28.06.2005 17:21:35, Wolfgang Denk wd@denx.de wrote:
In message 85W32HGVT4WOKE0XT1Y1XVTND0OM74.42c15f80@pc-block you wrote:
Well, then I don't get it. Perhaps you could have a look at my mail referenced above. There's an example of U-Boot relocating an absolute symbol.
I didn't see it. You claimed that there was an absolute symbol in an object file, but I have not seen the result of the linker run (i. e. the U-Boot ELF file, the System.map file or the u-boot.map file); nor do I know what you are doing in your linker script.
Is your symbol "fpgadata" really listed in the GOT?
You mentioned that it contains a bad value, but did you verify that this was indeed casued by relocation (i. e. was the value really off by the relocation distance) ?
Well, I did show you the output of the generated object itself (before it got linked against U-Boot) and all I did in my test-command in U-Boot was to print the address of the symbol. All I can think of is relocation. But I'll think again, do some more tests and send you the result tomorrow.
Well, I think there has to be a difference for the compiler in the next two cases:
char *walter = 0x4711; char *herbert = "Thommy, the cat";
No. There may be a difference for you, or for the resultof the code execution, but for the compiler it's all the same. AFAIK the ESP module of GCC has not been implemented yet :-)
Of course it's not the compiler, but the linker. When talking about compiler, I was speaking of the entire tool-chain, sorry, for this imprecision. But I can show you, that it is indeed two different thinks for the compiler (which reaches some information about this difference to the linker). I'll do this tomorrow, too.
The first one shouldn't be relocated by the compiler, but the last one has to be relocated, in order to make the program work. At least as far as I understand it, please correct me, if I'm wrong.
The _compiler_ does not do any relocation at all. He doesn't even know that such a thing exists. For the _compiler_ a pointer is just a pointer, in no way more special than an int.
But the compiler tags relocation marks for the linker, right?
I don't think that GCC/gas will normally generate any absolute symbols at all. If you manually define such symbols you are expected to understand what you are doing.
The emphasis is on "understand".
Thanks a lot, I got that one.
Again, I'd like to reference my above mentioned first request from 14.06.2005. I
think,
I know what I'm doing and what I want to do, but the generated absolute symbol is relocated by U-Boot.
You know what you did, but you posted here because you didn't understand the results, right? I don't understand it either, so I tend to avoid doing such things ;-)
If I avoided all things I don't understand, I wouldn't have much to do, would I?
Thanks for your suggestions, but my main problem is I'm not wanting to change any common code and want to solve my problem in the problem specific code.
I really don't understand why you need to statically intialize this pointer at all, or why you bother about it being relocated or not. You mentioned that this is an address to where the code is downloaded by TFTP first. So you will have to set up a TFTP transfer and all these things - so the address in RAM should be known. Why don't you simply use a plain assignment in your code, then?
I will explain this once more in detail tomorrow. The main problem lies in the fact, that I don't want to touch any common code, but want to achive a solution within my project's code, only.
Regards, Andreas Block