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From: tip-bot for Andy Lutomirski <tipbot@zytor.com>
To: linux-tip-commits@vger.kernel.org
Cc: mingo@kernel.org, ak@linux.intel.com, akpm@linux-foundation.org,
	linux-kernel@vger.kernel.org, chang.seok.bae@intel.com,
	luto@kernel.org, hpa@zytor.com, rdunlap@infradead.org,
	ravi.v.shankar@intel.com, tglx@linutronix.de
Subject: [tip:x86/cpu] x86/cpu: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE
Date: Sat, 22 Jun 2019 03:05:29 -0700	[thread overview]
Message-ID: <tip-b64ed19b93c368be0fb6acf05377e8e3a694c92b@git.kernel.org> (raw)
In-Reply-To: <1557309753-24073-4-git-send-email-chang.seok.bae@intel.com>

Commit-ID:  b64ed19b93c368be0fb6acf05377e8e3a694c92b
Gitweb:     https://git.kernel.org/tip/b64ed19b93c368be0fb6acf05377e8e3a694c92b
Author:     Andy Lutomirski <luto@kernel.org>
AuthorDate: Wed, 8 May 2019 03:02:18 -0700
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Sat, 22 Jun 2019 11:38:51 +0200

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

---
 Documentation/admin-guide/kernel-parameters.txt |  3 +++
 arch/x86/kernel/cpu/common.c                    | 24 ++++++++++++++++++++++++
 2 files changed, 27 insertions(+)

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
@@ -366,6 +366,22 @@ 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)
+{
+	unsafe_fsgsbase = true;
+	return 1;
+}
+__setup("unsafe_fsgsbase", setup_unsafe_fsgsbase);
+
 /*
  * Protection Keys are not available in 32-bit mode.
  */
@@ -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."

  reply	other threads:[~2019-06-22 10:06 UTC|newest]

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-08 10:02 [PATCH v7 00/18] x86: Enable FSGSBASE instructions Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 01/18] x86/fsgsbase/64: Fix ARCH_SET_FS/GS behaviors for a remote task Chang S. Bae
     [not found]   ` <74F4F506-2913-4013-9D81-A0C69FA8CDF1@intel.com>
     [not found]     ` <6420E1A5-B5AD-4028-AA91-AA4D5445AC83@intel.com>
2019-06-16 15:44       ` Bae, Chang Seok
2019-06-16 16:32         ` Thomas Gleixner
2019-06-22 10:04         ` [tip:x86/cpu] x86/ptrace: Prevent ptrace from clearing the FS/GS selector tip-bot for Chang S. Bae
2020-06-18 13:50         ` [tip: x86/fsgsbase] " tip-bot2 for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 02/18] selftests/x86/fsgsbase: Test ptracer-induced GSBASE write Chang S. Bae
2019-06-22 10:04   ` [tip:x86/cpu] " tip-bot for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 03/18] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
2019-06-22 10:05   ` tip-bot for Andy Lutomirski [this message]
2020-06-18 13:50   ` [tip: x86/fsgsbase] x86/cpu: " tip-bot2 for Andy Lutomirski
2019-05-08 10:02 ` [PATCH v7 04/18] kbuild: Raise the minimum required binutils version to 2.21 Chang S. Bae
2019-06-22 10:06   ` [tip:x86/cpu] " tip-bot for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 05/18] x86/fsgsbase/64: Add intrinsics for FSGSBASE instructions Chang S. Bae
2019-06-22 10:06   ` [tip:x86/cpu] " tip-bot for Andi Kleen
2020-06-18 13:50   ` [tip: x86/fsgsbase] " tip-bot2 for Andi Kleen
2019-05-08 10:02 ` [PATCH v7 06/18] x86/fsgsbase/64: Enable FSGSBASE instructions in the helper functions Chang S. Bae
2019-06-22 10:07   ` [tip:x86/cpu] x86/fsgsbase/64: Enable FSGSBASE instructions in " tip-bot for Chang S. Bae
2020-06-18 13:50   ` [tip: x86/fsgsbase] " tip-bot2 for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 07/18] x86/fsgsbase/64: Preserve FS/GS state in __switch_to() if FSGSBASE is on Chang S. Bae
2019-06-21 15:22   ` Thomas Gleixner
2019-06-22 10:08   ` [tip:x86/cpu] x86/process/64: Use FSBSBASE in switch_to() if available tip-bot for Andy Lutomirski
2020-06-18 13:50   ` [tip: x86/fsgsbase] " tip-bot2 for Andy Lutomirski
2019-05-08 10:02 ` [PATCH v7 08/18] x86/fsgsbase/64: When copying a thread, use the FSGSBASE instructions Chang S. Bae
2019-06-22 10:09   ` [tip:x86/cpu] x86/process/64: Use FSGSBASE instructions on thread copy and ptrace tip-bot for Chang S. Bae
2020-06-18 13:50   ` [tip: x86/fsgsbase] " tip-bot2 for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 09/18] x86/entry/64: Add the READ_MSR_GSBASE macro Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 10/18] x86/entry/64: Switch CR3 before SWAPGS on the paranoid entry Chang S. Bae
2019-06-22 10:09   ` [tip:x86/cpu] x86/entry/64: Switch CR3 before SWAPGS in " tip-bot for Chang S. Bae
2020-06-18 13:50   ` [tip: x86/fsgsbase] " tip-bot2 for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 11/18] x86/fsgsbase/64: Introduce the FIND_PERCPU_BASE macro Chang S. Bae
2019-06-22 10:10   ` [tip:x86/cpu] x86/entry/64: " tip-bot for Chang S. Bae
2020-06-18 13:50   ` [tip: x86/fsgsbase] " tip-bot2 for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 12/18] x86/fsgsbase/64: GSBASE handling with FSGSBASE in the paranoid path Chang S. Bae
2019-06-22 10:11   ` [tip:x86/cpu] x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit tip-bot for Chang S. Bae
2019-06-29  7:21   ` [PATCH v7 12/18] x86/fsgsbase/64: GSBASE handling with FSGSBASE in the paranoid path Bae, Chang Seok
2019-06-29  7:37     ` Thomas Gleixner
2020-06-18 13:50   ` [tip: x86/fsgsbase] x86/entry/64: Handle FSGSBASE enabled paranoid entry/exit tip-bot2 for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 13/18] x86/fsgsbase/64: Document GSBASE handling in the paranoid path Chang S. Bae
2019-06-22 10:11   ` [tip:x86/cpu] x86/entry/64: " tip-bot for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 14/18] selftests/x86/fsgsbase: Test WRGSBASE Chang S. Bae
2019-06-22 10:12   ` [tip:x86/cpu] selftests/x86/fsgsbase: Test RD/WRGSBASE tip-bot for Andy Lutomirski
2019-05-08 10:02 ` [PATCH v7 15/18] selftests/x86/fsgsbase: Test ptracer-induced GSBASE write with FSGSBASE Chang S. Bae
2019-06-22 10:13   ` [tip:x86/cpu] " tip-bot for Chang S. Bae
2019-05-08 10:02 ` [PATCH v7 16/18] x86/fsgsbase/64: Enable FSGSBASE by default and add a chicken bit Chang S. Bae
2019-06-22 10:14   ` [tip:x86/cpu] x86/cpu: Enable FSGSBASE on 64bit " tip-bot for Andy Lutomirski
2020-06-18 13:50   ` [tip: x86/fsgsbase] " tip-bot2 for Andy Lutomirski
2019-05-08 10:02 ` [PATCH v7 17/18] x86/elf: Enumerate kernel FSGSBASE capability in AT_HWCAP2 Chang S. Bae
2019-06-22 10:14   ` [tip:x86/cpu] " tip-bot for Andi Kleen
2020-06-18 13:50   ` [tip: x86/fsgsbase] " tip-bot2 for Andi Kleen
2019-05-08 10:02 ` [PATCH v7 18/18] x86/fsgsbase/64: Add documentation for FSGSBASE Chang S. Bae
2019-06-14  6:54   ` Thomas Gleixner
2019-06-14 20:07     ` Bae, Chang Seok
     [not found]       ` <89BE934A-A392-4CED-83E5-CA4FADDAE6DF@intel.com>
2019-06-16  8:39         ` Thomas Gleixner
2019-06-16 12:34           ` Thomas Gleixner
2019-06-16 15:34             ` Bae, Chang Seok
2019-06-16 16:05               ` Thomas Gleixner
2019-06-16 20:48                 ` Bae, Chang Seok
2019-06-16 22:00                   ` Thomas Gleixner
     [not found]                     ` <8E2E84B6-BCCC-424D-A1A7-604828B389FB@intel.com>
2019-06-17  5:18                       ` Thomas Gleixner
2019-06-16 15:54     ` Randy Dunlap
2019-06-16 16:07       ` Thomas Gleixner
2019-06-22 10:15     ` [tip:x86/cpu] Documentation/x86/64: Add documentation for GS/FS addressing mode tip-bot for Thomas Gleixner

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