[people/ms/linux.git] /

/* 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;
        }

        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;
        }

        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;
        }

        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;
        }

        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;
                }

                /* 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;
        }

        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;
                }

                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;
}