libc: add _get_tp() private function

which returns pointer to tcb

Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D29623

lib/libc/aarch64/gen/Makefile.inc

@@ -7,6 +7,7 @@ SRCS+=	_ctx_start.S \
 	flt_rounds.c \
 	fpgetmask.c \
 	fpsetmask.c \
+	_get_tp.c \
 	infinity.c \
 	ldexp.c \
 	makecontext.c \

lib/libc/aarch64/gen/_get_tp.c

@@ -0,0 +1,45 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were 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 <string.h>
+#include <stdint.h>
+#include "libc_private.h"
+
+void *
+_get_tp(void)
+{
+	void *res;
+
+	__asm __volatile("mrs	%0, tpidr_el0"  : "=r" (res));
+	return (res);
+}

lib/libc/amd64/gen/Makefile.inc

@@ -1,7 +1,7 @@
 #	@(#)Makefile.inc	8.1 (Berkeley) 6/4/93
 # $FreeBSD$
 
-SRCS+=	_setjmp.S _set_tp.c rfork_thread.S setjmp.S sigsetjmp.S \
+SRCS+=	_setjmp.S _get_tp.c _set_tp.c rfork_thread.S setjmp.S sigsetjmp.S \
 	fabs.S \
 	infinity.c ldexp.c makecontext.c signalcontext.c \
 	flt_rounds.c fpgetmask.c fpsetmask.c fpgetprec.c fpsetprec.c \

lib/libc/amd64/gen/_get_tp.c

@@ -0,0 +1,46 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were 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 <string.h>
+#include <stdint.h>
+#include "libc_private.h"
+
+void *
+_get_tp(void)
+{
+	void **res;
+
+	/* This function is used by rtld, avoid ifuncs. */
+	__asm __volatile("movq %%fs:0, %0" : "=r" (res));
+	return (&res[1]);
+}

lib/libc/arm/gen/Makefile.inc

@@ -4,6 +4,7 @@
 SRCS+=	\
 	__aeabi_read_tp.S \
 	_ctx_start.S \
+	_get_tp.c \
 	_set_tp.c \
 	_setjmp.S \
 	alloca.S \

lib/libc/arm/gen/_get_tp.c

@@ -0,0 +1,46 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were 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/param.h>
+#include <string.h>
+#include <stdint.h>
+#include "libc_private.h"
+
+void *
+_get_tp(void)
+{
+	void *res;
+
+	__asm __volatile("mrc  p15, 0, %0, c13, c0, 3" : "=r" (res));
+	return (res);
+}

lib/libc/i386/gen/Makefile.inc

@@ -1,6 +1,6 @@
 #	@(#)Makefile.inc	8.1 (Berkeley) 6/4/93
 # $FreeBSD$
 
-SRCS+=	_ctx_start.S _setjmp.S _set_tp.c fabs.S \
+SRCS+=	_ctx_start.S _setjmp.S _set_tp.c _get_tp.c fabs.S \
 	flt_rounds.c infinity.c ldexp.c makecontext.c \
 	rfork_thread.S setjmp.S signalcontext.c sigsetjmp.S

lib/libc/i386/gen/_get_tp.c

@@ -0,0 +1,45 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were 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 <string.h>
+#include <stdint.h>
+#include "libc_private.h"
+
+void *
+_get_tp(void)
+{
+	void **res;
+
+	__asm __volatile("movl %%gs:0, %0" : "=r" (res));
+	return (&res[1]);
+}

lib/libc/include/libc_private.h

@@ -261,8 +261,9 @@ void _init_tls(void);
 int _once(pthread_once_t *, void (*)(void));
 
 /*
- * Set the TLS thread pointer
+ * Get/set the TLS thread pointer
  */
+void *_get_tp(void);
 void _set_tp(void *tp);
 
 /*

lib/libc/mips/gen/Makefile.inc

@@ -6,6 +6,6 @@ SRCS+=	infinity.c fabs.c ldexp.c flt_rounds.c
 # SRCS+=	flt_rounds.c fpgetmask.c fpgetround.c fpgetsticky.c fpsetmask.c \
 #	fpsetround.c fpsetsticky.c
 
-SRCS+=	_ctx_start.S _set_tp.c _setjmp.S makecontext.c \
+SRCS+=	_ctx_start.S _get_tp.c _set_tp.c _setjmp.S makecontext.c \
 	setjmp.S signalcontext.c sigsetjmp.S \
 	trivial-getcontextx.c

lib/libc/mips/gen/_get_tp.c

@@ -0,0 +1,103 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were 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 <string.h>
+#include <stdint.h>
+#include <machine/sysarch.h>
+#include <machine/tls.h>
+
+#include "libc_private.h"
+
+#ifdef __mips_n64
+static void *
+_mips_get_tls(void)
+{
+	uint64_t _rv;
+
+	__asm__ __volatile__ (
+	    ".set\tpush\n\t"
+	    ".set\tmips64r2\n\t"
+	    "rdhwr\t%0, $29\n\t"
+	    ".set\tpop"
+	    : "=r" (_rv));
+	/*
+	 * XXXSS See 'git show c6be4f4d2d1b71c04de5d3bbb6933ce2dbcdb317'
+	 *
+	 * Remove the offset since this really a request to get the TLS
+	 * pointer via sysarch() (in theory).  Of course, this may go away
+	 * once the TLS code is rewritten.
+	 */
+	_rv = _rv - TLS_TP_OFFSET - TLS_TCB_SIZE;
+
+	return (void *)_rv;
+}
+
+#else /* mips 32 */
+
+static void *
+_mips_get_tls(void)
+{
+	uint32_t _rv;
+
+	__asm__ __volatile__ (
+	    ".set\tpush\n\t"
+	    ".set\tmips32r2\n\t"
+	    "rdhwr\t%0, $29\n\t"
+	    ".set\tpop"
+	    : "=r" (_rv));
+	/*
+	 * XXXSS See 'git show c6be4f4d2d1b71c04de5d3bbb6933ce2dbcdb317'
+	 *
+	 * Remove the offset since this really a request to get the TLS
+	 * pointer via sysarch() (in theory).  Of course, this may go away
+	 * once the TLS code is rewritten.
+	 */
+	_rv = _rv - TLS_TP_OFFSET - TLS_TCB_SIZE;
+
+	return (void *)_rv;
+}
+#endif /* ! __mips_n64 */
+
+void *
+_get_tp(void)
+{
+	void *res;
+
+#ifdef TLS_USE_SYSARCH
+	sysarch(MIPS_GET_TLS, &res);
+#else
+	res = _mips_get_tls();
+#endif
+	return (res);
+}

lib/libc/powerpc/gen/Makefile.common

@@ -3,4 +3,6 @@
 .PATH: ${LIBC_SRCTOP}/powerpc/gen
 
 SRCS += _ctx_start.S eabi.S infinity.c ldexp.c makecontext.c \
-	signalcontext.c syncicache.c _set_tp.c trivial-getcontextx.c
+	signalcontext.c syncicache.c _get_tp.c _set_tp.c trivial-getcontextx.c
+
+CFLAGS._get_tp.c+= ${RTLD_HDRS}

lib/libc/powerpc/gen/_get_tp.c

@@ -0,0 +1,47 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were 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 <string.h>
+#include <stdint.h>
+#include "libc_private.h"
+#include "rtld.h"
+
+void *
+_get_tp(void)
+{
+	Elf_Addr tp;
+
+	__asm __volatile("mr %0,2" : "=r" (tp));
+	return ((void *)(tp - TLS_TP_OFFSET - TLS_TCB_SIZE));
+}

lib/libc/powerpc64/gen/Makefile.inc

@@ -1,10 +1,11 @@
 # $FreeBSD$
 
 SRCS += _ctx_start.S fabs.S flt_rounds.c fpgetmask.c fpgetround.c \
-	fpgetsticky.c fpsetmask.c fpsetround.c \
+	fpgetsticky.c fpsetmask.c fpsetround.c _get_tp.c \
 	infinity.c ldexp.c makecontext.c _setjmp.S \
 	setjmp.S sigsetjmp.S signalcontext.c syncicache.c \
 	_set_tp.c \
 	trivial-getcontextx.c
 
+CFLAGS._get_tp.c+= ${RTLD_HDRS}
 

lib/libc/powerpc64/gen/_get_tp.c

@@ -0,0 +1,47 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were 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 <string.h>
+#include <stdint.h>
+#include "libc_private.h"
+#include "rtld.h"
+
+void *
+_get_tp(void)
+{
+	Elf_Addr tp;
+
+	__asm __volatile("mr %0,13" : "=r" (tp));
+	return ((void *)(tp - TLS_TP_OFFSET - TLS_TCB_SIZE));
+}

lib/libc/riscv/gen/Makefile.inc

@@ -5,6 +5,7 @@ SRCS+=	_ctx_start.S \
 	flt_rounds.c \
 	fpgetmask.c \
 	fpsetmask.c \
+	_get_tp.c \
 	infinity.c \
 	ldexp.c \
 	makecontext.c \
@@ -13,3 +14,5 @@ SRCS+=	_ctx_start.S \
 	setjmp.S \
 	sigsetjmp.S \
 	trivial-getcontextx.c
+
+CFLAGS._get_tp.c+= ${RTLD_HDRS}

lib/libc/riscv/gen/_get_tp.c

@@ -0,0 +1,47 @@
+/*-
+ * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
+ *
+ * Copyright (c) 2021 The FreeBSD Foundation
+ *
+ * This software were 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 <string.h>
+#include <stdint.h>
+#include "libc_private.h"
+#include "rtld.h"
+
+void *
+_get_tp(void)
+{
+	Elf_Addr tp;
+
+	__asm __volatile("mv %0, tp" : "=r" (tp));
+	return ((void *)(tp - TLS_TP_OFFSET - TLS_TCB_SIZE));
+}