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aarch64: Allow overriding HWCAP_CPUID feature check using HWCAP_MASK 

Now that LD_HWCAP_MASK (or glibc.tune.hwcap_mask) is read early enough
to influence cpu feature check in aarch64, use it to influence
multiarch selection.  Setting LD_HWCAP_MASK such that it clears
HWCAP_CPUID will now disable multiarch for the binary.

HWCAP_CPUID is also now set in HWCAP_IMPORTANT so that it is set by
default.  With this patch, this feature is only usable with
dyanmically linked binaries because LD_HWCAP_MASK is not read for
static binaries.  A future patch fixes that.

	* sysdeps/unix/sysv/linux/aarch64/cpu-features.c
	(init_cpu_features): Use glibc.tune.hwcap_mask.
	* sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h: New file.
This commit is contained in:
Siddhesh Poyarekar 2017-04-25 22:39:17 +05:30
parent ff08fc59e3
commit f82e9672ad
3 changed files with 54 additions and 4 deletions
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4
ChangeLog
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@ -1,5 +1,9 @@
2017-06-07 Siddhesh Poyarekar <siddhesh@sourceware.org>
* sysdeps/unix/sysv/linux/aarch64/cpu-features.c
(init_cpu_features): Use glibc.tune.hwcap_mask.
* sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h: New file.
* elf/dl-hwcaps.h: New file.
* elf/dl-hwcaps.c: Include it.
(_dl_important_hwcaps)[HAVE_TUNABLES]: Read and update

10
sysdeps/unix/sysv/linux/aarch64/cpu-features.c
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@ -18,18 +18,20 @@
#include <cpu-features.h>
#include <sys/auxv.h>
#include <elf/dl-hwcaps.h>
static inline void
init_cpu_features (struct cpu_features *cpu_features)
{
if (GLRO(dl_hwcap) & HWCAP_CPUID)
uint64_t hwcap_mask = GET_HWCAP_MASK();
uint64_t hwcap = GLRO (dl_hwcap) & hwcap_mask;
if (hwcap & HWCAP_CPUID)
{
register uint64_t id = 0;
asm volatile ("mrs %0, midr_el1" : "=r"(id));
cpu_features->midr_el1 = id;
}
else
{
cpu_features->midr_el1 = 0;
}
cpu_features->midr_el1 = 0;
}

44
sysdeps/unix/sysv/linux/aarch64/dl-procinfo.h Normal file
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@ -0,0 +1,44 @@
/* Processor capability information handling macros - aarch64 version.
Copyright (C) 2017 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#ifndef _DL_PROCINFO_H
#define _DL_PROCINFO_H 1
#include <sys/auxv.h>
/* We cannot provide a general printing function. */
#define _dl_procinfo(type, word) -1
/* There are no hardware capabilities defined. */
#define _dl_hwcap_string(idx) ""
/* HWCAP_CPUID should be available by default to influence IFUNC as well as
library search. */
#define HWCAP_IMPORTANT HWCAP_CPUID
/* There're no platforms to filter out. */
#define _DL_HWCAP_PLATFORM 0
/* We don't have any hardware capabilities. */
#define _DL_HWCAP_COUNT 0
#define _dl_string_hwcap(str) (-1)
#define _dl_string_platform(str) (-1)
#endif /* dl-procinfo.h */