linux-kernel - Re: [PATCH bpf-next v2] selftests/bpf: Fix cross compiling error when using userspace pt

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Date:   Thu, 23 Dec 2021 10:21:39 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Pu Lehui <pulehui@...wei.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, Martin Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        john fastabend <john.fastabend@...il.com>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next v2] selftests/bpf: Fix cross compiling error when
 using userspace pt_regs

On Wed, Dec 22, 2021 at 8:56 PM Pu Lehui <pulehui@...wei.com> wrote:
>
> When cross compiling arm64 bpf selftests in x86_64 host, the following
> error occur:
>
> progs/loop2.c:20:7: error: incomplete definition of type 'struct
> user_pt_regs'
>
> Some archs, like arm64 and riscv, use userspace pt_regs in bpf_tracing.h.
> When arm64 bpf selftests cross compiling in x86_64 host, clang cannot
> find the arch specific uapi ptrace.h. We can add arch specific header
> file directory to fix this issue.
>
> Signed-off-by: Pu Lehui <pulehui@...wei.com>
> ---
> v1->v2:
> - use vmlinux.h directly might lead to verifier fail.
> - use source arch header file directory suggested by Andrii Nakryiko.
>
>  tools/testing/selftests/bpf/Makefile | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
> index 42ffc24e9e71..1ecb6d192953 100644
> --- a/tools/testing/selftests/bpf/Makefile
> +++ b/tools/testing/selftests/bpf/Makefile
> @@ -12,6 +12,7 @@ BPFDIR := $(LIBDIR)/bpf
>  TOOLSINCDIR := $(TOOLSDIR)/include
>  BPFTOOLDIR := $(TOOLSDIR)/bpf/bpftool
>  APIDIR := $(TOOLSINCDIR)/uapi
> +ARCH_APIDIR := $(abspath ../../../../arch/$(SRCARCH)/include/uapi)
>  GENDIR := $(abspath ../../../../include/generated)
>  GENHDR := $(GENDIR)/autoconf.h
>
> @@ -294,7 +295,8 @@ MENDIAN=$(if $(IS_LITTLE_ENDIAN),-mlittle-endian,-mbig-endian)
>  CLANG_SYS_INCLUDES = $(call get_sys_includes,$(CLANG))
>  BPF_CFLAGS = -g -D__TARGET_ARCH_$(SRCARCH) $(MENDIAN)                  \
>              -I$(INCLUDE_DIR) -I$(CURDIR) -I$(APIDIR)                   \
> -            -I$(abspath $(OUTPUT)/../usr/include)
> +            -I$(abspath $(OUTPUT)/../usr/include)                      \
> +            -I$(ARCH_APIDIR)
>

This causes compilation error, see [0]. I think we'll have to wait for
my patch ([1]) to land and then add kernel-side variants for accessing
pt_regs.

  [0] https://github.com/kernel-patches/bpf/runs/4614606900?check_suite_focus=true
  [1] https://patchwork.kernel.org/project/netdevbpf/patch/20211222213924.1869758-1-andrii@kernel.org/


>  CLANG_CFLAGS = $(CLANG_SYS_INCLUDES) \
>                -Wno-compare-distinct-pointer-types
> --
> 2.25.1
>