nptl: Implement raise in terms of pthread_kill

Now that pthread_kill is provided by libc.so it is possible to
implement the generic POSIX implementation as
'pthread_kill(pthread_self(), sig)'.

For Linux implementation, pthread_kill read the targeting TID from
the TCB.  For raise, this it not possible because it would make raise
fail when issue after vfork (where creates the resulting process
has a different TID from the parent, but its TCB is not updated as
for pthread_create).  To make raise use pthread_kill, it is make
usable from vfork by getting the target thread id through gettid
syscall.

Checked on x86_64-linux-gnu and aarch64-linux-gnu.

1 files changed, 29 insertions, 13 deletions

diff --git a/nptl/pthread_kill.c b/nptl/pthread_kill.c
index ad7e011779..8982011ba8 100644
--- a/nptl/pthread_kill.c
+++ b/nptl/pthread_kill.c
@@ -28,24 +28,40 @@ __pthread_kill (pthread_t threadid, int signo)
   if (__is_internal_signal (signo))
     return EINVAL;
 
-  /* Force load of pd->tid into local variable or register.  Otherwise
-     if a thread exits between ESRCH test and tgkill, we might return
-     EINVAL, because pd->tid would be cleared by the kernel.  */
+  pid_t tid;
   struct pthread *pd = (struct pthread *) threadid;
-  pid_t tid = atomic_forced_read (pd->tid);
-  if (__glibc_unlikely (tid <= 0))
-    /* Not a valid thread handle.  */
-    return ESRCH;
 
-  /* We have a special syscall to do the work.  */
-  pid_t pid = __getpid ();
+  if (pd == THREAD_SELF)
+    /* It is a special case to handle raise() implementation after a vfork
+       call (which does not update the PD tid field).  */
+    tid = INLINE_SYSCALL_CALL (gettid);
+  else
+    /* Force load of pd->tid into local variable or register.  Otherwise
+       if a thread exits between ESRCH test and tgkill, we might return
+       EINVAL, because pd->tid would be cleared by the kernel.  */
+    tid = atomic_forced_read (pd->tid);
 
-  int val = INTERNAL_SYSCALL_CALL (tgkill, pid, tid, signo);
-  return (INTERNAL_SYSCALL_ERROR_P (val)
-	  ? INTERNAL_SYSCALL_ERRNO (val) : 0);
+  int val;
+  if (__glibc_likely (tid > 0))
+    {
+      pid_t pid = __getpid ();
+
+      val = INTERNAL_SYSCALL_CALL (tgkill, pid, tid, signo);
+      val = (INTERNAL_SYSCALL_ERROR_P (val)
+	    ? INTERNAL_SYSCALL_ERRNO (val) : 0);
+    }
+  else
+    val = ESRCH;
+
+  return val;
 }
+/* Some architectures (for instance arm) might pull raise through libgcc, so
+   avoid the symbol version if it ends up being used on ld.so.  */
+#if !IS_IN(rtld)
+libc_hidden_def (__pthread_kill)
 versioned_symbol (libc, __pthread_kill, pthread_kill, GLIBC_2_34);
 
-#if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
+# if OTHER_SHLIB_COMPAT (libpthread, GLIBC_2_0, GLIBC_2_34)
 compat_symbol (libc, __pthread_kill, pthread_kill, GLIBC_2_0);
+# endif
 #endif