| Message ID | 20240827123052.9002-1-lhruska@suse.cz (mailing list archive) |
|---|---|
| Headers | show |
| Series | livepatch: klp-convert tool - Minimal version | expand |
On Tue, Aug 27, 2024 at 02:30:45PM +0200, Lukas Hruska wrote: > Summary > ------- > > This is a significantly simplified version of the original klp-convert tool. > The klp-convert code has never got a proper review and also clean ups > were not easy. The last version was v7, see > https://lore.kernel.org/r/20230306140824.3858543-1-joe.lawrence@redhat.com > > The main change is that the tool does not longer search for the > symbols which would need the livepatch specific relocation entry. > Also klp.symbols file is not longer needed. > > Instead, the needed information is appended to the symbol declaration > via a new macro KLP_RELOC_SYMBOL(). It creates symbol with all needed > metadata. For example: > > extern char *saved_command_line \ > KLP_RELOC_SYMBOL(vmlinux, vmlinux, saved_command_line, 0); > > would create symbol > > $>readelf -r -W <compiled livepatch module>: > Relocation section '.rela.text' at offset 0x32e60 contains 10 entries: > Offset Info Type Symbol's Value Symbol's Name + Addend > [...] > 0000000000000068 0000003c00000002 R_X86_64_PC32 0000000000000000 .klp.sym.rela.vmlinux.vmlinux.saved_command_line,0 - 4 > [...] > > > The simplified klp-convert tool just transforms symbols > created by KLP_RELOC_SYMBOL() to object specific rela sections > and rela entries which would later be proceed when the livepatch > or the livepatched object is loaded. > > For example, klp-convert would replace the above symbols with: > > $> readelf -r -W <livepatch_module_proceed_by_klp_convert> > Relocation section '.klp.rela.vmlinux.text' at offset 0x5cb60 contains 1 entry: > Offset Info Type Symbol's Value Symbol's Name + Addend > 0000000000000068 0000003c00000002 R_X86_64_PC32 0000000000000000 .klp.sym.vmlinux.saved_command_line,0 - 4 > > > Note that similar macro was needed also in the original version > to handle more symbols of the same name (sympos). > > Given the above, add klp-convert tool; integrate klp-convert tool into > kbuild; add data-structure and macros to enable users to annotate > livepatch source code; make modpost stage compatible with livepatches; > update livepatch-sample and update documentation. > > > Testing > ------- > > The patchset selftests build and execute on x86_64, s390x, and ppc64le > for both default config (with added livepatch dependencies) and a larger > SLE-15-ish config. > > > Summary of changes in this minimal version v3 > ------------------------ > > - klp-convert: symbol format changes (suggested by jlawrence) > - samples: fixed name of added sample in Makefile (suggested by pmladek) > - selftests: added ibt test case as an example (DON'T MERGE) > - fixed all suggested small changes in v2 > > Previous versions > ----------------- > > RFC: > https://lore.kernel.org/r/cover.1477578530.git.jpoimboe@redhat.com/ > v2: > https://lore.kernel.org/r/f52d29f7-7d1b-ad3d-050b-a9fa8878faf2@redhat.com/ > v3: > https://lore.kernel.org/r/20190410155058.9437-1-joe.lawrence@redhat.com/ > v4: > https://lore.kernel.org/r/20190509143859.9050-1-joe.lawrence@redhat.com/ > v5: > (not posted) > https://github.com/joe-lawrence/klp-convert-tree/tree/klp-convert-v5-devel > v6: > https://lore.kernel.org/r/20220216163940.228309-1-joe.lawrence@redhat.com/ > v7: > https://lore.kernel.org/r/20230306140824.3858543-1-joe.lawrence@redhat.com/ > v1 minimal: > https://lore.kernel.org/r/20231106162513.17556-1-lhruska@suse.cz/ > v2 minimal: > https://lore.kernel.org/r/20240516133009.20224-1-lhruska@suse.cz/ > Hi Lukas, Thanks again for posting the patchset and trying a simpler approach. I tested with latest kpatch-build tree with no ill effects -- essentially klp-convert is safe to run against .ko files that already contain klp-relocations. I would prefer more extensive selftests for various klp-relocation types (as well as symbol position), however I believe wasn't the point of the minimal version of this patchset. We can add more tests later. Anyway, now we have two RFC / patchsets supporting in-tree creation of klp-relocations (klp-convert and Josh's objtool patchset). I think we need to figure out whether one precludes the other, can they co-exist, or does that even make sense. Since LPC is right around the corner, does it make sense for folks to sync up at some point and talk pros/cons to various approaches? We don't have a microconference this year, but perhaps over lunch or beers? -- Joe
On Thu, Sep 12, 2024 at 11:15:08AM -0400, Joe Lawrence wrote: > Anyway, now we have two RFC / patchsets supporting in-tree creation of > klp-relocations (klp-convert and Josh's objtool patchset). I think we > need to figure out whether one precludes the other, can they co-exist, > or does that even make sense. I haven't really thought about it, but it *might* be possible for klp-build to use klp-convert. I'll look at it more when I get a chance. > Since LPC is right around the corner, does it make sense for folks to > sync up at some point and talk pros/cons to various approaches? We > don't have a microconference this year, but perhaps over lunch or beers? Sure... or maybe at one of the evening events.
Summary ------- This is a significantly simplified version of the original klp-convert tool. The klp-convert code has never got a proper review and also clean ups were not easy. The last version was v7, see https://lore.kernel.org/r/20230306140824.3858543-1-joe.lawrence@redhat.com The main change is that the tool does not longer search for the symbols which would need the livepatch specific relocation entry. Also klp.symbols file is not longer needed. Instead, the needed information is appended to the symbol declaration via a new macro KLP_RELOC_SYMBOL(). It creates symbol with all needed metadata. For example: extern char *saved_command_line \ KLP_RELOC_SYMBOL(vmlinux, vmlinux, saved_command_line, 0); would create symbol $>readelf -r -W <compiled livepatch module>: Relocation section '.rela.text' at offset 0x32e60 contains 10 entries: Offset Info Type Symbol's Value Symbol's Name + Addend [...] 0000000000000068 0000003c00000002 R_X86_64_PC32 0000000000000000 .klp.sym.rela.vmlinux.vmlinux.saved_command_line,0 - 4 [...] The simplified klp-convert tool just transforms symbols created by KLP_RELOC_SYMBOL() to object specific rela sections and rela entries which would later be proceed when the livepatch or the livepatched object is loaded. For example, klp-convert would replace the above symbols with: $> readelf -r -W <livepatch_module_proceed_by_klp_convert> Relocation section '.klp.rela.vmlinux.text' at offset 0x5cb60 contains 1 entry: Offset Info Type Symbol's Value Symbol's Name + Addend 0000000000000068 0000003c00000002 R_X86_64_PC32 0000000000000000 .klp.sym.vmlinux.saved_command_line,0 - 4 Note that similar macro was needed also in the original version to handle more symbols of the same name (sympos). Given the above, add klp-convert tool; integrate klp-convert tool into kbuild; add data-structure and macros to enable users to annotate livepatch source code; make modpost stage compatible with livepatches; update livepatch-sample and update documentation. Testing ------- The patchset selftests build and execute on x86_64, s390x, and ppc64le for both default config (with added livepatch dependencies) and a larger SLE-15-ish config. Summary of changes in this minimal version v3 ------------------------ - klp-convert: symbol format changes (suggested by jlawrence) - samples: fixed name of added sample in Makefile (suggested by pmladek) - selftests: added ibt test case as an example (DON'T MERGE) - fixed all suggested small changes in v2 Previous versions ----------------- RFC: https://lore.kernel.org/r/cover.1477578530.git.jpoimboe@redhat.com/ v2: https://lore.kernel.org/r/f52d29f7-7d1b-ad3d-050b-a9fa8878faf2@redhat.com/ v3: https://lore.kernel.org/r/20190410155058.9437-1-joe.lawrence@redhat.com/ v4: https://lore.kernel.org/r/20190509143859.9050-1-joe.lawrence@redhat.com/ v5: (not posted) https://github.com/joe-lawrence/klp-convert-tree/tree/klp-convert-v5-devel v6: https://lore.kernel.org/r/20220216163940.228309-1-joe.lawrence@redhat.com/ v7: https://lore.kernel.org/r/20230306140824.3858543-1-joe.lawrence@redhat.com/ v1 minimal: https://lore.kernel.org/r/20231106162513.17556-1-lhruska@suse.cz/ v2 minimal: https://lore.kernel.org/r/20240516133009.20224-1-lhruska@suse.cz/