From: "Chang S. Bae" <chang.seok.bae@intel.com>
To: Andy Lutomirski <luto@kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@kernel.org>, "H . Peter Anvin" <hpa@zytor.com>,
Andi Kleen <ak@linux.intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>,
Markus T Metzger <markus.t.metzger@intel.com>,
Ravi Shankar <ravi.v.shankar@intel.com>,
"Chang S . Bae" <chang.seok.bae@intel.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: [PATCH v4 02/13] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE
Date: Wed, 16 Jan 2019 14:48:38 -0800 [thread overview]
Message-ID: <20190116224849.8617-3-chang.seok.bae@intel.com> (raw)
In-Reply-To: <20190116224849.8617-1-chang.seok.bae@intel.com>
From: Andy Lutomirski <luto@kernel.org>
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.
[ chang: Minor fix. Add the TAINT_INSECURE flag. ]
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
---
.../admin-guide/kernel-parameters.txt | 3 +++
arch/x86/kernel/cpu/common.c | 27 +++++++++++++++++++
2 files changed, 30 insertions(+)
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index d59dff450614..871260e3e832 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -2760,6 +2760,9 @@
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 cb28e98a0659..6e2cba21328f 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -365,6 +365,25 @@ 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)
+{
+ unsafe_fsgsbase = true;
+ add_taint(TAINT_INSECURE, LOCKDEP_STILL_OK);
+ return 1;
+}
+__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase);
+
/*
* Protection Keys are not available in 32-bit mode.
*/
@@ -1352,6 +1371,14 @@ 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."
--
2.19.1
next prev parent reply other threads:[~2019-01-16 22:49 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-16 22:48 [PATCH v4 00/13] x86: Enable FSGSBASE instructions Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 01/13] taint: Introduce a new taint flag (insecure) Chang S. Bae
2019-01-16 22:48 ` Chang S. Bae [this message]
2019-01-16 22:48 ` [PATCH v4 03/13] kbuild: Raise the minimum required binutils version to 2.21 Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 04/13] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions Chang S. Bae
2019-01-17 5:09 ` Andi Kleen
2019-01-17 18:04 ` Bae, Chang Seok
2019-01-16 22:48 ` [PATCH v4 05/13] x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 06/13] x86/fsgsbase/64: Preserve FS/GS state in __switch_to() if FSGSBASE is on Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 07/13] x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions if available Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 08/13] x86/fsgsbase/64: Introduce the FIND_PERCPU_BASE macro Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 09/13] x86/fsgsbase/64: Use the per-CPU base as GSBASE at the paranoid_entry Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 10/13] selftests/x86/fsgsbase: Test WRGSBASE Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 11/13] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 12/13] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2019-01-16 22:48 ` [PATCH v4 13/13] x86/fsgsbase/64: Add documentation for FSGSBASE Chang S. Bae
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