[PATCH v8 04/29] riscv: zicfiss / zicfilp enumeration

Deepak Gupta
2024-11-11T21:06:10Z

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 4bd054c54c21..8d12dc6c7d44 100644
--- a/arch/riscv/include/asm/cpufeature.h
+++ b/arch/riscv/include/asm/cpufeature.h
@@ -12,6 +12,7 @@
#include <linux/kconfig.h>
#include <linux/percpu-defs.h>
#include <linux/threads.h>
+#include <linux/smp.h>
#include <asm/hwcap.h>
#include <asm/cpufeature-macros.h>

@@ -135,4 +136,16 @@ 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_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 08d2a5697466..f81f62b32f72 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -98,6 +98,8 @@
#define RISCV_ISA_EXT_SSNPM 89
#define RISCV_ISA_EXT_ZABHA 90
#define RISCV_ISA_EXT_ZICCRSE 91
+#define RISCV_ISA_EXT_ZICFILP 92
+#define RISCV_ISA_EXT_ZICFISS 93

#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 eb904ca64ad0..0f2c466a51ee 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -318,6 +318,8 @@ const struct riscv_isa_ext_data riscv_isa_ext[] = {
__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(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),