[PATCH v7 28/32] riscv: kernel command line option to opt out of user cfi

[Deepak Gupta]

This commit adds a kernel command line option using which user cfi can be
disabled.

Signed-off-by: Deepak Gupta <debug at rivosinc.com>
---
 arch/riscv/kernel/usercfi.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/arch/riscv/kernel/usercfi.c b/arch/riscv/kernel/usercfi.c
index 04b0305943b1..223dfa482deb 100644
--- a/arch/riscv/kernel/usercfi.c
+++ b/arch/riscv/kernel/usercfi.c
@@ -17,6 +17,8 @@
 #include <asm/csr.h>
 #include <asm/usercfi.h>
 
+bool disable_riscv_usercfi;
+
 #define SHSTK_ENTRY_SIZE sizeof(void *)
 
 bool is_shstk_enabled(struct task_struct *task)
@@ -393,6 +395,9 @@ int arch_set_shadow_stack_status(struct task_struct *t, unsigned long status)
 	unsigned long size = 0, addr = 0;
 	bool enable_shstk = false;
 
+	if (disable_riscv_usercfi)
+		return 0;
+
 	if (!cpu_supports_shadow_stack())
 		return -EINVAL;
 
@@ -472,6 +477,9 @@ int arch_set_indir_br_lp_status(struct task_struct *t, unsigned long status)
 {
 	bool enable_indir_lp = false;
 
+	if (disable_riscv_usercfi)
+		return 0;
+
 	if (!cpu_supports_indirect_br_lp_instr())
 		return -EINVAL;
 
@@ -504,3 +512,15 @@ int arch_lock_indir_br_lp_status(struct task_struct *task,
 
 	return 0;
 }
+
+static int __init setup_global_riscv_enable(char *str)
+{
+	if (strcmp(str, "true") == 0)
+		disable_riscv_usercfi = true;
+
+	pr_info("Setting riscv usercfi to be %s\n", (disable_riscv_usercfi ? "disabled" : "enabled"));
+
+	return 1;
+}
+
+__setup("disable_riscv_usercfi=", setup_global_riscv_enable);

-- 
2.34.1