你好世界，裸机 Beagleboard [英] Hello world, bare metal Beagleboard

问题描述

我正在尝试在我的 Beagleboard-xm rev 上运行一个hello world"类型的程序.C，通过从汇编调用 C puts 函数.

I'm trying to get a 'hello world' type program running on my Beagleboard-xm rev. C, by calling a C puts function from assembly.

到目前为止，我一直在使用它作为参考:http://wiki.osdev.org/ARM_Beagleboard

So far I've been using this as a reference: http://wiki.osdev.org/ARM_Beagleboard

这是我目前所拥有的，但没有输出.

Here's what I have so far, but there's no output.

hello.c

volatile unsigned int * const UART3DR = (unsigned int *)0x49020000;

void puts(const char *s) {
  while(*s != '\0') { 
    *UART3DR = (unsigned int)(*s); 
    s++; 
  }
}

void hello() {
  puts("Hello, Beagleboard!\n");
}

boot.asm

.global start
start:
   ldr sp, =stack_bottom
   bl hello
   b .

linker.ld

ENTRY(start)

MEMORY
{
    ram : ORIGIN = 0x80200000, LENGTH = 0x10000
}

SECTIONS
{
    .hello : { hello.o(.text) } > ram
    .text : { *(.text) } > ram
    .data : { *(.data) } > ram
    .bss : { *(.bss) } > ram
     . = . + 0x5000; /* 4kB of stack memory */
    stack_bottom = .;

}

Makefile

ARMGNU = arm-linux-gnueabi

AOPS = --warn --fatal-warnings
COPS = -Wall -Werror -O2 -nostdlib -nostartfiles -ffreestanding

boot.bin: boot.asm
   $(ARMGNU)-as boot.asm -o boot.o
   $(ARMGNU)-gcc-4.6 -c $(COPS) hello.c -o hello.o
   $(ARMGNU)-ld -T linker.ld hello.o boot.o -o boot.elf
   $(ARMGNU)-objdump -D boot.elf > boot.list
   $(ARMGNU)-objcopy boot.elf -O srec boot.srec
   $(ARMGNU)-objcopy boot.elf -O binary boot.bin

像这样只使用 asm 文件即可.

Using just the asm file like this works.

.equ UART3.BASE,        0x49020000
start:
   ldr r0,=UART3.BASE
   mov r1,#'c'

以下是一些 Beagleboard/minicom 相关信息:http://paste.ubuntu.com/829072/

Here are some Beagleboard/minicom related info: http://paste.ubuntu.com/829072/

有什么指点吗?:)

我也试过

void hello() {
  *UART3DR = 'c';
}

我正在使用 minicom 并通过 ymodem 发送文件，然后我尝试使用以下命令运行它:

I'm using minicom and send the file via ymodem, then I try to run it with:

go 0x80200000

minicom 中的硬件和软件控制流关闭.

Hardware and software control flow in minicom are off.

推荐答案

应该对您有用.这是我从很久以前挖出来的一些代码，今晚没有在 beagleboard 上尝试它只是确保它已编译，它曾经工作过......

that should have worked for you. Here is some code I dug up from way back when, did not try it on a beagleboard tonight just made sure it compiled, it had worked at one time...

startup.s:

    .code 32

.globl _start
_start:

    bl main
hang: b hang

.globl PUT32
PUT32:
    str r1,[r0]
    bx lr

.globl GET32
GET32:
    ldr r0,[r0]
    bx lr

hello.c:

extern void PUT32 ( unsigned int, unsigned int );
extern unsigned int GET32 ( unsigned int );
void uart_send ( unsigned char x )
{
    while((GET32(0x49020014)&0x20)==0x00) continue;
    PUT32(0x49020000,x);
}
void hexstring ( unsigned int d )
{
    //unsigned int ra;
    unsigned int rb;
    unsigned int rc;

    rb=32;
    while(1)
    {
        rb-=4;
        rc=(d>>rb)&0xF;
        if(rc>9) rc+=0x37; else rc+=0x30;
        uart_send(rc);
        if(rb==0) break;
    }
    uart_send(0x0D);
    uart_send(0x0A);
}
int main ( void )
{
    hexstring(0x12345678);
    return(0);
}

memmap(链接脚本):

memmap (linker script):

MEMORY
{
    ram : ORIGIN = 0x82000000, LENGTH = 256K
}

SECTIONS
{
    ROM : { startup.o } > ram
}

生成文件:

CROSS_COMPILE = arm-none-eabi

AOPS = --warn --fatal-warnings 
COPS = -Wall -Werror -O2 -nostdlib -nostartfiles -ffreestanding 

all : hello.bin

hello.bin : startup.o hello.o memmap
    $(CROSS_COMPILE)-ld startup.o hello.o -T memmap -o hello.elf  
    $(CROSS_COMPILE)-objdump -D hello.elf > hello.list
    $(CROSS_COMPILE)-objcopy hello.elf -O binary hello.bin

startup.o : startup.s
    $(CROSS_COMPILE)-as $(AOPS) startup.s -o startup.o

hello.o : hello.c 
    $(CROSS_COMPILE)-gcc -c $(COPS) hello.c -o hello.o

clean :
    rm -f *.o
    rm -f *.elf
    rm -f *.bin
    rm -f *.list

看起来我只是将堆栈指针留在了引导加载程序所在的位置.同样，与您一样，假设引导加载程序已初始化串行端口.

Looks like I just left the stack pointer wherever the bootloader had it. Likewise, as you, assumed the bootloader had initialized the serial port.

我假设您的串行端口访问正常，您看到 uboot 并且您能够键入命令以将该程序(xmodem 或其他)下载到板子 ram 中?如果您不能这样做，则可能是您没有正确连接到串行端口.beagleboards 的串口有问题，可能需要自己制作电缆.

I assume you have serial port access working, you see uboot and you are able to type commands in order to download this program (xmodem, or whatever) into the boards ram? If you cant do that then it may be you are not connected to the serial port right. the beagleboards serial port is screwy, might need to make your own cable.

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