clone/kcmp: avoid CLONE_VM crashes during ld resolve

Testcases which spawn children via clone(CLONE_VM) are prone to races in dynamic linker during symbol resolution. CLONE_VM is causing both parent and child process to share same TLS, which rarely leads to a crashes, for example:

Program terminated with signal 4, Illegal instruction. [Switching to thread 1 (LWP 30351)]
(gdb) bt

  #0  _dl_x86_64_restore_sse () at ../sysdeps/x86_64/dl-trampoline.S:389
  #1  0x00007fefa1360625 in _dl_fixup (l=<optimized out>, reloc_arg=<optimized out>) at ../elf/dl-runtime.c:121
  #2  0x00007fefa13670c0 in _dl_runtime_resolve () at ../sysdeps/x86_64/dl-trampoline.S:87
  #3  0x0000000000402e4f in test_FILES () at clone02.c:332
  #4  child_fn () at clone02.c:272
  #5  0x00007fefa10887ad in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113

[Switching to thread 2 (LWP 30350)]
(gdb) bt
#0 0x00007fefa104f1f2 in __libc_wait (stat_loc=stat_loc@entry=0x7ffe0edb537c) at ../sysdeps/unix/sysv/linux/wait.c:30 #1 0x000000000040294a in main (ac=<optimized out>, av=<optimized out>) at clone02.c:154

See also:
http://www.mail-archive.com/[email protected]/msg01944.html

---
 testcases/kernel/syscalls/clone/Makefile | 2 ++
 testcases/kernel/syscalls/kcmp/Makefile  | 2 ++
 2 files changed, 4 insertions(+)

index bd617d806675..2ded37c0028f 100644
@@ -20,4 +20,6 @@ top_srcdir		?= ../../../..
 
 include $(top_srcdir)/include/mk/testcases.mk
 
+CFLAGS += -Wl,-z,now
+
 include $(top_srcdir)/include/mk/generic_leaf_target.mk

index 083a071b4eff..cb8a3dea3dc9 100644
@@ -21,4 +21,6 @@ top_srcdir		?= ../../../..
 
 include $(top_srcdir)/include/mk/testcases.mk
 
+CFLAGS += -Wl,-z,now
+
 include $(top_srcdir)/include/mk/generic_leaf_target.mk

1.8.3.1

Hi!
Looks good.

Cyril Hrubis
[email protected]

----- Original Message -----

Pushed.

Regards,
Jan