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@sifive.com>
Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
Link: https://lore.kernel.org/r/20250411073850.3699180-2-nylon.chen@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

Author: nylon7

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;