// SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause)

/*
 * resolve_btfids scans Elf object for .BTF_ids section and resolves
 * its symbols with BTF ID values.
 *
 * Each symbol points to 4 bytes data and is expected to have
 * following name syntax:
 *
 * __BTF_ID__<type>__<symbol>[__<id>]
 *
 * type is:
 *
 *   func    - lookup BTF_KIND_FUNC symbol with <symbol> name
 *             and store its ID into the data:
 *
 *             __BTF_ID__func__vfs_close__1:
 *             .zero 4
 *
 *   struct  - lookup BTF_KIND_STRUCT symbol with <symbol> name
 *             and store its ID into the data:
 *
 *             __BTF_ID__struct__sk_buff__1:
 *             .zero 4
 *
 *   union   - lookup BTF_KIND_UNION symbol with <symbol> name
 *             and store its ID into the data:
 *
 *             __BTF_ID__union__thread_union__1:
 *             .zero 4
 *
 *   typedef - lookup BTF_KIND_TYPEDEF symbol with <symbol> name
 *             and store its ID into the data:
 *
 *             __BTF_ID__typedef__pid_t__1:
 *             .zero 4
 *
 *   set     - store symbol size into first 4 bytes and sort following
 *             ID list
 *
 *             __BTF_ID__set__list:
 *             .zero 4
 *             list:
 *             __BTF_ID__func__vfs_getattr__3:
 *             .zero 4
 *             __BTF_ID__func__vfs_fallocate__4:
 *             .zero 4
 */

#define  _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <libelf.h>
#include <gelf.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <linux/rbtree.h>
#include <linux/zalloc.h>
#include <linux/err.h>
#include <bpf/btf.h>
#include <bpf/libbpf.h>
#include <parse-options.h>

#define BTF_IDS_SECTION ".BTF_ids"
#define BTF_ID          "__BTF_ID__"

#define BTF_STRUCT      "struct"
#define BTF_UNION       "union"
#define BTF_TYPEDEF     "typedef"
#define BTF_FUNC        "func"
#define BTF_SET         "set"

#define ADDR_CNT        100

struct btf_id {
        struct rb_node   rb_node;
        char            *name;
        union {
                int      id;
                int      cnt;
        };
        int              addr_cnt;
        bool             is_set;
        Elf64_Addr       addr[ADDR_CNT];
};

struct object {
        const char *path;
        const char *btf;
        const char *base_btf_path;

        struct {
                int              fd;
                Elf             *elf;
                Elf_Data        *symbols;
                Elf_Data        *idlist;
                int              symbols_shndx;
                int              idlist_shndx;
                size_t           strtabidx;
                unsigned long    idlist_addr;
        } efile;

        struct rb_root  sets;
        struct rb_root  structs;
        struct rb_root  unions;
        struct rb_root  typedefs;
        struct rb_root  funcs;

        int nr_funcs;
        int nr_structs;
        int nr_unions;
        int nr_typedefs;
};

static int verbose;

static int eprintf(int level, int var, const char *fmt, ...)
{
        va_list args;
        int ret = 0;

        if (var >= level) {
                va_start(args, fmt);
                ret = vfprintf(stderr, fmt, args);
                va_end(args);
        }
        return ret;
}

#ifndef pr_fmt
#define pr_fmt(fmt) fmt
#endif

#define pr_debug(fmt, ...) \
        eprintf(1, verbose, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debugN(n, fmt, ...) \
        eprintf(n, verbose, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_debug2(fmt, ...) pr_debugN(2, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_err(fmt, ...) \
        eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)
#define pr_info(fmt, ...) \
        eprintf(0, verbose, pr_fmt(fmt), ##__VA_ARGS__)

static bool is_btf_id(const char *name)
{
        return name && !strncmp(name, BTF_ID, sizeof(BTF_ID) - 1);
}

static struct btf_id *btf_id__find(struct rb_root *root, const char *name)
{
        struct rb_node *p = root->rb_node;
        struct btf_id *id;
        int cmp;

        while (p) {
                id = rb_entry(p, struct btf_id, rb_node);
                cmp = strcmp(id->name, name);
                if (cmp < 0)
                        p = p->rb_left;
                else if (cmp > 0)
                        p = p->rb_right;
                else
                        return id;
        }
        return NULL;
}

static struct btf_id *
btf_id__add(struct rb_root *root, char *name, bool unique)
{
        struct rb_node **p = &root->rb_node;
        struct rb_node *parent = NULL;
        struct btf_id *id;
        int cmp;

        while (*p != NULL) {
                parent = *p;
                id = rb_entry(parent, struct btf_id, rb_node);
                cmp = strcmp(id->name, name);
                if (cmp < 0)
                        p = &(*p)->rb_left;
                else if (cmp > 0)
                        p = &(*p)->rb_right;
                else
                        return unique ? NULL : id;
        }

        id = zalloc(sizeof(*id));
        if (id) {
                pr_debug("adding symbol %s\n", name);
                id->name = name;
                rb_link_node(&id->rb_node, parent, p);
                rb_insert_color(&id->rb_node, root);
        }
        return id;
}

static char *get_id(const char *prefix_end)
{
        /*
         * __BTF_ID__func__vfs_truncate__0
         * prefix_end =  ^
         * pos        =    ^
         */
        int len = strlen(prefix_end);
        int pos = sizeof("__") - 1;
        char *p, *id;

        if (pos >= len)
                return NULL;

        id = strdup(prefix_end + pos);
        if (id) {
                /*
                 * __BTF_ID__func__vfs_truncate__0
                 * id =            ^
                 *
                 * cut the unique id part
                 */
                p = strrchr(id, '_');
                p--;
                if (*p != '_') {
                        free(id);
                        return NULL;
                }
                *p = '\0';
        }
        return id;
}

static struct btf_id *add_set(struct object *obj, char *name)
{
        /*
         * __BTF_ID__set__name
         * name =    ^
         * id   =         ^
         */
        char *id = name + sizeof(BTF_SET "__") - 1;
        int len = strlen(name);

        if (id >= name + len) {
                pr_err("FAILED to parse set name: %s\n", name);
                return NULL;
        }

        return btf_id__add(&obj->sets, id, true);
}

static struct btf_id *add_symbol(struct rb_root *root, char *name, size_t size)
{
        char *id;

        id = get_id(name + size);
        if (!id) {
                pr_err("FAILED to parse symbol name: %s\n", name);
                return NULL;
        }

        return btf_id__add(root, id, false);
}

/* Older libelf.h and glibc elf.h might not yet define the ELF compression types. */
#ifndef SHF_COMPRESSED
#define SHF_COMPRESSED (1 << 11) /* Section with compressed data. */
#endif

/*
 * The data of compressed section should be aligned to 4
 * (for 32bit) or 8 (for 64 bit) bytes. The binutils ld
 * sets sh_addralign to 1, which makes libelf fail with
 * misaligned section error during the update:
 *    FAILED elf_update(WRITE): invalid section alignment
 *
 * While waiting for ld fix, we fix the compressed sections
 * sh_addralign value manualy.
 */
static int compressed_section_fix(Elf *elf, Elf_Scn *scn, GElf_Shdr *sh)
{
        int expected = gelf_getclass(elf) == ELFCLASS32 ? 4 : 8;

        if (!(sh->sh_flags & SHF_COMPRESSED))
                return 0;

        if (sh->sh_addralign == expected)
                return 0;

        pr_debug2(" - fixing wrong alignment sh_addralign %u, expected %u\n",
                  sh->sh_addralign, expected);

        sh->sh_addralign = expected;

        if (gelf_update_shdr(scn, sh) == 0) {
                pr_err("FAILED cannot update section header: %s\n",
                        elf_errmsg(-1));
                return -1;
        }
        return 0;
}

static int elf_collect(struct object *obj)
{
        Elf_Scn *scn = NULL;
        size_t shdrstrndx;
        int idx = 0;
        Elf *elf;
        int fd;

        fd = open(obj->path, O_RDWR, 0666);
        if (fd == -1) {
                pr_err("FAILED cannot open %s: %s\n",
                        obj->path, strerror(errno));
                return -1;
        }

        elf_version(EV_CURRENT);

        elf = elf_begin(fd, ELF_C_RDWR_MMAP, NULL);
        if (!elf) {
                close(fd);
                pr_err("FAILED cannot create ELF descriptor: %s\n",
                        elf_errmsg(-1));
                return -1;
        }

        obj->efile.fd  = fd;
        obj->efile.elf = elf;

        elf_flagelf(elf, ELF_C_SET, ELF_F_LAYOUT);

        if (elf_getshdrstrndx(elf, &shdrstrndx) != 0) {
                pr_err("FAILED cannot get shdr str ndx\n");
                return -1;
        }

        /*
         * Scan all the elf sections and look for save data
         * from .BTF_ids section and symbols.
         */
        while ((scn = elf_nextscn(elf, scn)) != NULL) {
                Elf_Data *data;
                GElf_Shdr sh;
                char *name;

                idx++;
                if (gelf_getshdr(scn, &sh) != &sh) {
                        pr_err("FAILED get section(%d) header\n", idx);
                        return -1;
                }

                name = elf_strptr(elf, shdrstrndx, sh.sh_name);
                if (!name) {
                        pr_err("FAILED get section(%d) name\n", idx);
                        return -1;
                }

                data = elf_getdata(scn, 0);
                if (!data) {
                        pr_err("FAILED to get section(%d) data from %s\n",
                                idx, name);
                        return -1;
                }

                pr_debug2("section(%d) %s, size %ld, link %d, flags %lx, type=%d\n",
                          idx, name, (unsigned long) data->d_size,
                          (int) sh.sh_link, (unsigned long) sh.sh_flags,
                          (int) sh.sh_type);

                if (sh.sh_type == SHT_SYMTAB) {
                        obj->efile.symbols       = data;
                        obj->efile.symbols_shndx = idx;
                        obj->efile.strtabidx     = sh.sh_link;
                } else if (!strcmp(name, BTF_IDS_SECTION)) {
                        obj->efile.idlist       = data;
                        obj->efile.idlist_shndx = idx;
                        obj->efile.idlist_addr  = sh.sh_addr;
                }

                if (compressed_section_fix(elf, scn, &sh))
                        return -1;
        }

        return 0;
}

static int symbols_collect(struct object *obj)
{
        Elf_Scn *scn = NULL;
        int n, i;
        GElf_Shdr sh;
        char *name;

        scn = elf_getscn(obj->efile.elf, obj->efile.symbols_shndx);
        if (!scn)
                return -1;

        if (gelf_getshdr(scn, &sh) != &sh)
                return -1;

        n = sh.sh_size / sh.sh_entsize;

        /*
         * Scan symbols and look for the ones starting with
         * __BTF_ID__* over .BTF_ids section.
         */
        for (i = 0; i < n; i++) {
                char *prefix;
                struct btf_id *id;
                GElf_Sym sym;

                if (!gelf_getsym(obj->efile.symbols, i, &sym))
                        return -1;

                if (sym.st_shndx != obj->efile.idlist_shndx)
                        continue;

                name = elf_strptr(obj->efile.elf, obj->efile.strtabidx,
                                  sym.st_name);

                if (!is_btf_id(name))
                        continue;

                /*
                 * __BTF_ID__TYPE__vfs_truncate__0
                 * prefix =  ^
                 */
                prefix = name + sizeof(BTF_ID) - 1;

                /* struct */
                if (!strncmp(prefix, BTF_STRUCT, sizeof(BTF_STRUCT) - 1)) {
                        obj->nr_structs++;
                        id = add_symbol(&obj->structs, prefix, sizeof(BTF_STRUCT) - 1);
                /* union  */
                } else if (!strncmp(prefix, BTF_UNION, sizeof(BTF_UNION) - 1)) {
                        obj->nr_unions++;
                        id = add_symbol(&obj->unions, prefix, sizeof(BTF_UNION) - 1);
                /* typedef */
                } else if (!strncmp(prefix, BTF_TYPEDEF, sizeof(BTF_TYPEDEF) - 1)) {
                        obj->nr_typedefs++;
                        id = add_symbol(&obj->typedefs, prefix, sizeof(BTF_TYPEDEF) - 1);
                /* func */
                } else if (!strncmp(prefix, BTF_FUNC, sizeof(BTF_FUNC) - 1)) {
                        obj->nr_funcs++;
                        id = add_symbol(&obj->funcs, prefix, sizeof(BTF_FUNC) - 1);
                /* set */
                } else if (!strncmp(prefix, BTF_SET, sizeof(BTF_SET) - 1)) {
                        id = add_set(obj, prefix);
                        /*
                         * SET objects store list's count, which is encoded
                         * in symbol's size, together with 'cnt' field hence
                         * that - 1.
                         */
                        if (id) {
                                id->cnt = sym.st_size / sizeof(int) - 1;
                                id->is_set = true;
                        }
                } else {
                        pr_err("FAILED unsupported prefix %s\n", prefix);
                        return -1;
                }

                if (!id)
                        return -ENOMEM;

                if (id->addr_cnt >= ADDR_CNT) {
                        pr_err("FAILED symbol %s crossed the number of allowed lists\n",
                                id->name);
                        return -1;
                }
                id->addr[id->addr_cnt++] = sym.st_value;
        }

        return 0;
}

static int symbols_resolve(struct object *obj)
{
        int nr_typedefs = obj->nr_typedefs;
        int nr_structs  = obj->nr_structs;
        int nr_unions   = obj->nr_unions;
        int nr_funcs    = obj->nr_funcs;
        struct btf *base_btf = NULL;
        int err, type_id;
        struct btf *btf;
        __u32 nr_types;

        if (obj->base_btf_path) {
                base_btf = btf__parse(obj->base_btf_path, NULL);
                err = libbpf_get_error(base_btf);
                if (err) {
                        pr_err("FAILED: load base BTF from %s: %s\n",
                               obj->base_btf_path, strerror(-err));
                        return -1;
                }
        }

        btf = btf__parse_split(obj->btf ?: obj->path, base_btf);
        err = libbpf_get_error(btf);
        if (err) {
                pr_err("FAILED: load BTF from %s: %s\n",
                        obj->btf ?: obj->path, strerror(-err));
                goto out;
        }

        err = -1;
        nr_types = btf__type_cnt(btf);

        /*
         * Iterate all the BTF types and search for collected symbol IDs.
         */
        for (type_id = 1; type_id < nr_types; type_id++) {
                const struct btf_type *type;
                struct rb_root *root;
                struct btf_id *id;
                const char *str;
                int *nr;

                type = btf__type_by_id(btf, type_id);
                if (!type) {
                        pr_err("FAILED: malformed BTF, can't resolve type for ID %d\n",
                                type_id);
                        goto out;
                }

                if (btf_is_func(type) && nr_funcs) {
                        nr   = &nr_funcs;
                        root = &obj->funcs;
                } else if (btf_is_struct(type) && nr_structs) {
                        nr   = &nr_structs;
                        root = &obj->structs;
                } else if (btf_is_union(type) && nr_unions) {
                        nr   = &nr_unions;
                        root = &obj->unions;
                } else if (btf_is_typedef(type) && nr_typedefs) {
                        nr   = &nr_typedefs;
                        root = &obj->typedefs;
                } else
                        continue;

                str = btf__name_by_offset(btf, type->name_off);
                if (!str) {
                        pr_err("FAILED: malformed BTF, can't resolve name for ID %d\n",
                                type_id);
                        goto out;
                }

                id = btf_id__find(root, str);
                if (id) {
                        if (id->id) {
                                pr_info("WARN: multiple IDs found for '%s': %d, %d - using %d\n",
                                        str, id->id, type_id, id->id);
                        } else {
                                id->id = type_id;
                                (*nr)--;
                        }
                }
        }

        err = 0;
out:
        btf__free(base_btf);
        btf__free(btf);
        return err;
}

static int id_patch(struct object *obj, struct btf_id *id)
{
        Elf_Data *data = obj->efile.idlist;
        int *ptr = data->d_buf;
        int i;

        if (!id->id && !id->is_set)
                pr_err("WARN: resolve_btfids: unresolved symbol %s\n", id->name);

        for (i = 0; i < id->addr_cnt; i++) {
                unsigned long addr = id->addr[i];
                unsigned long idx = addr - obj->efile.idlist_addr;

                pr_debug("patching addr %5lu: ID %7d [%s]\n",
                         idx, id->id, id->name);

                if (idx >= data->d_size) {
                        pr_err("FAILED patching index %lu out of bounds %lu\n",
                                idx, data->d_size);
                        return -1;
                }

                idx = idx / sizeof(int);
                ptr[idx] = id->id;
        }

        return 0;
}

static int __symbols_patch(struct object *obj, struct rb_root *root)
{
        struct rb_node *next;
        struct btf_id *id;

        next = rb_first(root);
        while (next) {
                id = rb_entry(next, struct btf_id, rb_node);

                if (id_patch(obj, id))
                        return -1;

                next = rb_next(next);
        }
        return 0;
}

static int cmp_id(const void *pa, const void *pb)
{
        const int *a = pa, *b = pb;

        return *a - *b;
}

static int sets_patch(struct object *obj)
{
        Elf_Data *data = obj->efile.idlist;
        int *ptr = data->d_buf;
        struct rb_node *next;

        next = rb_first(&obj->sets);
        while (next) {
                unsigned long addr, idx;
                struct btf_id *id;
                int *base;
                int cnt;

                id   = rb_entry(next, struct btf_id, rb_node);
                addr = id->addr[0];
                idx  = addr - obj->efile.idlist_addr;

                /* sets are unique */
                if (id->addr_cnt != 1) {
                        pr_err("FAILED malformed data for set '%s'\n",
                                id->name);
                        return -1;
                }

                idx = idx / sizeof(int);
                base = &ptr[idx] + 1;
                cnt = ptr[idx];

                pr_debug("sorting  addr %5lu: cnt %6d [%s]\n",
                         (idx + 1) * sizeof(int), cnt, id->name);

                qsort(base, cnt, sizeof(int), cmp_id);

                next = rb_next(next);
        }
        return 0;
}

static int symbols_patch(struct object *obj)
{
        int err;

        if (__symbols_patch(obj, &obj->structs)  ||
            __symbols_patch(obj, &obj->unions)   ||
            __symbols_patch(obj, &obj->typedefs) ||
            __symbols_patch(obj, &obj->funcs)    ||
            __symbols_patch(obj, &obj->sets))
                return -1;

        if (sets_patch(obj))
                return -1;

        /* Set type to ensure endian translation occurs. */
        obj->efile.idlist->d_type = ELF_T_WORD;

        elf_flagdata(obj->efile.idlist, ELF_C_SET, ELF_F_DIRTY);

        err = elf_update(obj->efile.elf, ELF_C_WRITE);
        if (err < 0) {
                pr_err("FAILED elf_update(WRITE): %s\n",
                        elf_errmsg(-1));
        }

        pr_debug("update %s for %s\n",
                 err >= 0 ? "ok" : "failed", obj->path);
        return err < 0 ? -1 : 0;
}

static const char * const resolve_btfids_usage[] = {
        "resolve_btfids [<options>] <ELF object>",
        NULL
};

int main(int argc, const char **argv)
{
        struct object obj = {
                .efile = {
                        .idlist_shndx  = -1,
                        .symbols_shndx = -1,
                },
                .structs  = RB_ROOT,
                .unions   = RB_ROOT,
                .typedefs = RB_ROOT,
                .funcs    = RB_ROOT,
                .sets     = RB_ROOT,
        };
        struct option btfid_options[] = {
                OPT_INCR('v', "verbose", &verbose,
                         "be more verbose (show errors, etc)"),
                OPT_STRING(0, "btf", &obj.btf, "BTF data",
                           "BTF data"),
                OPT_STRING('b', "btf_base", &obj.base_btf_path, "file",
                           "path of file providing base BTF"),
                OPT_END()
        };
        int err = -1;

        argc = parse_options(argc, argv, btfid_options, resolve_btfids_usage,
                             PARSE_OPT_STOP_AT_NON_OPTION);
        if (argc != 1)
                usage_with_options(resolve_btfids_usage, btfid_options);

        obj.path = argv[0];

        if (elf_collect(&obj))
                goto out;

        /*
         * We did not find .BTF_ids section or symbols section,
         * nothing to do..
         */
        if (obj.efile.idlist_shndx == -1 ||
            obj.efile.symbols_shndx == -1) {
                pr_debug("Cannot find .BTF_ids or symbols sections, nothing to do\n");
                err = 0;
                goto out;
        }

        if (symbols_collect(&obj))
                goto out;

        if (symbols_resolve(&obj))
                goto out;

        if (symbols_patch(&obj))
                goto out;

        err = 0;
out:
        if (obj.efile.elf) {
                elf_end(obj.efile.elf);
                close(obj.efile.fd);
        }
        return err;
}