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x86-64: Add glibc.cpu.prefer_map_32bit_exec [BZ #28656]
Crossing 2GB boundaries with indirect calls and jumps can use more branch prediction resources on Intel Golden Cove CPU (see the "Misprediction for Branches >2GB" section in Intel 64 and IA-32 Architectures Optimization Reference Manual.) There is visible performance improvement on workloads with many PLT calls when executable and shared libraries are mmapped below 2GB. Add the Prefer_MAP_32BIT_EXEC bit so that mmap will try to map executable or denywrite pages in shared libraries with MAP_32BIT first. NB: Prefer_MAP_32BIT_EXEC reduces bits available for address space layout randomization (ASLR), which is always disabled for SUID programs and can only be enabled by the tunable, glibc.cpu.prefer_map_32bit_exec, or the environment variable, LD_PREFER_MAP_32BIT_EXEC. This works only between shared libraries or between shared libraries and executables with addresses below 2GB. PIEs are usually loaded at a random address above 4GB by the kernel.
This commit is contained in:
H.J. Lu
parent
bde1218720
commit
317f1c0a8a
@ -35,27 +35,32 @@ tunables with minimum and maximum values:
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@example
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$ /lib64/ld-linux-x86-64.so.2 --list-tunables
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glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
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glibc.elision.skip_lock_after_retries: 3 (min: -2147483648, max: 2147483647)
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glibc.elision.skip_lock_after_retries: 3 (min: 0, max: 2147483647)
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glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
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glibc.malloc.perturb: 0 (min: 0, max: 255)
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glibc.cpu.x86_shared_cache_size: 0x100000 (min: 0x0, max: 0xffffffffffffffff)
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glibc.pthread.rseq: 1 (min: 0, max: 1)
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glibc.cpu.prefer_map_32bit_exec: 0 (min: 0, max: 1)
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glibc.mem.tagging: 0 (min: 0, max: 255)
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glibc.elision.tries: 3 (min: -2147483648, max: 2147483647)
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glibc.elision.tries: 3 (min: 0, max: 2147483647)
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glibc.elision.enable: 0 (min: 0, max: 1)
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glibc.cpu.x86_rep_movsb_threshold: 0x1000 (min: 0x100, max: 0xffffffffffffffff)
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glibc.malloc.hugetlb: 0x0 (min: 0x0, max: 0xffffffffffffffff)
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glibc.cpu.x86_rep_movsb_threshold: 0x2000 (min: 0x100, max: 0xffffffffffffffff)
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glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
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glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
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glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
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glibc.rtld.dynamic_sort: 2 (min: 1, max: 2)
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glibc.elision.skip_lock_busy: 3 (min: 0, max: 2147483647)
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glibc.malloc.top_pad: 0x20000 (min: 0x0, max: 0xffffffffffffffff)
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glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
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glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x4040, max: 0x0fffffffffffffff)
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glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x4040, max: 0xfffffffffffffff)
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glibc.cpu.x86_shstk:
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glibc.pthread.stack_cache_size: 0x2800000 (min: 0x0, max: 0xffffffffffffffff)
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glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
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glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
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glibc.elision.skip_trylock_internal_abort: 3 (min: -2147483648, max: 2147483647)
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glibc.malloc.mmap_max: 0 (min: 0, max: 2147483647)
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glibc.elision.skip_trylock_internal_abort: 3 (min: 0, max: 2147483647)
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glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0xffffffffffffffff)
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glibc.cpu.x86_ibt:
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glibc.cpu.hwcaps:
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glibc.elision.skip_lock_internal_abort: 3 (min: -2147483648, max: 2147483647)
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glibc.elision.skip_lock_internal_abort: 3 (min: 0, max: 2147483647)
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glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0xffffffffffffffff)
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glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
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glibc.cpu.x86_data_cache_size: 0x8000 (min: 0x0, max: 0xffffffffffffffff)
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@ -583,6 +588,16 @@ instead.
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This tunable is specific to i386 and x86-64.
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@end deftp
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@deftp Tunable glibc.cpu.prefer_map_32bit_exec
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When this tunable is set to \code{1}, shared libraries of non-setuid
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programs will be loaded below 2GB with MAP_32BIT.
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Note that the @env{LD_PREFER_MAP_32BIT_EXEC} environment is an alias of
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this tunable.
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This tunable is specific to 64-bit x86-64.
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@end deftp
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@node Memory Related Tunables
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@section Memory Related Tunables
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@cindex memory related tunables
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@ -1,2 +1,27 @@
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# The default ABI is 64.
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default-abi := 64
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ifeq ($(subdir),elf)
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ifneq ($(have-tunables),no)
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tests-map-32bit = \
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tst-map-32bit-1a \
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tst-map-32bit-1b \
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# tests-map-32bit
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tst-map-32bit-1a-no-pie = yes
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tst-map-32bit-1b-no-pie = yes
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tests += $(tests-map-32bit)
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modules-map-32bit = \
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tst-map-32bit-mod \
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# modules-map-32bit
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modules-names += $(modules-map-32bit)
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$(objpfx)tst-map-32bit-mod.so: $(libsupport)
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tst-map-32bit-1a-ENV = LD_PREFER_MAP_32BIT_EXEC=1
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$(objpfx)tst-map-32bit-1a: $(objpfx)tst-map-32bit-mod.so
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tst-map-32bit-1b-ENV = GLIBC_TUNABLES=glibc.cpu.prefer_map_32bit_exec=1
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$(objpfx)tst-map-32bit-1b: $(objpfx)tst-map-32bit-mod.so
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endif
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endif
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29
sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
Normal file
29
sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
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@ -0,0 +1,29 @@
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# x86-64 specific tunables.
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# Copyright (C) 2023 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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glibc {
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cpu {
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prefer_map_32bit_exec {
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type: INT_32
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minval: 0
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maxval: 1
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env_alias: LD_PREFER_MAP_32BIT_EXEC
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security_level: SXID_IGNORE
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}
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}
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}
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43
sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h
Normal file
43
sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h
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@ -0,0 +1,43 @@
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/* Linux mmap system call. x86-64 version.
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Copyright (C) 2015-2023 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 License as
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published by the Free Software Foundation; either version 2.1 of the
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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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#ifndef MMAP_X86_64_INTERNAL_H
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#define MMAP_X86_64_INTERNAL_H
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#include <ldsodefs.h>
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/* If the Prefer_MAP_32BIT_EXEC bit is set, try to map executable or
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denywrite pages with MAP_32BIT first. */
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#define MMAP_PREPARE(addr, len, prot, flags, fd, offset) \
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if ((addr) == NULL \
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&& (((prot) & PROT_EXEC) != 0 \
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|| ((flags) & MAP_DENYWRITE) != 0) \
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&& HAS_ARCH_FEATURE (Prefer_MAP_32BIT_EXEC)) \
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{ \
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void *ret = (void*) INLINE_SYSCALL_CALL (mmap, (addr), (len), \
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(prot), \
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(flags) | MAP_32BIT, \
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(fd), (offset)); \
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if (ret != MAP_FAILED) \
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return ret; \
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}
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#include_next <mmap_internal.h>
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#endif
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34
sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1a.c
Normal file
34
sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1a.c
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@ -0,0 +1,34 @@
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/* Check that LD_PREFER_MAP_32BIT_EXEC works in PDE and shared library.
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Copyright (C) 2023 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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#include <stdio.h>
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#include <stdint.h>
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#include <support/check.h>
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extern void dso_check_map_32bit (void);
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static int
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do_test (void)
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{
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printf ("do_test: %p\n", do_test);
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TEST_VERIFY ((uintptr_t) do_test < 0xffffffffUL);
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dso_check_map_32bit ();
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return 0;
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}
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#include <support/test-driver.c>
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1
sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1b.c
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1
sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1b.c
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@ -0,0 +1 @@
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#include "tst-map-32bit-1a.c"
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33
sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-mod.c
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33
sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-mod.c
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@ -0,0 +1,33 @@
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/* Check that LD_PREFER_MAP_32BIT_EXEC works in shared library.
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Copyright (C) 2023 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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#include <stdio.h>
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#include <stdint.h>
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#include <support/check.h>
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static void
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dso_do_test (void)
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{
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}
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void
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dso_check_map_32bit (void)
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{
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printf ("dso_do_test: %p\n", dso_do_test);
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TEST_VERIFY ((uintptr_t) dso_do_test < 0xffffffffUL);
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}
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@ -27,6 +27,16 @@
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extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *)
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attribute_hidden;
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# ifdef __LP64__
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static void
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TUNABLE_CALLBACK (set_prefer_map_32bit_exec) (tunable_val_t *valp)
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{
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if (valp->numval)
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GLRO(dl_x86_cpu_features).preferred[index_arch_Prefer_MAP_32BIT_EXEC]
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|= bit_arch_Prefer_MAP_32BIT_EXEC;
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}
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# endif
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# if CET_ENABLED
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extern void TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *)
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attribute_hidden;
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@ -705,6 +715,11 @@ no_cpuid:
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#if HAVE_TUNABLES
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TUNABLE_GET (hwcaps, tunable_val_t *, TUNABLE_CALLBACK (set_hwcaps));
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# ifdef __LP64__
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TUNABLE_GET (prefer_map_32bit_exec, tunable_val_t *,
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TUNABLE_CALLBACK (set_prefer_map_32bit_exec));
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# endif
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bool disable_xsave_features = false;
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if (!CPU_FEATURE_USABLE_P (cpu_features, OSXSAVE))
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@ -26,6 +26,7 @@ BIT (I586)
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BIT (I686)
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BIT (Slow_SSE4_2)
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BIT (AVX_Fast_Unaligned_Load)
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BIT (Prefer_MAP_32BIT_EXEC)
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BIT (Prefer_No_VZEROUPPER)
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BIT (Prefer_ERMS)
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BIT (Prefer_No_AVX512)
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