linux-kernel - [RFC PATCH v1 05/28] riscv: zicfiss/zicfilp enumeration

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Date: Wed, 24 Jan 2024 22:21:30 -0800
From: debug@...osinc.com
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Subject: [RFC PATCH v1 05/28] riscv: zicfiss/zicfilp enumeration

From: Deepak Gupta <debug@...osinc.com>

This patch adds support for detecting zicfiss and zicfilp. zicfiss and zicfilp
stands for unprivleged integer spec extension for shadow stack and branch
tracking on indirect branches, respectively.

This patch looks for zicfiss and zicfilp in device tree and accordinlgy lights
up bit in cpu feature bitmap. Furthermore this patch adds detection utility
functions to return whether shadow stack or landing pads are supported by
cpu.

Signed-off-by: Deepak Gupta <debug@...osinc.com>
---
 arch/riscv/include/asm/cpufeature.h | 18 ++++++++++++++++++
 arch/riscv/include/asm/hwcap.h      |  2 ++
 arch/riscv/include/asm/processor.h  |  1 +
 arch/riscv/kernel/cpufeature.c      |  2 ++
 4 files changed, 23 insertions(+)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index a418c3112cd6..216190731c55 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -133,4 +133,22 @@ static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, const unsi
 	return __riscv_isa_extension_available(hart_isa[cpu].isa, ext);
 }
 
+static inline bool cpu_supports_shadow_stack(void)
+{
+#ifdef CONFIG_RISCV_USER_CFI
+	return riscv_isa_extension_available(NULL, ZICFISS);
+#else
+	return false;
+#endif
+}
+
+static inline bool cpu_supports_indirect_br_lp_instr(void)
+{
+#ifdef CONFIG_RISCV_USER_CFI
+	return riscv_isa_extension_available(NULL, ZICFILP);
+#else
+	return false;
+#endif
+}
+
 #endif
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 06d30526ef3b..918165cfb4fa 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -57,6 +57,8 @@
 #define RISCV_ISA_EXT_ZIHPM		42
 #define RISCV_ISA_EXT_SMSTATEEN		43
 #define RISCV_ISA_EXT_ZICOND		44
+#define RISCV_ISA_EXT_ZICFISS	45
+#define RISCV_ISA_EXT_ZICFILP	46
 
 #define RISCV_ISA_EXT_MAX		64
 
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index f19f861cda54..ee2f51787ff8 100644
--- a/arch/riscv/include/asm/processor.h
+++ b/arch/riscv/include/asm/processor.h
@@ -13,6 +13,7 @@
 #include <vdso/processor.h>
 
 #include <asm/ptrace.h>
+#include <asm/hwcap.h>
 
 #ifdef CONFIG_64BIT
 #define DEFAULT_MAP_WINDOW	(UL(1) << (MMAP_VA_BITS - 1))
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 98623393fd1f..16624bc9a46b 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -185,6 +185,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_DATA(svinval, RISCV_ISA_EXT_SVINVAL),
 	__RISCV_ISA_EXT_DATA(svnapot, RISCV_ISA_EXT_SVNAPOT),
 	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
+	__RISCV_ISA_EXT_DATA(zicfiss, RISCV_ISA_EXT_ZICFISS),
+	__RISCV_ISA_EXT_DATA(zicfilp, RISCV_ISA_EXT_ZICFILP),
 };
 
 const size_t riscv_isa_ext_count = ARRAY_SIZE(riscv_isa_ext);
-- 
2.43.0