[SOLVED] Importing values from LD into C-code

[wolfram]

Hello. I have got some labels in my linker script, for example _sztext = SIZEOF(.text); etc. And I need to use them in my C-code. I know, what I must use keyword "export". But I don't know, what type I have to use? extern int sztext or extern char sztext?

[f2]

Try "extern unsigned long _sztext" in your C code.

[wolfram]

This post is allowed to delete.

[qw]

Symbols defined in linker scripts are not variables. Instead, they appear to the program as addresses. So you should use something similar to

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extern char sztext;
#define SIZEOF_TEXT ((uintptr_t)&sztext)

and then use SIZEOF_TEXT instead of sztext.

[wolfram]

Hobbes thank you.

[qw]

You're welcome!

[qw]

By the way, you can create variables in linker scripts as follows:

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_myvar = .;
LONG(0xdeadbeef)

and access them in C with:

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extern int myvar;
assert(myvar == 0xdeadbeef);

[neon]

I personally do not recommend relying on a linker script to define symbols. That creates an unnecessary dependency between your code and that linker. If this is not a concern, then it might be an option. If it is, then I would not recommend it.

[wolfram]

I personally do not recommend relying on a linker script to define symbols. That creates an unnecessary dependency between your code and that linker. If this is not a concern, then it might be an option. If it is, then I would not recommend it.

I use symbols from linker script for create Higher Half kernel. I need know, where start my text and data sections for correctly map theirs from additional section, where be my loading code. Have you got another idea, how create HHalf kernel, independent from linker?

P.S. I'm sorry for my English, it's not my native lang.

[neon]

Hello,

I use symbols from linker script for create Higher Half kernel. I need know, where start my text and data sections for correctly map theirs from additional section, where be my loading code. Have you got another idea, how create HHalf kernel, independent from linker?

The way I do it is a bit different sense I have a microkernel. Basically the generic boot loader loads and executes an OS-specific loader that both creates the initial environment for the kernel and kernel modules to run, and build a boot information structure to the kernel before passing control to the kernel.

Granted, my OS-specific loader does a little bit more, but thats the basic idea.