diff --git a/target/arm/arm-semi.c b/target/arm/arm-semi.c
index e5f1e2a..c21cbb9 100644
--- a/target/arm/arm-semi.c
+++ b/target/arm/arm-semi.c
@@ -384,6 +384,8 @@
  * setting the guest errno if appropriate.
  */
 typedef uint32_t sys_closefn(ARMCPU *cpu, GuestFD *gf);
+typedef uint32_t sys_writefn(ARMCPU *cpu, GuestFD *gf,
+                             target_ulong buf, uint32_t len);
 
 static uint32_t host_closefn(ARMCPU *cpu, GuestFD *gf)
 {
@@ -392,21 +394,51 @@
     return set_swi_errno(env, close(gf->hostfd));
 }
 
+static uint32_t host_writefn(ARMCPU *cpu, GuestFD *gf,
+                             target_ulong buf, uint32_t len)
+{
+    uint32_t ret;
+    CPUARMState *env = &cpu->env;
+    char *s = lock_user(VERIFY_READ, buf, len, 1);
+    if (!s) {
+        /* Return bytes not written on error */
+        return len;
+    }
+    ret = set_swi_errno(env, write(gf->hostfd, s, len));
+    unlock_user(s, buf, 0);
+    if (ret == (uint32_t)-1) {
+        ret = 0;
+    }
+    /* Return bytes not written */
+    return len - ret;
+}
+
 static uint32_t gdb_closefn(ARMCPU *cpu, GuestFD *gf)
 {
     return arm_gdb_syscall(cpu, arm_semi_cb, "close,%x", gf->hostfd);
 }
 
+static uint32_t gdb_writefn(ARMCPU *cpu, GuestFD *gf,
+                            target_ulong buf, uint32_t len)
+{
+    arm_semi_syscall_len = len;
+    return arm_gdb_syscall(cpu, arm_semi_cb, "write,%x,%x,%x",
+                           gf->hostfd, buf, len);
+}
+
 typedef struct GuestFDFunctions {
     sys_closefn *closefn;
+    sys_writefn *writefn;
 } GuestFDFunctions;
 
 static const GuestFDFunctions guestfd_fns[] = {
     [GuestFDHost] = {
         .closefn = host_closefn,
+        .writefn = host_writefn,
     },
     [GuestFDGDB] = {
         .closefn = gdb_closefn,
+        .writefn = gdb_writefn,
     },
 };
 
@@ -539,24 +571,7 @@
             return set_swi_errno(env, -1);
         }
 
-        if (use_gdb_syscalls()) {
-            arm_semi_syscall_len = len;
-            return arm_gdb_syscall(cpu, arm_semi_cb, "write,%x,%x,%x",
-                                   gf->hostfd, arg1, len);
-        } else {
-            s = lock_user(VERIFY_READ, arg1, len, 1);
-            if (!s) {
-                /* Return bytes not written on error */
-                return len;
-            }
-            ret = set_swi_errno(env, write(gf->hostfd, s, len));
-            unlock_user(s, arg1, 0);
-            if (ret == (uint32_t)-1) {
-                ret = 0;
-            }
-            /* Return bytes not written */
-            return len - ret;
-        }
+        return guestfd_fns[gf->type].writefn(cpu, gf, arg1, len);
     case TARGET_SYS_READ:
         GET_ARG(0);
         GET_ARG(1);