libdwelf: Add dwelf_dwarf_gnu_debugaltlink

Signed-off-by: Florian Weimer <fweimer@redhat.com>

libdwelf/ChangeLog

@@ -1,3 +1,11 @@
+2014-04-24  Florian Weimer  <fweimer@redhat.com>
+
+	* dwelf_dwarf_gnu_debugaltlink.c: New file.
+	* Makefile.am (libdwelf_a_SOURCES): Add it.
+	* libdwelf.h (dwelf_dwarf_gnu_debugaltlink): Declare new function.
+	* libdwelfP.h (dwelf_dwarf_gnu_debugaltlink): Add internal
+	declaration.
+
 2014-04-11  Mark Wielaard  <mjw@redhat.com>
 
 	* Makefile.am: New file.

libdwelf/Makefile.am

@@ -38,7 +38,7 @@ noinst_LIBRARIES = libdwelf.a libdwelf_pic.a
 pkginclude_HEADERS = libdwelf.h
 noinst_HEADERS = libdwelfP.h
 
-libdwelf_a_SOURCES = dwelf_elf_gnu_debuglink.c
+libdwelf_a_SOURCES = dwelf_elf_gnu_debuglink.c dwelf_dwarf_gnu_debugaltlink.c
 
 libdwelf = $(libdw)
 

libdwelf/dwelf_dwarf_gnu_debugaltlink.c

@@ -0,0 +1,62 @@
+/* Returns the file name and build ID stored in the .gnu_altdebuglink if found.
+   Copyright (C) 2014 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"
+
+ssize_t
+dwelf_dwarf_gnu_debugaltlink (Dwarf *dwarf,
+			      const char **name_p,
+			      const void **build_idp)
+{
+  Elf_Data *data = dwarf->sectiondata[IDX_gnu_debugaltlink];
+  if (data == NULL)
+    {
+      return 0;
+    }
+
+  const void *ptr = memchr (data->d_buf, '\0', data->d_size);
+  if (ptr == NULL)
+    {
+      __libdw_seterrno (DWARF_E_INVALID_ELF);
+      return -1;
+    }
+  size_t build_id_len = data->d_size - (ptr - data->d_buf + 1);
+  if (build_id_len == 0 || (size_t) (ssize_t) build_id_len != build_id_len)
+    {
+      __libdw_seterrno (DWARF_E_INVALID_ELF);
+      return -1;
+    }
+  *name_p = data->d_buf;
+  *build_idp = ptr + 1;
+  return build_id_len;
+}
+INTDEF(dwelf_dwarf_gnu_debugaltlink)

libdwelf/libdwelf.h

@@ -47,6 +47,16 @@ extern "C" {
    section or some other error occured.  */
 extern const char *dwelf_elf_gnu_debuglink (Elf *elf, GElf_Word *crc);
 
+/* Returns the name and build ID from the .gnu_debugaltlink section if
+   found in the ELF.  On success, pointers to the name and build ID
+   are written to *NAMEP and *BUILDID_P, and the positive length of
+   the build ID is returned.  Returns 0 if the ELF lacks a
+   .gnu_debugaltlink section.  Returns -1 in case of malformed data or
+   other errors.  */
+extern ssize_t dwelf_dwarf_gnu_debugaltlink (Dwarf *dwarf,
+					     const char **namep,
+					     const void **build_idp);
+
 #ifdef __cplusplus
 }
 #endif

libdwelf/libdwelfP.h

@@ -36,5 +36,6 @@
 
 /* Avoid PLT entries.  */
 INTDECL (dwelf_elf_gnu_debuglink)
+INTDECL (dwelf_dwarf_gnu_debugaltlink)
 
 #endif	/* libdwelfP.h */