nptl: Remove vfork IFUNC-based forwarder from libpthread [BZ #20188]

With commit f0b2132b35248c1f4a80f62a2c38cddcc802aa8c ("ld.so:
Support moving versioned symbols between sonames [BZ #24741]"), the
dynamic linker will find the definition of vfork in libc and binds
a vfork reference to that symbol, even if the soname in the version
reference says that the symbol should be located in libpthread.

As a result, the forwarder (whether it's IFUNC-based or a duplicate
of the libc implementation) is no longer necessary.

On older architectures, a placeholder symbol is required, to make sure
that the GLIBC_2.1.2 symbol version does not go away, or is turned in
to a weak symbol definition by the link editor.  (The symbol version
needs to preserved so that the symbol coverage check in
elf/dl-version.c does not fail for old binaries.)

mips32 is an outlier: It defined __vfork@@GLIBC_2.2, but the
baseline is GLIBC_2.0.  Since there are other @@GLIBC_2.2 symbols,
the placeholder symbol is not needed there.

1 files changed, 2 insertions, 3 deletions

diff --git a/nptl/Versions b/nptl/Versions
index e7f691da7a..6007fd03e7 100644
--- a/nptl/Versions
+++ b/nptl/Versions
@@ -36,7 +36,6 @@ libc {
     __libc_alloca_cutoff;
     # Internal libc interface to libpthread
     __libc_dl_error_tsd;
-    __libc_vfork;
     __libc_pthread_init;
     __libc_current_sigrtmin_private; __libc_current_sigrtmax_private;
     __libc_allocate_rtsig_private;
@@ -98,7 +97,7 @@ libpthread {
     sem_destroy; sem_getvalue; sem_init; sem_post; sem_trywait; sem_wait;
 
     # Special fork handling.
-    fork; __fork; vfork;
+    fork; __fork;
 
     # Cancellation points.
     close; __close; fcntl; __fcntl; read; __read; write; __write; accept;
@@ -152,7 +151,7 @@ libpthread {
   }
 
   GLIBC_2.1.2 {
-    __vfork;
+    __libpthread_version_placeholder;
   }
 
   GLIBC_2.2 {