Add tgkill syscall.

Use tgkill instead of tkill to implement pthread_kill.
This is safer in the event that the thread has already terminated
and its id has been reused by a different process.

Change-Id: Ied715e11d7eadeceead79f33db5e2b5722954ac9

libc/arch-arm/bionic/tgkill.S

@@ -0,0 +1,51 @@
+/*
+ * Copyright (C) 2008 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+/* unlike our auto-generated syscall stubs, this code saves lr
+   on the stack, as well as a few other registers. this makes
+   our stack unwinder happy, when we generate debug stack
+   traces after the C library or other parts of the system
+   abort due to a fatal runtime error (e.g. detection
+   of a corrupted malloc heap).
+*/
+
+#include <sys/linux-syscalls.h>
+#include <machine/asm.h>
+
+#ifndef __NR_tgkill
+#define __NR_tgkill  268
+#endif
+
+ENTRY(tgkill)
+    stmfd   sp!, {r4-r7, ip, lr}
+    ldr     r7, =__NR_tgkill
+    swi     #0
+    ldmfd   sp!, {r4-r7, ip, lr}
+    movs    r0, r0
+    bxpl    lr
+    b       __set_syscall_errno
+END(tgkill)