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glibc/glibc-RHEL-20172-1.patch
DJ Delorie b11febd624 x86-64: Add glibc.cpu.prefer_map_32bit_exec 
Resolves: RHEL-20172

Note: there are follow up patches which fix Hurd wrt this change,
but those lead to a rabbit hole of other required fixes that
become more and more invasive... One relevant change was to move
the tests specific to this change, but there has been no further
work upstream on those tests, so leaving that out should not
affect future merges.
2024-03-11 18:22:11 -04:00

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From 317f1c0a8a71a862b1e600ff5386b08e02cf4b95 Mon Sep 17 00:00:00 2001
From: "H.J. Lu" <hjl.tools@gmail.com>
Date: Thu, 26 Jan 2023 08:26:18 -0800
Subject: [PATCH] x86-64: Add glibc.cpu.prefer_map_32bit_exec [BZ #28656]
Content-type: text/plain; charset=UTF-8
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.
Conflicts:
manual/tunables.texi
(line numbers)
sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
(merged local @order list)
sysdeps/x86/cpu-features.c
(line numbers)
---
manual/tunables.texi | 33 ++++++++++----
sysdeps/unix/sysv/linux/x86_64/64/Makefile | 25 +++++++++++
.../sysv/linux/x86_64/64/dl-tunables.list | 29 +++++++++++++
.../unix/sysv/linux/x86_64/64/mmap_internal.h | 43 +++++++++++++++++++
.../sysv/linux/x86_64/64/tst-map-32bit-1a.c | 34 +++++++++++++++
.../sysv/linux/x86_64/64/tst-map-32bit-1b.c | 1 +
.../sysv/linux/x86_64/64/tst-map-32bit-mod.c | 33 ++++++++++++++
sysdeps/x86/cpu-features.c | 15 +++++++
...cpu-features-preferred_feature_index_1.def | 1 +
9 files changed, 205 insertions(+), 9 deletions(-)
create mode 100644 sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
create mode 100644 sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h
create mode 100644 sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1a.c
create mode 100644 sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1b.c
create mode 100644 sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-mod.c
diff --git a/manual/tunables.texi b/manual/tunables.texi
index 0be7231e36..c76c5c53cd 100644
--- a/manual/tunables.texi
+++ b/manual/tunables.texi
@@ -35,27 +35,32 @@ tunables with minimum and maximum values:
@example
$ /lib64/ld-linux-x86-64.so.2 --list-tunables
glibc.rtld.nns: 0x4 (min: 0x1, max: 0x10)
-glibc.elision.skip_lock_after_retries: 3 (min: -2147483648, max: 2147483647)
+glibc.elision.skip_lock_after_retries: 3 (min: 0, max: 2147483647)
glibc.malloc.trim_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
glibc.malloc.perturb: 0 (min: 0, max: 255)
glibc.cpu.x86_shared_cache_size: 0x100000 (min: 0x0, max: 0xffffffffffffffff)
+glibc.pthread.rseq: 1 (min: 0, max: 1)
+glibc.cpu.prefer_map_32bit_exec: 0 (min: 0, max: 1)
glibc.mem.tagging: 0 (min: 0, max: 255)
-glibc.elision.tries: 3 (min: -2147483648, max: 2147483647)
+glibc.elision.tries: 3 (min: 0, max: 2147483647)
glibc.elision.enable: 0 (min: 0, max: 1)
-glibc.cpu.x86_rep_movsb_threshold: 0x1000 (min: 0x100, max: 0xffffffffffffffff)
+glibc.malloc.hugetlb: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.cpu.x86_rep_movsb_threshold: 0x2000 (min: 0x100, max: 0xffffffffffffffff)
glibc.malloc.mxfast: 0x0 (min: 0x0, max: 0xffffffffffffffff)
-glibc.elision.skip_lock_busy: 3 (min: -2147483648, max: 2147483647)
-glibc.malloc.top_pad: 0x0 (min: 0x0, max: 0xffffffffffffffff)
+glibc.rtld.dynamic_sort: 2 (min: 1, max: 2)
+glibc.elision.skip_lock_busy: 3 (min: 0, max: 2147483647)
+glibc.malloc.top_pad: 0x20000 (min: 0x0, max: 0xffffffffffffffff)
glibc.cpu.x86_rep_stosb_threshold: 0x800 (min: 0x1, max: 0xffffffffffffffff)
-glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x4040, max: 0x0fffffffffffffff)
+glibc.cpu.x86_non_temporal_threshold: 0xc0000 (min: 0x4040, max: 0xfffffffffffffff)
glibc.cpu.x86_shstk:
+glibc.pthread.stack_cache_size: 0x2800000 (min: 0x0, max: 0xffffffffffffffff)
glibc.cpu.hwcap_mask: 0x6 (min: 0x0, max: 0xffffffffffffffff)
-glibc.malloc.mmap_max: 0 (min: -2147483648, max: 2147483647)
-glibc.elision.skip_trylock_internal_abort: 3 (min: -2147483648, max: 2147483647)
+glibc.malloc.mmap_max: 0 (min: 0, max: 2147483647)
+glibc.elision.skip_trylock_internal_abort: 3 (min: 0, max: 2147483647)
glibc.malloc.tcache_unsorted_limit: 0x0 (min: 0x0, max: 0xffffffffffffffff)
glibc.cpu.x86_ibt:
glibc.cpu.hwcaps:
-glibc.elision.skip_lock_internal_abort: 3 (min: -2147483648, max: 2147483647)
+glibc.elision.skip_lock_internal_abort: 3 (min: 0, max: 2147483647)
glibc.malloc.arena_max: 0x0 (min: 0x1, max: 0xffffffffffffffff)
glibc.malloc.mmap_threshold: 0x0 (min: 0x0, max: 0xffffffffffffffff)
glibc.cpu.x86_data_cache_size: 0x8000 (min: 0x0, max: 0xffffffffffffffff)
@@ -569,6 +574,16 @@ instead.
This tunable is specific to i386 and x86-64.
@end deftp
+@deftp Tunable glibc.cpu.prefer_map_32bit_exec
+When this tunable is set to \code{1}, shared libraries of non-setuid
+programs will be loaded below 2GB with MAP_32BIT.
+
+Note that the @env{LD_PREFER_MAP_32BIT_EXEC} environment is an alias of
+this tunable.
+
+This tunable is specific to 64-bit x86-64.
+@end deftp
+
@node Memory Related Tunables
@section Memory Related Tunables
@cindex memory related tunables
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/Makefile b/sysdeps/unix/sysv/linux/x86_64/64/Makefile
index a7b6dc5a53..8ff4f27786 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/Makefile
+++ b/sysdeps/unix/sysv/linux/x86_64/64/Makefile
@@ -1,2 +1,27 @@
# The default ABI is 64.
default-abi := 64
+
+ifeq ($(subdir),elf)
+ifneq ($(have-tunables),no)
+
+tests-map-32bit = \
+ tst-map-32bit-1a \
+ tst-map-32bit-1b \
+# tests-map-32bit
+tst-map-32bit-1a-no-pie = yes
+tst-map-32bit-1b-no-pie = yes
+tests += $(tests-map-32bit)
+
+modules-map-32bit = \
+ tst-map-32bit-mod \
+# modules-map-32bit
+modules-names += $(modules-map-32bit)
+
+$(objpfx)tst-map-32bit-mod.so: $(libsupport)
+tst-map-32bit-1a-ENV = LD_PREFER_MAP_32BIT_EXEC=1
+$(objpfx)tst-map-32bit-1a: $(objpfx)tst-map-32bit-mod.so
+tst-map-32bit-1b-ENV = GLIBC_TUNABLES=glibc.cpu.prefer_map_32bit_exec=1
+$(objpfx)tst-map-32bit-1b: $(objpfx)tst-map-32bit-mod.so
+
+endif
+endif
diff -rup a/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list b/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
--- a/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list 2024-03-06 17:52:50.968514369 -0500
+++ b/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list 2024-03-06 17:55:48.778264896 -0500
@@ -1,3 +1,33 @@
+# x86-64 specific tunables.
+# Copyright (C) 2023 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/>.
+
+glibc {
+ cpu {
+ prefer_map_32bit_exec {
+ type: INT_32
+ minval: 0
+ maxval: 1
+ env_alias: LD_PREFER_MAP_32BIT_EXEC
+ security_level: SXID_IGNORE
+ }
+ }
+}
+
# Order of tunables in RHEL 9.1.z.
@order glibc.rtld.nns
@order glibc.elision.skip_lock_after_retries
@@ -35,3 +65,5 @@
@order glibc.malloc.check
@order glibc.gmon.minarcs
@order glibc.gmon.maxarcs
+# Order of tunables in RHEL 9.5.z
+@order glibc.cpu.prefer_map_32bit_exec
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h b/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h
new file mode 100644
index 0000000000..33dec3f805
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h
@@ -0,0 +1,43 @@
+/* Linux mmap system call. x86-64 version.
+ Copyright (C) 2015-2023 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 or
+ denywrite pages with MAP_32BIT first. */
+#define MMAP_PREPARE(addr, len, prot, flags, fd, offset) \
+ if ((addr) == NULL \
+ && (((prot) & PROT_EXEC) != 0 \
+ || ((flags) & MAP_DENYWRITE) != 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/unix/sysv/linux/x86_64/64/tst-map-32bit-1a.c b/sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1a.c
new file mode 100644
index 0000000000..abc396589e
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1a.c
@@ -0,0 +1,34 @@
+/* Check that LD_PREFER_MAP_32BIT_EXEC works in PDE and shared library.
+ Copyright (C) 2023 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/>. */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <support/check.h>
+
+extern void dso_check_map_32bit (void);
+
+static int
+do_test (void)
+{
+ printf ("do_test: %p\n", do_test);
+ TEST_VERIFY ((uintptr_t) do_test < 0xffffffffUL);
+ dso_check_map_32bit ();
+ return 0;
+}
+
+#include <support/test-driver.c>
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1b.c b/sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1b.c
new file mode 100644
index 0000000000..34ab01c773
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-1b.c
@@ -0,0 +1 @@
+#include "tst-map-32bit-1a.c"
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-mod.c b/sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-mod.c
new file mode 100644
index 0000000000..78d4b6133c
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/64/tst-map-32bit-mod.c
@@ -0,0 +1,33 @@
+/* Check that LD_PREFER_MAP_32BIT_EXEC works in shared library.
+ Copyright (C) 2023 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/>. */
+
+#include <stdio.h>
+#include <stdint.h>
+#include <support/check.h>
+
+static void
+dso_do_test (void)
+{
+}
+
+void
+dso_check_map_32bit (void)
+{
+ printf ("dso_do_test: %p\n", dso_do_test);
+ TEST_VERIFY ((uintptr_t) dso_do_test < 0xffffffffUL);
+}
diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c
index a2197ed211..822688e21f 100644
--- a/sysdeps/x86/cpu-features.c
+++ b/sysdeps/x86/cpu-features.c
@@ -27,6 +27,16 @@
extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *)
attribute_hidden;
+# ifdef __LP64__
+static void
+TUNABLE_CALLBACK (set_prefer_map_32bit_exec) (tunable_val_t *valp)
+{
+ if (valp->numval)
+ GLRO(dl_x86_cpu_features).preferred[index_arch_Prefer_MAP_32BIT_EXEC]
+ |= bit_arch_Prefer_MAP_32BIT_EXEC;
+}
+# endif
+
# if CET_ENABLED
extern void TUNABLE_CALLBACK (set_x86_ibt) (tunable_val_t *)
attribute_hidden;
@@ -949,6 +959,11 @@ no_cpuid:
#if HAVE_TUNABLES
TUNABLE_GET (hwcaps, tunable_val_t *, TUNABLE_CALLBACK (set_hwcaps));
+# ifdef __LP64__
+ TUNABLE_GET (prefer_map_32bit_exec, tunable_val_t *,
+ TUNABLE_CALLBACK (set_prefer_map_32bit_exec));
+# endif
+
bool disable_xsave_features = false;
if (!CPU_FEATURE_USABLE_P (cpu_features, OSXSAVE))
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 e45f9cb159..d20c5b3196 100644
--- a/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def
+++ b/sysdeps/x86/include/cpu-features-preferred_feature_index_1.def
@@ -26,6 +26,7 @@ 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)
--
2.39.3
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