Messages in this thread | | | From | Ian Campbell <> | Date | Tue, 29 Jan 2008 20:38:32 +0000 | Subject | Re: PATCH/RFC: bzImage payload as compressed ELF file. |
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On Tue, 2008-01-29 at 10:34 -0800, H. Peter Anvin wrote: > Jeremy Fitzhardinge wrote: > > H. Peter Anvin wrote: > >> It's also easy enough to either use objdump -h or nm to extract info > >> from vmlinux; or for some of the simpler stuff, just parse the ELF > >> directly (perhaps using libelf). > >> > >> There is also the -R option to ld, which imports symbols from one > >> executable into another. > > > > Yes, I used -R, though it was necessary to generate a copy of vmlinux > > with a filtered symbol list to prevent collisions. But I'm not sure any > > of this is necessary with Ian's approach. > > > > Probably isn't. He just need the start and possibly length of the > payload section, which should be objdump -h or equivalently reading the > ELF section table.
I'm currently using "objcopy --extract-symbol -w -N \* -K input_data" to create a .o with just the symbol I'm interested in and using -R on that. There's also an option to add a prefix to all symbols which might be useful.
I finessed the length issue slightly since it happens that the word before the payload is the payload's length. I'm mulling a variety of options: * declare it compression scheme dependant. At least for gzip it knows when it has reached the end. * codify the length followed by data thing we happen to have now * add a length field to the header, using another 4 bytes (is there any pressure on the size of the header?).
I'd probably go with the later unless we are pressed for space in the header.
Ian. -- Ian Campbell
Man who falls in vat of molten optical glass makes spectacle of self.
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