user app can invoke kernel syscall!!!!

kernel/memory.x

@@ -1,22 +1,10 @@
 MEMORY {
-    /*
-     * The RP2350 has either external or internal flash.
-     *
-     * 2 MiB is a safe default here, although a Pico 2 has 4 MiB.
-     */
     FLASH : ORIGIN = 0x10000000, LENGTH = 4096K
-    /*
-     * RAM consists of 8 banks, SRAM0-SRAM7, with a striped mapping.
-     * This is usually good for performance, as it distributes load on
-     * those banks evenly.
-     */
     RAM : ORIGIN = 0x20000000, LENGTH = 512K
-    /*
-     * RAM banks 8 and 9 use a direct mapping. They can be used to have
-     * memory areas dedicated for some specific job, improving predictability
-     * of access times.
-     * Example: Separate stacks for core0 and core1.
-     */
+
+	/* Reserve a block of RAM for the user app */
+    USERAPP : ORIGIN = 0x20010000, LENGTH = 192K
+
     SRAM4 : ORIGIN = 0x20080000, LENGTH = 4K
     SRAM5 : ORIGIN = 0x20081000, LENGTH = 4K
 }
@@ -73,3 +61,11 @@ SECTIONS {
 
 PROVIDE(start_to_end = __end_block_addr - __start_block_addr);
 PROVIDE(end_to_start = __start_block_addr - __end_block_addr);
+
+SECTIONS {
+	.userapp (NOLOAD) :
+	{
+	    __userapp_start__ = ORIGIN(USERAPP);
+	    __userapp_end__   = ORIGIN(USERAPP) + LENGTH(USERAPP);
+	} > USERAPP
+}