libelf: Add elf_compress and elf_compress_gnu.

Signed-off-by: Mark Wielaard <[email protected]>

1 files changed, 490 insertions, 0 deletions

diff --git a/libelf/elf_compress.c b/libelf/elf_compress.c
new file mode 100644
index 00000000..17b80f2d
--- /dev/null
+++ b/libelf/elf_compress.c
@@ -0,0 +1,490 @@
+/* Compress or decompress a section.
+   Copyright (C) 2015 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 "libelfP.h"
+#include "common.h"
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/param.h>
+#include <unistd.h>
+#include <zlib.h>
+
+#ifndef MAX
+# define MAX(a, b) ((a) > (b) ? (a) : (b))
+#endif
+
+/* 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 NULL;
+    }
+
+  Elf_Data cdata;
+  cdata.d_buf = NULL;
+
+  /* Cleanup and return result.  Don't leak memory.  */
+  void *deflate_cleanup (void *result)
+  {
+    deflateEnd (&z);
+    free (out_buf);
+    if (ei_data != MY_ELFDATA)
+      free (cdata.d_buf);
+    return result;
+  }
+
+  /* Loop over data buffers.  */
+  int flush = Z_NO_FLUSH;
+  do
+    {
+      /* Convert to raw if different endianess.  */
+      cdata = *data;
+      if (ei_data != MY_ELFDATA)
+	{
+	  /* 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);
+	    }
+	  if (gelf_xlatetof (scn->elf, &cdata, data, ei_data) == NULL)
+	    return deflate_cleanup (NULL);
+	}
+
+      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);
+	    }
+	  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);
+
+	  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);
+		}
+	      out_buf = bigger;
+	      out_size += block;
+	    }
+	}
+      while (z.avail_out == 0); /* Need more output buffer.  */
+
+      if (ei_data != MY_ELFDATA)
+	{
+	  free (cdata.d_buf);
+	  cdata.d_buf = NULL;
+	}
+    }
+  while (flush != Z_FINISH); /* More data blocks.  */
+
+  zrc = deflateEnd (&z);
+  if (zrc != Z_OK)
+    {
+      __libelf_seterrno (ELF_E_COMPRESS_ERROR);
+      return deflate_cleanup (NULL);
+    }
+
+  *new_size = used;
+  return out_buf;
+}
+
+void *
+internal_function
+__libelf_decompress (void *buf_in, size_t size_in, size_t size_out)
+{
+  void *buf_out = malloc (size_out);
+  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 (likely (zrc == Z_OK))
+    zrc = inflateEnd (&z);
+
+  if (unlikely (zrc != Z_OK) || unlikely (z.avail_out != 0))
+    {
+      free (buf_out);
+      __libelf_seterrno (ELF_E_DECOMPRESS_ERROR);
+      return NULL;
+    }
+
+  return buf_out;
+}
+
+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 = __libelf_version;
+  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)
+    free (scn->rawdata_base);
+
+  scn->rawdata_base = buf;
+}
+
+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 = 1;
+	  shdr->sh_flags |= SHF_COMPRESSED;
+	}
+      else
+	{
+	  Elf64_Shdr *shdr = elf64_getshdr (scn);
+	  shdr->sh_size = new_size;
+	  shdr->sh_addralign = 1;
+	  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;
+	}
+
+      GElf_Chdr chdr;
+      if (gelf_getchdr (scn, &chdr) == NULL)
+	return -1;
+
+      if (chdr.ch_type != ELFCOMPRESS_ZLIB)
+	{
+	  __libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);
+	  return -1;
+	}
+
+      if (! powerof2 (chdr.ch_addralign))
+	{
+	  __libelf_seterrno (ELF_E_INVALID_ALIGN);
+	  return -1;
+	}
+
+      /* 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 -1;
+
+      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);
+      if (buf_out == NULL)
+	return -1;
+
+      /* 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 = chdr.ch_size;
+	  shdr->sh_addralign = chdr.ch_addralign;
+	  shdr->sh_flags &= ~SHF_COMPRESSED;
+	}
+      else
+	{
+	  Elf64_Shdr *shdr = elf64_getshdr (scn);
+	  shdr->sh_size = chdr.ch_size;
+	  shdr->sh_addralign = chdr.ch_addralign;
+	  shdr->sh_flags &= ~SHF_COMPRESSED;
+	}
+
+      __libelf_reset_rawdata (scn, buf_out, chdr.ch_size, chdr.ch_addralign,
+			      __libelf_data_type (elf, sh_type));
+
+      scn->zdata_base = buf_out;
+
+      return 1;
+    }
+  else
+    {
+      __libelf_seterrno (ELF_E_UNKNOWN_COMPRESSION_TYPE);
+      return -1;
+    }
+}