[PATCH 05/11] riscv: enable landing pad enforcement

[Deepak Gupta]

Enables landing pad enforcement by invoking a SBI FWFT call.

Signed-off-by: Deepak Gupta <debug at rivosinc.com>
---
 arch/riscv/kernel/asm-offsets.c |  1 +
 arch/riscv/kernel/head.S        | 19 +++++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/arch/riscv/kernel/asm-offsets.c b/arch/riscv/kernel/asm-offsets.c
index e4d55126dc3e..e6a9fad86fae 100644
--- a/arch/riscv/kernel/asm-offsets.c
+++ b/arch/riscv/kernel/asm-offsets.c
@@ -536,6 +536,7 @@ void asm_offsets(void)
 	DEFINE(SBI_EXT_FWFT, SBI_EXT_FWFT);
 	DEFINE(SBI_EXT_FWFT_SET, SBI_EXT_FWFT_SET);
 	DEFINE(SBI_FWFT_SHADOW_STACK, SBI_FWFT_SHADOW_STACK);
+	DEFINE(SBI_FWFT_LANDING_PAD, SBI_FWFT_LANDING_PAD);
 	DEFINE(SBI_FWFT_SET_FLAG_LOCK, SBI_FWFT_SET_FLAG_LOCK);
 #endif
 }
diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
index 9c99c5ad6fe8..59af044bf85c 100644
--- a/arch/riscv/kernel/head.S
+++ b/arch/riscv/kernel/head.S
@@ -185,6 +185,16 @@ secondary_start_sbi:
 1:
 #endif
 	scs_load_current
+
+#if defined(CONFIG_RISCV_SBI) && defined(CONFIG_RISCV_KERNEL_CFI)
+	li a7, SBI_EXT_FWFT
+	li a6, SBI_EXT_FWFT_SET
+	li a0, SBI_FWFT_LANDING_PAD
+	li a1, 1 /* enable landing pad for supervisor */
+	li a2, SBI_FWFT_SET_FLAG_LOCK
+	ecall	/* check for error condition and take appropriate action */
+#endif
+
 	call smp_callin
 #endif /* CONFIG_SMP */
 
@@ -359,6 +369,15 @@ SYM_CODE_START(_start_kernel)
 #endif
 	scs_load_current
 
+#if defined(CONFIG_RISCV_SBI) && defined(CONFIG_RISCV_KERNEL_CFI)
+	li a7, SBI_EXT_FWFT
+	li a6, SBI_EXT_FWFT_SET
+	li a0, SBI_FWFT_LANDING_PAD
+	li a1, 1 /* enable landing pad for supervisor */
+	li a2, SBI_FWFT_SET_FLAG_LOCK
+	ecall	/* check for error condition and take appropriate action */
+#endif
+
 #ifdef CONFIG_KASAN
 	call kasan_early_init
 #endif

-- 
2.43.0