[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] livepatch-build: What does getting no output from "readelf -wi xen-syms" usually mean?
On 12/27/19 5:06 PM, Andrew Cooper wrote: > On 02/12/2019 08:22, Andy Smith wrote: >> Hi, >> >> I've been looking into live patching for the first time. > > CC'ing livepatch maintainers. > >> >> Starting with a 4.12.1 build: >> >> $ cd ~/dev >> $ ls -l >> total 8 >> drwxr-xr-x 3 andy andy 4096 Oct 25 16:11 xen >> drwxr-xr-x 6 andy andy 4096 Dec 2 01:16 livepatch-build-tools >> >> (there is already a 4.12.1 hypervisor built in /xen and is what's >> running on this host with build_id >> b18af774b56b0c98cfa6940a725ba2ba26066929) >> >> $ cp -a xen xen-lptest >> $ cd livepatch-build-tools >> $ ./livepatch-build -j 1 -s /home/andy/dev/xen-lptest/xen-4.12.1 -c >> /home/andy/dev/xen-lptest/xen-4.12.1/xen/.config -p ./lptest.patch -o lptest >> -d --depends b18af774b56b0c98cfa6940a725ba2ba26066929 >> Building LivePatch patch: lptest >> >> Xen directory: /home/andy/dev/xen-lptest/xen-4.12.1 >> Patch file: /home/andy/dev/livepatch-build-tools/lptest.patch >> .config file: /home/andy/dev/xen-lptest/xen-4.12.1/xen/.config >> Output directory: /home/andy/dev/livepatch-build-tools/xsa310 > > As a note, XSA-310 isn't safe to livepatch. > > While (in general) you can build a livepatch, applying it is not safe > because the before/after logic is not symmetric with how references are > taken. > > Depending on the exact interaction of applying the livepatch with > pagetable deferral operations (VM start,migrate,shutdown, or large > quantities of pagetable changes, e.g. a fork() system call), you can end > up with too few or many references dropped. Too few generally results > in an unkillable zombie domain, while too many will hit various BUG()s > in the MM code and take the system down. > >> ================================================ >> >> Perform full initial build with 1 CPU(s)... >> Reading special section data >> ERROR: can't find special struct size. >> >> So it seems it completed the initial build without error but looking >> at the livepatch-build script it runs readelf like this: >> >> $ readelf -wi lptest/xen-syms >> $ >> >> For me this produces no output. I've probably done something simple >> wrong. Does that indicate some simple mistake in my process? > Your process looks correct. You need to use readelf from binutils. Are you perhaps using some other readelf (e.g. from busybox) which gives unexpected results? Even if lptest/xen-syms is invalid or empty, readelf should still give some error output. -- Ross Lagerwall _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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