[PATCH v3 05/29] riscv: zicfiss / zicfilp enumeration

Deepak Gupta
2024-04-03T23:41:43Z

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@rivosinc.com>
---
arch/riscv/include/asm/cpufeature.h | 13 +++++++++++++
arch/riscv/include/asm/hwcap.h | 2 ++
arch/riscv/include/asm/processor.h | 1 +
arch/riscv/kernel/cpufeature.c | 2 ++
4 files changed, 18 insertions(+)

diff --git a/arch/riscv/include/asm/cpufeature.h b/arch/riscv/include/asm/cpufeature.h
index 0bd11862b760..f0fb8d8ae273 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -8,6 +8,7 @@

#include <linux/bitmap.h>
#include <linux/jump_label.h>
+#include <linux/smp.h>
#include <asm/hwcap.h>
#include <asm/alternative-macros.h>
#include <asm/errno.h>
@@ -137,4 +138,16 @@ static __always_inline bool riscv_cpu_has_extension_unlikely(int cpu, const unsi

DECLARE_STATIC_KEY_FALSE(fast_misaligned_access_speed_key);

+static inline bool cpu_supports_shadow_stack(void)
+{
+ return (IS_ENABLED(CONFIG_RISCV_USER_CFI) &&
+ riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_ZICFISS));
+}
+
+static inline bool cpu_supports_indirect_br_lp_instr(void)
+{
+ return (IS_ENABLED(CONFIG_RISCV_USER_CFI) &&
+ riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_ZICFILP));
+}
+
#endif
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 1f2d2599c655..74b6c727f545 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -80,6 +80,8 @@
#define RISCV_ISA_EXT_ZFA 71
#define RISCV_ISA_EXT_ZTSO 72
#define RISCV_ISA_EXT_ZACAS 73
+#define RISCV_ISA_EXT_ZICFILP 74
+#define RISCV_ISA_EXT_ZICFISS 75

#define RISCV_ISA_EXT_XLINUXENVCFG 127

diff --git a/arch/riscv/include/asm/processor.h b/arch/riscv/include/asm/processor.h
index a8509cc31ab2..6c5b3d928b12 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 79a5a35fab96..d052cad5b82f 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -263,6 +263,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
__RISCV_ISA_EXT_DATA(h, RISCV_ISA_EXT_h),
__RISCV_ISA_EXT_SUPERSET(zicbom, RISCV_ISA_EXT_ZICBOM, riscv_xlinuxenvcfg_exts),
__RISCV_ISA_EXT_SUPERSET(zicboz, RISCV_ISA_EXT_ZICBOZ, riscv_xlinuxenvcfg_exts),
+ __RISCV_ISA_EXT_SUPERSET(zicfilp, RISCV_ISA_EXT_ZICFILP, riscv_xlinuxenvcfg_exts),
+ __RISCV_ISA_EXT_SUPERSET(zicfiss, RISCV_ISA_EXT_ZICFISS, riscv_xlinuxenvcfg_exts),
__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),
--
2.43.2