llext: add dynamic heap allocation support

Some applications require loading extensions into the memory which does
not exist during the boot time and cannot be allocated statically. Make
the application responsible for LLEXT heap allocation. Do not allocate
LLEXT heap statically.

Signed-off-by: Alex Ivanov <alexivanov@google.com>

Author: alexivanov-google

subsys/llext/Kconfig

@@ -60,6 +60,14 @@ config LLEXT_BUILD_PIC
 	  most internal linking is performed by the linker at build time. Select "y"
 	  to make use of that advantage.
 
+config LLEXT_HEAP_DYNAMIC
+	bool "Do not allocate static LLEXT heap"
+	default n
+	help
+	  Some applications require loading extensions into the memory which does not
+	  exist during the boot time and cannot be allocated statically. Make the application
+	  responsible for LLEXT heap allocation. Do not allocate LLEXT heap statically.
+
 config LLEXT_SHELL
 	bool "llext shell commands"
 	depends on SHELL

subsys/llext/llext_mem.c

@@ -27,7 +27,9 @@ LOG_MODULE_DECLARE(llext, CONFIG_LLEXT_LOG_LEVEL);
 #define LLEXT_PAGE_SIZE 32
 #endif
 
+#ifndef CONFIG_LLEXT_HEAP_DYNAMIC
 K_HEAP_DEFINE(llext_heap, CONFIG_LLEXT_HEAP_SIZE * 1024);
+#endif
 
 /*
  * Initialize the memory partition associated with the specified memory region