linked: enforce maximum size of sketch in linker script

Stop the build when a sketch exceeds the maximum size defined by the
'user_sketch' node in the device tree.

Signed-off-by: Luca Burelli <l.burelli@arduino.cc>

Author: pillo79

extra/build.sh

@@ -95,6 +95,7 @@ extra/gen_provides.py "${BUILD_DIR}/zephyr/zephyr.elf" -LF \
 	"+kheap_llext_heap" \
 	"+kheap__system_heap" \
 	"*sketch_base_addr=_sketch_start" \
+	"*sketch_max_size=_sketch_max_size" \
 	"malloc=__wrap_malloc" \
 	"free=__wrap_free" \
 	"realloc=__wrap_realloc" \

loader/main.c

@@ -66,6 +66,7 @@ void llext_entry(void *arg0, void *arg1, void *arg2)
 
 __attribute__((retain)) const uintptr_t sketch_base_addr = DT_REG_ADDR(DT_GPARENT(DT_NODELABEL(user_sketch))) +
 			      DT_REG_ADDR(DT_NODELABEL(user_sketch));
+__attribute__((retain)) const uintptr_t sketch_max_size = DT_REG_SIZE(DT_NODELABEL(user_sketch));
 
 static int loader(const struct shell *sh)
 {

variants/_linked/linker_script.ld

@@ -1,10 +1,9 @@
 INCLUDE "provides.ld"
 
-PROVIDE(TEXT_LENGTH = 0x100000);
-
 MEMORY
 {
-    FLASH (rx) : ORIGIN = _sketch_start + 16, LENGTH = TEXT_LENGTH
+    /* 16 below compensates for the zsk header that is added before the .bin */
+    FLASH (rx) : ORIGIN = _sketch_start + 16, LENGTH = _sketch_max_size - 16
     RAM (rwx) : ORIGIN = kheap_llext_heap, LENGTH = kheap_llext_heap_size
 }
 
@@ -117,4 +116,4 @@ SECTIONS {
     .got : {
         KEEP(*(.got .got.* .got.plt .got.plt*))
     }
-}
+}