/*      $NetBSD: symtab.c,v 1.10 2023/08/23 12:24:59 rin Exp $  */

/*-
* Copyright (c) 2012 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Christos Zoulas.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: symtab.c,v 1.10 2023/08/23 12:24:59 rin Exp $");

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <stdbool.h>
#include <err.h>
#include <dlfcn.h>

#include <libelf.h>
#include <gelf.h>
#ifndef ELF_ST_BIND
#define ELF_ST_BIND(x)          ((x) >> 4)
#endif
#ifndef ELF_ST_TYPE
#define ELF_ST_TYPE(x)          (((unsigned int)x) & 0xf)
#endif

#include "symbol.h"
#include "symtab.h"

#ifdef SYMTAB_DEBUG
#define DPRINTF(fmt, ...)       fprintf(stderr, "%s: " fmt "\n", __func__, __VA_ARGS__)
#else
#define DPRINTF(fmt, ...)
#endif

struct symbol {
       char *st_name;
       uintptr_t st_value;
       uintptr_t st_info;
};

struct symtab {
       size_t nsymbols;
       struct symbol *symbols;
       bool ispie;
};

static int
address_compare(const void *a, const void *b)
{
       const struct symbol *sa = a;
       const struct symbol *sb = b;
       return (int)(intmax_t)(sa->st_value - sb->st_value);
}

void
symtab_destroy(symtab_t *s)
{
       if (s == NULL)
               return;
       for (size_t i = 0; i < s->nsymbols; i++)
               free(s->symbols[i].st_name);
       free(s->symbols);
       free(s);
}

symtab_t *
symtab_create(int fd, int bind, int type)
{
       Elf *elf;
       symtab_t *st;
       Elf_Scn *scn = NULL;
       GElf_Ehdr ehdr;

       if (elf_version(EV_CURRENT) == EV_NONE) {
               warnx("Elf Library is out of date.");
               return NULL;
       }

       elf = elf_begin(fd, ELF_C_READ, NULL);
       if (elf == NULL) {
               warnx("Error opening elf file: %s", elf_errmsg(elf_errno()));
               return NULL;
       }
       st = calloc(1, sizeof(*st));
       if (st == NULL) {
               warnx("Error allocating symbol table");
               elf_end(elf);
               return NULL;
       }
       if (gelf_getehdr(elf, &ehdr) == NULL) {
               warnx("Error getting ELF Ehdr");
               elf_end(elf);
               return NULL;
       }

       st->ispie = ehdr.e_type == ET_DYN;

       while ((scn = elf_nextscn(elf, scn)) != NULL) {
               GElf_Shdr shdr;
               Elf_Data *edata;
               size_t ns;
               struct symbol *s;

               gelf_getshdr(scn, &shdr);
               if(shdr.sh_type != SHT_SYMTAB)
                       continue;

               edata = elf_getdata(scn, NULL);
               ns = shdr.sh_size / shdr.sh_entsize;
               s = calloc(ns, sizeof(*s));
               if (s == NULL) {
                       warn("Cannot allocate %zu symbols", ns);
                       goto out;
               }
               st->symbols = s;

               for (size_t i = 0; i < ns; i++) {
                       GElf_Sym sym;
                       gelf_getsym(edata, (int)i, &sym);

                       DPRINTF("%s@%#jx=%d,%d",
                           elf_strptr(elf, shdr.sh_link, sym.st_name),
                           (uintmax_t)sym.st_value, ELF_ST_BIND(sym.st_info),
                           ELF_ST_TYPE(sym.st_info));

                       if (bind != -1 &&
                           (unsigned)bind != ELF_ST_BIND(sym.st_info))
                               continue;

                       if (type != -1 &&
                           (unsigned)type != ELF_ST_TYPE(sym.st_info))
                               continue;

                       s->st_value = sym.st_value;
                       s->st_info = sym.st_info;
                       s->st_name = strdup(
                           elf_strptr(elf, shdr.sh_link, sym.st_name));
                       if (s->st_name == NULL) {
                               warn("Cannot allocate symbol");
                               goto out;
                       }
                       s++;
               }
               st->nsymbols = s - st->symbols;
               if (st->nsymbols == 0) {
                       warnx("No symbols found");
                       goto out;
               }
               qsort(st->symbols, st->nsymbols, sizeof(*st->symbols),
                   address_compare);
               elf_end(elf);
               return st;
       }
out:
       symtab_destroy(st);
       elf_end(elf);
       return NULL;
}


int
symtab_find(const symtab_t *st, const void *p, Dl_info *dli)
{
       struct symbol *s = st->symbols;
       size_t ns = st->nsymbols;
       size_t hi = ns;
       size_t lo = 0;
       size_t mid = ns / 2;
       uintptr_t fbase = st->ispie ? (uintptr_t)dli->dli_fbase : 0;
       uintptr_t dd, sd, me = (uintptr_t)p - fbase;
       uintptr_t sa = SYMBOL_CANONICALIZE(dli->dli_saddr);
       uintptr_t ad = sa - fbase;

       DPRINTF("[fbase=%#jx, saddr=%p, sa=%#jx, me=%#jx ad=%#jx]",
           (uintmax_t)fbase, dli->dli_saddr, (uintmax_t)sa,
           (uintmax_t)me, (uintmax_t)ad);

       for (;;) {
               if (s[mid].st_value < me)
                       lo = mid;
               else if (s[mid].st_value > me)
                       hi = mid;
               else
                       break;
               if (hi - lo == 1) {
                       mid = lo;
                       break;
               }
               mid = (hi + lo) / 2;
       }
       dd = me - ad;
       sd = me - s[mid].st_value;
       if (dd > sd) {
               dli->dli_saddr = (void *)s[mid].st_value;
               dli->dli_sname = s[mid].st_name;
               DPRINTF("me=%#jx -> [%#jx, %s]", (uintmax_t)me, (uintmax_t)sd,
                   dli->dli_sname);
       } else {
               DPRINTF("%#jx -> [%#jx, ***]", (uintmax_t)me, (uintmax_t)sd);
       }

       return 1;
}

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