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| author |   Andy Lutomirski <luto@kernel.org> | 2019-05-08 03:02:31 -0700 |
|---|---|---|
| committer |   Thomas Gleixner <tglx@linutronix.de> | 2019-06-22 11:38:56 +0200 |
| commit | 2032f1f96ee0da600633c6c627b9c0a2e0f8b8a6 (patch) | |
| tree | 7f52b8bf09a8120dac9635197be096a93eed110c /arch/x86/kernel/cpu/common.c | |
| parent | selftests/x86/fsgsbase: Test ptracer-induced GSBASE write with FSGSBASE (diff) | |
| download | linux-dev-2032f1f96ee0da600633c6c627b9c0a2e0f8b8a6.tar.xz linux-dev-2032f1f96ee0da600633c6c627b9c0a2e0f8b8a6.zip | |
x86/cpu: Enable FSGSBASE on 64bit by default and add a chicken bit
Now that FSGSBASE is fully supported, remove unsafe_fsgsbase, enable
FSGSBASE by default, and add nofsgsbase to disable it.
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Link: https://lkml.kernel.org/r/1557309753-24073-17-git-send-email-chang.seok.bae@intel.com
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 32 |
1 files changed, 14 insertions, 18 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 71defe2d1b7c..1305f16b6105 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -366,21 +366,21 @@ out: cr4_clear_bits(X86_CR4_UMIP); } -/* - * Temporary hack: FSGSBASE is unsafe until a few kernel code paths are - * updated. This allows us to get the kernel ready incrementally. - * - * Once all the pieces are in place, these will go away and be replaced with - * a nofsgsbase chicken flag. - */ -static bool unsafe_fsgsbase; - -static __init int setup_unsafe_fsgsbase(char *arg) +static __init int x86_nofsgsbase_setup(char *arg) { - unsafe_fsgsbase = true; + /* Require an exact match without trailing characters. */ + if (strlen(arg)) + return 0; + + /* Do not emit a message if the feature is not present. */ + if (!boot_cpu_has(X86_FEATURE_FSGSBASE)) + return 1; + + setup_clear_cpu_cap(X86_FEATURE_FSGSBASE); + pr_info("FSGSBASE disabled via kernel command line\n"); return 1; } -__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase); +__setup("nofsgsbase", x86_nofsgsbase_setup); /* * Protection Keys are not available in 32-bit mode. @@ -1387,12 +1387,8 @@ static void identify_cpu(struct cpuinfo_x86 *c) setup_umip(c); /* Enable FSGSBASE instructions if available. */ - if (cpu_has(c, X86_FEATURE_FSGSBASE)) { - if (unsafe_fsgsbase) - cr4_set_bits(X86_CR4_FSGSBASE); - else - clear_cpu_cap(c, X86_FEATURE_FSGSBASE); - } + if (cpu_has(c, X86_FEATURE_FSGSBASE)) + cr4_set_bits(X86_CR4_FSGSBASE); /* * The vendor-specific functions might have changed features. |