132 lines
6.5 KiB
Org Mode
132 lines
6.5 KiB
Org Mode
#+hugo_base_dir: ../
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* DONE Ubuntu debuginfod and source code indexing :english:ubuntu:debuginfod:debian:free_software:gdb:
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CLOSED: [2023-05-13 Sat 16:43]
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:PROPERTIES:
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:EXPORT_FILE_NAME: ubuntu-debuginfod-source-code-indexing
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:END:
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You might remember that in my [[/posts/debuginfod-is-coming-to-ubuntu/][last post]] about the [[https://debuginfod.ubuntu.com][Ubuntu debuginfod
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service]] I talked about wanting to extend it and make it index and
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serve source code from packages. I'm excited to announce that this is
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now a reality since the Ubuntu Lunar (23.04) release.
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The feature should work for a lot of packages from the archive, but
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not all of them. Keep reading to better understand why.
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** The problem
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While debugging a package in Ubuntu, one of the first steps you need
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to take is to install its source code. There are some problems with
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this:
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- =apt-get source= required =dpkg-dev= to be installed, which ends up
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pulling in a lot of other dependencies.
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- GDB needs to be taught how to find the source code for the package
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being debugged. This can usually be done by using the =dir=
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command, but finding the proper path to be is usually not trivial,
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and you find yourself having to use more "complex" commands like
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=set substitute-path=, for example.
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- You have to make sure that the version of the source package is the
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same as the version of the binary package(s) you want to debug.
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- If you want to debug the libraries that the package links against,
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you will face the same problems described above for each library.
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So yeah, not a trivial/pleasant task after all.
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** The solution...
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Debuginfod can index source code as well as debug symbols. It is
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smart enough to keep a relationship between the source package and the
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corresponding binary's Build-ID, which is what GDB will use when
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making a request for a specific source file. This means that, just
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like what happens for debug symbol files, the user does not need to
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keep track of the source package version.
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While indexing source code, debuginfod will also maintain a record of
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the relative pathname of each source file. No more fiddling with
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paths inside the debugger to get things working properly.
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Last, but not least, if there's a need for a library source file and
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if it's indexed by debuginfod, then it will get downloaded
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automatically as well.
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** ... but not a perfect one
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In order to make debuginfod happy when indexing source files, I had to
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patch =dpkg= and make it always use =-fdebug-prefix-map= when
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compiling stuff. This GCC option is used to remap pathnames inside
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the DWARF, which is needed because in Debian/Ubuntu we build our
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packages inside chroots and the build directories end up containing a
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bunch of random cruft (like =/build/ayusd-ASDSEA/something/here=). So
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we need to make sure the path prefix (the =/build/ayusd-ASDSEA= part)
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is uniform across all packages, and that's where =-fdebug-prefix-map=
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helps.
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This means that the package *must* honour =dpkg-buildflags= during its
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build process, otherwise the magic flag won't be passed and your DWARF
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will end up with bogus paths. This should not be a big problem,
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because most of our packages do honour =dpkg-buildflags=, and those
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who don't should be fixed anyway.
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** ... especially if you're using LTO
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Ubuntu enables [[https://gcc.gnu.org/onlinedocs/gccint/LTO-Overview.html][LTO]] by default, and unfortunately we are affected by an
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[[https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109805][annoying (and complex) bug]] that results in those bogus pathnames not
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being properly remapped. The bug doesn't affect all packages, but if
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you see GDB having trouble finding a source file whose full path
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starts without =/usr/src/...=, that is a good indication that you're
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being affected by this bug. Hopefully we should see some progress in
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the following weeks.
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** Your feedback is important to us
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If you have any comments, or if you found something strange that looks
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like a bug in the service, please reach out. You can either send an
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email to my [[https://lists.sr.ht/~sergiodj/public-inbox][public inbox]] (see below) or file a bug against the
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[[https://bugs.launchpad.net/ubuntu-debuginfod][ubuntu-debuginfod project on Launchpad]].
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* DONE Novo blog, novos links :pt_br:portugues:
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CLOSED: [2023-04-20 Thu 21:38]
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:PROPERTIES:
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:EXPORT_FILE_NAME: novo-blog-novos-links
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:END:
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Eu sei que não posto aqui há algum tempo, mas gostaria de avisar os
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meus leitores (hã!?) de que eu troquei a engine do blog pro [[https://gohugo.io][Hugo]].
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Além disso, vocês vão notar que as URLs dos posts mudaram também
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(elas não têm mais data, agora são só compostas pelo nome do post; mas
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veja abaixo), e que também houve uma mudança na tag =pt_br=:
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futuramente eu pretendo parar de postar coisas nela, e vou postar
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somente usando a tag [[/tags/portugues][=portugues=]]. Se você acompanha o RSS/ATOM da tag
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=pt_br=, por favor atualize o link.
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As URLs antigas ainda vão funcionar porque elas estão sendo
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redirecionadas pro lugar correto (cortesia do =mod_rewrite=). De
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qualquer modo, se você salvou alguma URL de um post antigo, sugiro que
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a atualize.
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No mais, tudo deve funcionar "como de costume" (TM). Estou postando
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direto do Emacs (usando [[https://gohugo.io][ox-hugo]]), e criei um setup bacana no [[https://sr.ht][Sourcehut]]
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pra automaticamente publicar os posts assim que eu der o push deles
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pro git. Hm, isso na verdade seria um bom tópico pra um post...
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* DONE New blog, new links :en_us:english:
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CLOSED: [2023-04-20 Thu 21:26]
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:PROPERTIES:
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:EXPORT_FILE_NAME: new-blog-new-links
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:END:
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I know I haven't posted in a while, but I'd like to let my readers
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(who!?) know that I've switched my blog's engine to [[https://gohugo.io][Hugo]]. Along with
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that change, there are also changes to post URLs (no more dates, only
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the post name; but see below) and also a change to the =en_us= tag:
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eventually, I will stop posting things under it and start posting
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solely under [[/tags/english][=english=]]. If you're subscribed to the =en_us= RSS/ATOM
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feed, please update it accordingly.
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The old URLs should still work because they're being redirected to the
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correct path now (thanks, =mod_rewrite=). Either way, if you have
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bookmarked some old post URL I'd suggest that you update it.
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Other than that, everything should be "the same" (TM). I'm posting
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from Emacs (using [[https://ox-hugo.scripter.co][ox-hugo]]), and made quite a cool setup with [[https://sr.ht][Sourcehut]]
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in order to automatically publish posts when I push them to the git
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repo. Hm, his would actually be a good topic for a post...
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