linux-kernel - [tip: x86/fred] x86/cpu: Add X86_CR4

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Date: Wed, 31 Jan 2024 21:14:53 -0000
From: "tip-bot2 for H. Peter Anvin (Intel)" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "H. Peter Anvin (Intel)" <hpa@...or.com>, Xin Li <xin3.li@...el.com>,
 Thomas Gleixner <tglx@...utronix.de>, "Borislav Petkov (AMD)" <bp@...en8.de>,
 Shan Kang <shan.kang@...el.com>, x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/fred] x86/cpu: Add X86_CR4_FRED macro

The following commit has been merged into the x86/fred branch of tip:

Commit-ID:     ff45746fbf005f96e42bea466698e3fdbf926013
Gitweb:        https://git.kernel.org/tip/ff45746fbf005f96e42bea466698e3fdbf926013
Author:        H. Peter Anvin (Intel) <hpa@...or.com>
AuthorDate:    Tue, 05 Dec 2023 02:50:00 -08:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Wed, 31 Jan 2024 22:00:38 +01:00

x86/cpu: Add X86_CR4_FRED macro

Add X86_CR4_FRED macro for the FRED bit in %cr4. This bit must not be
changed after initialization, so add it to the pinned CR4 bits.

Signed-off-by: H. Peter Anvin (Intel) <hpa@...or.com>
Signed-off-by: Xin Li <xin3.li@...el.com>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Tested-by: Shan Kang <shan.kang@...el.com>
Link: https://lore.kernel.org/r/20231205105030.8698-12-xin3.li@intel.com
---
 arch/x86/include/uapi/asm/processor-flags.h | 7 +++++++
 arch/x86/kernel/cpu/common.c                | 5 ++---
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/uapi/asm/processor-flags.h b/arch/x86/include/uapi/asm/processor-flags.h
index d898432..f1a4adc 100644
--- a/arch/x86/include/uapi/asm/processor-flags.h
+++ b/arch/x86/include/uapi/asm/processor-flags.h
@@ -139,6 +139,13 @@
 #define X86_CR4_LAM_SUP_BIT	28 /* LAM for supervisor pointers */
 #define X86_CR4_LAM_SUP		_BITUL(X86_CR4_LAM_SUP_BIT)
 
+#ifdef __x86_64__
+#define X86_CR4_FRED_BIT	32 /* enable FRED kernel entry */
+#define X86_CR4_FRED		_BITUL(X86_CR4_FRED_BIT)
+#else
+#define X86_CR4_FRED		(0)
+#endif
+
 /*
  * x86-64 Task Priority Register, CR8
  */
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 0b97bcd..c3a1757 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -382,9 +382,8 @@ out:
 }
 
 /* These bits should not change their value after CPU init is finished. */
-static const unsigned long cr4_pinned_mask =
-	X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
-	X86_CR4_FSGSBASE | X86_CR4_CET;
+static const unsigned long cr4_pinned_mask = X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_UMIP |
+					     X86_CR4_FSGSBASE | X86_CR4_CET | X86_CR4_FRED;
 static DEFINE_STATIC_KEY_FALSE_RO(cr_pinning);
 static unsigned long cr4_pinned_bits __ro_after_init;