On Mon, Apr 02, 2007 at 11:23:17PM -0600, Eric W. Biederman wrote: > Vivek Goyal <[EMAIL PROTECTED]> writes: > > >> I guess at this point the easy case is that we modify /sbin/kexec to > >> support > >> it. And the other bootloaders can come be upgraded if the feature is > >> interesting enough. > >> > >> > On i386, somebody already found an interesting usage of > > CONFIG_PHYSICAL_START > >> > where he was running his kernel above 16MB so that he can maximize on > >> > DMA ZONE. Can't think of any usage for x86_64 at the moment but I think > >> > down the line people might come up with such usages. > >> > >> Agreed. We do have CONFIG_PHYSICAL_ALIGN that can handle that case, > >> although I admit that is a bit of a hack. > >> > > > > Yes, but x86_64 will not have any of those options and only way to run > > kernel will be either use kexec or modify your boot-loader to so that > > it can handle relocatable images. > > True. > > >> > To me, retaining CONFIG_PHYSICAL_START gives added flexibility to the > >> > user, > >> > at the expense of reduced simplicity. We should definitely change the > >> > type > >> > of vmlinux to ET_DYN but at the same time it might still be worth to > >> > retain > >> > CONFIG_PHYSICAL_START option. > >> > >> I think something like CONFIG_PHYSICAL_START currently gives us very > >> little gain, and is hard to use correctly, and there are alternative > >> solutions. So if we can get rid of it, by only inconveniencing users > >> who want load their kernels at a weird address it is worth it. > >> > >> >> I think I can switch the vmlinux header type in about 100 lines or so > >> >> of code. Assuming I can ever get 30 minutes with the appropriate > >> >> kernel. > >> >> > >> > > >> > That would be awesome. Then vmlinux will be relocatable too. > >> > (Officially). > >> > >> Yes. For x86_64 I can do this. i386 is more difficult. (Although with > >> a little cleverness we can move the code that processes relocations into > >> vmlinux). > >> > > > > Performing relocations in vmlinux will be interesting. That way i386 vmlinux > > too will become relocatable and only piece of puzzle to solve will be to > > make vmlinux of type ET_DYN. > > Actually making vmlinux have type ET_DYN is the easier piece. Basically > the quick way to do this is to have an arch specific: "cmd_vmlinux__" > like uml does so we can edit things after the make. > > Changing an integer in an ELF header is simple. > > Inserting the code to perform the relocations feels a bit trickier but > we can probably just dump it in head.S like we do on x86_64. We still need > to insert the actual relocations to process though. Which requires all of the > post processing we currently do just called at a slightly different location.
Something like what kallsyms does? Read .tmp_vmlinux2, extract and filter relocations, pack them in relocs.S, build reloc.o and relink it back to .tmp_vmlinux2 to make vmlinux. Then arch/i386/kernel/head.S can perform the relocations. But any additiona step of re-linking after final kallsyms information has been generated can potentially spoil kallsyms data? Thanks Vivek - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
