Messages in this thread | | | Subject | Re: [PATCH v2 0/8] klp-convert | From | Joe Lawrence <> | Date | Tue, 26 Mar 2019 17:03:02 -0400 |
| |
On 3/26/19 4:18 PM, Joao Moreira wrote: > > > On 3/18/19 4:18 PM, Joe Lawrence wrote: >> On Fri, Mar 01, 2019 at 11:13:05AM -0300, Joao Moreira wrote: >>> Livepatches may use symbols which are not contained in its own scope, >>> and, because of that, may end up compiled with relocations that will >>> only be resolved during module load. Yet, when the referenced symbols are >>> not exported, solving this relocation requires information on the object >>> that holds the symbol (either vmlinux or modules) and its position inside >>> the object, as an object may contain multiple symbols with the same name. >>> Providing such information must be done accordingly to what is specified >>> in Documentation/livepatch/module-elf-format.txt. >>> >>> Currently, there is no trivial way to embed the required information as >>> requested in the final livepatch elf object. klp-convert solves this >>> problem in two different forms: (i) by relying on a symbol map, which is >>> built during kernel compilation, to automatically infers the relocation >>> targeted symbol, and, when such inference is not possible (ii) by using >>> annotations in the elf object to convert the relocation accordingly to >>> the specification, enabling it to be handled by the livepatch loader. >>> >>> Given the above, add support for symbol mapping in the form of >>> Symbols.list file; add klp-convert tool; integrate klp-convert tool into >>> kbuild; make livepatch modules discernible during kernel compilation >>> pipeline; 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. >>> >>> The patch was tested under three use-cases: >>> >>> use-case 1: There is a relocation in the lp that can be automatically >>> resolved by klp-convert (tested by removing the annotations from >>> samples/livepatch/livepatch-annotated-sample.c) >>> >>> use-case 2: There is a relocation in the lp that cannot be automatically >>> resolved, as the name of the respective symbol appears in multiple >>> objects. The livepatch contains an annotation to enable a correct >>> relocation - reproducible with this livepatch sample: >>> www.livewire.com.br/suse/klp/livepatch-sample.1.c >>> >>> use-case 3: There is a relocation in the lp that cannot be automatically >>> resolved similarly as 2, but no annotation was provided in the livepatch, >>> triggering an error during compilation - reproducible with this livepatch >>> sample: www.livewire.com.br/suse/klp/livepatch-sample.2.c >>> >>> In comparison with v1, this version of the patch-set: >>> - was rebased to kernel 4.19 >>> - adds a Symbols.list versioning information >>> - brings bug fixes and code improvements to klp-convert sources >>> >>> This is a patch-set repost, given that a typo in a mail address prevented >>> the original submission from being posted to lkml. >>> >>> [ ... snip ... ] >> >> Hi Joao, >> >> Apologies for taking so long to get to this patchset, but I finally >> spent last week reviewing and testing. My goal was to write a klp >> self-test based on the implementation and your sample module. Along the >> way I spotted a few minor bugs and other small suggestions. Instead of >> dumping a bunch of code or patch content in my replies, I posted my >> rebase and modified branch here: >> >> https://github.com/joe-lawrence/linux/tree/klp-convert-v2-rebase-review >> >> I added subject line [squash] tags to individual commits that should be >> considered fixups for patches in this set. Those commit logs also >> contain [joe: description] tags and my sign-offs for that purpose as >> well. >> >> Hopefully this form of feedback will be easy to digest. I'll reply to >> the individual patchs here with high-level comments and a pointer to the >> corresponding github patch. Let me know if there are any questions. If >> it is easier to simply repost as a v3 with those changes, I can do that >> as well -- whichever method is easier for you. >> > > Hi Joe, again thanks a lot for the review. To the things which I had > something to say, I already replied to the respective messages. If none > has issues with the fix for the ppc64le .TOC. symbols issue (on patch > 5/8) and with the fix for the multi-used-m Makefile (on patch 2/8), I > guess we are good for moving forward to a v3. >> If you don't mind, this is fine by me that you squash the changes and > post the newer version. In fact, I can't figure out why my patch > submissions did not appear in lkml (if someone knows what could be the > reason, please, let me know), so I guess it would be nice to have it > reachable this time.
I can do that... what I will do is collate all the comments, squash revisions, and update logs accordingly. I'll post it up on github to let the 0-day lkp bot run through it and you can take a look to double check the series, attributions, etc before I post it here.
BTW, something I *just* noticed when putting together that toy out-of-tree module to test out multi-object livepatch modules is that we aren't considering out-of-tree symbols in Symbols.list.
Perhaps we can save that for v4 or beyond, but maybe we want to re-arrange the klp-convert arguments to "klp-convert <input.ko> <out.ko> <Symbols.list> [Symbols.list ...]" where we treat everything after <out.ko> as a symbol list file? (This would assume we would generate a separate out-of-tree module Symbols.list file.) /thinking-out-loud
-- Joe
| |