ELF: Properly handle section symbols

When defining the section symbol, __start_FOO, for the section FOO:

1. Treat the common symbol, __start_FOO, in input object file as
definition.
2. Clear verinfo.verdef.

bfd/

	PR ld/26094
	* elflink.c (bfd_elf_define_start_stop): Handle common symbols.
	Clear verinfo.verdef.

ld/

	PR ld/26094
	* testsuite/ld-elf/pr26094-1.ver: New fike.
	* testsuite/ld-elf/pr26094-1a.c: Likewise.
	* testsuite/ld-elf/pr26094-1a.rd: Likewise.
	* testsuite/ld-elf/pr26094-1b.c: Likewise.
	* testsuite/ld-elf/pr26094-1b.rd: Likewise.
	* testsuite/ld-elf/pr26094-1c.c: Likewise.
	* testsuite/ld-elf/shared.exp: Run ld/26094 tests.

bfd/ChangeLog

@@ -1,3 +1,9 @@
+2020-06-10  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/26094
+	* elflink.c (bfd_elf_define_start_stop): Handle common symbols.
+	Clear verinfo.verdef.
+
 2020-06-09  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/18801

bfd/elflink.c

@@ -14802,12 +14802,16 @@ bfd_elf_define_start_stop (struct bfd_link_info *info,
 
   h = elf_link_hash_lookup (elf_hash_table (info), symbol,
 			    FALSE, FALSE, TRUE);
+  /* NB: Common symbols will be turned into definition later.  */
   if (h != NULL
       && (h->root.type == bfd_link_hash_undefined
 	  || h->root.type == bfd_link_hash_undefweak
-	  || ((h->ref_regular || h->def_dynamic) && !h->def_regular)))
+	  || ((h->ref_regular || h->def_dynamic)
+	      && !h->def_regular
+	      && h->root.type != bfd_link_hash_common)))
     {
       bfd_boolean was_dynamic = h->ref_dynamic || h->def_dynamic;
+      h->verinfo.verdef = NULL;
       h->root.type = bfd_link_hash_defined;
       h->root.u.def.section = sec;
       h->root.u.def.value = 0;

ld/ChangeLog

@@ -1,3 +1,14 @@
+2020-06-10  H.J. Lu  <hongjiu.lu@intel.com>
+
+	PR ld/26094
+	* testsuite/ld-elf/pr26094-1.ver: New fike.
+	* testsuite/ld-elf/pr26094-1a.c: Likewise.
+	* testsuite/ld-elf/pr26094-1a.rd: Likewise.
+	* testsuite/ld-elf/pr26094-1b.c: Likewise.
+	* testsuite/ld-elf/pr26094-1b.rd: Likewise.
+	* testsuite/ld-elf/pr26094-1c.c: Likewise.
+	* testsuite/ld-elf/shared.exp: Run ld/26094 tests.
+
 2020-06-09  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR ld/18801

ld/testsuite/ld-elf/pr26094-1.ver

@@ -0,0 +1,3 @@
+SOME_VERSION_NAME {
+        global: *;
+};

ld/testsuite/ld-elf/pr26094-1a.c

@@ -0,0 +1,7 @@
+char foo_data  __attribute__(( section("FOO") )) = { 0 };
+
+extern void * __start_FOO;
+
+void * foo() {
+    return  __start_FOO;
+}

ld/testsuite/ld-elf/pr26094-1a.rd

@@ -0,0 +1,8 @@
+#ld: -shared
+#readelf: --dyn-syms --wide
+#target: *-*-linux* *-*-gnu* arm*-*-uclinuxfdpiceabi
+#xfail: ![check_shared_lib_support]
+
+#...
+ +[0-9]+: +[0-9a-f]+ +[0-9a-f]+ +NOTYPE +GLOBAL +PROTECTED +[0-9]+ +___?start_FOO@@SOME_VERSION_NAME
+#pass

ld/testsuite/ld-elf/pr26094-1b.c

@@ -0,0 +1,6 @@
+extern void *foo();
+
+void main()
+{
+    foo();
+}

ld/testsuite/ld-elf/pr26094-1b.rd

@@ -0,0 +1,8 @@
+#ld:
+#readelf: --dyn-syms --wide
+#target: *-*-linux* *-*-gnu* arm*-*-uclinuxfdpiceabi
+#xfail: ![check_shared_lib_support]
+
+#...
+ +[0-9]+: +[0-9a-f]+ +[0-9a-f]+ +OBJECT +GLOBAL +PROTECTED +[0-9]+ +___?start_FOO@@SOME_VERSION_NAME
+#pass

ld/testsuite/ld-elf/pr26094-1c.c

@@ -0,0 +1,7 @@
+char foo_data  __attribute__(( section("FOO") )) = { 0 };
+
+void * __start_FOO;
+
+void * foo() {
+    return  __start_FOO;
+}

ld/testsuite/ld-elf/shared.exp

@@ -832,6 +832,25 @@ append build_tests {
 
 run_cc_link_tests $build_tests
 
+run_cc_link_tests [list \
+    [list \
+	"Build pr26094-1.so" \
+	"-shared -Wl,--version-script=pr26094-1.ver" \
+	"-fPIC" \
+	{pr26094-1a.c} \
+	{{readelf {--dyn-syms --wide} pr26094-1a.rd}} \
+	"pr26094-1.so" \
+    ] \
+    [list \
+	"Build pr26094-1" \
+	"-Wl,--no-as-needed tmpdir/pr26094-1.so" \
+	"-fcommon" \
+	{pr26094-1b.c pr26094-1c.c} \
+	{{readelf {--dyn-syms --wide} pr26094-1b.rd}} \
+	"pr26094-1" \
+    ] \
+]
+
 run_ld_link_tests [list \
     [list \
 	"pr22269-1 (static pie undefined weak)" \