entry.c

来自「Hermit-at-1.1.3,一款bootloader」· C语言 代码 · 共 55 行

/*
 * Initial C entry point of the boot loader.  Called by the assembly
 * language setup code in boot.S/init.S.
 *
 * Copyright (c) 2004 Atmark Techno, Inc. All Rights Reserved.
 *
 * Based on:
 * Copyright (c) 2000 Blue Mug, Inc.  All Rights Reserved.
 *
 * We must have a stack pointer, but there are no other preconditions.
 *
 * The generated text for this file lives in the .hermit.boot section
 * of the loader executable.  Symbols in the .hermit.boot section have
 * relocation addresses equal to their load addresses (see the link
 * map for details), so this section is designed to run from flash at
 * boot time.  In GNU linker terminology, these symbols have VMA ==
 * LMA ('info ld' for definitions).
 *
 * Pretty much all other symbols in the loader have VMAs within SRAM
 * or DRAM (depending on build configuration).  This means that their
 * load addresses (LMAs) are not equal to their VMAs.  Ergo most of
 * the loader must be relocated to RAM before it can run; we even
 * relocate the text segment to RAM, to make it possible to reprogram
 * the loader in flash.  This file handles the relocation.
 *
 * Until the relocation is done, the loader won't be able to access
 * any writeable data (.data segment stuff) or use zeroed global
 * memory (.bss).  Be careful when editing the code here!
 *
 * --miket
 */

#include <target/mem.h>

extern unsigned char __bss_start;
extern unsigned char __bss_end;

/* see loader.lds */
extern unsigned char __text_start_flash;
extern unsigned char __text_start;
extern unsigned char __text_end;
extern unsigned char __data_start_flash;
extern unsigned char __data_start;
extern unsigned char __data_end;

extern int hmain(void);

void entry(void)
{
	/* clear .bss */
        memset(&__bss_start, 0, &__bss_end - &__bss_start);
        hmain();
}