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nptl: Remove MULTI_PAGE_ALIASING [BZ #23554] 

MULTI_PAGE_ALIASING was introduced to mitigate an aliasing issue on
Pentium 4.  It is no longer needed for processors after Pentium 4.
This commit is contained in:
H.J. Lu 2021-03-19 12:53:40 -07:00
parent 9cbe4ed14e
commit 3e2f285c5f
4 changed files with 0 additions and 57 deletions
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10
nptl/allocatestack.c
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@ -31,7 +31,6 @@
#include <lowlevellock.h> #include <lowlevellock.h>
#include <futex-internal.h> #include <futex-internal.h>
#include <kernel-features.h> #include <kernel-features.h>
#include <stack-aliasing.h>
#ifndef NEED_SEPARATE_REGISTER_STACK #ifndef NEED_SEPARATE_REGISTER_STACK
@ -547,15 +546,6 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
pd = get_cached_stack (&size, &mem); pd = get_cached_stack (&size, &mem);
if (pd == NULL) if (pd == NULL)
{ {
/* To avoid aliasing effects on a larger scale than pages we
adjust the allocated stack size if necessary. This way
allocations directly following each other will not have
aliasing problems. */
#if MULTI_PAGE_ALIASING != 0
if ((size % MULTI_PAGE_ALIASING) == 0)
size += pagesize_m1 + 1;
#endif
/* If a guard page is required, avoid committing memory by first /* If a guard page is required, avoid committing memory by first
allocate with PROT_NONE and then reserve with required permission allocate with PROT_NONE and then reserve with required permission
excluding the guard page. */ excluding the guard page. */

23
nptl/stack-aliasing.h
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@ -1,23 +0,0 @@
/* Define macros for stack address aliasing issues for NPTL. Stub version.
Copyright (C) 2014-2021 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
<https://www.gnu.org/licenses/>. */
/* This is a number of bytes that is an alignment that should be avoided
when choosing the exact size of a new thread's stack. If the size
chosen is aligned to this, an extra page will be added to render the
size off-aligned. */
#define MULTI_PAGE_ALIASING 0

23
sysdeps/i386/i686/stack-aliasing.h
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@ -1,23 +0,0 @@
/* Define macros for stack address aliasing issues for NPTL. i686 version.
Copyright (C) 2014-2021 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
<https://www.gnu.org/licenses/>. */
/* What is useful is to avoid the 64k aliasing problem which reliably
happens if all stacks use sizes which are a multiple of 64k. Tell
the stack allocator to disturb this by allocation one more page if
necessary. */
#define MULTI_PAGE_ALIASING 65536

1
sysdeps/x86_64/stack-aliasing.h
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@ -1 +0,0 @@
#include <sysdeps/i386/i686/stack-aliasing.h>