lkml.org 
[lkml]   [2021]   [Jan]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: BTFIDS: FAILED unresolved symbol udp6_sock
    On Wed, Dec 30, 2020 at 5:28 AM Jiri Olsa <jolsa@redhat.com> wrote:
    >
    > On Wed, Dec 30, 2020 at 10:03:37AM +0100, Jiri Olsa wrote:
    > > On Tue, Dec 29, 2020 at 11:28:35PM +0000, Qais Yousef wrote:
    > > > Hi Jiri
    > > >
    > > > On 12/29/20 18:34, Jiri Olsa wrote:
    > > > > On Tue, Dec 29, 2020 at 03:13:52PM +0000, Qais Yousef wrote:
    > > > > > Hi
    > > > > >
    > > > > > When I enable CONFIG_DEBUG_INFO_BTF I get the following error in the BTFIDS
    > > > > > stage
    > > > > >
    > > > > > FAILED unresolved symbol udp6_sock
    > > > > >
    > > > > > I cross compile for arm64. My .config is attached.
    > > > > >
    > > > > > I managed to reproduce the problem on v5.9 and v5.10. Plus 5.11-rc1.
    > > > > >
    > > > > > Have you seen this before? I couldn't find a specific report about this
    > > > > > problem.
    > > > > >
    > > > > > Let me know if you need more info.
    > > > >
    > > > > hi,
    > > > > this looks like symptom of the gcc DWARF bug we were
    > > > > dealing with recently:
    > > > >
    > > > > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97060
    > > > > https://lore.kernel.org/lkml/CAE1WUT75gu9G62Q9uAALGN6vLX=o7vZ9uhqtVWnbUV81DgmFPw@mail.gmail.com/#r
    > > > >
    > > > > what pahole/gcc version are you using?
    > > >
    > > > I'm on gcc 9.3.0
    > > >
    > > > aarch64-linux-gnu-gcc (Ubuntu 9.3.0-17ubuntu1~20.04) 9.3.0
    > > >
    > > > I was on pahole v1.17. I moved to v1.19 but I still see the same problem.
    > >
    > > I can reproduce with your .config, but make 'defconfig' works,
    > > so I guess it's some config option issue, I'll check later today
    >
    > so your .config has
    > CONFIG_CRYPTO_DEV_BCM_SPU=y
    >
    > and that defines 'struct device_private' which
    > clashes with the same struct defined in drivers/base/base.h
    >
    > so several networking structs will be doubled, like net_device:
    >
    > $ bpftool btf dump file ../vmlinux.config | grep net_device\' | grep STRUCT
    > [2731] STRUCT 'net_device' size=2240 vlen=133
    > [113981] STRUCT 'net_device' size=2240 vlen=133
    >
    > each is using different 'struct device_private' when it's unwinded
    >
    > and that will confuse BTFIDS logic, becase we have multiple structs
    > with the same name, and we can't be sure which one to pick
    >
    > perhaps we should check on this in pahole and warn earlier with
    > better error message.. I'll check, but I'm not sure if pahole can
    > survive another hastab ;-)
    >
    > Andrii, any ideas on this? ;-)

    It's both unavoidable and correct from the C type system's
    perspective, so there is nothing for pahole to warn about. We used to
    have (for a long time) a similar clash with two completely different
    ring_buffer structs. Eventually they just got renamed to avoid
    duplication of related structs (task_struct and tons of other). But
    both BTF dedup and CO-RE relocation algorithms are designed to handle
    this correctly, so perhaps BTFIDS should be able to handle this as
    well?

    >
    > easy fix is the patch below that renames the bcm's structs,
    > it makes the kernel to compile.. but of course the new name
    > is probably wrong and we should push this through that code
    > authors

    In this case, I think renaming generic device_private name is a good
    thing regardless.

    >
    > jirka
    >
    >
    > ---

    [...]

    \
     
     \ /
      Last update: 2021-01-02 23:29    [W:3.636 / U:0.024 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site