/*

 * Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include <unistd.h>

#include <search.h>

#include <stdlib.h>

#include <string.h>

#include <db.h>

#include <fcntl.h>

#include "libproc_impl.h"

#include "symtab.h"

#ifndef __APPLE__

#include "salibelf.h"

#endif // __APPLE__

// ----------------------------------------------------

// functions for symbol lookups

// ----------------------------------------------------

typedef struct symtab_symbol {

  char *name;                // name like __ZThread_...

  uintptr_t offset;          // to loaded address

  uintptr_t size;            // size strlen

} symtab_symbol;

typedef struct symtab {

  char *strs;                // all symbols "__symbol1__'\0'__symbol2__...."

  size_t num_symbols;

  DB* hash_table;

  symtab_symbol* symbols;

} symtab_t;

#ifdef __APPLE__

void build_search_table(symtab_t *symtab) {

  int i;

  for (i = 0; i < symtab->num_symbols; i++) {

    DBT key, value;

    key.data = symtab->symbols[i].name;

    key.size = strlen(key.data) + 1;

    value.data = &(symtab->symbols[i]);

    value.size = sizeof(symtab_symbol);

    (*symtab->hash_table->put)(symtab->hash_table, &key, &value, 0);

    // check result

    if (is_debug()) {

      DBT rkey, rvalue;

      char* tmp = (char *)malloc(strlen(symtab->symbols[i].name) + 1);

      if (tmp == NULL) {

        print_debug("error allocating array in build_search_table\n");

      } else {

        strcpy(tmp, symtab->symbols[i].name);

        rkey.data = tmp;

        rkey.size = strlen(tmp) + 1;

        (*symtab->hash_table->get)(symtab->hash_table, &rkey, &rvalue, 0);

        // we may get a copy back so compare contents

        symtab_symbol *res = (symtab_symbol *)rvalue.data;

        if (strcmp(res->name, symtab->symbols[i].name)  ||

          res->offset != symtab->symbols[i].offset    ||

          res->size != symtab->symbols[i].size) {

            print_debug("error to get hash_table value!\n");

        }

        free(tmp);

      }

    }

  }

}

// read symbol table from given fd.

struct symtab* build_symtab(int fd) {

  symtab_t* symtab = NULL;

  int i;

  mach_header_64 header;

  off_t image_start;

  if (!get_arch_off(fd, CPU_TYPE_X86_64, &image_start)) {

    print_debug("failed in get fat header\n");

    return NULL;

  }

  lseek(fd, image_start, SEEK_SET);

  if (read(fd, (void *)&header, sizeof(mach_header_64)) != sizeof(mach_header_64)) {

    print_debug("reading header failed!\n");

    return NULL;

  }

  // header

  if (header.magic != MH_MAGIC_64) {

    print_debug("not a valid .dylib file\n");

    return NULL;

  }

  load_command lcmd;

  symtab_command symtabcmd;

  nlist_64 lentry;

  bool lcsymtab_exist = false;

  long filepos = ltell(fd);

  for (i = 0; i < header.ncmds; i++) {

    lseek(fd, filepos, SEEK_SET);

    if (read(fd, (void *)&lcmd, sizeof(load_command)) != sizeof(load_command)) {

      print_debug("read load_command failed for file\n");

      return NULL;

    }

    filepos += lcmd.cmdsize;  // next command position

    if (lcmd.cmd == LC_SYMTAB) {

      lseek(fd, -sizeof(load_command), SEEK_CUR);

      lcsymtab_exist = true;

      break;

    }

  }

  if (!lcsymtab_exist) {

    print_debug("No symtab command found!\n");

    return NULL;

  }

  if (read(fd, (void *)&symtabcmd, sizeof(symtab_command)) != sizeof(symtab_command)) {

    print_debug("read symtab_command failed for file");

    return NULL;

  }

  symtab = (symtab_t *)malloc(sizeof(symtab_t));

  if (symtab == NULL) {

    print_debug("out of memory: allocating symtab\n");

    return NULL;

  }

  // create hash table, we use berkeley db to

  // manipulate the hash table.

  symtab->hash_table = dbopen(NULL, O_CREAT | O_RDWR, 0600, DB_HASH, NULL);

  if (symtab->hash_table == NULL)

    goto quit;

  symtab->num_symbols = symtabcmd.nsyms;

  symtab->symbols = (symtab_symbol *)malloc(sizeof(symtab_symbol) * symtab->num_symbols);

  symtab->strs    = (char *)malloc(sizeof(char) * symtabcmd.strsize);

  if (symtab->symbols == NULL || symtab->strs == NULL) {

     print_debug("out of memory: allocating symtab.symbol or symtab.strs\n");

     goto quit;

  }

  lseek(fd, image_start + symtabcmd.symoff, SEEK_SET);

  for (i = 0; i < symtab->num_symbols; i++) {

    if (read(fd, (void *)&lentry, sizeof(nlist_64)) != sizeof(nlist_64)) {

      print_debug("read nlist_64 failed at %i\n", i);

      goto quit;

    }

    symtab->symbols[i].offset = lentry.n_value;

    symtab->symbols[i].size  = lentry.n_un.n_strx;        // index

  }

  // string table

  lseek(fd, image_start + symtabcmd.stroff, SEEK_SET);

  int size = read(fd, (void *)(symtab->strs), symtabcmd.strsize * sizeof(char));

  if (size != symtabcmd.strsize * sizeof(char)) {

     print_debug("reading string table failed\n");

     goto quit;

  }

  for (i = 0; i < symtab->num_symbols; i++) {

    symtab->symbols[i].name = symtab->strs + symtab->symbols[i].size;

    if (i > 0) {

      // fix size

      symtab->symbols[i - 1].size = symtab->symbols[i].size - symtab->symbols[i - 1].size;

      print_debug("%s size = %d\n", symtab->symbols[i - 1].name, symtab->symbols[i - 1].size);

    }

    if (i == symtab->num_symbols - 1) {

      // last index

      symtab->symbols[i].size =

            symtabcmd.strsize - symtab->symbols[i].size;

      print_debug("%s size = %d\n", symtab->symbols[i].name, symtab->symbols[i].size);

    }

  }

  // build a hashtable for fast query

  build_search_table(symtab);

  return symtab;

quit:

  if (symtab) destroy_symtab(symtab);

  return NULL;

}

#else // __APPLE__

struct elf_section {

  ELF_SHDR   *c_shdr;

  void       *c_data;

};

// read symbol table from given fd.

struct symtab* build_symtab(int fd) {

  ELF_EHDR ehdr;

  struct symtab* symtab = NULL;

  // Reading of elf header

  struct elf_section *scn_cache = NULL;

  int cnt = 0;

  ELF_SHDR* shbuf = NULL;

  ELF_SHDR* cursct = NULL;

  ELF_PHDR* phbuf = NULL;

  int symtab_found = 0;

  int dynsym_found = 0;

  uint32_t symsection = SHT_SYMTAB;

  uintptr_t baseaddr = (uintptr_t)-1;

  lseek(fd, (off_t)0L, SEEK_SET);

  if (! read_elf_header(fd, &ehdr)) {

    // not an elf

    return NULL;

  }

  // read ELF header

  if ((shbuf = read_section_header_table(fd, &ehdr)) == NULL) {

    goto quit;

  }

  baseaddr = find_base_address(fd, &ehdr);

  scn_cache = calloc(ehdr.e_shnum, sizeof(*scn_cache));

  if (scn_cache == NULL) {

    goto quit;

  }

  for (cursct = shbuf, cnt = 0; cnt < ehdr.e_shnum; cnt++) {

    scn_cache[cnt].c_shdr = cursct;

    if (cursct->sh_type == SHT_SYMTAB ||

        cursct->sh_type == SHT_STRTAB ||

        cursct->sh_type == SHT_DYNSYM) {

      if ( (scn_cache[cnt].c_data = read_section_data(fd, &ehdr, cursct)) == NULL) {

         goto quit;

      }

    }

    if (cursct->sh_type == SHT_SYMTAB)

       symtab_found++;

    if (cursct->sh_type == SHT_DYNSYM)

       dynsym_found++;

    cursct++;

  }

  if (!symtab_found && dynsym_found)

     symsection = SHT_DYNSYM;

  for (cnt = 1; cnt < ehdr.e_shnum; cnt++) {

    ELF_SHDR *shdr = scn_cache[cnt].c_shdr;

    if (shdr->sh_type == symsection) {

      ELF_SYM  *syms;

      int j, n;

      size_t size;

      // FIXME: there could be multiple data buffers associated with the

      // same ELF section. Here we can handle only one buffer. See man page

      // for elf_getdata on Solaris.

      // guarantee(symtab == NULL, "multiple symtab");

      symtab = calloc(1, sizeof(*symtab));

      if (symtab == NULL) {

         goto quit;

      }

      // the symbol table

      syms = (ELF_SYM *)scn_cache[cnt].c_data;

      // number of symbols

      n = shdr->sh_size / shdr->sh_entsize;

      // create hash table, we use berkeley db to

      // manipulate the hash table.

      symtab->hash_table = dbopen(NULL, O_CREAT | O_RDWR, 0600, DB_HASH, NULL);

      // guarantee(symtab->hash_table, "unexpected failure: dbopen");

      if (symtab->hash_table == NULL)

        goto bad;

      // shdr->sh_link points to the section that contains the actual strings

      // for symbol names. the st_name field in ELF_SYM is just the

      // string table index. we make a copy of the string table so the

      // strings will not be destroyed by elf_end.

      size = scn_cache[shdr->sh_link].c_shdr->sh_size;

      symtab->strs = malloc(size);

      if (symtab->strs == NULL)

        goto bad;

      memcpy(symtab->strs, scn_cache[shdr->sh_link].c_data, size);

      // allocate memory for storing symbol offset and size;

      symtab->num_symbols = n;

      symtab->symbols = calloc(n , sizeof(*symtab->symbols));

      if (symtab->symbols == NULL)

        goto bad;

      // copy symbols info our symtab and enter them info the hash table

      for (j = 0; j < n; j++, syms++) {

        DBT key, value;

        char *sym_name = symtab->strs + syms->st_name;

        // skip non-object and non-function symbols

        int st_type = ELF_ST_TYPE(syms->st_info);

        if ( st_type != STT_FUNC && st_type != STT_OBJECT)

           continue;

        // skip empty strings and undefined symbols

        if (*sym_name == '\0' || syms->st_shndx == SHN_UNDEF) continue;

        symtab->symbols[j].name   = sym_name;

        symtab->symbols[j].offset = syms->st_value - baseaddr;

        symtab->symbols[j].size   = syms->st_size;

        key.data = sym_name;

        key.size = strlen(sym_name) + 1;

        value.data = &(symtab->symbols[j]);

        value.size = sizeof(symtab_symbol);

        (*symtab->hash_table->put)(symtab->hash_table, &key, &value, 0);

      }

    }

  }

  goto quit;

bad:

  destroy_symtab(symtab);

  symtab = NULL;

quit:

  if (shbuf) free(shbuf);

  if (phbuf) free(phbuf);

  if (scn_cache) {

    for (cnt = 0; cnt < ehdr.e_shnum; cnt++) {

      if (scn_cache[cnt].c_data != NULL) {

        free(scn_cache[cnt].c_data);

      }

    }

    free(scn_cache);

  }

  return symtab;

}

#endif // __APPLE__

void destroy_symtab(symtab_t* symtab) {

  if (!symtab) return;

  free(symtab->strs);

  free(symtab->symbols);

  free(symtab);

}

uintptr_t search_symbol(struct symtab* symtab, uintptr_t base, const char *sym_name, int *sym_size) {

  DBT key, value;

  int ret;

  // library does not have symbol table

  if (!symtab || !symtab->hash_table) {

     return 0;

  }

  key.data = (char*)(uintptr_t)sym_name;

  key.size = strlen(sym_name) + 1;

  ret = (*symtab->hash_table->get)(symtab->hash_table, &key, &value, 0);

  if (ret == 0) {

    symtab_symbol *sym = value.data;

    uintptr_t rslt = (uintptr_t) ((char*)base + sym->offset);

    if (sym_size) *sym_size = sym->size;

    return rslt;

  }

  return 0;

}

const char* nearest_symbol(struct symtab* symtab, uintptr_t offset,

                           uintptr_t* poffset) {

  int n = 0;

  if (!symtab) return NULL;

  for (; n < symtab->num_symbols; n++) {

    symtab_symbol* sym = &(symtab->symbols[n]);

    if (sym->name != NULL &&

      offset >= sym->offset && offset < sym->offset + sym->size) {

      if (poffset) *poffset = (offset - sym->offset);

      return sym->name;

    }

  }

  return NULL;

}