1 files changed, 77 insertions, 0 deletions
diff --git a/libdwelf/dwelf_scn_gnu_compressed_size.c b/libdwelf/dwelf_scn_gnu_compressed_size.c
new file mode 100644
index 00000000..d39b702a
--- /dev/null
+++ b/libdwelf/dwelf_scn_gnu_compressed_size.c
@@ -0,0 +1,77 @@
+/* Return size of GNU compressed 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 "libdwelfP.h"
+#include "libelfP.h"
+
+ssize_t
+dwelf_scn_gnu_compressed_size (Elf_Scn *scn)
+{
+  if (scn == NULL)
+    return -1;
+
+  GElf_Shdr shdr;
+  if (gelf_getshdr (scn, &shdr) == NULL)
+    return -1;
+
+  /* Allocated or no bits sections can never be compressed.  */
+  if ((shdr.sh_flags & SHF_ALLOC) != 0
+      || shdr.sh_type == SHT_NULL
+      || shdr.sh_type == SHT_NOBITS)
+    return -1;
+
+  Elf_Data *d = elf_rawdata (scn, NULL);
+  if (d == NULL)
+    return -1;
+
+  if (d->d_size >= 4 + 8
+      && memcmp (d->d_buf, "ZLIB", 4) == 0)
+    {
+      /* There is a 12-byte header of "ZLIB" followed by
+	 an 8-byte big-endian size.  There is only one type and
+	 alignment isn't preserved separately.  */
+      uint64_t size;
+      memcpy (&size, d->d_buf + 4, sizeof size);
+      size = be64toh (size);
+
+      /* One more sanity check, size should be bigger than original
+	 data size plus some overhead (4 chars ZLIB + 8 bytes size + 6
+	 bytes zlib stream overhead + 5 bytes overhead max for one 16K
+	 block) and should fit into a size_t.  */
+      if (size + 4 + 8 + 6 + 5 < d->d_size || size > SIZE_MAX)
+	return -1;
+
+      return size;
+    }
+
+  return -1;
+}