[glibc] x86-64: Add glibc.cpu.prefer_map_32bit_exec [BZ #28656]

[glibc] x86-64: Add glibc.cpu.prefer_map_32bit_exec [BZ #28656]

[H.J. Lu]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=317f1c0a8a71a862b1e600ff5386b08e02cf4b95

commit 317f1c0a8a71a862b1e600ff5386b08e02cf4b95
Author: H.J. Lu <hjl.tools@gmail.com>
Date:   Thu Jan 26 08:26:18 2023 -0800

    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.

Diff:
---
 manual/tunables.texi                               | 33 ++++++++++++-----
 sysdeps/unix/sysv/linux/x86_64/64/Makefile         | 25 +++++++++++++
 sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list | 29 +++++++++++++++
 sysdeps/unix/sysv/linux/x86_64/64/mmap_internal.h  | 43 ++++++++++++++++++++++
 .../unix/sysv/linux/x86_64/64/tst-map-32bit-1a.c   | 34 +++++++++++++++++
 .../unix/sysv/linux/x86_64/64/tst-map-32bit-1b.c   |  1 +
 .../unix/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(-)

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)
@@ -583,6 +588,16 @@ 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 --git a/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list b/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
new file mode 100644
index 0000000000..0aab52e662
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/x86_64/64/dl-tunables.list
@@ -0,0 +1,29 @@
+# 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
+    }
+  }
+}
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;
@@ -705,6 +715,11 @@ 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)