Elf_Scn *
elf_nextscn (Elf *elf, Elf_Scn *scn)
{
+ Elf_ScnList *list;
Elf_Scn *result = NULL;
if (elf == NULL)
if (scn == NULL)
{
- /* If no section handle is given return the first (not 0th) section. */
+ /* If no section handle is given return the first (not 0th) section.
+ Set scn to the 0th section and perform nextscn. */
if (elf->class == ELFCLASS32
|| (offsetof (Elf, state.elf32.scns)
== offsetof (Elf, state.elf64.scns)))
- {
- if (elf->state.elf32.scns.cnt > 1)
- result = &elf->state.elf32.scns.data[1];
- }
+ list = &elf->state.elf32.scns;
else
- {
- if (elf->state.elf64.scns.cnt > 1)
- result = &elf->state.elf64.scns.data[1];
- }
+ list = &elf->state.elf64.scns;
+
+ scn = &list->data[0];
}
else
+ list = scn->list;
+
+ if (scn + 1 < &list->data[list->cnt])
+ result = scn + 1;
+ else if (scn + 1 == &list->data[list->max]
+ && (list = list->next) != NULL)
{
- Elf_ScnList *list = scn->list;
-
- if (scn + 1 < &list->data[list->cnt])
- result = scn + 1;
- else if (scn + 1 == &list->data[list->max]
- && (list = list->next) != NULL)
- {
- /* If there is another element in the section list it must
- have at least one entry. */
- assert (list->cnt > 0);
- result = &list->data[0];
- }
+ /* If there is another element in the section list it must
+ have at least one entry. */
+ assert (list->cnt > 0);
+ result = &list->data[0];
}
rwlock_unlock (elf->lock);
--- /dev/null
+/* Test program for adding a section to an empty 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>
+
+
+/* Index of last string added. Returned by add_string (). */
+static size_t stridx = 0;
+
+/* Adds a string and returns the offset in the section. */
+static size_t
+add_string (Elf_Scn *scn, char *str)
+{
+ size_t lastidx = stridx;
+ size_t size = strlen (str) + 1;
+
+ Elf_Data *data = elf_newdata (scn);
+ if (data == NULL)
+ {
+ printf ("cannot create data SHSTRTAB section: %s\n", elf_errmsg (-1));
+ exit (1);
+ }
+
+ data->d_buf = str;
+ data->d_type = ELF_T_BYTE;
+ data->d_size = size;
+ data->d_align = 1;
+ data->d_version = EV_CURRENT;
+
+ stridx += size;
+ printf ("add_string: '%s', stridx: %zd, lastidx: %zd\n",
+ str, stridx, lastidx);
+ return lastidx;
+}
+
+static void
+check_elf (const char *fname, int class, int use_mmap)
+{
+ printf ("\nfname: %s\n", fname);
+ stridx = 0; // Reset strtab strings index
+
+ 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_NONE;
+ 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);
+ }
+
+ // 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_RDWR, 0666);
+ if (fd == -1)
+ {
+ printf ("cannot (re)open `%s': %s\n", fname, strerror (errno));
+ exit (1);
+ }
+
+ elf = elf_begin (fd, use_mmap ? ELF_C_RDWR_MMAP : ELF_C_RDWR, NULL);
+ if (elf == NULL)
+ {
+ printf ("cannot create ELF descriptor read-only: %s\n", elf_errmsg (-1));
+ exit (1);
+ }
+
+ // There are no sections yet.
+ if (elf_nextscn (elf, NULL) != NULL)
+ {
+ printf ("Empty elf had a section???\n");
+ exit (1);
+ }
+
+ // Create strtab section.
+ Elf_Scn *scn = elf_newscn (elf);
+ if (scn == NULL)
+ {
+ printf ("cannot create strings section: %s\n", elf_errmsg (-1));
+ exit (1);
+ }
+
+ // Add an empty string to the table as NUL entry for section zero.
+ add_string (scn, "");
+
+ GElf_Shdr shdr_mem;
+ GElf_Shdr *shdr = gelf_getshdr (scn, &shdr_mem);
+ if (shdr == NULL)
+ {
+ printf ("cannot get header for strings section: %s\n", elf_errmsg (-1));
+ exit (1);
+ }
+
+ shdr->sh_type = SHT_STRTAB;
+ shdr->sh_flags = 0;
+ shdr->sh_addr = 0;
+ shdr->sh_link = SHN_UNDEF;
+ shdr->sh_info = SHN_UNDEF;
+ shdr->sh_addralign = 1;
+ shdr->sh_entsize = 0;
+ shdr->sh_name = add_string (scn, ".strtab");
+
+ // We have to store the section strtab index in the ELF header.
+ // So sections have actual names.
+ int ndx = elf_ndxscn (scn);
+ ehdr->e_shstrndx = ndx;
+
+ if (gelf_update_ehdr (elf, ehdr) == 0)
+ {
+ printf ("cannot update ELF header: %s\n", elf_errmsg (-1));
+ exit (1);
+ }
+
+ // Finished strtab section, update the header.
+ if (gelf_update_shdr (scn, shdr) == 0)
+ {
+ printf ("cannot update STRTAB section 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);
+
+ // And read it in one last time.
+ 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 new section there?
+ scn = elf_nextscn (elf, NULL);
+ if (scn == NULL)
+ {
+ printf ("cannot get new section: %s\n", elf_errmsg (-1));
+ exit (1);
+ }
+
+ shdr = gelf_getshdr (scn, &shdr_mem);
+ if (shdr == NULL)
+ {
+ printf ("cannot get header for new section: %s\n", elf_errmsg (-1));
+ exit (1);
+ }
+
+ size_t shstrndx;
+ if (elf_getshdrstrndx (elf, &shstrndx) < 0)
+ {
+ printf ("elf_getshdrstrndx: %s\n", elf_errmsg (-1));
+ exit (1);
+ }
+
+ const char *sname = elf_strptr (elf, shstrndx, shdr->sh_name);
+ if (sname == NULL || strcmp (sname, ".strtab") != 0)
+ {
+ printf ("Bad section name: %s\n", sname);
+ 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 ("empty.elf.32", ELFCLASS32, 0);
+ check_elf ("empty.elf.32.mmap", ELFCLASS32, 1);
+ check_elf ("empty.elf.64", ELFCLASS64, 0);
+ check_elf ("empty.elf.64.mmap", ELFCLASS64, 1);
+
+ return 0;
+}
projects / thirdparty / elfutils.git / commitdiff
