/* ELF strtab with GC and suffix merging support.

   Copyright (C) 2001-2023 Free Software Foundation, Inc.

   Written by Jakub Jelinek <jakub@redhat.com>.

   This file is part of BFD, the Binary File Descriptor library.

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

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program 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 for more details.

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

   along with this program; if not, write to the Free Software

   Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston,

   MA 02110-1301, USA.  */

#include "sysdep.h"

#include "bfd.h"

#include "libbfd.h"

#include "elf-bfd.h"

#include "hashtab.h"

#include "libiberty.h"

/* An entry in the strtab hash table.  */

struct elf_strtab_hash_entry

{

  struct bfd_hash_entry root;

  /* Length of this entry.  This includes the zero terminator.  */

  int len;

  unsigned int refcount;

  union {

    /* Index within the merged section.  */

    bfd_size_type index;

    /* Entry this is a suffix of (if len < 0).  */

    struct elf_strtab_hash_entry *suffix;

  } u;

};

/* The strtab hash table.  */

struct elf_strtab_hash

{

  struct bfd_hash_table table;

  /* Next available index.  */

  size_t size;

  /* Number of array entries alloced.  */

  size_t alloced;

  /* Final strtab size.  */

  bfd_size_type sec_size;

  /* Array of pointers to strtab entries.  */

  struct elf_strtab_hash_entry **array;

};

/* Routine to create an entry in a section merge hashtab.  */

static struct bfd_hash_entry *

elf_strtab_hash_newfunc (struct bfd_hash_entry *entry,

       struct bfd_hash_table *table,

       const char *string)

{

  /* Allocate the structure if it has not already been allocated by a

     subclass.  */

  if (entry == NULL)

    entry = (struct bfd_hash_entry *)

  bfd_hash_allocate (table, sizeof (struct elf_strtab_hash_entry));

  if (entry == NULL)

    return NULL;

  /* Call the allocation method of the superclass.  */

  entry = bfd_hash_newfunc (entry, table, string);

  if (entry)

    {

      /* Initialize the local fields.  */

      struct elf_strtab_hash_entry *ret;

      ret = (struct elf_strtab_hash_entry *) entry;

      ret->u.index = -1;

      ret->refcount = 0;

      ret->len = 0;

    }

  return entry;

}

/* Create a new hash table.  */

struct elf_strtab_hash *

_bfd_elf_strtab_init (void)

{

  struct elf_strtab_hash *table;

  size_t amt = sizeof (struct elf_strtab_hash);

  table = (struct elf_strtab_hash *) bfd_malloc (amt);

  if (table == NULL)

    return NULL;

  if (!bfd_hash_table_init (&table->table, elf_strtab_hash_newfunc,

          sizeof (struct elf_strtab_hash_entry)))

    {

      free (table);

      return NULL;

    }

  table->sec_size = 0;

  table->size = 1;

  table->alloced = 64;

  amt = sizeof (struct elf_strtab_hasn_entry *);

  table->array = ((struct elf_strtab_hash_entry **)

      bfd_malloc (table->alloced * amt));

  if (table->array == NULL)

    {

      free (table);

      return NULL;

    }

  table->array[0] = NULL;

  return table;

}

/* Free a strtab.  */

void

_bfd_elf_strtab_free (struct elf_strtab_hash *tab)

{

  bfd_hash_table_free (&tab->table);

  free (tab->array);

  free (tab);

}

/* Get the index of an entity in a hash table, adding it if it is not

   already present.  */

size_t

_bfd_elf_strtab_add (struct elf_strtab_hash *tab,

         const char *str,

         bool copy)

{

  register struct elf_strtab_hash_entry *entry;

  /* We handle this specially, since we don't want to do refcounting

     on it.  */

  if (*str == '\0')

    return 0;

  BFD_ASSERT (tab->sec_size == 0);

  entry = (struct elf_strtab_hash_entry *)

    bfd_hash_lookup (&tab->table, str, true, copy);

  if (entry == NULL)

    return (size_t) -1;

  entry->refcount++;

  if (entry->len == 0)

    {

      entry->len = strlen (str) + 1;

      /* 2G strings lose.  */

      BFD_ASSERT (entry->len > 0);

      if (tab->size == tab->alloced)

  {

    bfd_size_type amt = sizeof (struct elf_strtab_hash_entry *);

    tab->alloced *= 2;

    tab->array = (struct elf_strtab_hash_entry **)

        bfd_realloc_or_free (tab->array, tab->alloced * amt);

    if (tab->array == NULL)

      return (size_t) -1;

  }

      entry->u.index = tab->size++;

      tab->array[entry->u.index] = entry;

    }

  return entry->u.index;

}

void

_bfd_elf_strtab_addref (struct elf_strtab_hash *tab, size_t idx)

{

  if (idx == 0 || idx == (size_t) -1)

    return;

  BFD_ASSERT (tab->sec_size == 0);

  BFD_ASSERT (idx < tab->size);

  ++tab->array[idx]->refcount;

}

void

_bfd_elf_strtab_delref (struct elf_strtab_hash *tab, size_t idx)

{

  if (idx == 0 || idx == (size_t) -1)

    return;

  BFD_ASSERT (tab->sec_size == 0);

  BFD_ASSERT (idx < tab->size);

  BFD_ASSERT (tab->array[idx]->refcount > 0);

  --tab->array[idx]->refcount;

}

unsigned int

_bfd_elf_strtab_refcount (struct elf_strtab_hash *tab, size_t idx)

{

  return tab->array[idx]->refcount;

}

void

_bfd_elf_strtab_clear_all_refs (struct elf_strtab_hash *tab)

{

  size_t idx;

  for (idx = 1; idx < tab->size; idx++)

    tab->array[idx]->refcount = 0;

}

/* Save strtab refcounts prior to adding --as-needed library.  */

struct strtab_save

{

  size_t size;

  unsigned int refcount[1];

};

void *

_bfd_elf_strtab_save (struct elf_strtab_hash *tab)

{

  struct strtab_save *save;

  size_t idx, size;

  size = sizeof (*save) + (tab->size - 1) * sizeof (save->refcount[0]);

  save = bfd_malloc (size);

  if (save == NULL)

    return save;

  save->size = tab->size;

  for (idx = 1; idx < tab->size; idx++)

    save->refcount[idx] = tab->array[idx]->refcount;

  return save;

}

/* Restore strtab refcounts on finding --as-needed library not needed.  */

void

_bfd_elf_strtab_restore (struct elf_strtab_hash *tab, void *buf)

{

  size_t idx, curr_size = tab->size, save_size;

  struct strtab_save *save = (struct strtab_save *) buf;

  BFD_ASSERT (tab->sec_size == 0);

  save_size = 1;

  if (save != NULL)

    save_size = save->size;

  BFD_ASSERT (save_size <= curr_size);

  tab->size = save_size;

  for (idx = 1; idx < save_size; ++idx)

    tab->array[idx]->refcount = save->refcount[idx];

  for (; idx < curr_size; ++idx)

    {

      /* We don't remove entries from the hash table, just set their

   REFCOUNT to zero.  Setting LEN zero will result in the size

   growing if the entry is added again.  See _bfd_elf_strtab_add.  */

      tab->array[idx]->refcount = 0;

      tab->array[idx]->len = 0;

    }

}

bfd_size_type

_bfd_elf_strtab_size (struct elf_strtab_hash *tab)

{

  return tab->sec_size ? tab->sec_size : tab->size;

}

bfd_size_type

_bfd_elf_strtab_len (struct elf_strtab_hash *tab)

{

  return tab->size;

}

bfd_size_type

_bfd_elf_strtab_offset (struct elf_strtab_hash *tab, size_t idx)

{

  struct elf_strtab_hash_entry *entry;

  if (idx == 0)

    return 0;

  BFD_ASSERT (idx < tab->size);

  BFD_ASSERT (tab->sec_size);

  entry = tab->array[idx];

  BFD_ASSERT (entry->refcount > 0);

  entry->refcount--;

  return tab->array[idx]->u.index;

}

const char *

_bfd_elf_strtab_str (struct elf_strtab_hash *tab, size_t idx,

         bfd_size_type *offset)

{

  if (idx == 0)

    return NULL;

  BFD_ASSERT (idx < tab->size);

  BFD_ASSERT (tab->sec_size);

  if (tab->array[idx]->refcount == 0)

    return NULL;

  if (offset)

    *offset = tab->array[idx]->u.index;

  return tab->array[idx]->root.string;

}

bool

_bfd_elf_strtab_emit (register bfd *abfd, struct elf_strtab_hash *tab)

{

  bfd_size_type off = 1;

  size_t i;

  if (bfd_write ("", 1, abfd) != 1)

    return false;

  for (i = 1; i < tab->size; ++i)

    {

      register const char *str;

      register unsigned int len;

      BFD_ASSERT (tab->array[i]->refcount == 0);

      len = tab->array[i]->len;

      if ((int) len < 0)

  continue;

      str = tab->array[i]->root.string;

      if (bfd_write (str, len, abfd) != len)

  return false;

      off += len;

    }

  BFD_ASSERT (off == tab->sec_size);

  return true;

}

/* Compare two elf_strtab_hash_entry structures.  Called via qsort.

   Won't ever return zero as all entries differ, so there is no issue

   with qsort stability here.  */

static int

strrevcmp (const void *a, const void *b)

{

  struct elf_strtab_hash_entry *A = *(struct elf_strtab_hash_entry **) a;

  struct elf_strtab_hash_entry *B = *(struct elf_strtab_hash_entry **) b;

  unsigned int lenA = A->len;

  unsigned int lenB = B->len;

  const unsigned char *s = (const unsigned char *) A->root.string + lenA - 1;

  const unsigned char *t = (const unsigned char *) B->root.string + lenB - 1;

  int l = lenA < lenB ? lenA : lenB;

  while (l)

    {

      if (*s != *t)

  return (int) *s - (int) *t;

      s--;

      t--;

      l--;

    }

  return lenA - lenB;

}

static inline int

is_suffix (const struct elf_strtab_hash_entry *A,

     const struct elf_strtab_hash_entry *B)

{

  if (A->len <= B->len)

    /* B cannot be a suffix of A unless A is equal to B, which is guaranteed

       not to be equal by the hash table.  */

    return 0;

  return memcmp (A->root.string + (A->len - B->len),

     B->root.string, B->len - 1) == 0;

}

/* This function assigns final string table offsets for used strings,

   merging strings matching suffixes of longer strings if possible.  */

void

_bfd_elf_strtab_finalize (struct elf_strtab_hash *tab)

{

  struct elf_strtab_hash_entry **array, **a, *e;

  bfd_size_type amt, sec_size;

  size_t size, i;

  /* Sort the strings by suffix and length.  */

  amt = tab->size;

  amt *= sizeof (struct elf_strtab_hash_entry *);

  array = (struct elf_strtab_hash_entry **) bfd_malloc (amt);

  if (array == NULL)

    goto alloc_failure;

  for (i = 1, a = array; i < tab->size; ++i)

    {

      e = tab->array[i];

      if (e->refcount)

  {

    *a++ = e;

    /* Adjust the length to not include the zero terminator.  */

    e->len -= 1;

  }

      else

  e->len = 0;

    }

  size = a - array;

  if (size != 0)

    {

      qsort (array, size, sizeof (struct elf_strtab_hash_entry *), strrevcmp);

      /* Loop over the sorted array and merge suffixes.  Start from the

   end because we want eg.

   s1 -> "d"

   s2 -> "bcd"

   s3 -> "abcd"

   to end up as

   s3 -> "abcd"

   s2 _____^

   s1 _______^

   ie. we don't want s1 pointing into the old s2.  */

      e = *--a;

      e->len += 1;

      while (--a >= array)

  {

    struct elf_strtab_hash_entry *cmp = *a;

    cmp->len += 1;

    if (is_suffix (e, cmp))

      {

        cmp->u.suffix = e;

        cmp->len = -cmp->len;

      }

    else

      e = cmp;

  }

    }

 alloc_failure:

  free (array);

  /* Assign positions to the strings we want to keep.  */

  sec_size = 1;

  for (i = 1; i < tab->size; ++i)

    {

      e = tab->array[i];

      if (e->refcount && e->len > 0)

  {

    e->u.index = sec_size;

    sec_size += e->len;

  }

    }

  tab->sec_size = sec_size;

  /* Adjust the rest.  */

  for (i = 1; i < tab->size; ++i)

    {

      e = tab->array[i];

      if (e->refcount && e->len < 0)

  e->u.index = e->u.suffix->u.index + (e->u.suffix->len + e->len);

    }

}