perf symbols: Fix annotation of objects with debuginfo files

Commit 73cdf0c6 ("perf symbols: Record text offset in dso
to calculate objdump address") started storing the offset of
the text section for all DSOs:

       if (elf_section_by_name(elf, &ehdr, &tshdr, ".text", NULL))
               dso->text_offset = tshdr.sh_addr - tshdr.sh_offset;

Unfortunately this breaks debuginfo files, because we need to calculate
the offset of the text section in the associated executable file. As a
result perf annotate returns junk for all debuginfo files.

Fix this by using runtime_ss->elf which should point at the executable
when parsing a debuginfo file.
Signed-off-by: Anton Blanchard <anton@samba.org>
Reviewed-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Tested-by: Wang Nan <wangnan0@huawei.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org # v4.6+
Fixes: 73cdf0c6 ("perf symbols: Record text offset in dso to calculate objdump address")
Link: http://lkml.kernel.org/r/20160813115533.6de17912@krytenSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/symbol-elf.c

@@ -837,7 +837,8 @@ int dso__load_sym(struct dso *dso, struct map *map,
 	sec = syms_ss->symtab;
 	shdr = syms_ss->symshdr;
 
-	if (elf_section_by_name(elf, &ehdr, &tshdr, ".text", NULL))
+	if (elf_section_by_name(runtime_ss->elf, &runtime_ss->ehdr, &tshdr,
+				".text", NULL))
 		dso->text_offset = tshdr.sh_addr - tshdr.sh_offset;
 
 	if (runtime_ss->opdsec)