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| author | Andy Lutomirski <luto@kernel.org> | 2019-05-08 12:02:18 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-06-22 11:38:51 +0200 |
| commit | b64ed19b93c368be0fb6acf05377e8e3a694c92b (patch) | |
| tree | 60dc3d25693703da8c47b46e3bac7ca38dd292a4 | |
| parent | selftests/x86/fsgsbase: Test ptracer-induced GSBASE write (diff) | |
| download | linux-b64ed19b93c368be0fb6acf05377e8e3a694c92b.tar.xz linux-b64ed19b93c368be0fb6acf05377e8e3a694c92b.zip | |
x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE
This is temporary. It will allow the next few patches to be tested
incrementally.
Setting unsafe_fsgsbase is a root hole. Don't do 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>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Ravi Shankar <ravi.v.shankar@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Link: https://lkml.kernel.org/r/1557309753-24073-4-git-send-email-chang.seok.bae@intel.com
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 24 |
2 files changed, 27 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 138f6664b2e2..b0fa5273b0fc 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2857,6 +2857,9 @@ 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. + no_console_suspend [HW] Never suspend the console Disable suspending of consoles during suspend and diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index dad20bc891d5..71defe2d1b7c 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -367,6 +367,22 @@ out: } /* + * 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) +{ + unsafe_fsgsbase = true; + return 1; +} +__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase); + +/* * Protection Keys are not available in 32-bit mode. */ static bool pku_disabled; @@ -1370,6 +1386,14 @@ static void identify_cpu(struct cpuinfo_x86 *c) setup_smap(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); + } + /* * The vendor-specific functions might have changed features. * Now we do "generic changes." |