linux-kernel - [PATCH 1/2] riscv: misaligned: Add handling for ZCB instructions

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Message-Id: <20250411073850.3699180-2-nylon.chen@sifive.com>
Date: Fri, 11 Apr 2025 15:38:49 +0800
From: Nylon Chen <nylon.chen@...ive.com>
To: linux-kernel@...r.kernel.org
Cc: linux-riscv@...ts.infradead.org,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	alex@...ti.fr,
	charlie@...osinc.com,
	jesse@...osinc.com,
	evan@...osinc.com,
	nylon.chen@...ive.com,
	cleger@...osinc.com,
	zhangchunyan@...as.ac.cn,
	samuel.holland@...ive.com,
	zong.li@...ive.com
Subject: [PATCH 1/2] riscv: misaligned: Add handling for ZCB instructions

Add support for the Zcb extension's compressed half-word instructions
(C.LHU, C.LH, and C.SH) in the RISC-V misaligned access trap handler.

Signed-off-by: Zong Li <zong.li@...ive.com>
Signed-off-by: Nylon Chen <nylon.chen@...ive.com>
---
 arch/riscv/kernel/traps_misaligned.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/riscv/kernel/traps_misaligned.c b/arch/riscv/kernel/traps_misaligned.c
index 7cc108aed74e..d7275dfb6b7e 100644
--- a/arch/riscv/kernel/traps_misaligned.c
+++ b/arch/riscv/kernel/traps_misaligned.c
@@ -88,6 +88,13 @@
 #define INSN_MATCH_C_FSWSP		0xe002
 #define INSN_MASK_C_FSWSP		0xe003
 
+#define INSN_MATCH_C_LHU		0x8400
+#define INSN_MASK_C_LHU			0xfc43
+#define INSN_MATCH_C_LH			0x8440
+#define INSN_MASK_C_LH			0xfc43
+#define INSN_MATCH_C_SH			0x8c00
+#define INSN_MASK_C_SH			0xfc43
+
 #define INSN_LEN(insn)			((((insn) & 0x3) < 0x3) ? 2 : 4)
 
 #if defined(CONFIG_64BIT)
@@ -431,6 +438,13 @@ static int handle_scalar_misaligned_load(struct pt_regs *regs)
 		fp = 1;
 		len = 4;
 #endif
+	} else if ((insn & INSN_MASK_C_LHU) == INSN_MATCH_C_LHU) {
+		len = 2;
+		insn = RVC_RS2S(insn) << SH_RD;
+	} else if ((insn & INSN_MASK_C_LH) == INSN_MATCH_C_LH) {
+		len = 2;
+		shift = 8 * (sizeof(ulong) - len);
+		insn = RVC_RS2S(insn) << SH_RD;
 	} else {
 		regs->epc = epc;
 		return -1;
@@ -530,6 +544,9 @@ static int handle_scalar_misaligned_store(struct pt_regs *regs)
 		len = 4;
 		val.data_ulong = GET_F32_RS2C(insn, regs);
 #endif
+	} else if ((insn & INSN_MASK_C_SH) == INSN_MATCH_C_SH) {
+		len = 2;
+		val.data_ulong = GET_RS2S(insn, regs);
 	} else {
 		regs->epc = epc;
 		return -1;
-- 
2.34.1