[tip: x86/fred] x86/cpu: Add X86_CR4_FRED macro

From: tip-bot2 for H. Peter Anvin (Intel)
Date: Wed Jan 31 2024 - 02:26:18 EST


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

Commit-ID: 95d34efac1a0aff6da00ad177168d99c60a3b7cd
Gitweb: https://git.kernel.org/tip/95d34efac1a0aff6da00ad177168d99c60a3b7cd
Author: H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
AuthorDate: Tue, 05 Dec 2023 02:50:00 -08:00
Committer: Borislav Petkov (AMD) <bp@xxxxxxxxx>
CommitterDate: Tue, 30 Jan 2024 18:20:34 +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@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Link: https://lore.kernel.org/r/20231205105030.8698-12-xin3.li@xxxxxxxxx

---
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;