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[PowerPC] Define powerpc IFUNC kernel/userspace ABI.

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This is a prerequisite for anything IFUNC in the ELFv2 / clang switch.

Since probing cpu info on powerpc is a privileged operation, define that we
pass AT_HWCAP / AT_HWCAP2 through as cpu_features and cpu_features2 to ifunc
resolvers.

This is particularly important when dealing with non-PLT GNU IFUNC, which is
not allowed to PLT call from resolvers and therefore can't access global
variables.

The naming convention "cpu_features"/"cpu_features2" is an existing FreeBSD
PowerPC convention and matches the way we treat these variables in
machine/cpu.h.

The underlying variables are u_long, however, as per the commit message for
r332868, only the low 32 bits are ever used, so the underlying flags are
compatible across all of PowerPC.

The resolver prototype is defined to reserve the maximum number of
register-passed parameters the various PowerPC ABIs allow. This leaves
plenty of room for growth without needing to resort to passing via the
stack in the future.

Reviewed by:	jhibbits
Differential Revision:	https://reviews.freebsd.org/D22787
This commit is contained in:
Brandon Bergren 2019-12-24 20:13:29 +00:00
parent 509798ea65
commit 057832282f
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=356061
1 changed files with 60 additions and 0 deletions
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sys/powerpc/include/ifunc.h Normal file
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/*-
* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
*
* Copyright (c) 2019 Brandon Bergren <bdragon@FreeBSD.org>
* Copyright (c) 2015-2018 The FreeBSD Foundation. All rights reserved.
*
* Part of this software was 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.
*
* $FreeBSD$
*/
#ifndef __POWERPC_IFUNC_H
#define __POWERPC_IFUNC_H
#include <sys/types.h>
#define DEFINE_IFUNC(qual, ret_type, name, args) \
static ret_type (*name##_resolver(void))args __used; \
qual ret_type name args __attribute__((ifunc(#name "_resolver"))); \
static ret_type (*name##_resolver(void))args
#define DEFINE_UIFUNC(qual, ret_type, name, args) \
static ret_type (*name##_resolver(register_t, register_t, \
register_t, register_t, register_t, register_t, register_t, \
register_t))args __used; \
qual ret_type name args __attribute__((ifunc(#name "_resolver"))); \
static ret_type (*name##_resolver( \
register_t cpu_features, \
register_t cpu_features2, \
register_t arg3 __unused, \
register_t arg4 __unused, \
register_t arg5 __unused, \
register_t arg6 __unused, \
register_t arg7 __unused, \
register_t arg8 __unused))args
#endif