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  • efficient way to detect linker script files?

    From Serafeim (Serafi) Zanikolas@21:1/5 to All on Tue Oct 22 23:10:02 2024
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    hi,

    I'd like to discover all installed linker scripts, for the purposes of #823531 (check for broken linker scripts files). it's not clear to me that there's a convention I could rely on to avoid brute forcing filetype detection of everything under /lib/${DEB_HOST_GNU_TYPE} (that'd be /lib/x86_64-linux-gnu in my system).

    my intuition would be to only look in /lib/${DEB_HOST_GNU_TYPE}/ldscripts, and ignore *.so named files, but a few linker scripts break both of those assumptions:

    /lib/x86_64-linux-gnu/libc.so
    /lib/x86_64-linux-gnu/libm.a
    /lib/x86_64-linux-gnu/libusb.so

    are these misplaced and misnamed? I didn't find any relevant guidance skimming through policy.

    thanks,
    serafi

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  • From Guillem Jover@21:1/5 to All on Wed Oct 23 01:50:01 2024
    Hi!

    On Tue, 2024-10-22 at 23:00:29 +0200, Serafeim (Serafi) Zanikolas wrote:
    I'd like to discover all installed linker scripts, for the purposes of #823531 (check for broken linker scripts files). it's not clear to me
    that there's a convention I could rely on to avoid brute forcing
    filetype detection of everything under /lib/${DEB_HOST_GNU_TYPE}
    (that'd be /lib/x86_64-linux-gnu in my system).

    The current convention is to have "GNU ld script" on the first line,
    by way of ldconfig(8) otherwise complaining about an unknown file format.

    Perhaps if you want to avoid having to open all the files, then a
    heuristic could be to discard files bigger than some threshold. Linker
    scripts should in general not be that big.

    my intuition would be to only look in /lib/${DEB_HOST_GNU_TYPE}/ldscripts, and ignore *.so named files, but a few linker scripts break both of those assumptions:

    I think checking for stuff under /ldscripts/ might also be good, but I
    assume the bug report you mention was precisely concerned about *.so or
    *.a linker scripts under /usr/lib. These are needed when you want to transparently move functions around or provide them in different
    libraries but not require users to specify different libraries to link
    to, while not breaking compilation.

    /lib/x86_64-linux-gnu/libc.so
    /lib/x86_64-linux-gnu/libm.a
    /lib/x86_64-linux-gnu/libusb.so

    Another one I'm aware of would be libbsd.so, where it was added to transparently redirect code linking against it that used MD5 functions
    into linking against libmd.so when needed. Instead of requiring a
    SOVERSION bump.

    are these misplaced and misnamed? I didn't find any relevant guidance skimming through policy.

    These are fine, but perhaps not very common. I don't think the Debian
    policy has anything about it, I guess because of the above.

    Thanks,
    Guillem

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  • From Serafeim (Serafi) Zanikolas@21:1/5 to All on Wed Oct 23 21:50:01 2024
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    hola Guillem,

    thanks so much for such a thorough response :)

    to summarize, I'll look for:

    - files matching /lib/${DEB_HOST_GNU_TYPE}/*.{a,so} that are below a certain
    size and contain "GNU ld script" in the first line (if they're text files)
    - all files under /lib/${DEB_HOST_GNU_TYPE}/ldscripts

    moltissimes gràcies,
    serafi

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