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2dc33b928b
Make glibc MTE-safe on systems where MTE is available. This allows using heap tagging with an LD_PRELOADed malloc implementation that enables MTE. We don't document this as guaranteed contract yet, so glibc may not be MTE safe when HWCAP2_MTE is set (older glibcs certainly aren't). This is mainly for testing and debugging. The HWCAP flag is not exposed in public headers until Linux adds it to its uapi. The HWCAP value reservation will be in Linux 5.9.
48 lines
1.9 KiB
C
48 lines
1.9 KiB
C
/* Multiple versions of strlen. AARCH64 version.
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Copyright (C) 2018-2020 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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/* Define multiple versions only for the definition in libc. */
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#if IS_IN (libc)
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/* Redefine strlen so that the compiler won't complain about the type
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mismatch with the IFUNC selector in strong_alias, below. */
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# undef strlen
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# define strlen __redirect_strlen
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# include <string.h>
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# include <init-arch.h>
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/* This should check HWCAP2_MTE when it is available: current
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linux kernel does not expose it, but its value is reserved.
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This is needed to make glibc MTE-safe on future systems in
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case user code enables MTE. The ABI contract for enabling
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MTE is not yet specified, but it can be useful for at least
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debugging which does not need a contract. */
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#define FUTURE_HWCAP2_MTE (1 << 18)
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#define MTE_ENABLED() (GLRO(dl_hwcap2) & FUTURE_HWCAP2_MTE)
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extern __typeof (__redirect_strlen) __strlen;
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extern __typeof (__redirect_strlen) __strlen_mte attribute_hidden;
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extern __typeof (__redirect_strlen) __strlen_asimd attribute_hidden;
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libc_ifunc (__strlen, (MTE_ENABLED () ? __strlen_mte : __strlen_asimd));
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# undef strlen
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strong_alias (__strlen, strlen);
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#endif
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