linux-kernel - [PATCH 3/8] riscv: insn: Add get_insn

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Message-ID: <20250805193955.798277-4-jesse@rivosinc.com>
Date: Tue,  5 Aug 2025 12:39:50 -0700
From: Jesse Taube <jesse@...osinc.com>
To: linux-riscv@...ts.infradead.org
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
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Subject: [PATCH 3/8] riscv: insn: Add get_insn_nofault

get_insn_nofault uses get_insn with pagefaults dissabled, allowing it to
be called in an atomic context.

Signed-off-by: Jesse Taube <jesse@...osinc.com>
---
Unsure if copy_from_kernel_nofault is an acceptable replacement for
direct dereference in __read_insn.

RFC -> V1:
 - Add new function instead of using copy_from_user_nofault
---
 arch/riscv/include/asm/insn.h |  1 +
 arch/riscv/kernel/insn.c      | 14 ++++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/arch/riscv/include/asm/insn.h b/arch/riscv/include/asm/insn.h
index ba74e5b8262c..f87e0a48f786 100644
--- a/arch/riscv/include/asm/insn.h
+++ b/arch/riscv/include/asm/insn.h
@@ -553,6 +553,7 @@ static inline void riscv_insn_insert_utype_itype_imm(u32 *utype_insn, u32 *itype
 #include <asm/ptrace.h>
 
 int get_insn(struct pt_regs *regs, ulong epc, ulong *r_insn);
+int get_insn_nofault(struct pt_regs *regs, ulong epc, ulong *r_insn);
 unsigned long get_step_address(struct pt_regs *regs, u32 code);
 
 #endif /* _ASM_RISCV_INSN_H */
diff --git a/arch/riscv/kernel/insn.c b/arch/riscv/kernel/insn.c
index dd2a6ef9fd25..c8f77c0093c9 100644
--- a/arch/riscv/kernel/insn.c
+++ b/arch/riscv/kernel/insn.c
@@ -2,6 +2,9 @@
 /*
  * Copyright 2025 Rivos, Inc
  */
+
+#include <linux/uaccess.h>
+
 #include <asm/insn.h>
 #include <asm/ptrace.h>
 #include <asm/uaccess.h>
@@ -74,6 +77,17 @@ int get_insn(struct pt_regs *regs, ulong epc, ulong *r_insn)
 	}
 }
 
+int get_insn_nofault(struct pt_regs *regs, ulong epc, ulong *r_insn)
+{
+	int ret;
+
+	pagefault_disable();
+	ret = get_insn(regs, epc, r_insn);
+	pagefault_enable();
+
+	return ret;
+}
+
 /* Calculate the new address for after a step */
 unsigned long get_step_address(struct pt_regs *regs, u32 code)
 {
-- 
2.43.0