"J. William Campbell" <jwilliamcampb...@comcast.net> wrote on 2010/10/04 19:59:47: > On 10/4/2010 10:06 AM, Wolfgang Denk wrote: > Dear "J. William Campbell", > > In message <4ca9f294.8080...@comcast.net> you wrote:
> > Yes, I think Wolfgang is correct. This is not going to be easy to do in > general. To run anywhere, the code must be true Position Independent > code. If you intend to use any C code in the initialization, this will > result in needing -fPIC for at least that code. I am not sure you can > mix -fPIC and non -fPIC code in the same link, but I expect not. I am a > bit surprised that it is possible to get even the initialization code to > be Position Independent, but it appears that on at least some PPC it is > possible/has been done. > > Not really. On PowerPC, only the first 20 or 30 lines of assembler > code in start.S are position independent; then we compute the link > (resp. execution) address and branch to it. From then, we run from the > very address range we were linked for (starting at TEXT_BASE). > Hi Wolfgang, > You are of course correct. I was referring more to Jocke's ( > joakim.tjernl...@transmode.se) statements regarding: > Yes, that is there today. I am talking about linking to any TEXT_BASE(say 0) > but burn and run into another address. I impl. this quite some time > ago for PPC(search for LINK_OFF) > > I understand from his comment that he had achieved total PIC for the > initialization, that would run at any location regardless > of TEXT_BASE. I think this code was not accepted into mainline, so it is not a > problem at present. However, any relocation code > added would have to be modified by Jocke if he wished to preserve that > capability. I am amazed that he was able to get the > rest of u-boot to work under the constraints you pointed out. It must have > been quite tedious. :), actually it wasn't that bad. Wolfgang nearly accepted the code even :) Mainly, I had to wrap code that accessed global data with a LINK_OFF() function that calculated the offset and only in code that executed before relocation. And fix a few things in start.S to be PIC. Jocke _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
