[PATCH v15 03/27] riscv: zicfiss / zicfilp enumeration

[Deepak Gupta]

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.

Reviewed-by: Zong Li <zong.li at sifive.com>
Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>
Signed-off-by: Deepak Gupta <debug at rivosinc.com>
---
 arch/riscv/include/asm/cpufeature.h | 12 ++++++++++++
 arch/riscv/include/asm/hwcap.h      |  2 ++
 arch/riscv/include/asm/processor.h  |  1 +
 arch/riscv/kernel/cpufeature.c      | 13 +++++++++++++
 4 files changed, 28 insertions(+)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 3a87f612035c..100f4b53ba5d 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -146,4 +146,16 @@ 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)
+{
+	return (IS_ENABLED(CONFIG_RISCV_USER_CFI) &&
+		riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICFISS));
+}
+
+static inline bool cpu_supports_indirect_br_lp_instr(void)
+{
+	return (IS_ENABLED(CONFIG_RISCV_USER_CFI) &&
+		riscv_has_extension_unlikely(RISCV_ISA_EXT_ZICFILP));
+}
+
 #endif
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index e3cbf203cdde..abc33ca1302e 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -105,6 +105,8 @@
 #define RISCV_ISA_EXT_ZVFBFWMA		96
 #define RISCV_ISA_EXT_ZAAMO		97
 #define RISCV_ISA_EXT_ZALRSC		98
+#define RISCV_ISA_EXT_ZICFILP		99
+#define RISCV_ISA_EXT_ZICFISS		100
 
 #define RISCV_ISA_EXT_XLINUXENVCFG	127
 
diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index 5f56eb9d114a..e3aba3336e63 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>
 
 #define arch_get_mmap_end(addr, len, flags)			\
 ({								\
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 2054f6c4b0ae..98e55467557b 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -258,6 +258,15 @@ static int riscv_ext_svadu_validate(const struct riscv_isa_ext_data *data,
 	return 0;
 }
 
+static int riscv_cfi_validate(const struct riscv_isa_ext_data *data,
+			      const unsigned long *isa_bitmap)
+{
+	if (!IS_ENABLED(CONFIG_RISCV_USER_CFI))
+		return -EINVAL;
+
+	return 0;
+}
+
 static const unsigned int riscv_a_exts[] = {
 	RISCV_ISA_EXT_ZAAMO,
 	RISCV_ISA_EXT_ZALRSC,
@@ -444,6 +453,10 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts, riscv_ext_zicbom_validate),
 	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts, riscv_ext_zicboz_validate),
 	__RISCV_ISA_EXT_DATA(ziccrse, RISCV_ISA_EXT_ZICCRSE),
+	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicfilp, RISCV_ISA_EXT_ZICFILP, riscv_xlinuxenvcfg_exts,
+					  riscv_cfi_validate),
+	__RISCV_ISA_EXT_SUPERSET_VALIDATE(zicfiss, RISCV_ISA_EXT_ZICFISS, riscv_xlinuxenvcfg_exts,
+					  riscv_cfi_validate),
 	__RISCV_ISA_EXT_DATA(zicntr, RISCV_ISA_EXT_ZICNTR),
 	__RISCV_ISA_EXT_DATA(zicond, RISCV_ISA_EXT_ZICOND),
 	__RISCV_ISA_EXT_DATA(zicsr, RISCV_ISA_EXT_ZICSR),

-- 
2.43.0