Dear Steve, In message <539746c4.9040...@broadcom.com> you wrote: > > There could be "many" reasons why the CONFIG_SYS_TEXT_BASE is not > aligned on a 0x1000 byte boundary (Darwin has attempted to document his > particular use-case...)
We should be more precise here and ask for any _good_ reasons. I can think of many good reasons to keep the text base aligned. As for the reasons to use an unaligned address that were brought up here, I still think that it would have been better to use an aligned taxe base and do the rest with a customized linker script. > But we think that the solution to support this is relatively > straightforward: > (1) after determining the "relocation address" (which will be on a > 0x1000 byte boundary), > (2) add "CONFIG_SYS_TEXT_BASE % 4096" to that "relocation address" > (which effectively makes the "relocation offset" a multiple of 0x1000 > too...) > So, in the scenario #1, (CONFIG_SYS_TEXT_BASE % 4096) = 0, so this > algorithm changes nothing. > And in scenario #2, (CONFIG_SYS_TEXT_BASE % 4096) = 0x20, therefore, we > would now get the following: > the relocation offset is: 0x77f9b000 > therefore, after relocation: > _start symbol is at 0xfff9b020 (0x88000020+0x77f9b000) > vectors symbol is at 0xfff9b800 (0x88000800+0x77f9b000) I still cannot understand why _start and CONFIG_SYS_TEXT_BASE would have to be the same. There is no such requirement. What exactly prevents you from assigning _start a location at offset 0x20 to the start of the text segment, i. e. CONFIG_SYS_TEXT_BASE ? Then everything should be still the same for you, and no voodoo coding would be needed. > (3) HOWEVER, shifting the address UP may cause the end of the relocated > code to run past the end of the available memory... So we could: This problem is void if you just use a poperly aligned text base in combination with a prope start.S resp. linker script to make sure _start is where you want it. > I trust that everyone will find this explanation acceptable... No, I do not see a good reason to add such code. Best regards, Wolfgang Denk -- DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: w...@denx.de Let the programmers be many and the managers few -- then all will be productive. -- Geoffrey James, "The Tao of Programming" _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
