libelf: Allow updating phdrs for any e_type.

elf[32|64]_updatenull would sanity check the e_type before allowing to
update the phdrs. This prevents creating an ET_REL file with phdrs. It
also prevents creating any vendor specific ELF file having phdrs. We
only check this when updating/writing out the file. But we would just
read such files. Don't prevent people from creating unexpected ELF files.
elflint will warn for such files.

While writing a new testcase for this another bug was found that
prevented updating a just created phdr because elf_getphdrnum would
sanity check the phdr offset in the file (which doesn't exist yet).
Fix that by only doing such a sanity check if the phdrs haven't been
read in or created yet.

This second bug should have been found by the existing elfshphehdr
test, but that test contained a typo checking elf_getphdrnum.
It tested that the called failed when there were no phdrs, but then
elf_getphdrnum should simply succeed and return zero.

https://bugzilla.redhat.com/show_bug.cgi?id=1352232

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

1 files changed, 197 insertions, 0 deletions

diff --git a/tests/vendorelf.c b/tests/vendorelf.c
new file mode 100644
index 00000000..bc13cce3
--- /dev/null
+++ b/tests/vendorelf.c
@@ -0,0 +1,197 @@
+/* Test program for adding a program header to a vendor specific ELF file.
+   Copyright (C) 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 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.
+
+   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 a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include ELFUTILS_HEADER(elf)
+#include <gelf.h>
+
+void
+check_elf (const char *fname, int class, int use_mmap)
+{
+  printf ("\nfname: %s\n", fname);
+
+  int fd = open (fname, O_RDWR | O_CREAT | O_TRUNC, 0666);
+  if (fd == -1)
+    {
+      printf ("cannot open `%s': %s\n", fname, strerror (errno));
+      exit (1);
+    }
+
+  Elf *elf = elf_begin (fd, use_mmap ? ELF_C_WRITE_MMAP : ELF_C_WRITE, NULL);
+  if (elf == NULL)
+    {
+      printf ("cannot create ELF descriptor: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  // Create an ELF header.
+  if (gelf_newehdr (elf, class) == 0)
+    {
+      printf ("cannot create ELF header: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  GElf_Ehdr ehdr_mem;
+  GElf_Ehdr *ehdr = gelf_getehdr (elf, &ehdr_mem);
+  if (ehdr == NULL)
+    {
+      printf ("cannot get ELF header: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  // Initialize header.
+  ehdr->e_ident[EI_DATA] = class == ELFCLASS64 ? ELFDATA2LSB : ELFDATA2MSB;
+  ehdr->e_ident[EI_OSABI] = ELFOSABI_GNU;
+  ehdr->e_type = ET_LOOS + 1;
+  ehdr->e_machine = EM_X86_64;
+  ehdr->e_version = EV_CURRENT;
+
+  if (gelf_update_ehdr (elf, ehdr) == 0)
+    {
+      printf ("cannot update ELF header: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  // Create a program header.
+  if (gelf_newphdr (elf, 1) == 0)
+    {
+      printf ("cannot create program header: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  GElf_Phdr phdr;
+  if (gelf_getphdr (elf, 0, &phdr) == NULL)
+    {
+      printf ("cannot get program header: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  // Some random values to check later.
+  phdr.p_type = PT_NULL;
+  phdr.p_offset = 0;
+  phdr.p_vaddr = 0;
+  phdr.p_paddr = 1;
+  phdr.p_filesz = 0;
+  phdr.p_memsz = 1024;
+  phdr.p_flags = PF_R;
+  phdr.p_align = 16;
+
+  if (gelf_update_phdr (elf, 0, &phdr) == 0)
+    {
+      printf ("cannot update program header: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  // Write everything to disk.
+  if (elf_update (elf, ELF_C_WRITE) < 0)
+    {
+      printf ("failure in elf_update(WRITE): %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  if (elf_end (elf) != 0)
+    {
+      printf ("failure in elf_end: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  close (fd);
+
+  /* Reread the ELF from disk now.  */
+  fd = open (fname, O_RDONLY, 0666);
+  if (fd == -1)
+    {
+      printf ("cannot open `%s' read-only: %s\n", fname, strerror (errno));
+      exit (1);
+    }
+
+  elf = elf_begin (fd, use_mmap ? ELF_C_READ_MMAP : ELF_C_READ, NULL);
+  if (elf == NULL)
+    {
+      printf ("cannot create ELF descriptor read-only: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  // Is our phdr there?
+  size_t phnum;
+  if (elf_getphdrnum (elf, &phnum) != 0)
+    {
+      printf ("cannot get phdr num: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  if (phnum != 1)
+    {
+      printf ("Expected just 1 phdr, got: %zd\n", phnum);
+      exit (1);
+    }
+
+  if (gelf_getphdr (elf, 0, &phdr) == NULL)
+    {
+      printf ("cannot get program header from file: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  if (phdr.p_type != PT_NULL
+      || phdr.p_offset != 0
+      || phdr.p_vaddr != 0
+      || phdr.p_paddr != 1
+      || phdr.p_filesz != 0
+      || phdr.p_memsz != 1024
+      || phdr.p_flags != PF_R
+      || phdr.p_align != 16)
+    {
+      printf ("Unexpected phdr values\n");
+      exit (1);
+    }
+
+  if (elf_end (elf) != 0)
+    {
+      printf ("failure in elf_end: %s\n", elf_errmsg (-1));
+      exit (1);
+    }
+
+  close (fd);
+
+  unlink (fname);
+}
+
+int
+main (int argc __attribute__ ((unused)),
+      char *argv[] __attribute__ ((unused)))
+{
+  elf_version (EV_CURRENT);
+
+  check_elf ("vendor.elf.32", ELFCLASS32, 0);
+  check_elf ("vendor.elf.32.mmap", ELFCLASS32, 1);
+  check_elf ("vendor.elf.64", ELFCLASS64, 0);
+  check_elf ("vendor.elf.64.mmap", ELFCLASS64, 1);
+
+  return 0;
+}