Add PrgData and DevDscr linker sections + data

Author: 9names

link.x

@@ -35,6 +35,30 @@ SECTIONS {
         . = ALIGN(4);
     }
 
+     /* Section for data, specified by flashloader standard. */
+    PrgData : {
+      /*
+       * We're explicitly putting a single object here (PRGDATA_Start in main.c) as this is required by some tools.
+       * It is not used by this algorithm
+       */
+        KEEP(*(PrgData))
+
+        . = ALIGN(4);
+    }
+
+    /* Description of the flash algorithm */
+    DevDscr . : {
+        /* The device data content is only for external tools,
+         * and usually not referenced by the code.
+         * All rules have exceptions: device data is used by this flash algo.
+         *
+         * The KEEP statement ensures it's not removed by accident.
+         */
+        KEEP(*(DeviceData))
+
+        . = ALIGN(4);
+    }
+
     /DISCARD/ : {
         /* Unused exception related info that only wastes space */
         *(.ARM.exidx);

src/main.rs

@@ -105,3 +105,13 @@ impl Drop for RP2040Algo {
         (self.funcs.flash_enter_cmd_xip)();
     }
 }
+
+/// Some tools (eg Segger's debugger) require the PrgData section to exist in the target binary
+///
+/// They scan the flashloader binary for this symbol to determine the section location
+/// If they cannot find it, the tool exits. This variable serves no other purpose
+#[allow(non_upper_case_globals)]
+#[no_mangle]
+#[used]
+#[link_section = "PrgData"]
+pub static mut PRGDATA_Start: usize = 0;