Test DSOs for executable stack.

Add a text program, built to run on the host, to check all newly
built DSOs for executable stacks and fail if the stack information
is missing or indicates executable stacks.

1 files changed, 158 insertions, 0 deletions

diff --git a/elf/check-execstack.c b/elf/check-execstack.c
new file mode 100644
index 0000000..55cf487
--- /dev/null
+++ b/elf/check-execstack.c
@@ -0,0 +1,158 @@
+/* Check for executable stacks in DSOs.
+   Copyright (C) 2009 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+   Contribute by Ulrich Drepper <drepper@redhat.com>. 2009.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library 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
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <byteswap.h>
+#include <elf.h>
+#include <endian.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+
+#ifdef BITS
+
+# define AB(name) _AB (name, BITS)
+# define _AB(name, bits) __AB (name, bits)
+# define __AB(name, bits) name##bits
+# define E(name) _E (name, BITS)
+# define _E(name, bits) __E (name, bits)
+# define __E(name, bits) Elf##bits##_##name
+# define SWAP(val) \
+  ({ __typeof (val) __res;						      \
+     if (((ehdr.e_ident[EI_DATA] == ELFDATA2MSB				      \
+	   && BYTE_ORDER == LITTLE_ENDIAN)				      \
+	  || (ehdr.e_ident[EI_DATA] == ELFDATA2LSB			      \
+	      && BYTE_ORDER == BIG_ENDIAN))				      \
+	 && sizeof (val) != 1)						      \
+       {								      \
+	 if (sizeof (val) == 2)						      \
+	   __res = bswap_16 (val);					      \
+	 else if (sizeof (val) == 4)					      \
+	   __res = bswap_32 (val);					      \
+	 else								      \
+	   __res = bswap_64 (val);					      \
+       }								      \
+     else								      \
+       __res = (val);							      \
+     __res; })
+
+
+static int
+AB(handle_file) (const char *fname, int fd)
+{
+  E(Ehdr) ehdr;
+
+  if (pread (fd, &ehdr, sizeof (ehdr), 0) != sizeof (ehdr))
+    {
+    read_error:
+      printf ("%s: read error: %m\n", fname);
+      return 1;
+    }
+
+  const size_t phnum = SWAP (ehdr.e_phnum);
+  const size_t phentsize = SWAP (ehdr.e_phentsize);
+
+  /* Read the program header.  */
+  E(Phdr) *phdr = alloca (phentsize * phnum);
+  if (pread (fd, phdr, phentsize * phnum, SWAP (ehdr.e_phoff))
+      != phentsize * phnum)
+    goto read_error;
+
+  /* Search for the PT_GNU_STACK entry.  */
+  for (size_t cnt = 0; cnt < phnum; ++cnt)
+    if (SWAP (phdr[cnt].p_type) == PT_GNU_STACK)
+      {
+	unsigned int flags = SWAP(phdr[cnt].p_flags);
+	if (flags & PF_X)
+	  {
+	    printf ("%s: executable stack signaled\n", fname);
+	    return 1;
+	  }
+
+	return 0;
+      }
+
+  printf ("%s: no PT_GNU_STACK entry\n", fname);
+  return 1;
+}
+
+# undef BITS
+#else
+
+# define BITS 32
+# include "check-execstack.c"
+
+# define BITS 64
+# include "check-execstack.c"
+
+
+static int
+handle_file (const char *fname)
+{
+  int fd = open (fname, O_RDONLY);
+  if (fd == -1)
+    {
+      printf ("cannot open %s: %m\n", fname);
+      return 1;
+    }
+
+  /* Read was is supposed to be the ELF header.  Read the initial
+     bytes to determine whether this is a 32 or 64 bit file.  */
+  char ident[EI_NIDENT];
+  if (read (fd, ident, EI_NIDENT) != EI_NIDENT)
+    {
+      printf ("%s: read error: %m\n", fname);
+      close (fd);
+      return 1;
+    }
+
+  if (memcmp (&ident[EI_MAG0], ELFMAG, SELFMAG) != 0)
+    {
+      printf ("%s: not an ELF file\n", fname);
+      close (fd);
+      return 1;
+    }
+
+  int result;
+  if (ident[EI_CLASS] == ELFCLASS64)
+    result = handle_file64 (fname, fd);
+  else
+    result = handle_file32 (fname, fd);
+
+  close (fd);
+
+  return result;
+}
+
+
+int
+main (int argc, char *argv[])
+{
+  int cnt;
+  int result = 0;
+
+  for (cnt = 1; cnt < argc; ++cnt)
+    result |= handle_file (argv[cnt]);
+
+  return result;
+}
+#endif