/*

 * Copyright (c) 2003, 2010, 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 <sys/procfs.h>

#include <search.h>

#include <stdlib.h>

#include <string.h>

#include "symtab.h"

#include "salibelf.h"

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

// functions for symbol lookups

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

struct elf_section {

  ELF_SHDR   *c_shdr;

  void       *c_data;

};

struct elf_symbol {

  char *name;

  uintptr_t offset;

  uintptr_t size;

};

typedef struct symtab {

  char *strs;

  size_t num_symbols;

  struct elf_symbol *symbols;

  struct hsearch_data *hash_table;

} symtab_t;

// Directory that contains global debuginfo files.  In theory it

// should be possible to change this, but in a Java environment there

// is no obvious place to put a user interface to do it.  Maybe this

// could be set with an environment variable.

static const char debug_file_directory[] = "/usr/lib/debug";

/* The CRC used in gnu_debuglink, retrieved from

   http://sourceware.org/gdb/current/onlinedocs/gdb/Separate-Debug-Files.html#Separate-Debug-Files. */

unsigned int gnu_debuglink_crc32 (unsigned int crc,

                                  unsigned char *buf, size_t len)

{

  static const unsigned int crc32_table[256] =

    {

      0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,

      0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,

      0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,

      0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,

      0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,

      0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,

      0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,

      0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,

      0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,

      0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,

      0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,

      0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,

      0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,

      0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,

      0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,

      0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,

      0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,

      0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,

      0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,

      0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,

      0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,

      0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,

      0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,

      0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,

      0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,

      0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,

      0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,

      0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,

      0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,

      0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,

      0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,

      0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,

      0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,

      0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,

      0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,

      0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,

      0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,

      0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,

      0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,

      0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,

      0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,

      0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,

      0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,

      0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,

      0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,

      0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,

      0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,

      0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,

      0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,

      0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,

      0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,

      0x2d02ef8d

    };

  unsigned char *end;

  crc = ~crc & 0xffffffff;

  for (end = buf + len; buf < end; ++buf)

    crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);

  return ~crc & 0xffffffff;

}

/* Open a debuginfo file and check its CRC.  If it exists and the CRC

   matches return its fd.  */

static int

open_debug_file (const char *pathname, unsigned int crc)

{

  unsigned int file_crc = 0;

  unsigned char buffer[8 * 1024];

  int fd = pathmap_open(pathname);

  if (fd < 0)

    return -1;

  lseek(fd, 0, SEEK_SET);

  for (;;) {

    int len = read(fd, buffer, sizeof buffer);

    if (len <= 0)

      break;

    file_crc = gnu_debuglink_crc32(file_crc, buffer, len);

  }

  if (crc == file_crc)

    return fd;

  else {

    close(fd);

    return -1;

  }

}

/* Find an ELF section.  */

static struct elf_section *find_section_by_name(char *name,

                                                int fd,

                                                ELF_EHDR *ehdr,

                                                ELF_SHDR *shbuf,

                                                struct elf_section *scn_cache)

{

  ELF_SHDR* cursct = NULL;

  char *strtab;

  int cnt;

  if (scn_cache[ehdr->e_shstrndx].c_data == NULL) {

    if ((scn_cache[ehdr->e_shstrndx].c_data

         = read_section_data(fd, ehdr, cursct)) == NULL) {

      return NULL;

    }

  }

  strtab = scn_cache[ehdr->e_shstrndx].c_data;

  for (cursct = shbuf, cnt = 0;

       cnt < ehdr->e_shnum;

       cnt++, cursct++) {

    if (strcmp(cursct->sh_name + strtab, name) == 0) {

      scn_cache[cnt].c_data = read_section_data(fd, ehdr, cursct);

      return &scn_cache[cnt];

    }

  }

  return NULL;

}

/* Look for a ".gnu_debuglink" section.  If one exists, try to open a

   suitable debuginfo file.  */

static int open_file_from_debug_link(const char *name,

                                     int fd,

                                     ELF_EHDR *ehdr,

                                     ELF_SHDR *shbuf,

                                     struct elf_section *scn_cache)

{

  int debug_fd;

  struct elf_section *debug_link = find_section_by_name(".gnu_debuglink", fd, ehdr,

                                                        shbuf, scn_cache);

  if (debug_link == NULL)

    return -1;

  char *debug_filename = debug_link->c_data;

  int offset = (strlen(debug_filename) + 4) >> 2;

  static unsigned int crc;

  crc = ((unsigned int*)debug_link->c_data)[offset];

  char *debug_pathname = malloc(strlen(debug_filename)

                                + strlen(name)

                                + strlen(".debug/")

                                + strlen(debug_file_directory)

                                + 2);

  strcpy(debug_pathname, name);

  char *last_slash = strrchr(debug_pathname, '/');

  if (last_slash == NULL)

    return -1;

  /* Look in the same directory as the object.  */

  strcpy(last_slash+1, debug_filename);

  debug_fd = open_debug_file(debug_pathname, crc);

  if (debug_fd >= 0) {

    free(debug_pathname);

    return debug_fd;

  }

  /* Look in a subdirectory named ".debug".  */

  strcpy(last_slash+1, ".debug/");

  strcat(last_slash, debug_filename);

  debug_fd = open_debug_file(debug_pathname, crc);

  if (debug_fd >= 0) {

    free(debug_pathname);

    return debug_fd;

  }

  /* Look in /usr/lib/debug + the full pathname.  */

  strcpy(debug_pathname, debug_file_directory);

  strcat(debug_pathname, name);

  last_slash = strrchr(debug_pathname, '/');

  strcpy(last_slash+1, debug_filename);

  debug_fd = open_debug_file(debug_pathname, crc);

  if (debug_fd >= 0) {

    free(debug_pathname);

    return debug_fd;

  }

  free(debug_pathname);

  return -1;

}

static struct symtab* build_symtab_internal(int fd, const char *filename, bool try_debuginfo);

/* Look for a ".gnu_debuglink" section.  If one exists, try to open a

   suitable debuginfo file and read a symbol table from it.  */

static struct symtab *build_symtab_from_debug_link(const char *name,

                                     int fd,

                                     ELF_EHDR *ehdr,

                                     ELF_SHDR *shbuf,

                                     struct elf_section *scn_cache)

{

  fd = open_file_from_debug_link(name, fd, ehdr, shbuf, scn_cache);

  if (fd >= 0) {

    struct symtab *symtab = build_symtab_internal(fd, NULL, /* try_debuginfo */ false);

    close(fd);

    return symtab;

  }

  return NULL;

}

// Given a build_id, find the associated debuginfo file

static char *

build_id_to_debug_filename (size_t size, unsigned char *data)

{

  char *filename, *s;

  filename = malloc(strlen (debug_file_directory) + (sizeof "/.build-id/" - 1) + 1

                    + 2 * size + (sizeof ".debug" - 1) + 1);

  s = filename + sprintf (filename, "%s/.build-id/", debug_file_directory);

  if (size > 0)

    {

      size--;

      s += sprintf (s, "%02x", *data++);

    }

  if (size > 0)

    *s++ = '/';

  while (size-- > 0)

    s += sprintf (s, "%02x", *data++);

  strcpy (s, ".debug");

  return filename;

}

// Read a build ID note.  Try to open any associated debuginfo file

// and return its symtab

static struct symtab* build_symtab_from_build_id(Elf64_Nhdr *note)

{

  int fd;

  struct symtab *symtab = NULL;

  unsigned char *bytes

    = (unsigned char*)(note+1) + note->n_namesz;

  unsigned char *filename

    = (build_id_to_debug_filename (note->n_descsz, bytes));

  fd = pathmap_open(filename);

  if (fd >= 0) {

    symtab = build_symtab_internal(fd, NULL, /* try_debuginfo */ false);

    close(fd);

  }

  free(filename);

  return symtab;

}

// read symbol table from given fd.  If try_debuginfo) is true, also

// try to open an associated debuginfo file

static struct symtab* build_symtab_internal(int fd, const char *filename, bool try_debuginfo) {

  ELF_EHDR ehdr;

  char *names = NULL;

  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;

  ELF_PHDR* phdr = NULL;

  int sym_section = SHT_DYNSYM;

  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 = (struct elf_section *)

              calloc(ehdr.e_shnum * sizeof(struct elf_section), 1);

  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_NOTE || 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) {

      // Full symbol table available so use that

      sym_section = cursct->sh_type;

    }

    cursct++;

  }

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

    ELF_SHDR *shdr = scn_cache[cnt].c_shdr;

    if (shdr->sh_type == sym_section) {

      ELF_SYM  *syms;

      int j, n, rslt;

      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 = (struct symtab*)calloc(1, sizeof(struct 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 hcreate_r, hsearch_r and hdestroy_r to

      // manipulate the hash table.

      symtab->hash_table = (struct hsearch_data*) calloc(1, sizeof(struct hsearch_data));

      rslt = hcreate_r(n, symtab->hash_table);

      // guarantee(rslt, "unexpected failure: hcreate_r");

      // 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 = (char *)malloc(size);

      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 = (struct elf_symbol *)calloc(n , sizeof(struct elf_symbol));

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

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

        ENTRY item, *ret;

        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;

        item.key = sym_name;

        item.data = (void *)&(symtab->symbols[j]);

        hsearch_r(item, ENTER, &ret, symtab->hash_table);

      }

    }

  }

  // Look for a separate debuginfo file.

  if (try_debuginfo) {

    // We prefer a debug symtab to an object's own symtab, so look in

    // the debuginfo file.  We stash a copy of the old symtab in case

    // there is no debuginfo.

    struct symtab* prev_symtab = symtab;

    symtab = NULL;

#ifdef NT_GNU_BUILD_ID

    // First we look for a Build ID

    for (cursct = shbuf, cnt = 0;

         symtab == NULL && cnt < ehdr.e_shnum;

         cnt++) {

      if (cursct->sh_type == SHT_NOTE) {

        Elf64_Nhdr *note = (Elf64_Nhdr *)scn_cache[cnt].c_data;

        if (note->n_type == NT_GNU_BUILD_ID) {

          symtab = build_symtab_from_build_id(note);

        }

      }

      cursct++;

    }

#endif

    // Then, if that doesn't work, the debug link

    if (symtab == NULL) {

      symtab = build_symtab_from_debug_link(filename, fd, &ehdr, shbuf,

                                            scn_cache);

    }

    // If we still haven't found a symtab, use the object's own symtab.

    if (symtab != NULL) {

      if (prev_symtab != NULL)

        destroy_symtab(prev_symtab);

    } else {

      symtab = prev_symtab;

    }

  }

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;

}

struct symtab* build_symtab(int fd, const char *filename) {

  return build_symtab_internal(fd, filename, /* try_debuginfo */ true);

}

void destroy_symtab(struct symtab* symtab) {

  if (!symtab) return;

  if (symtab->strs) free(symtab->strs);

  if (symtab->symbols) free(symtab->symbols);

  if (symtab->hash_table) {

     hdestroy_r(symtab->hash_table);

     free(symtab->hash_table);

  }

  free(symtab);

}