Implement symbol resolver

Author: KenVanHoeylandt

components/elf_loader/include/private/elf_symbol.h

@@ -12,7 +12,7 @@
 extern "C" {
 #endif
 
-#define ESP_ELFSYM_EXPORT(_sym)     { #_sym, &_sym }
+#define ESP_ELFSYM_EXPORT(_sym)     { #_sym, (void*)&_sym }
 #define ESP_ELFSYM_END              { NULL,  NULL }
 
 /** @brief Function symbol description */
@@ -31,6 +31,24 @@ struct esp_elfsym {
  */
 uintptr_t elf_find_sym(const char *sym_name);
 
+
+/**
+ * @brief Resolves a symbol name (e.g. function name) to its address.
+ *
+ * @param sym_name - Symbol name
+ * @return Symbol address if success or 0 if failed.
+ */
+typedef uintptr_t (*symbol_resolver)(const char *sym_name);
+
+/**
+ * @brief Override the internal symbol resolver.
+ * The default resolver is based on static lists that are determined by KConfig.
+ * This override allows for an arbitrary implementation.
+ *
+ * @param resolver the resolver function
+ */
+void elf_set_symbol_resolver(symbol_resolver resolver);
+
 #ifdef __cplusplus
 }
 #endif

components/elf_loader/src/esp_elf.c

@@ -19,12 +19,27 @@
 
 #include "private/elf_symbol.h"
 #include "private/elf_platform.h"
+#include "esp_elf.h"
 
 #define stype(_s, _t)               ((_s)->type == (_t))
 #define sflags(_s, _f)              (((_s)->flags & (_f)) == (_f))
 #define ADDR_OFFSET                 (0x400)
 
+uintptr_t elf_find_sym_default(const char *sym_name);
+
 static const char *TAG = "ELF";
+static symbol_resolver current_resolver = elf_find_sym_default;
+
+/**
+ * @brief Find symbol address by name.
+ *
+ * @param sym_name - Symbol name
+ *
+ * @return Symbol address if success or 0 if failed.
+ */
+uintptr_t elf_find_sym(const char *sym_name) {
+    return current_resolver(sym_name);
+}
 
 #if CONFIG_ELF_LOADER_BUS_ADDRESS_MIRROR
 
@@ -306,6 +321,18 @@ static int esp_elf_load_segment(esp_elf_t *elf, const uint8_t *pbuf)
 }
 #endif
 
+/**
+ * @brief Override the internal symbol resolver.
+ * The default resolver is based on static lists that are determined by KConfig.
+ * This override allows for an arbitrary implementation.
+ *
+ * @param resolver the resolver function
+ */
+void elf_set_symbol_resolver(symbol_resolver resolver) {
+    current_resolver = resolver;
+}
+
+
 /**
  * @brief Map symbol's address of ELF to physic space.
  *

components/elf_loader/src/esp_elf_symbol.c

@@ -156,7 +156,7 @@ static const struct esp_elfsym g_esp_espidf_elfsyms[] = {
  *
  * @return Symbol address if success or 0 if failed.
  */
-uintptr_t elf_find_sym(const char *sym_name)
+uintptr_t elf_find_sym_default(const char *sym_name)
 {
     const struct esp_elfsym *syms;