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

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Message-ID: <CAFhGd8qmXD6VN+nuXKtV_Uz14gzY1Kqo7tmOAhgYpTBdCnoJRQ@mail.gmail.com>
Date:   Tue, 22 Aug 2023 13:57:04 -0700
From:   Justin Stitt <justinstitt@...gle.com>
To:     Benjamin Tissoires <benjamin.tissoires@...hat.com>
Cc:     Nick Desaulniers <ndesaulniers@...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

On Tue, Aug 22, 2023 at 1:52 PM Benjamin Tissoires
<benjamin.tissoires@...hat.com> wrote:
>
> 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).

In my original email I pasted the invocation I used which includes the
headers target. What are the "proper flags" in this case?

>
> 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
> >
>