nptl: restore .interp section in libpthread.so

In commit 02657da, .interp section
was removed from libpthread.so.  This led to an error:

  $ /lib64/libpthread.so.0
  Native POSIX Threads Library by Ulrich Drepper et al
  Copyright (C) 2015 Free Software Foundation, Inc.
  This is free software; see the source for copying conditions.
  There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A
  PARTICULAR PURPOSE.
  Forced unwind support included.
  Segmentation fault

  (gdb) bt
  #0  0x00000000000055a6 in _exit@plt ()

Unfortunately, there is no way to add a regression test for the bug
because .interp specifies the path to dynamic linker of the target
system.

[BZ #18479]
* nptl/pt-interp.c: New file.
* nptl/Makefile (libpthread-routines, libpthread-shared-only-routines):
Add pt-interp.
[$(build-shared) = yes] ($(objpfx)pt-interp.os): Depend on
$(common-objpfx)runtime-linker.h.

ChangeLog

@@ -1,3 +1,12 @@
+2015-06-10  Gleb Fotengauer-Malinovskiy  <glebfm@altlinux.org>
+
+	[BZ #18479]
+	* nptl/pt-interp.c: New file.
+	* nptl/Makefile (libpthread-routines, libpthread-shared-only-routines):
+	Add pt-interp.
+	[[$(build-shared) = yes] ($(objpfx)pt-interp.os): Depend on
+	$(common-objpfx)runtime-linker.h.
+
 2015-06-10  Dmitry V. Levin  <ldv@altlinux.org>
 
 	* Makeconfig (+interp): Remove unused variable.

NEWS

@@ -20,7 +20,7 @@ Version 2.22
   18111, 18116, 18125, 18128, 18138, 18185, 18196, 18197, 18206, 18210,
   18211, 18217, 18220, 18221, 18234, 18244, 18247, 18287, 18319, 18324,
   18333, 18346, 18397, 18409, 18410, 18412, 18418, 18422, 18434, 18444,
-  18468, 18469, 18470, 18483, 18495, 18496, 18497, 18498, 18507.
+  18468, 18469, 18470, 18479, 18483, 18495, 18496, 18497, 18498, 18507.
 
 * Cache information can be queried via sysconf() function on s390 e.g. with
   _SC_LEVEL1_ICACHE_SIZE as argument.

nptl/Makefile

@@ -33,7 +33,7 @@ routines = alloca_cutoff forward libc-lowlevellock libc-cancellation \
 	   register-atfork unregister-atfork
 shared-only-routines = forward
 
-libpthread-routines = nptl-init vars events version \
+libpthread-routines = nptl-init vars events version pt-interp \
 		      pthread_create pthread_exit pthread_detach \
 		      pthread_join pthread_tryjoin pthread_timedjoin \
 		      pthread_self pthread_equal pthread_yield \
@@ -138,7 +138,8 @@ libpthread-routines = nptl-init vars events version \
 #		      pthread_setgid pthread_setegid pthread_setregid \
 #		      pthread_setresgid
 
-libpthread-shared-only-routines = version pt-allocrtsig unwind-forcedunwind
+libpthread-shared-only-routines = version pt-interp pt-allocrtsig \
+				  unwind-forcedunwind
 libpthread-static-only-routines = pthread_atfork
 
 # Since cancellation handling is in large parts handled using exceptions
@@ -608,6 +609,8 @@ $(objpfx)banner.h: Banner
 generated += banner.h
 # Give libpthread.so an entry point and make it directly runnable itself.
 LDFLAGS-pthread.so += -e __nptl_main
+# pt-interp.c exists just to get the runtime linker path into libpthread.so.
+$(objpfx)pt-interp.os: $(common-objpfx)runtime-linker.h
 endif
 
 ifeq ($(run-built-tests),yes)

nptl/pt-interp.c

@@ -0,0 +1 @@
+#include <elf/interp.c>