Re: How printf output messages to kernel with uclibc lib

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On Saturday 31 January 2009 07:18, loody wrote:
> > Dear all:
> >   I am porting kernel on my arm platform and I wrote a userspace
> > program, hello world.
> >   But I cannot see the "hello world".
> >
> >   my environment is:
> >   1. uclinux.dist 2008
> >   2. and I put my source code under user and compile it.
> >   3. I use arm-linux-2006 to compile kernel
> >   4. I use arm-linux-2007 to compile my hello world.
> hi:
> I have one question about my problem.
> Can I replace the kernel execute command, "/init", as "/hello"; that
> means the first user space program is hello, not standard int.
> Is that the problem which make printt not workable?
> 
> I have no idea whether kernel has to do something in "init" such that
> "hello" can call printf to show message.

[f]printf ultimately results in write() syscalls performed on
open file descriptors. 

If you have trouble verifying that your userspace programs
are able to execute, start with this test program:

int main() {
	write(1, "Hello\n", 6);
	for (;;)
		continue;
}

Compile it and run as init. You should see "Hello"
message. If you don't, your toolchain is producing broken
executables.
--
vda

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