Re: [PATCH 4/3] selftests/hid: more fixes to build with older kernel

[Eduard Zingerman]

On Fri, 2023-08-25 at 18:23 +0000, Justin Stitt wrote:
> On Fri, Aug 25, 2023 at 10:36:30AM +0200, Benjamin Tissoires wrote:
> > These fixes have been triggered by [0]:
> > basically, if you do not recompile the kernel first, and are
> > running on an old kernel, vmlinux.h doesn't have the required
> > symbols and the compilation fails.
> > 
> > The tests will fail if you run them on that very same machine,
> > of course, but the binary should compile.
> > 
> > And while I was sorting out why it was failing, I realized I
> > could do a couple of improvements on the Makefile.
> > 
> > [0] https://lore.kernel.org/linux-input/56ba8125-2c6f-a9c9-d498-0ca1c153dcb2@xxxxxxxxxx/T/#t
> > 
> > Signed-off-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>
> > ---
> > Benjamin Tissoires (3):
> >       selftests/hid: ensure we can compile the tests on kernels pre-6.3
> >       selftests/hid: do not manually call headers_install
> >       selftests/hid: force using our compiled libbpf headers
> > 
> >  tools/testing/selftests/hid/Makefile                | 10 ++++------
> >  tools/testing/selftests/hid/progs/hid.c             |  3 ---
> >  tools/testing/selftests/hid/progs/hid_bpf_helpers.h | 20 ++++++++++++++++++++
> >  3 files changed, 24 insertions(+), 9 deletions(-)
> > ---
> > base-commit: 1d7546042f8fdc4bc39ab91ec966203e2d64f8bd
> > change-id: 20230825-wip-selftests-9a7502b56542
> > 
> > Best regards,
> > --
> > Benjamin Tissoires <bentiss@xxxxxxxxxx>
> > 
> 
> Benjamin, thanks for the work here. Your series fixed up _some_ of the
> errors I had while building on my 6.3.11 kernel. I'm proposing a single
> patch that should be applied on top of your series that fully fixes
> _all_ of the build errors I'm experiencing.
> 
> Can you let me know if it works and potentially formulate a new series
> so that `b4 shazam` applies it cleanly?
> 
> PATCH BELOW
> ---
> From 5378d70e1b3f7f75656332f9bff65a37122bb288 Mon Sep 17 00:00:00 2001
> From: Justin Stitt <justinstitt@xxxxxxxxxx>
> Date: Fri, 25 Aug 2023 18:10:33 +0000
> Subject: [PATCH 4/3] selftests/hid: more fixes to build with older kernel
> 
> I had to use the clever trick [1] on some other symbols to get my builds
> working.
> 
> Apply this patch on top of Benjamin's series [2].
> 
> This is now a n=4 patch series which has fixed my builds when running:
> > $ make LLVM=1 -j128 ARCH=x86_64 mrproper headers
> > $ make LLVM=1 -j128 ARCH=x86_64 -C tools/testing/selftests TARGETS=hid
> 
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/testing/selftests/bpf/progs/bpf_iter.h#n3
> [2]: https://lore.kernel.org/all/20230825-wip-selftests-v1-0-c862769020a8@xxxxxxxxxx/
> Signed-off-by: Justin Stitt <justinstitt@xxxxxxxxxx>
> ---
>  .../selftests/hid/progs/hid_bpf_helpers.h     | 29 +++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 
> diff --git a/tools/testing/selftests/hid/progs/hid_bpf_helpers.h b/tools/testing/selftests/hid/progs/hid_bpf_helpers.h
> index 749097f8f4d9..e2eace2c0029 100644
> --- a/tools/testing/selftests/hid/progs/hid_bpf_helpers.h
> +++ b/tools/testing/selftests/hid/progs/hid_bpf_helpers.h
> @@ -7,12 +7,26 @@
> 
>  /* "undefine" structs in vmlinux.h, because we "override" them below */
>  #define hid_bpf_ctx hid_bpf_ctx___not_used
> +#define hid_report_type hid_report_type___not_used
> +#define hid_class_request hid_class_request___not_used
> +#define hid_bpf_attach_flags hid_bpf_attach_flags___not_used
>  #include "vmlinux.h"
>  #undef hid_bpf_ctx
> +#undef hid_report_type
> +#undef hid_class_request
> +#undef hid_bpf_attach_flags
> 
>  #include <bpf/bpf_helpers.h>
>  #include <bpf/bpf_tracing.h>
> +#include <linux/const.h>
> 
> +enum hid_report_type {
> +	HID_INPUT_REPORT		= 0,
> +	HID_OUTPUT_REPORT		= 1,
> +	HID_FEATURE_REPORT		= 2,
> +
> +	HID_REPORT_TYPES,
> +};
> 
>  struct hid_bpf_ctx {
>  	__u32 index;
> @@ -25,6 +39,21 @@ struct hid_bpf_ctx {
>  	};
>  };

Note, vmlinux.h has the following preamble/postamble:

    #ifndef BPF_NO_PRESERVE_ACCESS_INDEX
    #pragma clang attribute push (__attribute__((preserve_access_index)), apply_to = record)
    #endif
    ...
    #ifndef BPF_NO_PRESERVE_ACCESS_INDEX
    #pragma clang attribute pop
    #endif

You might want to use it or add __attribute__((preserve_access_index))
to structure definitions, depending on whether or not you need CO-RE
functionality for these tests.

> 
> +enum hid_class_request {
> +	HID_REQ_GET_REPORT		= 0x01,
> +	HID_REQ_GET_IDLE		= 0x02,
> +	HID_REQ_GET_PROTOCOL		= 0x03,
> +	HID_REQ_SET_REPORT		= 0x09,
> +	HID_REQ_SET_IDLE		= 0x0A,
> +	HID_REQ_SET_PROTOCOL		= 0x0B,
> +};
> +
> +enum hid_bpf_attach_flags {
> +	HID_BPF_FLAG_NONE = 0,
> +	HID_BPF_FLAG_INSERT_HEAD = _BITUL(0),
> +	HID_BPF_FLAG_MAX,
> +};
> +
>  /* following are kfuncs exported by HID for HID-BPF */
>  extern __u8 *hid_bpf_get_data(struct hid_bpf_ctx *ctx,
>  			      unsigned int offset,
> --
> 2.42.0.rc1.204.g551eb34607-goog
>