From 743113d42e6cad77477769a3de5542d33443ae76 Mon Sep 17 00:00:00 2001 From: "H.J. Lu" Date: Wed, 15 Mar 2023 17:42:54 -0700 Subject: x86: Set FSGSBASE to active if enabled by kernel Linux kernel uses AT_HWCAP2 to indicate if FSGSBASE instructions are enabled. If the HWCAP2_FSGSBASE bit in AT_HWCAP2 is set, FSGSBASE instructions can be used in user space. Define dl_check_hwcap2 to set the FSGSBASE feature to active on Linux when the HWCAP2_FSGSBASE bit is set. Add a test to verify that FSGSBASE is active on current kernels. NB: This test will fail if the kernel doesn't set the HWCAP2_FSGSBASE bit in AT_HWCAP2 while fsgsbase shows up in /proc/cpuinfo. Reviewed-by: Florian Weimer --- sysdeps/unix/sysv/linux/x86/dl-hwcap2.h | 27 +++++++++++++++++++++++++++ sysdeps/x86/cpu-features.c | 3 +++ sysdeps/x86/dl-hwcap2.h | 21 +++++++++++++++++++++ sysdeps/x86/tst-cpu-features-cpuinfo.c | 7 +++++++ 4 files changed, 58 insertions(+) create mode 100644 sysdeps/unix/sysv/linux/x86/dl-hwcap2.h create mode 100644 sysdeps/x86/dl-hwcap2.h (limited to 'sysdeps') diff --git a/sysdeps/unix/sysv/linux/x86/dl-hwcap2.h b/sysdeps/unix/sysv/linux/x86/dl-hwcap2.h new file mode 100644 index 0000000000..28f38ea510 --- /dev/null +++ b/sysdeps/unix/sysv/linux/x86/dl-hwcap2.h @@ -0,0 +1,27 @@ +/* Handle AT_HWCAP2. Linux/x86 version. + Copyright (C) 2023 Free Software Foundation, Inc. + + 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 + . */ + +/* The following must match the kernel's . */ +#define HWCAP2_RING3MWAIT (1 << 0) +#define HWCAP2_FSGSBASE (1 << 1) + +static inline void +dl_check_hwcap2 (struct cpu_features *cpu_features) +{ + if ((GLRO(dl_hwcap2) & HWCAP2_FSGSBASE) != 0) + CPU_FEATURE_SET_ACTIVE (cpu_features, FSGSBASE); +} diff --git a/sysdeps/x86/cpu-features.c b/sysdeps/x86/cpu-features.c index 978eb29f72..95ad48b501 100644 --- a/sysdeps/x86/cpu-features.c +++ b/sysdeps/x86/cpu-features.c @@ -22,6 +22,7 @@ #include #include #include +#include extern void TUNABLE_CALLBACK (set_hwcaps) (tunable_val_t *) attribute_hidden; @@ -299,6 +300,8 @@ update_active (struct cpu_features *cpu_features) CPU_FEATURE_SET_ACTIVE (cpu_features, WIDE_KL); } + dl_check_hwcap2 (cpu_features); + cpu_features->isa_1 = get_isa_level (cpu_features); } diff --git a/sysdeps/x86/dl-hwcap2.h b/sysdeps/x86/dl-hwcap2.h new file mode 100644 index 0000000000..73cd6cc37d --- /dev/null +++ b/sysdeps/x86/dl-hwcap2.h @@ -0,0 +1,21 @@ +/* Handle AT_HWCAP2. Generic x86 version. + Copyright (C) 2023 Free Software Foundation, Inc. + + 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 + . */ + +static inline void +dl_check_hwcap2 (struct cpu_features *cpu_features) +{ +} diff --git a/sysdeps/x86/tst-cpu-features-cpuinfo.c b/sysdeps/x86/tst-cpu-features-cpuinfo.c index e963592c4b..18d64375ca 100644 --- a/sysdeps/x86/tst-cpu-features-cpuinfo.c +++ b/sysdeps/x86/tst-cpu-features-cpuinfo.c @@ -96,6 +96,11 @@ check_proc (const char *proc_name, const char *search_name, int flag, CPU_FEATURE_USABLE (name), \ "HAS_CPU_FEATURE (" #name ")") +#define CHECK_PROC_ACTIVE(str, name) \ + check_proc (#str, " "#str" ", CPU_FEATURE_USABLE (name), \ + CPU_FEATURE_USABLE (name), \ + "CPU_FEATURE_USABLE (" #name ")") + static int do_test (int argc, char **argv) { @@ -298,6 +303,8 @@ do_test (int argc, char **argv) fails += CHECK_PROC (xsaves, XSAVES); fails += CHECK_PROC (xtpr, XTPRUPDCTRL); + fails += CHECK_PROC_ACTIVE (fsgsbase, FSGSBASE); + printf ("%d differences between /proc/cpuinfo and glibc code.\n", fails); return (fails != 0); -- cgit 1.4.1