Rewrote crt0, init, and chainloading code

start.s, init.c, linker.ld and linker.specs are meant
to be re-used by user applications, should they remove the defines
from init.c and the .chainloader* sections from the linker script

fusee/fusee-primary/src/init.c

@@ -0,0 +1,130 @@
+#include <stdint.h>
+#include <stddef.h>
+#include <string.h>
+#include <malloc.h>
+#include <sys/iosupport.h>
+#include "utils.h"
+
+void __libc_init_array(void);
+void __libc_fini_array(void);
+
+extern uint8_t __bss_start__[], __bss_end__[];
+extern uint8_t __heap_start__[], __heap_end__[];
+
+extern char *fake_heap_start;
+extern char *fake_heap_end;
+
+int __program_argc;
+void **__program_argv;
+
+void __attribute__((noreturn)) __program_exit(int rc);
+void __attribute__((noreturn)) (*__program_exit_callback)(int rc) = NULL;
+
+static void __program_parse_argc_argv(int argc, char *argdata);
+static void __program_cleanup_argv(void);
+
+static void __program_init_heap(void) {
+    fake_heap_start = (char*)__heap_start__;
+    fake_heap_end   = (char*)__heap_end__;
+}
+
+static void __program_init_newlib_hooks(void) {
+    __syscalls.exit = __program_exit; /* For exit, etc. */
+}
+
+static void __program_move_additional_sections(void) {
+#if defined(FUSEE_STAGE1_SRC) || defined(FUSEE_STAGE2_SRC)
+    extern uint8_t __chainloader_lma__[], __chainloader_start__[], __chainloader_bss_start__[], __chainloader_end__[];
+    memcpy(__chainloader_start__, __chainloader_lma__, __chainloader_bss_start__ - __chainloader_start__);
+    memset(__chainloader_bss_start__, 0, __chainloader_end__ - __chainloader_bss_start__);
+#endif
+}
+
+void __program_init(int argc, char *argdata) {
+    /* Zero-fill the .bss section */
+    memset(__bss_start__, 0, __bss_end__ - __bss_start__);
+
+    __program_init_heap();
+    __program_init_newlib_hooks();
+    __program_parse_argc_argv(argc, argdata);
+
+    /* Once argv is parsed, we can discard the low IRAM region */
+    __program_move_additional_sections();
+    __libc_init_array();
+}
+
+void __program_exit(int rc) {
+    __libc_fini_array();
+    __program_cleanup_argv();
+    if (__program_exit_callback == NULL) {
+        /* Default callback */
+        generic_panic();
+    } else {
+        __program_exit_callback(rc);
+    }
+    for (;;);
+}
+
+#ifdef FUSEE_STAGE1_SRC
+static void __program_parse_argc_argv(int argc, char *argdata) {
+    __program_argc = 0;
+    __program_argv = NULL;
+}
+#elif defined(FUSEE_STAGE2_SRC)
+#include "stage2.h"
+static void __program_parse_argc_argv(int argc, char *argdata) {
+    size_t pos = 0, len;
+
+    __program_argc = argc;
+
+    __program_argv = malloc(argc * sizeof(void **));
+    if (__program_argv == NULL) {
+        generic_panic();
+    }
+
+    len = strlen(argdata);
+    __program_argv[0] = malloc(len + 1);
+    if (__program_argv[0] == NULL) {
+        generic_panic();
+    }
+    strcpy((char *)__program_argv[0], argdata);
+    pos += len + 1;
+
+    __program_argv[1] = malloc(len + 1);
+    if (__program_argv[1] == NULL) {
+        generic_panic();
+    }
+    memcpy(__program_argv[1], argdata + pos, sizeof(stage2_args_t));
+}
+#else
+static void __program_parse_argc_argv(int argc, char *argdata) {
+    size_t pos = 0, len;
+
+    __program_argc = argc;
+
+    __program_argv = malloc(argc * sizeof(void **));
+    if (__program_argv == NULL) {
+        generic_panic();
+    }
+
+    for (int i = 0; i < argc; i++) {
+        len = strlen(argdata + pos);
+        __program_argv[i] = malloc(len + 1);
+        if (__program_argv[i] == NULL) {
+            generic_panic();
+        }
+        strcpy((char *)__program_argv[i], argdata + pos);
+        pos += len + 1;
+    }
+}
+#endif
+
+static void __program_cleanup_argv(void) {
+#ifndef FUSEE_STAGE1_SRC
+    for (int i = 0; i < __program_argc; i++) {
+        free(__program_argv[i]);
+        __program_argv[i] = NULL;
+    }
+    free(__program_argv);
+#endif
+}