commit ea5814467a02c9d2d7608b6445c5d60e2a81d3ee

Author: H.J. Lu <hjl.tools@gmail.com>

Date:   Fri Dec 10 13:00:09 2021 -0800

    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>

diff --git a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h b/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h

deleted file mode 100644

index 5b9696e2de8e5482..0000000000000000

--- a/sysdeps/unix/sysv/linux/x86_64/64/dl-librecon.h

+++ /dev/null

@@ -1,45 +0,0 @@

-/* Optional code to distinguish library flavours.  x86-64 version.

-   Copyright (C) 2015-2021 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/>.  */

-

-#ifndef _DL_LIBRECON_H

-

-#include <sysdeps/unix/sysv/linux/dl-librecon.h>

-

-/* Recognizing extra environment variables.  For 64-bit applications,

-   branch prediction performance may be negatively impacted when the

-   target of a branch is more than 4GB away from the branch.  Add the

-   Prefer_MAP_32BIT_EXEC bit so that mmap will try to map executable

-   pages with MAP_32BIT first.  NB: MAP_32BIT will map to lower 2GB,

-   not lower 4GB, address.  Prefer_MAP_32BIT_EXEC reduces bits available

-   for address space layout randomization (ASLR).  Prefer_MAP_32BIT_EXEC

-   is always disabled for SUID programs and can be enabled by setting

-   environment variable, LD_PREFER_MAP_32BIT_EXEC.  */

-#define EXTRA_LD_ENVVARS \

-  case 21:								  \

-    if (!__libc_enable_secure						  \

-	&& memcmp (envline, "PREFER_MAP_32BIT_EXEC", 21) == 0)		  \

-      GLRO(dl_x86_cpu_features).preferred[index_arch_Prefer_MAP_32BIT_EXEC] \

-	|= bit_arch_Prefer_MAP_32BIT_EXEC;				  \

-    break;

-

-/* Extra unsecure variables.  The names are all stuffed in a single

-   string which means they have to be terminated with a '\0' explicitly.  */

-#define EXTRA_UNSECURE_ENVVARS \

-  "LD_PREFER_MAP_32BIT_EXEC\0"

-

-#endif /* dl-librecon.h */

diff --git a/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h b/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h

deleted file mode 100644

index 18177d2cb3ae645f..0000000000000000

--- a/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h

+++ /dev/null

@@ -1,42 +0,0 @@

-/* Linux mmap system call.  x86-64 version.

-   Copyright (C) 2015-2021 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/>.  */

-

-#ifndef MMAP_X86_64_INTERNAL_H

-#define MMAP_X86_64_INTERNAL_H

-

-#include <ldsodefs.h>

-

-/* If the Prefer_MAP_32BIT_EXEC bit is set, try to map executable pages

-   with MAP_32BIT first.  */

-#define MMAP_PREPARE(addr, len, prot, flags, fd, offset)		\

-  if ((addr) == NULL							\

-      && ((prot) & PROT_EXEC) != 0					\

-      && HAS_ARCH_FEATURE (Prefer_MAP_32BIT_EXEC))			\

-    {									\

-      void *ret = (void*) INLINE_SYSCALL_CALL (mmap, (addr), (len),	\

-					      (prot),			\

-					      (flags) | MAP_32BIT,	\

-					      (fd), (offset));		\

-      if (ret != MAP_FAILED)						\

-	return ret;							\

-    }

-

-#include_next <mmap_internal.h>

-

-#endif

diff --git a/sysdeps/x86/cpu-tunables.c b/sysdeps/x86/cpu-tunables.c

index 00fe5045eb56eb07..58f2fad4323d5d91 100644

--- a/sysdeps/x86/cpu-tunables.c

+++ b/sysdeps/x86/cpu-tunables.c

@@ -260,13 +260,6 @@ TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *valp)

 		 20);

 	    }

 	  break;

-	case 21:

-	    {

-	      CHECK_GLIBC_IFUNC_PREFERRED_BOTH (n, cpu_features,

-						Prefer_MAP_32BIT_EXEC,

-						disable, 21);

-	    }

-	  break;

 	case 23:

 	    {

 	      CHECK_GLIBC_IFUNC_PREFERRED_NEED_BOTH

diff --git a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def

index d7c93f00c5928a30..3bdc76cf71007948 100644

--- a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def

+++ b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def

@@ -26,7 +26,6 @@ BIT (I586)

 BIT (I686)

 BIT (Slow_SSE4_2)

 BIT (AVX_Fast_Unaligned_Load)

-BIT (Prefer_MAP_32BIT_EXEC)

 BIT (Prefer_No_VZEROUPPER)

 BIT (Prefer_ERMS)

 BIT (Prefer_No_AVX512)