From 29879bdc832b3287067872faf4c1f759268348c9 Mon Sep 17 00:00:00 2001
From: visa <visa@openbsd.org>
Date: Thu, 20 Apr 2017 16:07:52 +0000
Subject: [PATCH] Get TCB address using the RDHWR instruction instead of
 __get_tcb(). This gives fast access to the address on systems that implement
 the UserLocal register. TCB caching is still used when running in the
 single-threaded mode in order not to penalize old systems.

The kernel counterpart of this change must be in place before
using this diff!

With guenther@
---
 include/tib.h                 |  8 +++-----
 lib/libc/include/cancel.h     |  9 +++++----
 sys/arch/mips64/include/tcb.h | 21 ++++++++++++++++++++-
 3 files changed, 28 insertions(+), 10 deletions(-)

diff --git a/include/tib.h b/include/tib.h
index 7dff1168ec9..597d2496bcd 100644
--- a/include/tib.h
+++ b/include/tib.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tib.h,v 1.3 2016/05/07 19:05:21 guenther Exp $	*/
+/*	$OpenBSD: tib.h,v 1.4 2017/04/20 16:07:52 visa Exp $	*/
 /*
  * Copyright (c) 2011,2014 Philip Guenther <guenther@openbsd.org>
  *
@@ -84,11 +84,9 @@
  */
 
 
-/* If <machine/tcb.h> doesn't provide a better way, then use the default */
-#ifdef	TCB_GET
+/* All archs but mips64 have fast TCB_GET() and don't need caching */
+#ifndef	__mips64__
 # define TCB_HAVE_MD_GET	1
-#else
-# define TCB_GET()		__get_tcb()
 #endif
 #ifdef	TCB_SET
 # define TCB_HAVE_MD_SET	1
diff --git a/lib/libc/include/cancel.h b/lib/libc/include/cancel.h
index a858b80a1c2..ada417d3e12 100644
--- a/lib/libc/include/cancel.h
+++ b/lib/libc/include/cancel.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: cancel.h,v 1.2 2016/05/10 05:42:31 guenther Exp $ */
+/*	$OpenBSD: cancel.h,v 1.3 2017/04/20 16:07:52 visa Exp $ */
 /*
  * Copyright (c) 2015 Philip Guenther <guenther@openbsd.org>
  *
@@ -26,11 +26,12 @@ __BEGIN_HIDDEN_DECLS
 __dead void	_thread_canceled(void);
 __END_HIDDEN_DECLS
 
-#ifdef __LIBC__
+#if defined(__LIBC__) && !defined(TCB_HAVE_MD_SET)
 /*
- * Redirect macros that would use the syscall to instead use our callback
+ * Override TIB_GET macro to use the caching callback
  */
-#define __get_tcb()	_thread_cb.tc_tcb()
+#undef TIB_GET
+#define TIB_GET()	TCB_TO_TIB(_thread_cb.tc_tcb())
 #endif
 
 #define PREP_CANCEL_POINT(tib)						\
diff --git a/sys/arch/mips64/include/tcb.h b/sys/arch/mips64/include/tcb.h
index 3c1ab597ea7..6e7a6b7bedc 100644
--- a/sys/arch/mips64/include/tcb.h
+++ b/sys/arch/mips64/include/tcb.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: tcb.h,v 1.3 2017/04/20 15:42:26 visa Exp $	*/
+/*	$OpenBSD: tcb.h,v 1.4 2017/04/20 16:07:52 visa Exp $	*/
 
 /*
  * Copyright (c) 2011 Philip Guenther <guenther@openbsd.org>
@@ -42,6 +42,25 @@ __mips64_set_tcb(struct proc *p, void *tcb)
 /* ELF TLS ABI calls for small TCB, with static TLS data after it */
 #define TLS_VARIANT	1
 
+static inline void *
+__mips64_get_tcb(void)
+{
+	void *tcb;
+
+	/*
+	 * This invokes emulation in kernel if the system does not implement
+	 * the RDHWR instruction or the UserLocal register.
+	 */
+	__asm__ volatile (
+	"	.set	push\n"
+	"	.set	mips64r2\n"
+	"	rdhwr	%0, $29\n"
+	"	.set	pop\n" : "=r" (tcb));
+	return tcb;
+}
+
+#define TCB_GET()		__mips64_get_tcb()
+
 #endif /* _KERNEL */
 
 #endif /* _MACHINE_TCB_H_ */
-- 
2.20.1