[PowerPC] Implement VDSO timebase access on powerpc*

Implement the remaining pieces needed to allow userland timestamp reading.

Rewritten based on an intial essay into the problem by Justin Hibbits.
(Copyright changed to my own on his request.)

Tested on ppc64 (POWER9 Talos II), powerpcspe (e500v2 RB800), and
powerpc (g4 PowerBook).

Reviewed by:	jhibbits (in irc)
Sponsored by:	Tag1 Consulting, Inc.
Differential Revision:	https://reviews.freebsd.org/D26347

lib/libc/powerpc/Makefile.inc

@@ -1,7 +1,5 @@
 # $FreeBSD$
 
-SRCS+=	trivial-vdso_tc.c
-
 # Long double is 64-bits
 SRCS+=machdep_ldisd.c
 SYM_MAPS+=${LIBC_SRCTOP}/powerpc/Symbol.map

lib/libc/powerpc/sys/Makefile.inc

@@ -1,3 +1,4 @@
 # $FreeBSD$
 
+SRCS+=	__vdso_gettc.c
 MDASM+=	cerror.S

lib/libc/powerpc/sys/__vdso_gettc.c

@@ -0,0 +1,68 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2020 Brandon Bergren <bdragon@FreeBSD.org>
+ *
+ * This software was developed by Konstantin Belousov
+ * 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/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/elf.h>
+#include <sys/time.h>
+#include <sys/vdso.h>
+
+#include <machine/cpufunc.h>
+#include <machine/spr.h>
+
+#include <errno.h>
+
+#include "libc_private.h"
+
+#pragma weak __vdso_gettc
+int
+__vdso_gettc(const struct vdso_timehands *th, u_int *tc)
+{
+
+	if (__predict_false(th->th_algo != VDSO_TH_ALGO_PPC_TB))
+	    return (ENOSYS);
+	/*
+	 * While the timebase is a 64 bit quantity, we are only interested
+	 * in the lower 32 bits of it.
+	 */
+	*tc = mfspr(TBR_TBL);
+
+	return (0);
+}
+
+#pragma weak __vdso_gettimekeep
+int
+__vdso_gettimekeep(struct vdso_timekeep **tk)
+{
+
+	return (_elf_aux_info(AT_TIMEKEEP, tk, sizeof(*tk)));
+}

lib/libc/powerpc64/Makefile.inc

@@ -1,7 +1,5 @@
 # $FreeBSD$
 
-SRCS+=	trivial-vdso_tc.c
-
 # Long double is 64-bits
 SRCS+=machdep_ldisd.c
 SYM_MAPS+=${LIBC_SRCTOP}/powerpc64/Symbol.map

lib/libc/powerpc64/sys/Makefile.inc

@@ -1,3 +1,4 @@
 # $FreeBSD$
 
+SRCS+=	__vdso_gettc.c
 MDASM+=	cerror.S

lib/libc/powerpc64/sys/__vdso_gettc.c

@@ -0,0 +1,65 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2020 Brandon Bergren <bdragon@FreeBSD.org>
+ *
+ * This software was developed by Konstantin Belousov
+ * 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/cdefs.h>
+__FBSDID("$FreeBSD$");
+
+#include <sys/types.h>
+#include <sys/elf.h>
+#include <sys/time.h>
+#include <sys/vdso.h>
+
+#include <machine/cpufunc.h>
+
+#include <errno.h>
+
+#include "libc_private.h"
+
+#pragma weak __vdso_gettc
+int
+__vdso_gettc(const struct vdso_timehands *th, u_int *tc)
+{
+	u_quad_t tb;
+
+	if (__predict_false(th->th_algo != VDSO_TH_ALGO_PPC_TB))
+		return (ENOSYS);
+
+	__asm __volatile ("mftb %0" : "=r"(tb));
+	*tc = tb;
+	return (0);
+}
+
+#pragma weak __vdso_gettimekeep
+int
+__vdso_gettimekeep(struct vdso_timekeep **tk)
+{
+
+	return (_elf_aux_info(AT_TIMEKEEP, tk, sizeof(*tk)));
+}

lib/libc/powerpcspe/Makefile.inc

@@ -1,7 +1,6 @@
 # $FreeBSD$
 
 CFLAGS+= -I${LIBC_SRCTOP}/powerpc
-SRCS+=	trivial-vdso_tc.c
 
 # Long double is 64-bits
 SRCS+=machdep_ldisd.c

sys/powerpc/include/vdso.h

@@ -33,6 +33,8 @@
 #define	VDSO_TIMEHANDS_MD			\
 	uint32_t	th_res[8];
 
+#define	VDSO_TH_ALGO_PPC_TB	VDSO_TH_ALGO_1
+
 #ifdef _KERNEL
 #ifdef COMPAT_FREEBSD32
 

sys/powerpc/powerpc/clock.c

@@ -69,6 +69,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/sysctl.h>
 #include <sys/timeet.h>
 #include <sys/timetc.h>
+#include <sys/vdso.h>
 
 #include <dev/ofw/openfirm.h>
 
@@ -90,6 +91,12 @@ static int		decr_et_start(struct eventtimer *et,
     sbintime_t first, sbintime_t period);
 static int		decr_et_stop(struct eventtimer *et);
 static timecounter_get_t	decr_get_timecount;
+static uint32_t decr_vdso_timehands(struct vdso_timehands *vdso_th,
+    struct timecounter *tc);
+#ifdef COMPAT_FREEBSD32
+static uint32_t decr_vdso_timehands32(struct vdso_timehands32 *vdso_th32,
+    struct timecounter *tc);
+#endif
 
 struct decr_state {
 	int	mode;	/* 0 - off, 1 - periodic, 2 - one-shot. */
@@ -99,11 +106,14 @@ DPCPU_DEFINE_STATIC(struct decr_state, decr_state);
 
 static struct eventtimer	decr_et;
 static struct timecounter	decr_tc = {
-	decr_get_timecount,	/* get_timecount */
+	.tc_get_timecount = 		decr_get_timecount,
-	0,			/* no poll_pps */
+	.tc_counter_mask = 		~0u,
-	~0u,			/* counter_mask */
+	.tc_name = 			"timebase",
-	0,			/* frequency */
+	.tc_quality = 			1000,
-	"timebase"		/* name */
+	.tc_fill_vdso_timehands = 	decr_vdso_timehands,
+#ifdef COMPAT_FREEBSD32
+	.tc_fill_vdso_timehands32 = 	decr_vdso_timehands32,
+#endif
 };
 
 /*
@@ -224,6 +234,25 @@ decr_tc_init(void)
 	et_register(&decr_et);
 }
 
+uint32_t
+decr_vdso_timehands(struct vdso_timehands *vdso_th, struct timecounter *tc)
+{
+	vdso_th->th_algo = VDSO_TH_ALGO_PPC_TB;
+	bzero(vdso_th->th_res, sizeof(vdso_th->th_res));
+	return (initialized == 1);
+}
+
+#ifdef COMPAT_FREEBSD32
+uint32_t
+decr_vdso_timehands32(struct vdso_timehands32 *vdso_th32,
+    struct timecounter *tc)
+{
+	vdso_th32->th_algo = VDSO_TH_ALGO_PPC_TB;
+	bzero(vdso_th32->th_res, sizeof(vdso_th32->th_res));
+	return (initialized == 1);
+}
+#endif
+
 /*
  * Event timer start method.
  */

sys/powerpc/powerpc/elf32_machdep.c

@@ -122,7 +122,8 @@ struct sysentvec elf32_freebsd_sysvec = {
 	.sv_fixlimit	= NULL,
 #endif
 	.sv_maxssiz	= NULL,
-	.sv_flags	= SV_ABI_FREEBSD | SV_ILP32 | SV_SHP | SV_ASLR,
+	.sv_flags	= SV_ABI_FREEBSD | SV_ILP32 | SV_SHP | SV_ASLR |
+			    SV_TIMEKEEP,
 	.sv_set_syscall_retval = cpu_set_syscall_retval,
 	.sv_fetch_syscall_args = cpu_fetch_syscall_args,
 	.sv_shared_page_base = FREEBSD32_SHAREDPAGE,

sys/powerpc/powerpc/elf64_machdep.c

@@ -83,7 +83,8 @@ struct sysentvec elf64_freebsd_sysvec_v1 = {
 	.sv_setregs	= exec_setregs_funcdesc,
 	.sv_fixlimit	= NULL,
 	.sv_maxssiz	= NULL,
-	.sv_flags	= SV_ABI_FREEBSD | SV_LP64 | SV_SHP | SV_ASLR,
+	.sv_flags	= SV_ABI_FREEBSD | SV_LP64 | SV_SHP | SV_ASLR |
+			    SV_TIMEKEEP,
 	.sv_set_syscall_retval = cpu_set_syscall_retval,
 	.sv_fetch_syscall_args = cpu_fetch_syscall_args,
 	.sv_syscallnames = syscallnames,
@@ -120,7 +121,8 @@ struct sysentvec elf64_freebsd_sysvec_v2 = {
 	.sv_setregs	= exec_setregs,
 	.sv_fixlimit	= NULL,
 	.sv_maxssiz	= NULL,
-	.sv_flags	= SV_ABI_FREEBSD | SV_LP64 | SV_SHP,
+	.sv_flags	= SV_ABI_FREEBSD | SV_LP64 | SV_SHP |
+			    SV_TIMEKEEP,
 	.sv_set_syscall_retval = cpu_set_syscall_retval,
 	.sv_fetch_syscall_args = cpu_fetch_syscall_args,
 	.sv_syscallnames = syscallnames,