[U-Boot] debug uboot from ram for x86 board

[U-Boot] debug uboot from ram for x86 board

[LanceZ]

Hi there,

I am trying to add some codes(driver) to u boot, but I do not have jtag or
other debugging tools. what I can use are :serial port/ethernet, so I can
use tftp and loadb to download the bin to ram.

Currently, I tried to use "loadb" to load the sample(hello_world) to ram and
then execute it, I always failed .here are the output for my testing.

I rename hello_world to rt61test
then rebuild all uboot
use nm command get follows:

00040000 T rt61test
00040098 T dummy

then start my board
In:    serial
Out:   serial
Err:   serial
Net:   i82559#0
boot > loadb 0x40000
## Ready for binary (kermit) download to 0x00040000 at 115200 bps...
## Start Addr      = 0x00040000
boot > go 40000
## Starting application at 0x00040000 ...
Invalid Instruction at 0000:00000000

I also tried other address for loadb(loadb 0x1000000)

I got the same error result

 Appreciate anyone can give me a direction or explain the error

Thanks
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[U-Boot] debug uboot from ram for x86 board

[Graeme Russ]

On Thu, Dec 25, 2008 at 4:52 PM, LanceZ <Lance.Zhang@taihootech.com> wrote:
>
> Hi there,
>
> I am trying to add some codes(driver) to u boot, but I do not have jtag or
> other debugging tools. what I can use are :serial port/ethernet, so I can
> use tftp and loadb to download the bin to ram.
>
> Currently, I tried to use "loadb" to load the sample(hello_world) to ram and
> then execute it, I always failed .here are the output for my testing.
>
> I rename hello_world to rt61test
> then rebuild all uboot
> use nm command get follows:
>
> 00040000 T rt61test
> 00040098 T dummy
>
> then start my board
> In:    serial
> Out:   serial
> Err:   serial
> Net:   i82559#0
> boot > loadb 0x40000
> ## Ready for binary (kermit) download to 0x00040000 at 115200 bps...
> ## Start Addr      = 0x00040000
> boot > go 40000
> ## Starting application at 0x00040000 ...
> Invalid Instruction at 0000:00000000
>
> I also tried other address for loadb(loadb 0x1000000)
>
> I got the same error result
>
>  Appreciate anyone can give me a direction or explain the error
>
> Thanks

Hi Lance,

I have the same problem. I am in the process of finalising some other x86
common code to make the custom board port more seemless before I dig deeper.

I do, however, feel that a look at the nios code (lib_nios/board.c) might
shed some light on the issue. Specifically the comment in do_go_exec:

unsigned long do_go_exec (ulong (*entry)(int, char *[]), int argc, char *argv[])

{
	/*
	 * x86 does not use a dedicated register to pass the pointer
	 * to the global_data
	 */
	argv[-1] = (char *)gd;
	return entry (argc, argv);
}

I think the lib_i386 implementation of do_go_exec() is not right

Regards,

Graeme

[U-Boot] debug uboot from ram for x86 board

[Lance Zhang]

Hi Graeme
>I have the same problem. I am in the process of finalising some other
x86
>common code to make the custom board port more seemless before I dig
deeper.

>I do, however, feel that a look at the nios code (lib_nios/board.c)
might
>shed some light on the issue. Specifically the comment in do_go_exec:
>
>unsigned long do_go_exec (ulong (*entry)(int, char *[]), int argc, char
*argv[])
>
>{
>	/*
>	 * x86 does not use a dedicated register to pass the pointer
>	 * to the global_data
>	 */
>	argv[-1] = (char *)gd;
>	return entry (argc, argv);
>}

>I think the lib_i386 implementation of do_go_exec() is not right
I carefully read the codes related to the do_go function, and I find
that(u boot 1.1.6):
In do_go() functions:
#if defined(CONFIG_I386)
	/*
	 * x86 does not use a dedicated register to pass the pointer
	 * to the global_data
	 */
	argv[0] = (char *)gd;
#endif

But in app_startup function:
void app_startup(char **argv)
{
	unsigned long * cp = &__bss_start;

	/* Zero out BSS */
	while (cp < &_end) {
		*cp++ = 0;
	}

#if defined(CONFIG_I386)
	/* x86 does not have a dedicated register for passing
global_data */
	global_data = (gd_t *)argv[-1];
	jt = global_data->jt;
#endif
}

The gd is not in the same place :see do_go is argv[0], and app_startup
is (gd_t *)argv[-1].

But later I modified the global_data = (gd_t *)argv[-1]; in app_startup
function to global_data = (gd_t *)argv[0], the change still does not
make sense.

Any ideas?  Maybe I should change the argv[0] = (char *)gd; in do_go
function to argv[-1] = (char *)gd;

Thanks
Lance Zhang

[U-Boot] debug uboot from ram for x86 board

[Lance Zhang]

> I carefully read the codes related to the do_go function, and I find
that(u
> boot 1.1.6):
> In do_go() functions:
> #if defined(CONFIG_I386)
> 	/*
> 	 * x86 does not use a dedicated register to pass the pointer
> 	 * to the global_data
> 	 */
> 	argv[0] = (char *)gd;
> #endif
> 
> But in app_startup function:
> void app_startup(char **argv)
> {
> 	unsigned long * cp = &__bss_start;
> 
> 	/* Zero out BSS */
> 	while (cp < &_end) {
> 		*cp++ = 0;
> 	}
> 
> #if defined(CONFIG_I386)
> 	/* x86 does not have a dedicated register for passing
global_data */
> 	global_data = (gd_t *)argv[-1];
> 	jt = global_data->jt;
> #endif
> }
> 
> The gd is not in the same place :see do_go is argv[0], and app_startup
is (gd_t
> *)argv[-1].
> 
> But later I modified the global_data = (gd_t *)argv[-1]; in
app_startup
> function to global_data = (gd_t *)argv[0], the change still does not
make sense.
> 
> Any ideas?  Maybe I should change the argv[0] = (char *)gd; in do_go
function
> to argv[-1] = (char *)gd;
> 
Later, I tried remove the function bodies, and the main function like
this:
int _main (int argc, char *argv[])
{
	return (8);
}
And got the following result:
boot > go 01000000
## Starting application at 0x01000000 ...
## Application terminated, rc = 0x8

I am sure app_startup and do_go are not consistent, so I can not use any
printf or some other function calls.  

Currently I can not update the flash as I do not have jtag tools. Later
I will update flash and see if it could fix the problem.

Thanks in advance