libdwfl: Fix and test aux_sym address_sync with relocated ELF

The aux_sym address_sync already worked with a full prelink, which has
.gnu.prelink_undo, but it failed on plain relocations with prelink -r.

Now it uses the difference in ehdr.e_entry as a first offset guess, and
the tests confirm this seems to work fine.

Signed-off-by: Josh Stone <jistone@redhat.com>

libdwfl/ChangeLog

@@ -1,3 +1,8 @@
+2013-11-18  Josh Stone  <jistone@redhat.com>
+
+	* dwfl_module_getdwarf.c (find_aux_address_sync): New function.
+	(find_aux_sym): Use it.
+
 2013-11-14  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	Code cleanup: Remove const in prototype

libdwfl/dwfl_module_getdwarf.c

@@ -816,6 +816,33 @@ find_dynsym (Dwfl_Module *mod)
     }
 }
 
+
+#if USE_LZMA
+/* Try to find the offset between the main file and .gnu_debugdata.  */
+static bool
+find_aux_address_sync (Dwfl_Module *mod)
+{
+  /* Don't trust the phdrs in the minisymtab elf file to be setup correctly.
+     The address_sync is equal to the main file it is embedded in at first.  */
+  mod->aux_sym.address_sync = mod->main.address_sync;
+
+  /* Adjust address_sync for the difference in entry addresses, attempting to
+     account for ELF relocation changes after aux was split.  */
+  GElf_Ehdr ehdr_main, ehdr_aux;
+  if (unlikely (gelf_getehdr (mod->main.elf, &ehdr_main) == NULL)
+      || unlikely (gelf_getehdr (mod->aux_sym.elf, &ehdr_aux) == NULL))
+    return false;
+  mod->aux_sym.address_sync += ehdr_aux.e_entry - ehdr_main.e_entry;
+
+  /* The shdrs are setup OK to make find_prelink_address_sync () do the right
+     thing, which is possibly more reliable, but it needs .gnu.prelink_undo.  */
+  if (mod->aux_sym.address_sync != 0)
+    return find_prelink_address_sync (mod, &mod->aux_sym) == DWFL_E_NOERROR;
+
+  return true;
+}
+#endif
+
 /* Try to find the auxiliary symbol table embedded in the main elf file
    section .gnu_debugdata.  Only matters if the symbol information comes
    from the main file dynsym.  No harm done if not found.  */
@@ -879,21 +906,11 @@ find_aux_sym (Dwfl_Module *mod __attribute__ ((unused)),
 	      mod->aux_sym.elf->flags |= ELF_F_MALLOCED;
 	      if (open_elf (mod, &mod->aux_sym) != DWFL_E_NOERROR)
 		return;
-	      /* Don't trust the phdrs in the minisymtab elf file to be
-		 setup correctly.  The address_sync is equal to the main
-		 file it is embedded in at first.  The shdrs are setup
-		 OK to make find_prelink_address_sync () do the right
-		 thing if necessary though.  */
-	      mod->aux_sym.address_sync = mod->main.address_sync;
-	      if (mod->aux_sym.address_sync != 0)
+	      if (! find_aux_address_sync (mod))
 		{
-		  error = find_prelink_address_sync (mod, &mod->aux_sym);
-		  if (error != DWFL_E_NOERROR)
-		    {
-		      elf_end (mod->aux_sym.elf);
-		      mod->aux_sym.elf = NULL;
-		      return;
-		    }
+		  elf_end (mod->aux_sym.elf);
+		  mod->aux_sym.elf = NULL;
+		  return;
 		}
 
 	      /* So far, so good. Get minisymtab table data and cache it. */

tests/ChangeLog

@@ -1,3 +1,10 @@
+2013-11-18  Josh Stone  <jistone@redhat.com>
+
+	* testfilebazdbg_plr.bz2: New testfile.
+	* testfilebazmin_plr.bz2: Likewise.
+	* Makefile.am (EXTRA_DIST): Add the above files.
+	* run-dwflsyms.sh: Add prelink -r tests.
+
 2013-11-15  Mark Wielaard  <mjw@redhat.com>
 
 	* testfilebazmdb.bz2: Regenerated.

tests/Makefile.am

@@ -190,6 +190,7 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh \
 	     testfilebazmin.bz2 testfilebazdbg.debug.bz2 testfilebazmdb.bz2 \
 	     testfilebaztab.bz2 testfilebasmin.bz2 \
 	     testfilebazdbg_pl.bz2 testfilebazmin_pl.bz2 \
+	     testfilebazdbg_plr.bz2 testfilebazmin_plr.bz2 \
 	     run-dwflsyms.sh \
 	     run-unstrip-n.sh testcore-rtlib.bz2 testcore-rtlib-ppc.bz2 \
 	     run-low_high_pc.sh testfile_low_high_pc.bz2 \

tests/run-dwflsyms.sh

@@ -19,14 +19,18 @@
 
 # Tests dwfl_module_{addrsym,getsym,relocate_address}
 # See run-readelf-s.sh for how to generate test binaries.
+# In addition, *_pl files were created from their base file
+# with prelink -N, and *_plr with prelink -r 0x4200000000.
 
 testfiles testfilebaztab
 testfiles testfilebazdbg testfilebazdbg.debug
 testfiles testfilebazdbg_pl
+testfiles testfilebazdbg_plr
 testfiles testfilebazdyn
 testfiles testfilebazmdb
 testfiles testfilebazmin
 testfiles testfilebazmin_pl
+testfiles testfilebazmin_plr
 testfiles testfilebasmin
 
 tempfiles testfile.dynsym.in testfile.symtab.in testfile.minsym.in dwflsyms.out
@@ -328,6 +332,9 @@ cat testfile.symtab.in \
 cat testfile.symtab_pl.in \
   | testrun_compare ${abs_builddir}/dwflsyms -e testfilebazdbg_pl
 
+sed s/0x3000/0x4200/g testfile.symtab_pl.in \
+  | testrun_compare ${abs_builddir}/dwflsyms -e testfilebazdbg_plr
+
 cat testfile.dynsym.in \
   | testrun_compare ${abs_builddir}/dwflsyms -e testfilebazdyn
 
@@ -340,6 +347,9 @@ cat testfile.minsym.in \
 cat testfile.minsym_pl.in \
   | testrun_compare ${abs_builddir}/dwflsyms -e testfilebazmin_pl
 
+sed s/0x3000/0x4200/g testfile.minsym_pl.in \
+  | testrun_compare ${abs_builddir}/dwflsyms -e testfilebazmin_plr
+
 testrun_compare ${abs_builddir}/dwflsyms -e testfilebasmin <<\EOF
    0: NOTYPE	LOCAL	 (0) 0
    1: FUNC	LOCAL	foo (18) 0x400168, rel: 0x400168