[PATCH 16/24] arm64: Refactor KERNEL_GCR_EL1 out of <sysreg.h>

["Pierre-Clément Tosi" <ptosi@google.com>]

Rework the constant to make the resulting sysreg value (and computation)
obvious at the usage site and clearly indicate that the GCR_EL1.Exclude
is specifically set by a KASAN policy.

As a result, <sysreg.h> is now KASAN-agnostic and writers of GCR_EL1
explicitly depend on KASAN headers, as they should.

Signed-off-by: Pierre-Clément Tosi <ptosi@google.com>
---
 arch/arm64/include/asm/mte-kasan.h | 16 ++++++++++++++++
 arch/arm64/include/asm/sysreg.h    | 16 ----------------
 arch/arm64/kernel/entry.S          |  3 ++-
 arch/arm64/kernel/mte.c            |  4 +++-
 4 files changed, 21 insertions(+), 18 deletions(-)

diff --git a/arch/arm64/include/asm/mte-kasan.h b/arch/arm64/include/asm/mte-kasan.h
index 9d00e9460b0f..6f63c788470a 100644
--- a/arch/arm64/include/asm/mte-kasan.h
+++ b/arch/arm64/include/asm/mte-kasan.h
@@ -5,10 +5,26 @@
 #ifndef __ASM_MTE_KASAN_H
 #define __ASM_MTE_KASAN_H
 
+#include <linux/bits.h>
+#include <linux/const.h>
+#include <linux/kasan-tags.h>
+
 #include <asm/compiler.h>
 #include <asm/cputype.h>
 #include <asm/mte-def.h>
 
+/*
+ * KASAN always uses a whole byte for its tags. With CONFIG_KASAN_HW_TAGS it
+ * only uses tags in the range 0xF0-0xFF, which we map to MTE tags 0x0-0xF.
+ */
+#ifdef CONFIG_KASAN_HW_TAGS
+#define __MTE_TAG_MIN		(KASAN_TAG_MIN & 0xf)
+#define __MTE_TAG_MAX		(KASAN_TAG_MAX & 0xf)
+#define KASAN_GCR_INCL		GENMASK(__MTE_TAG_MAX, __MTE_TAG_MIN)
+#else
+#define KASAN_GCR_INCL		UL(0)
+#endif
+
 #ifndef __ASSEMBLER__
 
 #include <linux/types.h>
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h
index 51c6a54d7146..7d82c769ae69 100644
--- a/arch/arm64/include/asm/sysreg.h
+++ b/arch/arm64/include/asm/sysreg.h
@@ -11,7 +11,6 @@
 
 #include <linux/bits.h>
 #include <linux/stringify.h>
-#include <linux/kasan-tags.h>
 #include <linux/kconfig.h>
 
 #include <asm/gpr-num.h>
@@ -921,21 +920,6 @@
 #define SYS_GCR_EL1_RRND	(BIT(16))
 #define SYS_GCR_EL1_EXCL_MASK	0xffffUL
 
-#ifdef CONFIG_KASAN_HW_TAGS
-/*
- * KASAN always uses a whole byte for its tags. With CONFIG_KASAN_HW_TAGS it
- * only uses tags in the range 0xF0-0xFF, which we map to MTE tags 0x0-0xF.
- */
-#define __MTE_TAG_MIN		(KASAN_TAG_MIN & 0xf)
-#define __MTE_TAG_MAX		(KASAN_TAG_MAX & 0xf)
-#define __MTE_TAG_INCL		GENMASK(__MTE_TAG_MAX, __MTE_TAG_MIN)
-#define KERNEL_GCR_EL1_EXCL	(SYS_GCR_EL1_EXCL_MASK & ~__MTE_TAG_INCL)
-#else
-#define KERNEL_GCR_EL1_EXCL	SYS_GCR_EL1_EXCL_MASK
-#endif
-
-#define KERNEL_GCR_EL1		(SYS_GCR_EL1_RRND | KERNEL_GCR_EL1_EXCL)
-
 /* RGSR_EL1 Definitions */
 #define SYS_RGSR_EL1_TAG_MASK	0xfUL
 #define SYS_RGSR_EL1_SEED_SHIFT	8
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 8d17f61d1b5b..d1d9a7a049a7 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -21,6 +21,7 @@
 #include <asm/esr.h>
 #include <asm/irq.h>
 #include <asm/memory.h>
+#include <asm/mte-kasan.h>
 #include <asm/mmu.h>
 #include <asm/processor.h>
 #include <asm/ptrace.h>
@@ -176,7 +177,7 @@ alternative_else_nop_endif
 alternative_cb	ARM64_ALWAYS_SYSTEM, kasan_hw_tags_enable
 	b	1f
 alternative_cb_end
-	mov	\tmp, KERNEL_GCR_EL1
+	mov	\tmp, #(SYS_GCR_EL1_RRND | (SYS_GCR_EL1_EXCL_MASK & ~KASAN_GCR_INCL))
 	msr_s	SYS_GCR_EL1, \tmp
 1:
 #endif
diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c
index 0d998289edcb..725f48faec3e 100644
--- a/arch/arm64/kernel/mte.c
+++ b/arch/arm64/kernel/mte.c
@@ -23,6 +23,7 @@
 #include <asm/barrier.h>
 #include <asm/cpufeature.h>
 #include <asm/mte.h>
+#include <asm/mte-kasan.h>
 #include <asm/ptrace.h>
 #include <asm/sysreg.h>
 
@@ -320,7 +321,8 @@ void mte_cpu_setup(void)
 			 MAIR_ATTRIDX(MAIR_ATTR_NORMAL_TAGGED,
 				      MT_NORMAL_TAGGED));
 
-	write_sysreg_s(KERNEL_GCR_EL1, SYS_GCR_EL1);
+	write_sysreg_s(SYS_GCR_EL1_RRND | (SYS_GCR_EL1_EXCL_MASK & ~KASAN_GCR_INCL),
+		       SYS_GCR_EL1);
 
 	/*
 	 * If GCR_EL1.RRND=1 is implemented the same way as RRND=0, then

-- 
2.56.0.455.g6c5a503b38-goog