romdisk: fix a bug that prevented MMU-less targets to execute program…

…s with `exec`

romdisk/misc.asm

@@ -61,10 +61,9 @@ _exec_main_merge:
     ; Execute the program stored in BC with the parameters in DE
     PUBLIC exec_main_bc_de
 exec_main_bc_de:
-    ld h, EXEC_PRESERVE_PROGRAM
     ; Keep the file name so that we can show it in case of error
     push bc
-    EXEC()
+    call try_exec_bc_de
     pop hl
     ; If an error occurred while executing, A will not be 0
     or a
@@ -92,6 +91,30 @@ exec_main_error:
     inc bc
     jp error_print
 
+
+    ; Execute the program pointed by BC, this routien will automatically
+    ; determine whether to override or preserve the current program, depending
+    ; on the kernel configuration structure.
+    ; Parameters:
+    ;   BC - Program path/name
+    ;   DE - Parameter (optional)
+    PUBLIC try_exec_bc_de
+try_exec_bc_de:
+    ; Check if the kernel has MMU support, if that's the case, this init program can be
+    ; preserved in memory while the subprogram executes.
+    KERNEL_CONFIG(hl)
+    inc hl  ; point to MMU capability
+    ld a, (hl)
+    ; Prepare parameter before testing the MMU capability
+    ld h, EXEC_PRESERVE_PROGRAM
+    or a    ; A = 0 <=> no MMU capability, cannot preserve
+    jr nz, _process_command_exec
+    ld h, EXEC_OVERRIDE_PROGRAM
+_process_command_exec:
+    EXEC()
+    ret
+
+
     ; Reset the board
     PUBLIC reset_main
 reset_main:

romdisk/parse.asm

@@ -27,6 +27,7 @@
         EXTERN init_static_buffer
         EXTERN exec_main_bc_de
         EXTERN exec_main_ret_success
+        EXTERN try_exec_bc_de
 
         ; Parse and execute the command line passed as a parameter.
         ; Parameters:
@@ -176,18 +177,8 @@ _process_command_not_path:
         ex de, hl
         push bc
         ld bc, init_static_buffer
-        ; Check if the kernel has MMU support, if that's the case, this init program can be
-        ; preserved in memory while the subprogram executes.
-        KERNEL_CONFIG(hl)
-        inc hl  ; point to MMU capability
-        ld a, (hl)
-        ; Prepare parameter before testing the MMU capability
-        ld h, EXEC_PRESERVE_PROGRAM
-        or a    ; A = 0 <=> no MMU capability, cannot preserve
-        jr nz, _process_command_exec
-        ld h, EXEC_OVERRIDE_PROGRAM
-_process_command_exec:
-        EXEC()
+        ; Execute program whose name is pointed by BC
+        call try_exec_bc_de
         ; Pop the original command name and command length
         pop bc
         pop hl