From: Andy Lutomirski <l...@kernel.org> Now that FSGSBASE is fully supported, remove unsafe_fsgsbase, enable FSGSBASE by default, and add nofsgsbase to disable it.
Signed-off-by: Andy Lutomirski <l...@kernel.org> Signed-off-by: Chang S. Bae <chang.seok....@intel.com> Reviewed-by: Andi Kleen <a...@linux.intel.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Thomas Gleixner <t...@linutronix.de> Cc: Ingo Molnar <mi...@kernel.org> Cc: Dave Hansen <dave.han...@linux.intel.com> --- .../admin-guide/kernel-parameters.txt | 3 +- arch/x86/kernel/cpu/common.c | 35 ++++++++----------- 2 files changed, 15 insertions(+), 23 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index dfc2023b796b..72ed1a5ed832 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2729,8 +2729,7 @@ no5lvl [X86-64] Disable 5-level paging mode. Forces kernel to use 4-level paging instead. - unsafe_fsgsbase [X86] Allow FSGSBASE instructions. This will be - replaced with a nofsgsbase flag. + nofsgsbase [X86] Disables FSGSBASE instructions. no_console_suspend [HW] Never suspend the console diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 6c54e6d2fdfb..f20edc754532 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -365,24 +365,21 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c) 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. Setting - * unsafe_fsgsbase and TAINT_INSECURE flags will allow the series to be - * bisected if necessary. - * - * 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; - add_taint(TAINT_INSECURE, LOCKDEP_STILL_OK); + /* 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("nofsgsbase: FSGSBASE disabled\n"); return 1; } -__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase); +__setup("nofsgsbase", x86_nofsgsbase_setup); /* * Protection Keys are not available in 32-bit mode. @@ -1372,12 +1369,8 @@ 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. -- 2.19.1