From 317f1c0a8a71a862b1e600ff5386b08e02cf4b95 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Thu, 26 Jan 2023 08:26:18 -0800 Subject: 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. --- 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 +++++++++++++++++ 6 files changed, 165 insertions(+) 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 (limited to 'sysdeps/unix') 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 +# . + +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 + . */ + +#ifndef MMAP_X86_64_INTERNAL_H +#define MMAP_X86_64_INTERNAL_H + +#include + +/* 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 + +#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 + . */ + +#include +#include +#include + +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 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 + . */ + +#include +#include +#include + +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); +} -- cgit 1.4.1