On 14.09.23 г. 7:47 ч., Xin Li wrote:
From: "H. Peter Anvin (Intel)" <hpa@xxxxxxxxx>
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>
Tested-by: Shan Kang <shan.kang@xxxxxxxxx>
Signed-off-by: Xin Li <xin3.li@xxxxxxxxx>
---
Changes since v9:
* Avoid a type cast by defining X86_CR4_FRED as 0 on 32-bit (Thomas
Gleixner).
---
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 d898432947ff..f1a4adc78272 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)
nit: s/BITUL/BITULL I guess if __x86_64__ is defined then we are
guaranteed that unsigned long will be a 64 bit, but for the sake of
clarity I'd rather have this spelled out explicitly by using BITULL
+#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 317b4877e9c7..42511209469b 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -400,9 +400,8 @@ static __always_inline void setup_umip(struct cpuinfo_x86 *c)
}
/* 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;
