linux-kernel - Re: selftests: hid: trouble building with clang due to missing header

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Message-ID: <CAO-hwJLio2dWs01VAhCgmub5GVxRU-3RFQifviOL0OTaqj9Ktg@mail.gmail.com>
Date:   Tue, 22 Aug 2023 22:51:45 +0200
From:   Benjamin Tissoires <benjamin.tissoires@...hat.com>
To:     Nick Desaulniers <ndesaulniers@...gle.com>
Cc:     Justin Stitt <justinstitt@...gle.com>,
        linux-kselftest@...r.kernel.org, bpf@...r.kernel.org,
        linux-input@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Kees Cook <keescook@...gle.com>
Subject: Re: selftests: hid: trouble building with clang due to missing header

Justin,

On Tue, Aug 22, 2023 at 10:44 PM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> + Ben, author of commit dbb60c8a26da ("selftests: add tests for the
> HID-bpf initial implementation")
>
> On Tue, Aug 22, 2023 at 1:34 PM Justin Stitt <justinstitt@...gle.com> wrote:
> >
> > Hi, I'd like to get some help with building the kselftest target.
> >
> > I am running into some warnings within the hid tree:
> > | progs/hid_bpf_helpers.h:9:38: error: declaration of 'struct
> > hid_bpf_ctx' will \
> > |       not be visible outside of this function [-Werror,-Wvisibility]
> > |     9 | extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
> > |       |                                      ^
> > | progs/hid.c:23:35: error: incompatible pointer types passing 'struct
> > hid_bpf_ctx *' \
> > |       to parameter of type 'struct hid_bpf_ctx *'
> > [-Werror,-Wincompatible-pointer-types]
> > |    23 |         __u8 *rw_data = hid_bpf_get_data(hid_ctx, 0 /*
> > offset */, 3 /* size */);
> >
> > This warning, amongst others, is due to some symbol not being included.
> > In this case, `struct hid_bpf_ctx` is not being defined anywhere that I
> > can see inside of the testing tree itself.
> >
> > Instead, `struct hid_bpf_ctx` is defined and implemented at
> > `include/linux/hid_bpf.h`. AFAIK, I cannot just include this header as
> > the tools directory is a separate entity from kbuild and these tests are
> > meant to be built/ran without relying on kernel headers. Am I correct in
> > this assumption? At any rate, the include itself doesn't work. How can I
> > properly include this struct definition and fix the warning(s)?
> >
> > Please note that we cannot just forward declare the struct as it is
> > being dereferenced and would then yield a completely different
> > error/warning for an incomplete type. We need the entire implementation
> > for the struct included.
> >
> > Other symbols also defined in `include/linux/hid_bpf.h` that we need are
> > `struct hid_report_type` and `HID_BPF_FLAG...`
> >
> > Here's the invocation I am running to build kselftest:
> > `$ make LLVM=1 ARCH=x86_64 mrproper headers && make LLVM=1 ARCH=x86_64
> > -j128 V=1 -C tools/testing/selftests`

I think I fixed the same issue in the script I am running to launch
those tests in a VM. This was in commit
f9abdcc617dad5f14bbc2ebe96ee99f3e6de0c4e (in the v6.5-rc+ series).

And in the commit log, I wrote:
```
According to commit 01d6c48a828b ("Documentation: kselftest:
"make headers" is a prerequisite"), running the kselftests requires
to run "make headers" first.
```

So my assumption is that you also need to run "make headers" with the
proper flags before compiling the selftests themselves (I might be
wrong but that's how I read the commit).

Cheers,
Benjamin

> >
> > If anyone is currently getting clean builds of kselftest with clang,
> > what invocation works for you?
> >
> >
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1698
> > Full-build-log:
> > https://gist.github.com/JustinStitt/b217f6e47c1d762e5e1cc6c3532f1bbb
> > (V=1)
> >
> > Thanks.
> > Justin
>
>
>
> --
> Thanks,
> ~Nick Desaulniers
>