kernel March 2018

kernel@lists.fedoraproject.org

11 participants
12 discussions

Please remember to give karma for F26 kernels
by Laura Abbott 29 Mar '18

29 Mar '18

As we approach the release of F28 we've started to see a fall off in karma for F26. If you have an F26 system around, please remember to test new kernels and give karma. Thanks, Laura

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Re: Feature request: improved build-id generation
by Laura Abbott 26 Mar '18

26 Mar '18

ArOn 03/16/2018 11:37 AM, Cary Coutant wrote: >>> Then I'm stating my case poorly. I want a way to inject additional >>> data into the has computation. >> >> At one point, we proposed doing this via a linker- or assembler-oriented >> extra "salt" parameter, which would be hashed into the buildid. This >> would most naturally be a n-v-r-a string, so the build is reproducible. >> Such a salt could be naturally injected via an environment variable set >> by rpmbuild. >> >> https://bugzilla.redhat.com/show_bug.cgi?id=1002341 (salt!) >> https://bugzilla.redhat.com/show_bug.cgi?id=1550152 (life without salt) > > I don't have a problem with adding a --build-id-salt="some arbitrary > string" option, and I think "salt" is exactly the right term for this. > I'd much prefer providing that than having you use a linker script. > (I'm somewhat puzzled that you find the linker script option less > objectionable than an object file with a note section.) > > As Nick said earlier, it's not that we don't care about your feature > request. I simply wanted to explore the options, and I gave you a > couple of options that require no new features at all. > > My other comments have been about the unnecessary conflating of a new > option like --build-id-salt with the choice of hashing algorithm. > At least in the kernel we already have the infrastructure for customizations to linker scripts so it's fairly easy to expand on that. I have a prototype which should work, I just need to clean it up for review to see if it's feasible to merge vs. adding a --build-id-salt option. Thanks, Laura > -cary >

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[PATCH] kernel-tools.spec: Adding bpftool package
by Jiri Olsa 26 Mar '18

26 Mar '18

hi, please consider attached change that adds bpftool sub package to be generated within kernel-tools spec. The reason to have bpftool in separate rpm is to have minimal dependency for sosreport that will depend on it. The bpftool rpm contains following files: $ rpm -ql -p bpftool-4.16.0-0.rc5.git0.1.fc29.x86_64.rpm /etc/bash_completion.d/bpftool /usr/sbin/bpftool /usr/share/man/man8/bpftool-cgroup.8.gz /usr/share/man/man8/bpftool-map.8.gz /usr/share/man/man8/bpftool-prog.8.gz /usr/share/man/man8/bpftool.8.gz thanks, jirka --- kernel-tools.spec | 23 ++++++++++++++++++++++- 1 file changed, 22 insertions(+), 1 deletion(-) diff --git a/kernel-tools.spec b/kernel-tools.spec index c8cbcff104fd..2d190d0497b6 100644 --- a/kernel-tools.spec +++ b/kernel-tools.spec @@ -69,7 +69,7 @@ BuildRequires: kmod, patch, bash, tar, git BuildRequires: bzip2, xz, findutils, gzip, m4, perl-interpreter, perl(Carp), perl-devel, perl-generators, make, diffutils, gawk BuildRequires: gcc, binutils, redhat-rpm-config, hmaccalc BuildRequires: net-tools, hostname, bc, elfutils-devel -BuildRequires: zlib-devel binutils-devel newt-devel python2-devel perl(ExtUtils::Embed) bison flex xz-devel +BuildRequires: zlib-devel binutils-devel newt-devel python2-devel python2-docutils perl(ExtUtils::Embed) bison flex xz-devel BuildRequires: audit-libs-devel glibc-devel glibc-static %ifnarch s390x %{arm} BuildRequires: numactl-devel @@ -164,6 +164,13 @@ Provides: kernel-tools-devel This package contains the development files for the tools/ directory from the kernel source. +%package -n bpftool +Summary: Inspection and simple manipulation of eBPF programs and maps +License: GPLv2 +%description -n bpftool +This package contains the bpftool, which allows inspection and simple +manipulation of eBPF programs and maps. + %prep %setup -q -n kernel-%{kversion}%{?dist} -c @@ -233,6 +240,9 @@ popd pushd tools/gpio/ make popd +pushd tools/bpf/bpftool +make +popd ### ### install @@ -299,6 +309,9 @@ popd pushd tools/kvm/kvm_stat make INSTALL_ROOT=%{buildroot} install-tools popd +pushd tools/bpf/bpftool +make DESTDIR=%{buildroot} prefix=%{_prefix} bash_compdir=%{_sysconfdir}/bash_completion.d/ mandir=%{_mandir} install doc-install +popd ### ### scripts @@ -368,6 +381,14 @@ popd %{_includedir}/cpufreq.h %{_includedir}/cpuidle.h +%files -n bpftool +%{_sbindir}/bpftool +%{_sysconfdir}/bash_completion.d/bpftool +%{_mandir}/man8/bpftool-cgroup.8.gz +%{_mandir}/man8/bpftool-map.8.gz +%{_mandir}/man8/bpftool-prog.8.gz +%{_mandir}/man8/bpftool.8.gz + %changelog * Mon Mar 12 2018 Jeremy Cline <jeremy(a)jcline.org> - 4.16.0-0.rc5.git0.1 - Linux 4.16-rc5 -- 2.13.6

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Kernel change broken wireguard builds in unexpected way
by Bruno Wolff III 25 Mar '18

25 Mar '18

Normally when a kernel change causes a problem there is a compile error, but I'm seeing a make problem. Builds work with kernel-4.16.0-0.rc6.git0.2.fc28.x86_64, but not with kernel-4.16.0-0.rc6.git2.2.fc29.x86_64. The error output is: [bruno@cerberus src]$ make KERNELDIR=/lib/modules/4.16.0-0.rc6.git2.2.fc29.x86_64/build clean all CLEAN /home/bruno/WireGuard/src/.tmp_versions CLEAN /home/bruno/WireGuard/src/Module.symvers CLEAN /home/bruno/WireGuard/src/tools/{wg,*.o,*.d} make[2]: *** No rule to make target '/home/bruno/WireGuard/src/main.o', needed by '/home/bruno/WireGuard/src/wireguard.o'. Stop. make[1]: *** [Makefile:1556: _module_/home/bruno/WireGuard/src] Error 2 make: *** [Makefile:36: module] Error 2 Is this something Fedora specific? I wouldn't expect an rc6 change to cause an issue like this. I'm going to try building an upstream kernel to see if the problem is upstream, but I probably won't have an answer until tomorrow.

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Re: Feature request: improved build-id generation
by Frank Ch. Eigler 16 Mar '18

16 Mar '18

Andy Lutomirski <luto(a)kernel.org> writes: > [...] > Then I'm stating my case poorly. I want a way to inject additional > data into the has computation. At one point, we proposed doing this via a linker- or assembler-oriented extra "salt" parameter, which would be hashed into the buildid. This would most naturally be a n-v-r-a string, so the build is reproducible. Such a salt could be naturally injected via an environment variable set by rpmbuild. https://bugzilla.redhat.com/show_bug.cgi?id=1002341 (salt!) https://bugzilla.redhat.com/show_bug.cgi?id=1550152 (life without salt) - FChE

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Re: Feature request: improved build-id generation
by Laura Abbott 16 Mar '18

16 Mar '18

On 03/15/2018 06:32 AM, Nick Clifton wrote: > Hi Mark, > >> That might be an interesting alternative. Could you use this for e.g. >> inserting a .comment section fragment with an unique (version) string? >> That would be stripped away, but should still count for the build-id >> hash calculation. > > If you know the value you want to store ahead of time, then it is easy: > > % cat comment.t > SECTIONS > { > .comment (INFO) : > { > BYTE (0x12); > BYTE (0x34); > BYTE (0x56); > BYTE (0x78); > } > } > > % gcc hello.c -Wl,comment.t > % readelf -x.comment a.out > > Hex dump of section '.comment': > 0x00000000 4743433a 2028474e 55292037 2e332e31 GCC: (GNU) 7.3.1 > 0x00000010 20323031 38303133 30202852 65642048 20180130 (Red H > 0x00000020 61742037 2e332e31 2d322900 4743433a at 7.3.1-2).GCC: > 0x00000030 2028474e 55292037 2e322e31 20323031 (GNU) 7.2.1 201 > 0x00000040 37303931 35202852 65642048 61742037 70915 (Red Hat 7 > 0x00000050 2e322e31 2d322900 12345678 .2.1-2)..4Vx > > (Note how the value has been appended to the .comment section). > > Unfortunately the linker does not have a STRING() operator to insert > ascii codes into a section, so you have to construct the bytes by > hand. Eg: > > % cat comment.t > SECTIONS > { > .comment (INFO) : > { > BYTE (0x41); > BYTE (0x42); > BYTE (0x43); > BYTE (0x00); > } > } > > % gcc hello.c -Wl,comment.t > % readelf -p.comment a.out > > String dump of section '.comment': > [ 0] GCC: (GNU) 7.3.1 20180130 (Red Hat 7.3.1-2) > [ 2c] GCC: (GNU) 7.2.1 20170915 (Red Hat 7.2.1-2) > [ 58] ABC > > A simple perl or python script could be used to create the comment.t > linker script fragment. > > Cheers > Nick > I think this approach looks promising. I'm going to see about prototyping this approach. Thanks, Laura

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Re: Feature request: improved build-id generation
by Mark Wielaard 15 Mar '18

15 Mar '18

On Thu, 2018-03-15 at 11:36 +0000, Nick Clifton wrote: > > > I think Fedora should be able to ask its tool chain to insert the > > > extra data rather than hacking it in after the fact. > > I'll just note that another way to insert data into a linked binary > is to use a linker script fragment referenced from the command line. > I doubt that this would be any better than creating a "magic .o" file, > but it is worth knowing. That might be an interesting alternative. Could you use this for e.g. inserting a .comment section fragment with an unique (version) string? That would be stripped away, but should still count for the build-id hash calculation. Cheers, Mark

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Re: Feature request: improved build-id generation
by Mark Wielaard 15 Mar '18

15 Mar '18

On Thu, 2018-03-15 at 00:45 -0700, Cary Coutant wrote: > > > To inject explicit out-of-band data into the hash computation, you > > > could insert an object with nothing but a note section, or even use > > > --defsym to create a symbol table entry with your extra key(s). > > > > Fedora wants to insert extra data into the build-id of all packages in > > its repository, and it does so right now by post-processing the > > package. This is ugly, and it flat-out doesn't work for the kernel, > > which is apparently breaking a legitimate debugging use case. > > > > I think Fedora should be able to ask its tool chain to insert the > > extra data rather than hacking it in after the fact. Asking Fedora to > > use --defsym for this purpose is IMO a non-starter, as is asking > > Fedora to come up with some magic .o file and linking it into every > > object. > > I understand your objection to the magic .o file, but why exactly is > --defsym a "non-starter"? It's pretty close to what you're asking for > (except for the spelling), it's already available, and it has the > advantage of adding the extra data to the binary in a form where it > can be easily extracted (e.g., with "nm"). > > I don't understand the need for forcing two otherwise-identical > binaries to have different build ids, simply because they're part of > different distributions. Perhaps it would help if you could explain > why you need that. In theory two different build environments could produce the same identical binary. Even different source files could if they express the same algorithm and the compiler optimizes them the same way. But you might still want to identify which came from which build. The build-id is used to identify the build (environment) that produced the binary. If the build environment is identical then in theory it should produce identical binaries and build-ids. But this isn't necessarily the other way around. For a distro it is nice to have unique build-id identifiers for different package version builds. Then if you just have e.g. a core file with a build-id in it, you can map it back to which package build it came from. The linker doesn't see the whole build environment, but it often has enough to differentiate if there is debuginfo involved, which contains the source file paths, compiler versions, command line options, etc. I think in the case Andy is interested in, the vdso, just isn't "unique" enough (it contains mostly assembly without debuginfo). The vdso is also slightly special because it is build and then "inserted" into the kernel image (so it can be mapped into the process space at runtime). Which makes it difficult to "post-process". If using new command line flags is out of the question, could the linker use an environment variable as seed for the build-id hash computation? Then a package build could just set e.g. BUILD_ID_ENV="<package-version>". That could also be used for other purposes to capture anything from the build environment that might make a build unique. Cheers, Mark

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proper debuginfo for embedded vDSO
by Laura Abbott 15 Mar '18

15 Mar '18

Hi, The kernel still doesn't have 100% parallel debuginfo because we can't update the vDSO binary embedded in the the image. I'd like to see about updating debugedit to be smart enough to do the recalculation of the buildid for both the vmlinux and the embedded vDSO. I'd like to avoid too tight a coupling between the kernel and debugedit so if we want/need to change how the vDSO is generated it won't break too many things. My idea is to stick the location of the vDSO in an ELF note so debugedit knows where to look. As long as the kernel can generate this section correctly, debugedit can find the embedded build-id and update accordingly. Obviously this would need approval from a wider audience but I'm looking to get some early feedback before I spend too much time prototyping something that has no chance of going anywhere. Thoughts? Thanks, Laura

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Re: Feature request: improved build-id generation
by Linus Torvalds 15 Mar '18

15 Mar '18

On Wed, Mar 14, 2018 at 6:01 PM, Alan Modra <amodra(a)gmail.com> wrote: > On Wed, Mar 14, 2018 at 04:40:25PM -0700, Andy Lutomirski wrote: >> >> I realize that the security issue here is barely relevant, but git’s use of SHA1 is *not* okay, and git is migrating away for a reason. > > Hmm, that's news to me. Heh, I've always been a bit suspicious of > git's reliability. ;-) I'm afraid Andy has listened to a few too many hard-liner security people - the bad kind that don't know shades of gray, and the kind that aren't generally worth listening to. SHA1 with the known attack weakness fixed (aka "Hardened SHA1", the way git already does) in a non-certificate environment is fine. The fact is, data identification is different from some kind of security that depends on the key. I wouldn't use even hardened SHA1 for some security certificate. But for file ID's? Andy is confused. Linus

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kernel March 2018