Fix emulation of misaligned RVC loads/stores

We were accidentally advancing the PC by 4, not 2.

machine/misaligned_ldst.c

@@ -3,6 +3,7 @@
 #include "unprivileged_memory.h"
 #include "mtrap.h"
 #include "config.h"
+#include "pk.h"
 
 union byte_array {
   uint8_t bytes[8];
@@ -15,6 +16,7 @@ void misaligned_load_trap(uintptr_t* regs, uintptr_t mcause, uintptr_t mepc)
   union byte_array val;
   uintptr_t mstatus;
   insn_t insn = get_insn(mepc, &mstatus);
+  uintptr_t npc = mepc + insn_len(insn);
   uintptr_t addr = read_csr(mbadaddr);
 
   int shift = 0, fp = 0, len;
@@ -74,7 +76,7 @@ void misaligned_load_trap(uintptr_t* regs, uintptr_t mcause, uintptr_t mepc)
   else
     SET_F32_RD(insn, regs, val.intx);
 
-  write_csr(mepc, mepc + 4);
+  write_csr(mepc, npc);
 }
 
 void misaligned_store_trap(uintptr_t* regs, uintptr_t mcause, uintptr_t mepc)
@@ -82,6 +84,7 @@ void misaligned_store_trap(uintptr_t* regs, uintptr_t mcause, uintptr_t mepc)
   union byte_array val;
   uintptr_t mstatus;
   insn_t insn = get_insn(mepc, &mstatus);
+  uintptr_t npc = mepc + insn_len(insn);
   int len;
 
   val.intx = GET_RS2(insn, regs);
@@ -130,5 +133,5 @@ void misaligned_store_trap(uintptr_t* regs, uintptr_t mcause, uintptr_t mepc)
   for (int i = 0; i < len; i++)
     store_uint8_t((void *)(addr + i), val.bytes[i], mepc);
 
-  write_csr(mepc, mepc + 4);
+  write_csr(mepc, npc);
 }