x86-64: Remove LD_PREFER_MAP_32BIT_EXEC support [BZ #28656]
Remove the LD_PREFER_MAP_32BIT_EXEC environment variable support since the first PT_LOAD segment is no longer executable due to defaulting to -z separate-code. This fixes [BZ #28656]. Reviewed-by: Florian Weimer <fweimer@redhat.com>
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H.J. Lu
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f1eeef945d
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ea5814467a
4
NEWS
4
NEWS
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@ -9,6 +9,10 @@ Version 2.35
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Major new features:
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* The LD_PREFER_MAP_32BIT_EXEC environment variable support has been
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removed since the first PT_LOAD segment is no longer executable due
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to defaulting to -z separate-code.
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* Unicode 14.0.0 Support: Character encoding, character type info, and
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transliteration tables are all updated to Unicode 14.0.0, using
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generator scripts contributed by Mike FABIAN (Red Hat).
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@ -1,45 +0,0 @@
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/* Optional code to distinguish library flavours. x86-64 version.
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Copyright (C) 2015-2021 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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#ifndef _DL_LIBRECON_H
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#include <sysdeps/unix/sysv/linux/dl-librecon.h>
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/* Recognizing extra environment variables. For 64-bit applications,
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branch prediction performance may be negatively impacted when the
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target of a branch is more than 4GB away from the branch. Add the
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Prefer_MAP_32BIT_EXEC bit so that mmap will try to map executable
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pages with MAP_32BIT first. NB: MAP_32BIT will map to lower 2GB,
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not lower 4GB, address. Prefer_MAP_32BIT_EXEC reduces bits available
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for address space layout randomization (ASLR). Prefer_MAP_32BIT_EXEC
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is always disabled for SUID programs and can be enabled by setting
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environment variable, LD_PREFER_MAP_32BIT_EXEC. */
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#define EXTRA_LD_ENVVARS \
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case 21: \
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if (!__libc_enable_secure \
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&& memcmp (envline, "PREFER_MAP_32BIT_EXEC", 21) == 0) \
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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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break;
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/* Extra unsecure variables. The names are all stuffed in a single
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string which means they have to be terminated with a '\0' explicitly. */
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#define EXTRA_UNSECURE_ENVVARS \
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"LD_PREFER_MAP_32BIT_EXEC\0"
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#endif /* dl-librecon.h */
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@ -1,42 +0,0 @@
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/* Linux mmap system call. x86-64 version.
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Copyright (C) 2015-2021 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 pages
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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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&& 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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@ -258,13 +258,6 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)
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20);
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}
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break;
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case 21:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,
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Prefer_MAP_32BIT_EXEC,
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disable, 21);
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}
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break;
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case 23:
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{
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CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH
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@ -26,7 +26,6 @@ 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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