x86: provide userspace implementation of sched_getcpu() where possible

(cherry picked from commit f239545591a821386f9bdb84c02044884ad415b5)

2 files changed, 82 insertions, 1 deletions

diff --git a/lib/libc/x86/sys/Makefile.inc b/lib/libc/x86/sys/Makefile.inc
index 8aa4948a3295..ef0bfbdbe706 100644
--- a/lib/libc/x86/sys/Makefile.inc
+++ b/lib/libc/x86/sys/Makefile.inc
@@ -5,7 +5,7 @@
 SRCS+= \
 	__vdso_gettc.c \
 	pkru.c \
-	sched_getcpu_gen.c
+	sched_getcpu_x86.c
 
 MAN+=	\
 	pkru.3
diff --git a/lib/libc/x86/sys/sched_getcpu_x86.c b/lib/libc/x86/sys/sched_getcpu_x86.c
new file mode 100644
index 000000000000..13ba18ef5e36
--- /dev/null
+++ b/lib/libc/x86/sys/sched_getcpu_x86.c
@@ -0,0 +1,81 @@
+/*-
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were developed by Konstantin Belousov <kib@FreeBSD.org>
+ * under sponsorship from the FreeBSD Foundation.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. 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 AUTHOR 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 AUTHOR 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.
+ */
+
+#include <sys/param.h>
+#include <machine/cpufunc.h>
+#include <machine/specialreg.h>
+#include <machine/sysarch.h>
+#include <x86/ifunc.h>
+#include <errno.h>
+#include <sched.h>
+#include "libc_private.h"
+
+static int
+sched_getcpu_sys(void)
+{
+	return (__sys_sched_getcpu());
+}
+
+static int
+sched_getcpu_rdpid(void)
+{
+	register_t res;
+
+	__asm("rdpid	%0" : "=r" (res));
+	return ((int)res);
+}
+
+static int
+sched_getcpu_rdtscp(void)
+{
+	int res;
+
+	__asm("rdtscp" : "=c" (res) : : "eax", "edx");
+	return (res);
+}
+
+DEFINE_UIFUNC(, int, sched_getcpu, (void))
+{
+	u_int amd_feature, cpu_exthigh, p[4];
+
+	if ((cpu_stdext_feature2 & CPUID_STDEXT2_RDPID) != 0)
+		return (sched_getcpu_rdpid);
+
+	amd_feature = 0;
+	if (cpu_feature != 0) {
+		do_cpuid(0x80000000, p);
+		cpu_exthigh = p[0];
+		if (cpu_exthigh >= 0x80000001) {
+			do_cpuid(0x80000001, p);
+			amd_feature = p[3];
+		}
+	}
+
+	return ((amd_feature & AMDID_RDTSCP) == 0 ?
+	    sched_getcpu_sys : sched_getcpu_rdtscp);
+}