/* Compress or decompress a section.

   Copyright (C) 2015, 2016 Red Hat, Inc.

   This file is part of elfutils.

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

   it under the terms of either

     * the GNU Lesser General Public License as published by the Free

       Software Foundation; either version 3 of the License, or (at

       your option) any later version

   or

     * the GNU General Public License as published by the Free

       Software Foundation; either version 2 of the License, or (at

       your option) any later version

   or both in parallel, as here.

   elfutils 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 copies of the GNU General Public License and

   the GNU Lesser General Public License along with this program.  If

   not, see <http://www.gnu.org/licenses/>.  */

#ifdef HAVE_CONFIG_H

# include <config.h>

#endif

#include <libelf.h>

#include <system.h>

#include "libelfP.h"

#include "common.h"

#include <stddef.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <zlib.h>

/* Cleanup and return result.  Don't leak memory.  */

static void *

do_deflate_cleanup (void *result, z_stream *z, void *out_buf,

                    Elf_Data *cdatap)

{

  deflateEnd (z);

  free (out_buf);

  if (cdatap != NULL)

    free (cdatap->d_buf);

  return result;

}

#define deflate_cleanup(result, cdata) \

    do_deflate_cleanup(result, &z, out_buf, cdata)

/* Given a section, uses the (in-memory) Elf_Data to extract the

   original data size (including the given header size) and data

   alignment.  Returns a buffer that has at least hsize bytes (for the

   caller to fill in with a header) plus zlib compressed date.  Also

   returns the new buffer size in new_size (hsize + compressed data

   size).  Returns (void *) -1 when FORCE is false and the compressed

   data would be bigger than the original data.  */

void *

internal_function

__libelf_compress (Elf_Scn *scn, size_t hsize, int ei_data,

		   size_t *orig_size, size_t *orig_addralign,

		   size_t *new_size, bool force)

{

  /* The compressed data is the on-disk data.  We simplify the

     implementation a bit by asking for the (converted) in-memory

     data (which might be all there is if the user created it with

     elf_newdata) and then convert back to raw if needed before

     compressing.  Should be made a bit more clever to directly

     use raw if that is directly available.  */

  Elf_Data *data = elf_getdata (scn, NULL);

  if (data == NULL)

    return NULL;

  /* When not forced and we immediately know we would use more data by

     compressing, because of the header plus zlib overhead (five bytes

     per 16 KB block, plus a one-time overhead of six bytes for the

     entire stream), don't do anything.  */

  Elf_Data *next_data = elf_getdata (scn, data);

  if (next_data == NULL && !force

      && data->d_size <= hsize + 5 + 6)

    return (void *) -1;

  *orig_addralign = data->d_align;

  *orig_size = data->d_size;

  /* Guess an output block size. 1/8th of the original Elf_Data plus

     hsize.  Make the first chunk twice that size (25%), then increase

     by a block (12.5%) when necessary.  */

  size_t block = (data->d_size / 8) + hsize;

  size_t out_size = 2 * block;

  void *out_buf = malloc (out_size);

  if (out_buf == NULL)

    {

      __libelf_seterrno (ELF_E_NOMEM);

      return NULL;

    }

  /* Caller gets to fill in the header at the start.  Just skip it here.  */

  size_t used = hsize;

  z_stream z;

  z.zalloc = Z_NULL;

  z.zfree = Z_NULL;

  z.opaque = Z_NULL;

  int zrc = deflateInit (&z, Z_BEST_COMPRESSION);

  if (zrc != Z_OK)

    {

      __libelf_seterrno (ELF_E_COMPRESS_ERROR);

      return deflate_cleanup(NULL, NULL);

    }

  Elf_Data cdata;

  cdata.d_buf = NULL;

  /* Loop over data buffers.  */

  int flush = Z_NO_FLUSH;

  do

    {

      /* Convert to raw if different endianess.  */

      cdata = *data;

      bool convert = ei_data != MY_ELFDATA && data->d_size > 0;

      if (convert)

	{

	  /* Don't do this conversion in place, we might want to keep

	     the original data around, caller decides.  */

	  cdata.d_buf = malloc (data->d_size);

	  if (cdata.d_buf == NULL)

	    {

	      __libelf_seterrno (ELF_E_NOMEM);

	      return deflate_cleanup (NULL, NULL);

	    }

	  if (gelf_xlatetof (scn->elf, &cdata, data, ei_data) == NULL)

	    return deflate_cleanup (NULL, &cdata);

	}

      z.avail_in = cdata.d_size;

      z.next_in = cdata.d_buf;

      /* Get next buffer to see if this is the last one.  */

      data = next_data;

      if (data != NULL)

	{

	  *orig_addralign = MAX (*orig_addralign, data->d_align);

	  *orig_size += data->d_size;

	  next_data = elf_getdata (scn, data);

	}

      else

	flush = Z_FINISH;

      /* Flush one data buffer.  */

      do

	{

	  z.avail_out = out_size - used;

	  z.next_out = out_buf + used;

	  zrc = deflate (&z, flush);

	  if (zrc == Z_STREAM_ERROR)

	    {

	      __libelf_seterrno (ELF_E_COMPRESS_ERROR);

	      return deflate_cleanup (NULL, convert ? &cdata : NULL);

	    }

	  used += (out_size - used) - z.avail_out;

	  /* Bail out if we are sure the user doesn't want the

	     compression forced and we are using more compressed data

	     than original data.  */

	  if (!force && flush == Z_FINISH && used >= *orig_size)

	    return deflate_cleanup ((void *) -1, convert ? &cdata : NULL);

	  if (z.avail_out == 0)

	    {

	      void *bigger = realloc (out_buf, out_size + block);

	      if (bigger == NULL)

		{

		  __libelf_seterrno (ELF_E_NOMEM);

		  return deflate_cleanup (NULL, convert ? &cdata : NULL);

		}

	      out_buf = bigger;

	      out_size += block;

	    }

	}

      while (z.avail_out == 0); /* Need more output buffer.  */

      if (convert)

	{

	  free (cdata.d_buf);

	  cdata.d_buf = NULL;

	}

    }

  while (flush != Z_FINISH); /* More data blocks.  */

  if (zrc != Z_STREAM_END)

    {

      __libelf_seterrno (ELF_E_COMPRESS_ERROR);

      return deflate_cleanup (NULL, NULL);

    }

  deflateEnd (&z);

  *new_size = used;

  return out_buf;

}

void *

internal_function

__libelf_decompress (void *buf_in, size_t size_in, size_t size_out)

{

  /* Catch highly unlikely compression ratios so we don't allocate

     some giant amount of memory for nothing. The max compression

     factor 1032:1 comes from http://www.zlib.net/zlib_tech.html  */

  if (unlikely (size_out / 1032 > size_in))

    {

      __libelf_seterrno (ELF_E_INVALID_DATA);

      return NULL;

    }

  /* Malloc might return NULL when requestion zero size.  This is highly

     unlikely, it would only happen when the compression was forced.

     But we do need a non-NULL buffer to return and set as result.

     Just make sure to always allocate at least 1 byte.  */

  void *buf_out = malloc (size_out ?: 1);

  if (unlikely (buf_out == NULL))

    {

      __libelf_seterrno (ELF_E_NOMEM);

      return NULL;

    }

  z_stream z =

    {

      .next_in = buf_in,

      .avail_in = size_in,

      .next_out = buf_out,

      .avail_out = size_out

    };

  int zrc = inflateInit (&z);

  while (z.avail_in > 0 && likely (zrc == Z_OK))

    {

      z.next_out = buf_out + (size_out - z.avail_out);

      zrc = inflate (&z, Z_FINISH);

      if (unlikely (zrc != Z_STREAM_END))

	{

	  zrc = Z_DATA_ERROR;

	  break;

	}

      zrc = inflateReset (&z);

    }

  if (unlikely (zrc != Z_OK) || unlikely (z.avail_out != 0))

    {

      free (buf_out);

      buf_out = NULL;

      __libelf_seterrno (ELF_E_DECOMPRESS_ERROR);

    }

  inflateEnd(&z);

  return buf_out;

}

void *

internal_function

__libelf_decompress_elf (Elf_Scn *scn, size_t *size_out, size_t *addralign)

{

  GElf_Chdr chdr;

  if (gelf_getchdr (scn, &chdr) == NULL)

    return NULL;

  if (chdr.ch_type != ELFCOMPRESS_ZLIB)

    {

      __libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);

      return NULL;

    }

  if (! powerof2 (chdr.ch_addralign))

    {

      __libelf_seterrno (ELF_E_INVALID_ALIGN);

      return NULL;

    }

  /* Take the in-memory representation, so we can even handle a

     section that has just been constructed (maybe it was copied

     over from some other ELF file first with elf_newdata).  This

     is slightly inefficient when the raw data needs to be

     converted since then we'll be converting the whole buffer and

     not just Chdr.  */

  Elf_Data *data = elf_getdata (scn, NULL);

  if (data == NULL)

    return NULL;

  int elfclass = scn->elf->class;

  size_t hsize = (elfclass == ELFCLASS32

		  ? sizeof (Elf32_Chdr) : sizeof (Elf64_Chdr));

  size_t size_in = data->d_size - hsize;

  void *buf_in = data->d_buf + hsize;

  void *buf_out = __libelf_decompress (buf_in, size_in, chdr.ch_size);

  *size_out = chdr.ch_size;

  *addralign = chdr.ch_addralign;

  return buf_out;

}

/* Assumes buf is a malloced buffer.  */

void

internal_function

__libelf_reset_rawdata (Elf_Scn *scn, void *buf, size_t size, size_t align,

			Elf_Type type)

{

  /* This is the new raw data, replace and possibly free old data.  */

  scn->rawdata.d.d_off = 0;

  scn->rawdata.d.d_version = EV_CURRENT;

  scn->rawdata.d.d_buf = buf;

  scn->rawdata.d.d_size = size;

  scn->rawdata.d.d_align = align;

  scn->rawdata.d.d_type = type;

  /* Existing existing data is no longer valid.  */

  scn->data_list_rear = NULL;

  if (scn->data_base != scn->rawdata_base)

    free (scn->data_base);

  scn->data_base = NULL;

  if (scn->elf->map_address == NULL

      || scn->rawdata_base == scn->zdata_base

      || (scn->flags & ELF_F_MALLOCED) != 0)

    free (scn->rawdata_base);

  scn->rawdata_base = buf;

  scn->flags |= ELF_F_MALLOCED;

  /* Pretend we (tried to) read the data from the file and setup the

     data (might have to convert the Chdr to native format).  */

  scn->data_read = 1;

  scn->flags |= ELF_F_FILEDATA;

  __libelf_set_data_list_rdlock (scn, 1);

}

int

elf_compress (Elf_Scn *scn, int type, unsigned int flags)

{

  if (scn == NULL)

    return -1;

  if ((flags & ~ELF_CHF_FORCE) != 0)

    {

      __libelf_seterrno (ELF_E_INVALID_OPERAND);

      return -1;

    }

  bool force = (flags & ELF_CHF_FORCE) != 0;

  Elf *elf = scn->elf;

  GElf_Ehdr ehdr;

  if (gelf_getehdr (elf, &ehdr) == NULL)

    return -1;

  int elfclass = elf->class;

  int elfdata = ehdr.e_ident[EI_DATA];

  Elf64_Xword sh_flags;

  Elf64_Word sh_type;

  Elf64_Xword sh_addralign;

  if (elfclass == ELFCLASS32)

    {

      Elf32_Shdr *shdr = elf32_getshdr (scn);

      if (shdr == NULL)

	return -1;

      sh_flags = shdr->sh_flags;

      sh_type = shdr->sh_type;

      sh_addralign = shdr->sh_addralign;

    }

  else

    {

      Elf64_Shdr *shdr = elf64_getshdr (scn);

      if (shdr == NULL)

	return -1;

      sh_flags = shdr->sh_flags;

      sh_type = shdr->sh_type;

      sh_addralign = shdr->sh_addralign;

    }

  if ((sh_flags & SHF_ALLOC) != 0)

    {

      __libelf_seterrno (ELF_E_INVALID_SECTION_FLAGS);

      return -1;

    }

  if (sh_type == SHT_NULL || sh_type == SHT_NOBITS)

    {

      __libelf_seterrno (ELF_E_INVALID_SECTION_TYPE);

      return -1;

    }

  int compressed = (sh_flags & SHF_COMPRESSED);

  if (type == ELFCOMPRESS_ZLIB)

    {

      /* Compress/Deflate.  */

      if (compressed == 1)

	{

	  __libelf_seterrno (ELF_E_ALREADY_COMPRESSED);

	  return -1;

	}

      size_t hsize = (elfclass == ELFCLASS32

		      ? sizeof (Elf32_Chdr) : sizeof (Elf64_Chdr));

      size_t orig_size, orig_addralign, new_size;

      void *out_buf = __libelf_compress (scn, hsize, elfdata,

					 &orig_size, &orig_addralign,

					 &new_size, force);

      /* Compression would make section larger, don't change anything.  */

      if (out_buf == (void *) -1)

	return 0;

      /* Compression failed, return error.  */

      if (out_buf == NULL)

	return -1;

      /* Put the header in front of the data.  */

      if (elfclass == ELFCLASS32)

	{

	  Elf32_Chdr chdr;

	  chdr.ch_type = ELFCOMPRESS_ZLIB;

	  chdr.ch_size = orig_size;

	  chdr.ch_addralign = orig_addralign;

	  if (elfdata != MY_ELFDATA)

	    {

	      CONVERT (chdr.ch_type);

	      CONVERT (chdr.ch_size);

	      CONVERT (chdr.ch_addralign);

	    }

	  memcpy (out_buf, &chdr, sizeof (Elf32_Chdr));

	}

      else

	{

	  Elf64_Chdr chdr;

	  chdr.ch_type = ELFCOMPRESS_ZLIB;

	  chdr.ch_reserved = 0;

	  chdr.ch_size = orig_size;

	  chdr.ch_addralign = sh_addralign;

	  if (elfdata != MY_ELFDATA)

	    {

	      CONVERT (chdr.ch_type);

	      CONVERT (chdr.ch_reserved);

	      CONVERT (chdr.ch_size);

	      CONVERT (chdr.ch_addralign);

	    }

	  memcpy (out_buf, &chdr, sizeof (Elf64_Chdr));

	}

      /* Note we keep the sh_entsize as is, we assume it is setup

	 correctly and ignored when SHF_COMPRESSED is set.  */

      if (elfclass == ELFCLASS32)

	{

	  Elf32_Shdr *shdr = elf32_getshdr (scn);

	  shdr->sh_size = new_size;

	  shdr->sh_addralign = __libelf_type_align (ELFCLASS32, ELF_T_CHDR);

	  shdr->sh_flags |= SHF_COMPRESSED;

	}

      else

	{

	  Elf64_Shdr *shdr = elf64_getshdr (scn);

	  shdr->sh_size = new_size;

	  shdr->sh_addralign = __libelf_type_align (ELFCLASS64, ELF_T_CHDR);

	  shdr->sh_flags |= SHF_COMPRESSED;

	}

      __libelf_reset_rawdata (scn, out_buf, new_size, 1, ELF_T_CHDR);

      /* The section is now compressed, we could keep the uncompressed

	 data around, but since that might have been multiple Elf_Data

	 buffers let the user uncompress it explicitly again if they

	 want it to simplify bookkeeping.  */

      scn->zdata_base = NULL;

      return 1;

    }

  else if (type == 0)

    {

      /* Decompress/Inflate.  */

      if (compressed == 0)

	{

	  __libelf_seterrno (ELF_E_NOT_COMPRESSED);

	  return -1;

	}

      /* If the data is already decompressed (by elf_strptr), then we

	 only need to setup the rawdata and section header. XXX what

	 about elf_newdata?  */

      if (scn->zdata_base == NULL)

	{

	  size_t size_out, addralign;

	  void *buf_out = __libelf_decompress_elf (scn, &size_out, &addralign);

	  if (buf_out == NULL)

	    return -1;

	  scn->zdata_base = buf_out;

	  scn->zdata_size = size_out;

	  scn->zdata_align = addralign;

	}

      /* Note we keep the sh_entsize as is, we assume it is setup

	 correctly and ignored when SHF_COMPRESSED is set.  */

      if (elfclass == ELFCLASS32)

	{

	  Elf32_Shdr *shdr = elf32_getshdr (scn);

	  shdr->sh_size = scn->zdata_size;

	  shdr->sh_addralign = scn->zdata_align;

	  shdr->sh_flags &= ~SHF_COMPRESSED;

	}

      else

	{

	  Elf64_Shdr *shdr = elf64_getshdr (scn);

	  shdr->sh_size = scn->zdata_size;

	  shdr->sh_addralign = scn->zdata_align;

	  shdr->sh_flags &= ~SHF_COMPRESSED;

	}

      __libelf_reset_rawdata (scn, scn->zdata_base,

			      scn->zdata_size, scn->zdata_align,

			      __libelf_data_type (elf, sh_type,

						  scn->zdata_align));

      return 1;

    }

  else

    {

      __libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);

      return -1;

    }

}