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144 lines
5.5 KiB
144 lines
5.5 KiB
2 years ago
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commit ea5814467a02c9d2d7608b6445c5d60e2a81d3ee
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Author: H.J. Lu <hjl.tools@gmail.com>
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Date: Fri Dec 10 13:00:09 2021 -0800
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x86-64: Remove LD_PREFER_MAP_32BIT_EXEC support [BZ #28656]
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Remove the LD_PREFER_MAP_32BIT_EXEC environment variable support since
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the first PT_LOAD segment is no longer executable due to defaulting to
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-z separate-code.
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This fixes [BZ #28656].
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Reviewed-by: Florian Weimer <fweimer@redhat.com>
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diff --git a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h b/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h
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deleted file mode 100644
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index 5b9696e2de8e5482..0000000000000000
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--- a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h
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+++ /dev/null
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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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-
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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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-
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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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-
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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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-
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-#ifndef _DL_LIBRECON_H
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-
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-#include <sysdeps/unix/sysv/linux/dl-librecon.h>
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-
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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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-
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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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-
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-#endif /* dl-librecon.h */
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diff --git a/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h b/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h
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deleted file mode 100644
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index 18177d2cb3ae645f..0000000000000000
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--- a/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h
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+++ /dev/null
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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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-
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- This file is part of the GNU C Library.
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-
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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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-
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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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-
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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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-
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-#ifndef MMAP_X86_64_INTERNAL_H
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-#define MMAP_X86_64_INTERNAL_H
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-
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-#include <ldsodefs.h>
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-
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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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-
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-#include_next <mmap_internal.h>
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-
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-#endif
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diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c
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index 00fe5045eb56eb07..58f2fad4323d5d91 100644
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--- a/sysdeps/x86/cpu-tunables.c
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+++ b/sysdeps/x86/cpu-tunables.c
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@@ -260,13 +260,6 @@ 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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diff --git a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def
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index d7c93f00c5928a30..3bdc76cf71007948 100644
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--- a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def
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+++ b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def
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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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