From 852722fdfd87c8446079714509a1988d75287f2c Mon Sep 17 00:00:00 2001
From: kib <kib@FreeBSD.org>
Date: Thu, 10 May 2018 15:01:43 +0000
Subject: [PATCH] Make fpusave() and fpurestore() on amd64 ifuncs.

From now on, linking amd64 kernel requires either lld or newer ld.bfd.

Reviewed by:	jhb (as part of the large patch)
Discussed with:	emaste
Sponsored by:	The FreeBSD Foundation
Differential revision:	https://reviews.freebsd.org/D13838
---
 sys/amd64/amd64/fpu.c | 62 ++++++++++++++++++++++++++++++++-----------
 1 file changed, 46 insertions(+), 16 deletions(-)

diff --git a/sys/amd64/amd64/fpu.c b/sys/amd64/amd64/fpu.c
index c3b254ef5ab9..5abd82f665df 100644
--- a/sys/amd64/amd64/fpu.c
+++ b/sys/amd64/amd64/fpu.c
@@ -61,6 +61,7 @@ __FBSDID("$FreeBSD$");
 #include <machine/specialreg.h>
 #include <machine/segments.h>
 #include <machine/ucontext.h>
+#include <x86/ifunc.h>
 
 /*
  * Floating point support.
@@ -151,24 +152,58 @@ struct xsave_area_elm_descr {
 	u_int	size;
 } *xsave_area_desc;
 
-void
-fpusave(void *addr)
+static void
+fpusave_xsave(void *addr)
 {
 
-	if (use_xsave)
-		xsave((char *)addr, xsave_mask);
-	else
-		fxsave((char *)addr);
+	xsave((char *)addr, xsave_mask);
 }
 
-void
-fpurestore(void *addr)
+static void
+fpurestore_xrstor(void *addr)
+{
+
+	xrstor((char *)addr, xsave_mask);
+}
+
+static void
+fpusave_fxsave(void *addr)
+{
+
+	fxsave((char *)addr);
+}
+
+static void
+fpurestore_fxrstor(void *addr)
+{
+
+	fxrstor((char *)addr);
+}
+
+static void
+init_xsave(void)
 {
 
 	if (use_xsave)
-		xrstor((char *)addr, xsave_mask);
-	else
-		fxrstor((char *)addr);
+		return;
+	if ((cpu_feature2 & CPUID2_XSAVE) == 0)
+		return;
+	use_xsave = 1;
+	TUNABLE_INT_FETCH("hw.use_xsave", &use_xsave);
+}
+
+DEFINE_IFUNC(, void, fpusave, (void *), static)
+{
+
+	init_xsave();
+	return (use_xsave ? fpusave_xsave : fpusave_fxsave);
+}
+
+DEFINE_IFUNC(, void, fpurestore, (void *), static)
+{
+
+	init_xsave();
+	return (use_xsave ? fpurestore_xrstor : fpurestore_fxrstor);
 }
 
 void
@@ -207,13 +242,8 @@ fpuinit_bsp1(void)
 	uint64_t xsave_mask_user;
 	bool old_wp;
 
-	if ((cpu_feature2 & CPUID2_XSAVE) != 0) {
-		use_xsave = 1;
-		TUNABLE_INT_FETCH("hw.use_xsave", &use_xsave);
-	}
 	if (!use_xsave)
 		return;
-
 	cpuid_count(0xd, 0x0, cp);
 	xsave_mask = XFEATURE_ENABLED_X87 | XFEATURE_ENABLED_SSE;
 	if ((cp[0] & xsave_mask) != xsave_mask)