states;

	return 0;

nomem:
	kvfree(resolved_sizes);
	kvfree(resolved_ids);
	kvfree(visit_states);
	return -ENOMEM;
}

static void btf_verifier_env_free(struct btf_verifier_env *env)
{
	kvfree(env->visit_states);
	kfree(env);
}

static bool env_type_is_resolve_sink(const struct btf_verifier_env *env,
				     const struct btf_type *next_type)
{
	switch (env->resolve_mode) {
	case RESOLVE_TBD:
		/* int, enum or void is a sink */
		return !btf_type_needs_resolve(next_type);
	case RESOLVE_PTR:
		/* int, enum, void, struct or array is a sink for ptr */
		return !btf_type_is_modifier(next_type) &&
			!btf_type_is_ptr(next_type);
	case RESOLVE_STRUCT_OR_ARRAY:
		/* int, enum, void or ptr is a sink for struct and array */
		return !btf_type_is_modifier(next_type) &&
			!btf_type_is_array(next_type) &&
			!btf_type_is_struct(next_type);
	default:
		BUG();
	}
}

static bool env_type_is_resolved(const struct btf_verifier_env *env,
				 u32 type_id)
{
	return env->visit_states[type_id] == RESOLVED;
}

static int env_stack_push(struct btf_verifier_env *env,
			  const struct btf_type *t, u32 type_id)
{
	struct resolve_vertex *v;

	if (env->top_stack == MAX_RESOLVE_DEPTH)
		return -E2BIG;

	if (env->visit_states[type_id] != NOT_VISITED)
		return -EEXIST;

	env->visit_states[type_id] = VISITED;

	v = &env->stack[env->top_stack++];
	v->t = t;
	v->type_id = type_id;
	v->next_member = 0;

	if (env->resolve_mode == RESOLVE_TBD) {
		if (btf_type_is_ptr(t))
			env->resolve_mode = RESOLVE_PTR;
		else if (btf_type_is_struct(t) || btf_type_is_array(t))
			env->resolve_mode = RESOLVE_STRUCT_OR_ARRAY;
	}

	return 0;
}

static void env_stack_set_next_member(struct btf_verifier_env *env,
				      u16 next_member)
{
	env->stack[env->top_stack - 1].next_member = next_member;
}

static void env_stack_pop_resolved(struct btf_verifier_env *env,
				   u32 resolved_type_id,
				   u32 resolved_size)
{
	u32 type_id = env->stack[--(env->top_stack)].type_id;
	struct btf *btf = env->btf;

	btf->resolved_sizes[type_id] = resolved_size;
	btf->resolved_ids[type_id] = resolved_type_id;
	env->visit_states[type_id] = RESOLVED;
}

static const struct resolve_vertex *env_stack_peak(struct btf_verifier_env *env)
{
	return env->top_stack ? &env->stack[env->top_stack - 1] : NULL;
}

/* The input param "type_id" must point to a needs_resolve type */
static const struct btf_type *btf_type_id_resolve(const struct btf *btf,
						  u32 *type_id)
{
	*type_id = btf->resolved_ids[*type_id];
	return btf_type_by_id(btf, *type_id);
}

const struct btf_type *btf_type_id_size(const struct btf *btf,
					u32 *type_id, u32 *ret_size)
{
	const struct btf_type *size_type;
	u32 size_type_id = *type_id;
	u32 size = 0;

	size_type = btf_type_by_id(btf, size_type_id);
	if (btf_type_is_void_or_null(size_type))
		return NULL;

	if (btf_type_has_size(size_type)) {
		size = size_type->size;
	} else if (btf_type_is_array(size_type)) {
		size = btf->resolved_sizes[size_type_id];
	} else if (btf_type_is_ptr(size_type)) {
		size = sizeof(void *);
	} else {
		if (WARN_ON_ONCE(!btf_type_is_modifier(size_type)))
			return NULL;

		size = btf->resolved_sizes[size_type_id];
		size_type_id = btf->resolved_ids[size_type_id];
		size_type = btf_type_by_id(btf, size_type_id);
		if (btf_type_is_void(size_type))
			return NULL;
	}

	*type_id = size_type_id;
	if (ret_size)
		*ret_size = size;

	return size_type;
}

static int btf_df_check_member(struct btf_verifier_env *env,
			       const struct btf_type *struct_type,
			       const struct btf_member *member,
			       const struct btf_type *member_type)
{
	btf_verifier_log_basic(env, struct_type,
			       "Unsupported check_member");
	return -EINVAL;
}

static int btf_df_resolve(struct btf_verifier_env *env,
			  const struct resolve_vertex *v)
{
	btf_verifier_log_basic(env, v->t, "Unsupported resolve");
	return -EINVAL;
}

static void btf_df_seq_show(const struct btf *btf, const struct btf_type *t,
			    u32 type_id, void *data, u8 bits_offsets,
			    struct seq_file *m)
{
	seq_printf(m, "<unsupported kind:%u>", BTF_INFO_KIND(t->info));
}

static int btf_int_check_member(struct btf_verifier_env *env,
				const struct btf_type *struct_type,
				const struct btf_member *member,
				const struct btf_type *member_type)
{
	u32 int_data = btf_type_int(member_type);
	u32 struct_bits_off = member->offset;
	u32 struct_size = struct_type->size;
	u32 nr_copy_bits;
	u32 bytes_offset;

	if (U32_MAX - struct_bits_off < BTF_INT_OFFSET(int_data)) {
		btf_verifier_log_member(env, struct_type, member,
					"bits_offset exceeds U32_MAX");
		return -EINVAL;
	}

	struct_bits_off += BTF_INT_OFFSET(int_data);
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	nr_copy_bits = BTF_INT_BITS(int_data) +
		BITS_PER_BYTE_MASKED(struct_bits_off);

	if (nr_copy_bits > BITS_PER_U64) {
		btf_verifier_log_member(env, struct_type, member,
					"nr_copy_bits exceeds 64");
		return -EINVAL;
	}

	if (struct_size < bytes_offset ||
	    struct_size - bytes_offset < BITS_ROUNDUP_BYTES(nr_copy_bits)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static s32 btf_int_check_meta(struct btf_verifier_env *env,
			      const struct btf_type *t,
			      u32 meta_left)
{
	u32 int_data, nr_bits, meta_needed = sizeof(int_data);
	u16 encoding;

	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	int_data = btf_type_int(t);
	if (int_data & ~BTF_INT_MASK) {
		btf_verifier_log_basic(env, t, "Invalid int_data:%x",
				       int_data);
		return -EINVAL;
	}

	nr_bits = BTF_INT_BITS(int_data) + BTF_INT_OFFSET(int_data);

	if (nr_bits > BITS_PER_U64) {
		btf_verifier_log_type(env, t, "nr_bits exceeds %zu",
				      BITS_PER_U64);
		return -EINVAL;
	}

	if (BITS_ROUNDUP_BYTES(nr_bits) > t->size) {
		btf_verifier_log_type(env, t, "nr_bits exceeds type_size");
		return -EINVAL;
	}

	/*
	 * Only one of the encoding bits is allowed and it
	 * should be sufficient for the pretty print purpose (i.e. decoding).
	 * Multiple bits can be allowed later if it is found
	 * to be insufficient.
	 */
	encoding = BTF_INT_ENCODING(int_data);
	if (encoding &&
	    encoding != BTF_INT_SIGNED &&
	    encoding != BTF_INT_CHAR &&
	    encoding != BTF_INT_BOOL) {
		btf_verifier_log_type(env, t, "Unsupported encoding");
		return -ENOTSUPP;
	}

	btf_verifier_log_type(env, t, NULL);

	return meta_needed;
}

static void btf_int_log(struct btf_verifier_env *env,
			const struct btf_type *t)
{
	int int_data = btf_type_int(t);

	btf_verifier_log(env,
			 "size=%u bits_offset=%u nr_bits=%u encoding=%s",
			 t->size, BTF_INT_OFFSET(int_data),
			 BTF_INT_BITS(int_data),
			 btf_int_encoding_str(BTF_INT_ENCODING(int_data)));
}

static void btf_int_bits_seq_show(const struct btf *btf,
				  const struct btf_type *t,
				  void *data, u8 bits_offset,
				  struct seq_file *m)
{
	u16 left_shift_bits, right_shift_bits;
	u32 int_data = btf_type_int(t);
	u8 nr_bits = BTF_INT_BITS(int_data);
	u8 total_bits_offset;
	u8 nr_copy_bytes;
	u8 nr_copy_bits;
	u64 print_num;

	/*
	 * bits_offset is at most 7.
	 * BTF_INT_OFFSET() cannot exceed 64 bits.
	 */
	total_bits_offset = bits_offset + BTF_INT_OFFSET(int_data);
	data += BITS_ROUNDDOWN_BYTES(total_bits_offset);
	bits_offset = BITS_PER_BYTE_MASKED(total_bits_offset);
	nr_copy_bits = nr_bits + bits_offset;
	nr_copy_bytes = BITS_ROUNDUP_BYTES(nr_copy_bits);

	print_num = 0;
	memcpy(&print_num, data, nr_copy_bytes);

#ifdef __BIG_ENDIAN_BITFIELD
	left_shift_bits = bits_offset;
#else
	left_shift_bits = BITS_PER_U64 - nr_copy_bits;
#endif
	right_shift_bits = BITS_PER_U64 - nr_bits;

	print_num <<= left_shift_bits;
	print_num >>= right_shift_bits;

	seq_printf(m, "0x%llx", print_num);
}

static void btf_int_seq_show(const struct btf *btf, const struct btf_type *t,
			     u32 type_id, void *data, u8 bits_offset,
			     struct seq_file *m)
{
	u32 int_data = btf_type_int(t);
	u8 encoding = BTF_INT_ENCODING(int_data);
	bool sign = encoding & BTF_INT_SIGNED;
	u8 nr_bits = BTF_INT_BITS(int_data);

	if (bits_offset || BTF_INT_OFFSET(int_data) ||
	    BITS_PER_BYTE_MASKED(nr_bits)) {
		btf_int_bits_seq_show(btf, t, data, bits_offset, m);
		return;
	}

	switch (nr_bits) {
	case 64:
		if (sign)
			seq_printf(m, "%lld", *(s64 *)data);
		else
			seq_printf(m, "%llu", *(u64 *)data);
		break;
	case 32:
		if (sign)
			seq_printf(m, "%d", *(s32 *)data);
		else
			seq_printf(m, "%u", *(u32 *)data);
		break;
	case 16:
		if (sign)
			seq_printf(m, "%d", *(s16 *)data);
		else
			seq_printf(m, "%u", *(u16 *)data);
		break;
	case 8:
		if (sign)
			seq_printf(m, "%d", *(s8 *)data);
		else
			seq_printf(m, "%u", *(u8 *)data);
		break;
	default:
		btf_int_bits_seq_show(btf, t, data, bits_offset, m);
	}
}

static const struct btf_kind_operations int_ops = {
	.check_meta = btf_int_check_meta,
	.resolve = btf_df_resolve,
	.check_member = btf_int_check_member,
	.log_details = btf_int_log,
	.seq_show = btf_int_seq_show,
};

static int btf_modifier_check_member(struct btf_verifier_env *env,
				     const struct btf_type *struct_type,
				     const struct btf_member *member,
				     const struct btf_type *member_type)
{
	const struct btf_type *resolved_type;
	u32 resolved_type_id = member->type;
	struct btf_member resolved_member;
	struct btf *btf = env->btf;

	resolved_type = btf_type_id_size(btf, &resolved_type_id, NULL);
	if (!resolved_type) {
		btf_verifier_log_member(env, struct_type, member,
					"Invalid member");
		return -EINVAL;
	}

	resolved_member = *member;
	resolved_member.type = resolved_type_id;

	return btf_type_ops(resolved_type)->check_member(env, struct_type,
							 &resolved_member,
							 resolved_type);
}

static int btf_ptr_check_member(struct btf_verifier_env *env,
				const struct btf_type *struct_type,
				const struct btf_member *member,
				const struct btf_type *member_type)
{
	u32 struct_size, struct_bits_off, bytes_offset;

	struct_size = struct_type->size;
	struct_bits_off = member->offset;
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);

	if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member is not byte aligned");
		return -EINVAL;
	}

	if (struct_size - bytes_offset < sizeof(void *)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static int btf_ref_type_check_meta(struct btf_verifier_env *env,
				   const struct btf_type *t,
				   u32 meta_left)
{
	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	if (!BTF_TYPE_ID_VALID(t->type)) {
		btf_verifier_log_type(env, t, "Invalid type_id");
		return -EINVAL;
	}

	/* typedef type must have a valid name, and other ref types,
	 * volatile, const, restrict, should have a null name.
	 */
	if (BTF_INFO_KIND(t->info) == BTF_KIND_TYPEDEF) {
		if (!t->name_off ||
		    !btf_name_valid_identifier(env->btf, t->name_off)) {
			btf_verifier_log_type(env, t, "Invalid name");
			return -EINVAL;
		}
	} else {
		if (t->name_off) {
			btf_verifier_log_type(env, t, "Invalid name");
			return -EINVAL;
		}
	}

	btf_verifier_log_type(env, t, NULL);

	return 0;
}

static int btf_modifier_resolve(struct btf_verifier_env *env,
				const struct resolve_vertex *v)
{
	const struct btf_type *t = v->t;
	const struct btf_type *next_type;
	u32 next_type_id = t->type;
	struct btf *btf = env->btf;
	u32 next_type_size = 0;

	next_type = btf_type_by_id(btf, next_type_id);
	if (!next_type) {
		btf_verifier_log_type(env, v->t, "Invalid type_id");
		return -EINVAL;
	}

	/* "typedef void new_void", "const void"...etc */
	if (btf_type_is_void(next_type))
		goto resolved;

	if (!env_type_is_resolve_sink(env, next_type) &&
	    !env_type_is_resolved(env, next_type_id))
		return env_stack_push(env, next_type, next_type_id);

	/* Figure out the resolved next_type_id with size.
	 * They will be stored in the current modifier's
	 * resolved_ids and resolved_sizes such that it can
	 * save us a few type-following when we use it later (e.g. in
	 * pretty print).
	 */
	if (!btf_type_id_size(btf, &next_type_id, &next_type_size) &&
	    !btf_type_is_void(btf_type_id_resolve(btf, &next_type_id))) {
		btf_verifier_log_type(env, v->t, "Invalid type_id");
		return -EINVAL;
	}

resolved:
	env_stack_pop_resolved(env, next_type_id, next_type_size);

	return 0;
}

static int btf_ptr_resolve(struct btf_verifier_env *env,
			   const struct resolve_vertex *v)
{
	const struct btf_type *next_type;
	const struct btf_type *t = v->t;
	u32 next_type_id = t->type;
	struct btf *btf = env->btf;
	u32 next_type_size = 0;

	next_type = btf_type_by_id(btf, next_type_id);
	if (!next_type) {
		btf_verifier_log_type(env, v->t, "Invalid type_id");
		return -EINVAL;
	}

	/* "void *" */
	if (btf_type_is_void(next_type))
		goto resolved;

	if (!env_type_is_resolve_sink(env, next_type) &&
	    !env_type_is_resolved(env, next_type_id))
		return env_stack_push(env, next_type, next_type_id);

	/* If the modifier was RESOLVED during RESOLVE_STRUCT_OR_ARRAY,
	 * the modifier may have stopped resolving when it was resolved
	 * to a ptr (last-resolved-ptr).
	 *
	 * We now need to continue from the last-resolved-ptr to
	 * ensure the last-resolved-ptr will not referring back to
	 * the currenct ptr (t).
	 */
	if (btf_type_is_modifier(next_type)) {
		const struct btf_type *resolved_type;
		u32 resolved_type_id;

		resolved_type_id = next_type_id;
		resolved_type = btf_type_id_resolve(btf, &resolved_type_id);

		if (btf_type_is_ptr(resolved_type) &&
		    !env_type_is_resolve_sink(env, resolved_type) &&
		    !env_type_is_resolved(env, resolved_type_id))
			return env_stack_push(env, resolved_type,
					      resolved_type_id);
	}

	if (!btf_type_id_size(btf, &next_type_id, &next_type_size) &&
	    !btf_type_is_void(btf_type_id_resolve(btf, &next_type_id))) {
		btf_verifier_log_type(env, v->t, "Invalid type_id");
		return -EINVAL;
	}

resolved:
	env_stack_pop_resolved(env, next_type_id, 0);

	return 0;
}

static void btf_modifier_seq_show(const struct btf *btf,
				  const struct btf_type *t,
				  u32 type_id, void *data,
				  u8 bits_offset, struct seq_file *m)
{
	t = btf_type_id_resolve(btf, &type_id);

	btf_type_ops(t)->seq_show(btf, t, type_id, data, bits_offset, m);
}

static void btf_ptr_seq_show(const struct btf *btf, const struct btf_type *t,
			     u32 type_id, void *data, u8 bits_offset,
			     struct seq_file *m)
{
	/* It is a hashed value */
	seq_printf(m, "%p", *(void **)data);
}

static void btf_ref_type_log(struct btf_verifier_env *env,
			     const struct btf_type *t)
{
	btf_verifier_log(env, "type_id=%u", t->type);
}

static struct btf_kind_operations modifier_ops = {
	.check_meta = btf_ref_type_check_meta,
	.resolve = btf_modifier_resolve,
	.check_member = btf_modifier_check_member,
	.log_details = btf_ref_type_log,
	.seq_show = btf_modifier_seq_show,
};

static struct btf_kind_operations ptr_ops = {
	.check_meta = btf_ref_type_check_meta,
	.resolve = btf_ptr_resolve,
	.check_member = btf_ptr_check_member,
	.log_details = btf_ref_type_log,
	.seq_show = btf_ptr_seq_show,
};

static s32 btf_fwd_check_meta(struct btf_verifier_env *env,
			      const struct btf_type *t,
			      u32 meta_left)
{
	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	if (t->type) {
		btf_verifier_log_type(env, t, "type != 0");
		return -EINVAL;
	}

	/* fwd type must have a valid name */
	if (!t->name_off ||
	    !btf_name_valid_identifier(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	return 0;
}

static struct btf_kind_operations fwd_ops = {
	.check_meta = btf_fwd_check_meta,
	.resolve = btf_df_resolve,
	.check_member = btf_df_check_member,
	.log_details = btf_ref_type_log,
	.seq_show = btf_df_seq_show,
};

static int btf_array_check_member(struct btf_verifier_env *env,
				  const struct btf_type *struct_type,
				  const struct btf_member *member,
				  const struct btf_type *member_type)
{
	u32 struct_bits_off = member->offset;
	u32 struct_size, bytes_offset;
	u32 array_type_id, array_size;
	struct btf *btf = env->btf;

	if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member is not byte aligned");
		return -EINVAL;
	}

	array_type_id = member->type;
	btf_type_id_size(btf, &array_type_id, &array_size);
	struct_size = struct_type->size;
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	if (struct_size - bytes_offset < array_size) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static s32 btf_array_check_meta(struct btf_verifier_env *env,
				const struct btf_type *t,
				u32 meta_left)
{
	const struct btf_array *array = btf_type_array(t);
	u32 meta_needed = sizeof(*array);

	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	/* array type should not have a name */
	if (t->name_off) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	if (btf_type_vlen(t)) {
		btf_verifier_log_type(env, t, "vlen != 0");
		return -EINVAL;
	}

	if (t->size) {
		btf_verifier_log_type(env, t, "size != 0");
		return -EINVAL;
	}

	/* Array elem type and index type cannot be in type void,
	 * so !array->type and !array->index_type are not allowed.
	 */
	if (!array->type || !BTF_TYPE_ID_VALID(array->type)) {
		btf_verifier_log_type(env, t, "Invalid elem");
		return -EINVAL;
	}

	if (!array->index_type || !BTF_TYPE_ID_VALID(array->index_type)) {
		btf_verifier_log_type(env, t, "Invalid index");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	return meta_needed;
}

static int btf_array_resolve(struct btf_verifier_env *env,
			     const struct resolve_vertex *v)
{
	const struct btf_array *array = btf_type_array(v->t);
	const struct btf_type *elem_type, *index_type;
	u32 elem_type_id, index_type_id;
	struct btf *btf = env->btf;
	u32 elem_size;

	/* Check array->index_type */
	index_type_id = array->index_type;
	index_type = btf_type_by_id(btf, index_type_id);
	if (btf_type_is_void_or_null(index_type)) {
		btf_verifier_log_type(env, v->t, "Invalid index");
		return -EINVAL;
	}

	if (!env_type_is_resolve_sink(env, index_type) &&
	    !env_type_is_resolved(env, index_type_id))
		return env_stack_push(env, index_type, index_type_id);

	index_type = btf_type_id_size(btf, &index_type_id, NULL);
	if (!index_type || !btf_type_is_int(index_type) ||
	    !btf_type_int_is_regular(index_type)) {
		btf_verifier_log_type(env, v->t, "Invalid index");
		return -EINVAL;
	}

	/* Check array->type */
	elem_type_id = array->type;
	elem_type = btf_type_by_id(btf, elem_type_id);
	if (btf_type_is_void_or_null(elem_type)) {
		btf_verifier_log_type(env, v->t,
				      "Invalid elem");
		return -EINVAL;
	}

	if (!env_type_is_resolve_sink(env, elem_type) &&
	    !env_type_is_resolved(env, elem_type_id))
		return env_stack_push(env, elem_type, elem_type_id);

	elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
	if (!elem_type) {
		btf_verifier_log_type(env, v->t, "Invalid elem");
		return -EINVAL;
	}

	if (btf_type_is_int(elem_type) && !btf_type_int_is_regular(elem_type)) {
		btf_verifier_log_type(env, v->t, "Invalid array of int");
		return -EINVAL;
	}

	if (array->nelems && elem_size > U32_MAX / array->nelems) {
		btf_verifier_log_type(env, v->t,
				      "Array size overflows U32_MAX");
		return -EINVAL;
	}

	env_stack_pop_resolved(env, elem_type_id, elem_size * array->nelems);

	return 0;
}

static void btf_array_log(struct btf_verifier_env *env,
			  const struct btf_type *t)
{
	const struct btf_array *array = btf_type_array(t);

	btf_verifier_log(env, "type_id=%u index_type_id=%u nr_elems=%u",
			 array->type, array->index_type, array->nelems);
}

static void btf_array_seq_show(const struct btf *btf, const struct btf_type *t,
			       u32 type_id, void *data, u8 bits_offset,
			       struct seq_file *m)
{
	const struct btf_array *array = btf_type_array(t);
	const struct btf_kind_operations *elem_ops;
	const struct btf_type *elem_type;
	u32 i, elem_size, elem_type_id;

	elem_type_id = array->type;
	elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
	elem_ops = btf_type_ops(elem_type);
	seq_puts(m, "[");
	for (i = 0; i < array->nelems; i++) {
		if (i)
			seq_puts(m, ",");

		elem_ops->seq_show(btf, elem_type, elem_type_id, data,
				   bits_offset, m);
		data += elem_size;
	}
	seq_puts(m, "]");
}

static struct btf_kind_operations array_ops = {
	.check_meta = btf_array_check_meta,
	.resolve = btf_array_resolve,
	.check_member = btf_array_check_member,
	.log_details = btf_array_log,
	.seq_show = btf_array_seq_show,
};

static int btf_struct_check_member(struct btf_verifier_env *env,
				   const struct btf_type *struct_type,
				   const struct btf_member *member,
				   const struct btf_type *member_type)
{
	u32 struct_bits_off = member->offset;
	u32 struct_size, bytes_offset;

	if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member is not byte aligned");
		return -EINVAL;
	}

	struct_size = struct_type->size;
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	if (struct_size - bytes_offset < member_type->size) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static s32 btf_struct_check_meta(struct btf_verifier_env *env,
				 const struct btf_type *t,
				 u32 meta_left)
{
	bool is_union = BTF_INFO_KIND(t->info) == BTF_KIND_UNION;
	const struct btf_member *member;
	u32 meta_needed, last_offset;
	struct btf *btf = env->btf;
	u32 struct_size = t->size;
	u16 i;

	meta_needed = btf_type_vlen(t) * sizeof(*member);
	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	/* struct type either no name or a valid one */
	if (t->name_off &&
	    !btf_name_valid_identifier(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	last_offset = 0;
	for_each_member(i, t, member) {
		if (!btf_name_offset_valid(btf, member->name_off)) {
			btf_verifier_log_member(env, t, member,
						"Invalid member name_offset:%u",
						member->name_off);
			return -EINVAL;
		}

		/* struct member either no name or a valid one */
		if (member->name_off &&
		    !btf_name_valid_identifier(btf, member->name_off)) {
			btf_verifier_log_member(env, t, member, "Invalid name");
			return -EINVAL;
		}
		/* A member cannot be in type void */
		if (!member->type || !BTF_TYPE_ID_VALID(member->type)) {
			btf_verifier_log_member(env, t, member,
						"Invalid type_id");
			return -EINVAL;
		}

		if (is_union && member->offset) {
			btf_verifier_log_member(env, t, member,
						"Invalid member bits_offset");
			return -EINVAL;
		}

		/*
		 * ">" instead of ">=" because the last member could be
		 * "char a[0];"
		 */
		if (last_offset > member->offset) {
			btf_verifier_log_member(env, t, member,
						"Invalid member bits_offset");
			return -EINVAL;
		}

		if (BITS_ROUNDUP_BYTES(member->offset) > struct_size) {
			btf_verifier_log_member(env, t, member,
						"Memmber bits_offset exceeds its struct size");
			return -EINVAL;
		}

		btf_verifier_log_member(env, t, member, NULL);
		last_offset = member->offset;
	}

	return meta_needed;
}

static int btf_struct_resolve(struct btf_verifier_env *env,
			      const struct resolve_vertex *v)
{
	const struct btf_member *member;
	int err;
	u16 i;

	/* Before continue resolving the next_member,
	 * ensure the last member is indeed resolved to a
	 * type with size info.
	 */
	if (v->next_member) {
		const struct btf_type *last_member_type;
		const struct btf_member *last_member;
		u16 last_member_type_id;

		last_member = btf_type_member(v->t) + v->next_member - 1;
		last_member_type_id = last_member->type;
		if (WARN_ON_ONCE(!env_type_is_resolved(env,
						       last_member_type_id)))
			return -EINVAL;

		last_member_type = btf_type_by_id(env->btf,
						  last_member_type_id);
		err = btf_type_ops(last_member_type)->check_member(env, v->t,
							last_member,
							last_member_type);
		if (err)
			return err;
	}

	for_each_member_from(i, v->next_member, v->t, member) {
		u32 member_type_id = member->type;
		const struct btf_type *member_type = btf_type_by_id(env->btf,
								member_type_id);

		if (btf_type_is_void_or_null(member_type)) {
			btf_verifier_log_member(env, v->t, member,
						"Invalid member");
			return -EINVAL;
		}

		if (!env_type_is_resolve_sink(env, member_type) &&
		    !env_type_is_resolved(env, member_type_id)) {
			env_stack_set_next_member(env, i + 1);
			return env_stack_push(env, member_type, member_type_id);
		}

		err = btf_type_ops(member_type)->check_member(env, v->t,
							      member,
							      member_type);
		if (err)
			return err;
	}

	env_stack_pop_resolved(env, 0, 0);

	return 0;
}

static void btf_struct_log(struct btf_verifier_env *env,
			   const struct btf_type *t)
{
	btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

static void btf_struct_seq_show(const struct btf *btf, const struct btf_type *t,
				u32 type_id, void *data, u8 bits_offset,
				struct seq_file *m)
{
	const char *seq = BTF_INFO_KIND(t->info) == BTF_KIND_UNION ? "|" : ",";
	const struct btf_member *member;
	u32 i;

	seq_puts(m, "{");
	for_each_member(i, t, member) {
		const struct btf_type *member_type = btf_type_by_id(btf,
								member->type);
		u32 member_offset = member->offset;
		u32 bytes_offset = BITS_ROUNDDOWN_BYTES(member_offset);
		u8 bits8_offset = BITS_PER_BYTE_MASKED(member_offset);
		const struct btf_kind_operations *ops;

		if (i)
			seq_puts(m, seq);

		ops = btf_type_ops(member_type);
		ops->seq_show(btf, member_type, member->type,
			      data + bytes_offset, bits8_offset, m);
	}
	seq_puts(m, "}");
}

static struct btf_kind_operations struct_ops = {
	.check_meta = btf_struct_check_meta,
	.resolve = btf_struct_resolve,
	.check_member = btf_struct_check_member,
	.log_details = btf_struct_log,
	.seq_show = btf_struct_seq_show,
};

static int btf_enum_check_member(struct btf_verifier_env *env,
				 const struct btf_type *struct_type,
				 const struct btf_member *member,
				 const struct btf_type *member_type)
{
	u32 struct_bits_off = member->offset;
	u32 struct_size, bytes_offset;

	if (BITS_PER_BYTE_MASKED(struct_bits_off)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member is not byte aligned");
		return -EINVAL;
	}

	struct_size = struct_type->size;
	bytes_offset = BITS_ROUNDDOWN_BYTES(struct_bits_off);
	if (struct_size - bytes_offset < sizeof(int)) {
		btf_verifier_log_member(env, struct_type, member,
					"Member exceeds struct_size");
		return -EINVAL;
	}

	return 0;
}

static s32 btf_enum_check_meta(struct btf_verifier_env *env,
			       const struct btf_type *t,
			       u32 meta_left)
{
	const struct btf_enum *enums = btf_type_enum(t);
	struct btf *btf = env->btf;
	u16 i, nr_enums;
	u32 meta_needed;

	nr_enums = btf_type_vlen(t);
	meta_needed = nr_enums * sizeof(*enums);

	if (meta_left < meta_needed) {
		btf_verifier_log_basic(env, t,
				       "meta_left:%u meta_needed:%u",
				       meta_left, meta_needed);
		return -EINVAL;
	}

	if (t->size != sizeof(int)) {
		btf_verifier_log_type(env, t, "Expected size:%zu",
				      sizeof(int));
		return -EINVAL;
	}

	/* enum type either no name or a valid one */
	if (t->name_off &&
	    !btf_name_valid_identifier(env->btf, t->name_off)) {
		btf_verifier_log_type(env, t, "Invalid name");
		return -EINVAL;
	}

	btf_verifier_log_type(env, t, NULL);

	for (i = 0; i < nr_enums; i++) {
		if (!btf_name_offset_valid(btf, enums[i].name_off)) {
			btf_verifier_log(env, "\tInvalid name_offset:%u",
					 enums[i].name_off);
			return -EINVAL;
		}

		/* enum member must have a valid name */
		if (!enums[i].name_off ||
		    !btf_name_valid_identifier(btf, enums[i].name_off)) {
			btf_verifier_log_type(env, t, "Invalid name");
			return -EINVAL;
		}


		btf_verifier_log(env, "\t%s val=%d\n",
				 btf_name_by_offset(btf, enums[i].name_off),
				 enums[i].val);
	}

	return meta_needed;
}

static void btf_enum_log(struct btf_verifier_env *env,
			 const struct btf_type *t)
{
	btf_verifier_log(env, "size=%u vlen=%u", t->size, btf_type_vlen(t));
}

static void btf_enum_seq_show(const struct btf *btf, const struct btf_type *t,
			      u32 type_id, void *data, u8 bits_offset,
			      struct seq_file *m)
{
	const struct btf_enum *enums = btf_type_enum(t);
	u32 i, nr_enums = btf_type_vlen(t);
	int v = *(int *)data;

	for (i = 0; i < nr_enums; i++) {
		if (v == enums[i].val) {
			seq_printf(m, "%s",
				   btf_name_by_offset(btf, enums[i].name_off));
			return;
		}
	}

	seq_printf(m, "%d", v);
}

static struct btf_kind_operations enum_ops = {
	.check_meta = btf_enum_check_meta,
	.resolve = btf_df_resolve,
	.check_member = btf_enum_check_member,
	.log_details = btf_enum_log,
	.seq_show = btf_enum_seq_show,
};

static const struct btf_kind_operations * const kind_ops[NR_BTF_KINDS] = {
	[BTF_KIND_INT] = &int_ops,
	[BTF_KIND_PTR] = &ptr_ops,
	[BTF_KIND_ARRAY] = &array_ops,
	[BTF_KIND_STRUCT] = &struct_ops,
	[BTF_KIND_UNION] = &struct_ops,
	[BTF_KIND_ENUM] = &enum_ops,
	[BTF_KIND_FWD] = &fwd_ops,
	[BTF_KIND_TYPEDEF] = &modifier_ops,
	[BTF_KIND_VOLATILE] = &modifier_ops,
	[BTF_KIND_CONST] = &modifier_ops,
	[BTF_KIND_RESTRICT] = &modifier_ops,
};

static s32 btf_check_meta(struct btf_verifier_env *env,
			  const struct btf_type *t,
			  u32 meta_left)
{
	u32 saved_meta_left = meta_left;
	s32 var_meta_size;

	if (meta_left < sizeof(*t)) {
		btf_verifier_log(env, "[%u] meta_left:%u meta_needed:%zu",
				 env->log_type_id, meta_left, sizeof(*t));
		return -EINVAL;
	}
	meta_left -= sizeof(*t);

	if (t->info & ~BTF_INFO_MASK) {
		btf_verifier_log(env, "[%u] Invalid btf_info:%x",
				 env->log_type_id, t->info);
		return -EINVAL;
	}

	if (BTF_INFO_KIND(t->info) > BTF_KIND_MAX ||
	    BTF_INFO_KIND(t->info) == BTF_KIND_UNKN) {
		btf_verifier_log(env, "[%u] Invalid kind:%u",
				 env->log_type_id, BTF_INFO_KIND(t->info));
		return -EINVAL;
	}

	if (!btf_name_offset_valid(env->btf, t->name_off)) {
		btf_verifier_log(env, "[%u] Invalid name_offset:%u",
				 env->log_type_id, t->name_off);
		return -EINVAL;
	}

	var_meta_size = btf_type_ops(t)->check_meta(env, t, meta_left);
	if (var_meta_size < 0)
		return var_meta_size;

	meta_left -= var_meta_size;

	return saved_meta_left - meta_left;
}

static int btf_check_all_metas(struct btf_verifier_env *env)
{
	struct btf *btf = env->btf;
	struct btf_header *hdr;
	void *cur, *end;

	hdr = &btf->hdr;
	cur = btf->nohdr_data + hdr->type_off;
	end = cur + hdr->type_len;

	env->log_type_id = 1;
	while (cur < end) {
		struct btf_type *t = cur;
		s32 meta_size;

		meta_size = btf_check_meta(env, t, end - cur);
		if (meta_size < 0)
			return meta_size;

		btf_add_type(env, t);
		cur += meta_size;
		env->log_type_id++;
	}

	return 0;
}

static int btf_resolve(struct btf_verifier_env *env,
		       const struct btf_type *t, u32 type_id)
{
	const struct resolve_vertex *v;
	int err = 0;

	env->resolve_mode = RESOLVE_TBD;
	env_stack_push(env, t, type_id);
	while (!err && (v = env_stack_peak(env))) {
		env->log_type_id = v->type_id;
		err = btf_type_ops(v->t)->resolve(env, v);
	}

	env->log_type_id = type_id;
	if (err == -E2BIG)
		btf_verifier_log_type(env, t,
				      "Exceeded max resolving depth:%u",
				      MAX_RESOLVE_DEPTH);
	else if (err == -EEXIST)
		btf_verifier_log_type(env, t, "Loop detected");

	return err;
}

static bool btf_resolve_valid(struct btf_verifier_env *env,
			      const struct btf_type *t,
			      u32 type_id)
{
	struct btf *btf = env->btf;

	if (!env_type_is_resolved(env, type_id))
		return false;

	if (btf_type_is_struct(t))
		return !btf->resolved_ids[type_id] &&
			!btf->resolved_sizes[type_id];

	if (btf_type_is_modifier(t) || btf_type_is_ptr(t)) {
		t = btf_type_id_resolve(btf, &type_id);
		return t && !btf_type_is_modifier(t);
	}

	if (btf_type_is_array(t)) {
		const struct btf_array *array = btf_type_array(t);
		const struct btf_type *elem_type;
		u32 elem_type_id = array->type;
		u32 elem_size;

		elem_type = btf_type_id_size(btf, &elem_type_id, &elem_size);
		return elem_type && !btf_type_is_modifier(elem_type) &&
			(array->nelems * elem_size ==
			 btf->resolved_sizes[type_id]);
	}

	return false;
}

static int btf_check_all_types(struct btf_verifier_env *env)
{
	struct btf *btf = env->btf;
	u32 type_id;
	int err;

	err = env_resolve_init(env);
	if (err)
		return err;

	env->phase++;
	for (type_id = 1; type_id <= btf->nr_types; type_id++) {
		const struct btf_type *t = btf_type_by_id(btf, type_id);

		env->log_type_id = type_id;
		if (btf_type_needs_resolve(t) &&
		    !env_type_is_resolved(env, type_id)) {
			err = btf_resolve(env, t, type_id);
			if (err)
				return err;
		}

		if (btf_type_needs_resolve(t) &&
		    !btf_resolve_valid(env, t, type_id)) {
			btf_verifier_log_type(env, t, "Invalid resolve state");
			return -EINVAL;
		}
	}

	return 0;
}

static int btf_parse_type_sec(struct btf_verifier_env *env)
{
	const struct btf_header *hdr = &env->btf->hdr;
	int err;

	/* Type section must align to 4 bytes */
	if (hdr->type_off & (sizeof(u32) - 1)) {
		btf_verifier_log(env, "Unaligned type_off");
		return -EINVAL;
	}

	if (!hdr->type_len) {
		btf_verifier_log(env, "No type found");
		return -EINVAL;
	}

	err = btf_check_all_metas(env);
	if (err)
		return err;

	return btf_check_all_types(env);
}

static int btf_parse_str_sec(struct btf_verifier_env *env)
{
	const struct btf_header *hdr;
	struct btf *btf = env->btf;
	const char *start, *end;

	hdr = &btf->hdr;
	start = btf->nohdr_data + hdr->str_off;
	end = start + hdr->str_len;

	if (end != btf->data + btf->data_size) {
		btf_verifier_log(env, "String section is not at the end");
		return -EINVAL;
	}

	if (!hdr->str_len || hdr->str_len - 1 > BTF_MAX_NAME_OFFSET ||
	    start[0] || end[-1]) {
		btf_verifier_log(env, "Invalid string section");
		return -EINVAL;
	}

	btf->strings = start;

	return 0;
}

static const size_t btf_sec_info_offset[] = {
	offsetof(struct btf_header, type_off),
	offsetof(struct btf_header, str_off),
};

static int btf_sec_info_cmp(const void *a, const void *b)
{
	const struct btf_sec_info *x = a;
	const struct btf_sec_info *y = b;

	return (int)(x->off - y->off) ? : (int)(x->len - y->len);
}

static int btf_check_sec_info(struct btf_verifier_env *env,
			      u32 btf_data_size)
{
	struct btf_sec_info secs[ARRAY_SIZE(btf_sec_info_offset)];
	u32 total, expected_total, i;
	const struct btf_header *hdr;
	const struct btf *btf;

	btf = env->btf;
	hdr = &btf->hdr;

	/* Populate the secs from hdr */
	for (i = 0; i < ARRAY_SIZE(btf_sec_info_offset); i++)
		secs[i] = *(struct btf_sec_info *)((void *)hdr +
						   btf_sec_info_offset[i]);

	sort(secs, ARRAY_SIZE(btf_sec_info_offset),
	     sizeof(struct btf_sec_info), btf_sec_info_cmp, NULL);

	/* Check for gaps and overlap among sections */
	total = 0;
	expected_total = btf_data_size - hdr->hdr_len;
	for (i = 0; i < ARRAY_SIZE(btf_sec_info_offset); i++) {
		if (expected_total < secs[i].off) {
			btf_verifier_log(env, "Invalid section offset");
			return -EINVAL;
		}
		if (total < secs[i].off) {
			/* gap */
			btf_verifier_log(env, "Unsupported section found");
			return -EINVAL;
		}
		if (total > secs[i].off) {
			btf_verifier_log(env, "Section overlap found");
			return -EINVAL;
		}
		if (expected_total - total < secs[i].len) {
			btf_verifier_log(env,
					 "Total section length too long");
			return -EINVAL;
		}
		total += secs[i].len;
	}

	/* There is data other than hdr and known sections */
	if (expected_total != total) {
		btf_verifier_log(env, "Unsupported section found");
		return -EINVAL;
	}

	return 0;
}

static int btf_parse_hdr(struct btf_verifier_env *env)
{
	u32 hdr_len, hdr_copy, btf_data_size;
	const struct btf_header *hdr;
	struct btf *btf;
	int err;

	btf = env->btf;
	btf_data_size = btf->data_size;

	if (btf_data_size <
	    offsetof(struct btf_header, hdr_len) + sizeof(hdr->hdr_len)) {
		btf_verifier_log(env, "hdr_len not found");
		return -EINVAL;
	}

	hdr = btf->data;
	hdr_len = hdr->hdr_len;
	if (btf_data_size < hdr_len) {
		btf_verifier_log(env, "btf_header not found");
		return -EINVAL;
	}

	/* Ensure the unsupported header fields are zero */
	if (hdr_len > sizeof(btf->hdr)) {
		u8 *expected_zero = btf->data + sizeof(btf->hdr);
		u8 *end = btf->data + hdr_len;

		for (; expected_zero < end; expected_zero++) {
			if (*expected_zero) {
				btf_verifier_log(env, "Unsupported btf_header");
				return -E2BIG;
			}
		}
	}

	hdr_copy = min_t(u32, hdr_len, sizeof(btf->hdr));
	memcpy(&btf->hdr, btf->data, hdr_copy);

	hdr = &btf->hdr;

	btf_verifier_log_hdr(env, btf_data_size);

	if (hdr->magic != BTF_MAGIC) {
		btf_verifier_log(env, "Invalid magic");
		return -EINVAL;
	}

	if (hdr->version != BTF_VERSION) {
		btf_verifier_log(env, "Unsupported version");
		return -ENOTSUPP;
	}

	if (hdr->flags) {
		btf_verifier_log(env, "Unsupported flags");
		return -ENOTSUPP;
	}

	if (btf_data_size == hdr->hdr_len) {
		btf_verifier_log(env, "No data");
		return -EINVAL;
	}

	err = btf_check_sec_info(env, btf_data_size);
	if (err)
		return err;

	return 0;
}

static struct btf *btf_parse(void __user *btf_data, u32 btf_data_size,
			     u32 log_level, char __user *log_ubuf, u32 log_size)
{
	struct btf_verifier_env *env = NULL;
	struct bpf_verifier_log *log;
	struct btf *btf = NULL;
	u8 *data;
	int err;

	if (btf_data_size > BTF_MAX_SIZE)
		return ERR_PTR(-E2BIG);

	env = kzalloc(sizeof(*env), GFP_KERNEL | __GFP_NOWARN);
	if (!env)
		return ERR_PTR(-ENOMEM);

	log = &env->log;
	if (log_level || log_ubuf || log_size) {
		/* user requested verbose verifier output
		 * and supplied buffer to store the verification trace
		 */
		log->level = log_level;
		log->ubuf = log_ubuf;
		log->len_total = log_size;

		/* log attributes have to be sane */
		if (log->len_total < 128 || log->len_total > UINT_MAX >> 8 ||
		    !log->level || !log->ubuf) {
			err = -EINVAL;
			goto errout;
		}
	}

	btf = kzalloc(sizeof(*btf), GFP_KERNEL | __GFP_NOWARN);
	if (!btf) {
		err = -ENOMEM;
		goto errout;
	}
	env->btf = btf;

	data = kvmalloc(btf_data_size, GFP_KERNEL | __GFP_NOWARN);
	if (!data) {
		err = -ENOMEM;
		goto errout;
	}

	btf->data = data;
	btf->data_size = btf_data_size;

	if (copy_from_user(data, btf_data, btf_data_size)) {
		err = -EFAULT;
		goto errout;
	}

	err = btf_parse_hdr(env);
	if (err)
		goto errout;

	btf->nohdr_data = btf->data + btf->hdr.hdr_len;

	err = btf_parse_str_sec(env);
	if (err)
		goto errout;

	err = btf_parse_type_sec(env);
	if (err)
		goto errout;

	if (log->level && bpf_verifier_log_full(log)) {
		err = -ENOSPC;
		goto errout;
	}

	btf_verifier_env_free(env);
	refcount_set(&btf->refcnt, 1);
	return btf;

errout:
	btf_verifier_env_free(env);
	if (btf)
		btf_free(btf);
	return ERR_PTR(err);
}

void btf_type_seq_show(const struct btf *btf, u32 type_id, void *obj,
		       struct seq_file *m)
{
	const struct btf_type *t = btf_type_by_id(btf, type_id);

	btf_type_ops(t)->seq_show(btf, t, type_id, obj, 0, m);
}

static int btf_release(struct inode *inode, struct file *filp)
{
	btf_put(filp->private_data);
	return 0;
}

const struct file_operations btf_fops = {
	.release	= btf_release,
};

static int __btf_new_fd(struct btf *btf)
{
	return anon_inode_getfd("btf", &btf_fops, btf, O_RDONLY | O_CLOEXEC);
}

int btf_new_fd(const union bpf_attr *attr)
{
	struct btf *btf;
	int ret;

	btf = btf_parse(u64_to_user_ptr(attr->btf),
			attr->btf_size, attr->btf_log_level,
			u64_to_user_ptr(attr->btf_log_buf),
			attr->btf_log_size);
	if (IS_ERR(btf))
		return PTR_ERR(btf);

	ret = btf_alloc_id(btf);
	if (ret) {
		btf_free(btf);
		return ret;
	}

	/*
	 * The BTF ID is published to the userspace.
	 * All BTF free must go through call_rcu() from
	 * now on (i.e. free by calling btf_put()).
	 */

	ret = __btf_new_fd(btf);
	if (ret < 0)
		btf_put(btf);

	return ret;
}

struct btf *btf_get_by_fd(int fd)
{
	struct btf *btf;
	struct fd f;

	f = fdget(fd);

	if (!f.file)
		return ERR_PTR(-EBADF);

	if (f.file->f_op != &btf_fops) {
		fdput(f);
		return ERR_PTR(-EINVAL);
	}

	btf = f.file->private_data;
	refcount_inc(&btf->refcnt);
	fdput(f);

	return btf;
}

int btf_get_info_by_fd(const struct btf *btf,
		       const union bpf_attr *attr,
		       union bpf_attr __user *uattr)
{
	struct bpf_btf_info __user *uinfo;
	struct bpf_btf_info info = {};
	u32 info_copy, btf_copy;
	void __user *ubtf;
	u32 uinfo_len;

	uinfo = u64_to_user_ptr(attr->info.info);
	uinfo_len = attr->info.info_len;

	info_copy = min_t(u32, uinfo_len, sizeof(info));
	if (copy_from_user(&info, uinfo, info_copy))
		return -EFAULT;

	info.id = btf->id;
	ubtf = u64_to_user_ptr(info.btf);
	btf_copy = min_t(u32, btf->data_size, info.btf_size);
	if (copy_to_user(ubtf, btf->data, btf_copy))
		return -EFAULT;
	info.btf_size = btf->data_size;

	if (copy_to_user(uinfo, &info, info_copy) ||
	    put_user(info_copy, &uattr->info.info_len))
		return -EFAULT;

	return 0;
}

int btf_get_fd_by_id(u32 id)
{
	struct btf *btf;
	int fd;

	rcu_read_lock();
	btf = idr_find(&btf_idr, id);
	if (!btf || !refcount_inc_not_zero(&btf->refcnt))
		btf = ERR_PTR(-ENOENT);
	rcu_read_unlock();

	if (IS_ERR(btf))
		return PTR_ERR(btf);

	fd = __btf_new_fd(btf);
	if (fd < 0)
		btf_put(btf);

	return fd;
}

u32 btf_id(const struct btf *btf)
{
	return btf->id;
}