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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 04/13] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions
Date: Wed, 16 Jan 2019 14:48:40 -0800	[thread overview]
Message-ID: <20190116224849.8617-5-chang.seok.bae@intel.com> (raw)
In-Reply-To: <20190116224849.8617-1-chang.seok.bae@intel.com>

From: Andi Kleen <ak@linux.intel.com>

Add C intrinsics and assembler macros for the new FSBASE and GSBASE
instructions.

Very straight forward. Used in followon patches.

[ luto: Rename the variables from FS and GS to FSBASE and GSBASE and
  make <asm/fsgsbase.h> safe to include on 32-bit kernels. ]

v2: Use __always_inline

[ chang: Revise the changelog. Place them in <asm/fsgsbase.h>. Replace
  the macros with GAS-compatible ones. ]

If GCC supports it, we can add -mfsgsbase to CFLAGS and use the builtins
here for extra performance.

[ chang: Use FSGSBASE instructions directly instead of .byte ]

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com>
Reviewed-by: Andy Lutomirski <luto@kernel.org> # C parts only
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
---
 arch/x86/include/asm/fsgsbase.h | 64 +++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

diff --git a/arch/x86/include/asm/fsgsbase.h b/arch/x86/include/asm/fsgsbase.h
index bca4c743de77..09b34ee0cfd4 100644
--- a/arch/x86/include/asm/fsgsbase.h
+++ b/arch/x86/include/asm/fsgsbase.h
@@ -19,6 +19,36 @@ extern unsigned long x86_gsbase_read_task(struct task_struct *task);
 extern void x86_fsbase_write_task(struct task_struct *task, unsigned long fsbase);
 extern void x86_gsbase_write_task(struct task_struct *task, unsigned long gsbase);
 
+/* Must be protected by X86_FEATURE_FSGSBASE check. */
+
+static __always_inline unsigned long rdfsbase(void)
+{
+	unsigned long fsbase;
+
+	asm volatile("rdfsbase %0" : "=r" (fsbase) :: "memory");
+
+	return fsbase;
+}
+
+static __always_inline unsigned long rdgsbase(void)
+{
+	unsigned long gsbase;
+
+	asm volatile("rdgsbase %0" : "=r" (gsbase) :: "memory");
+
+	return gsbase;
+}
+
+static __always_inline void wrfsbase(unsigned long fsbase)
+{
+	asm volatile("wrfsbase %0" :: "r" (fsbase) : "memory");
+}
+
+static __always_inline void wrgsbase(unsigned long gsbase)
+{
+	asm volatile("wrgsbase %0" :: "r" (gsbase) : "memory");
+}
+
 /* Helper functions for reading/writing FS/GS base */
 
 static inline unsigned long x86_fsbase_read_cpu(void)
@@ -51,6 +81,40 @@ static inline void x86_gsbase_write_cpu_inactive(unsigned long gsbase)
 
 #endif /* CONFIG_X86_64 */
 
+#else /* __ASSEMBLY__ */
+
+#ifdef CONFIG_X86_64
+
+#include <asm/inst.h>
+
+.macro RDGSBASE opd
+	REG_TYPE rdgsbase_opd_type \opd
+	.if rdgsbase_opd_type == REG_TYPE_R64
+	R64_NUM rdgsbase_opd \opd
+	.byte 0xf3
+	PFX_REX rdgsbase_opd 0 W = 1
+	.else
+	.error "RDGSBASE: only for 64-bit value"
+	.endif
+	.byte 0xf, 0xae
+	MODRM 0xc0 rdgsbase_opd 1
+.endm
+
+.macro WRGSBASE opd
+	REG_TYPE wrgsbase_opd_type \opd
+	.if wrgsbase_opd_type == REG_TYPE_R64
+	R64_NUM wrgsbase_opd \opd
+	.byte 0xf3
+	PFX_REX wrgsbase_opd 0 W = 1
+	.else
+	.error "WRGSBASE: only for 64-bit value"
+	.endif
+	.byte 0xf, 0xae
+	MODRM 0xd0 wrgsbase_opd 1
+.endm
+
+#endif /* CONFIG_X86_64 */
+
 #endif /* __ASSEMBLY__ */
 
 #endif /* _ASM_FSGSBASE_H */
-- 
2.19.1


  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 ` [PATCH v4 02/13] x86/fsgsbase/64: Add 'unsafe_fsgsbase' to enable CR4.FSGSBASE Chang S. Bae
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 ` Chang S. Bae [this message]
2019-01-17  5:09   ` [PATCH v4 04/13] x86/fsgsbase/64: Add intrinsics/macros for FSGSBASE instructions 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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