netdev - Re: [PATCH bpf-next] selftests/bpf: Fix building error when using userspace pt

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Date:   Mon, 20 Dec 2021 22:02:19 +0800
From:   Pu Lehui <pulehui@...wei.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.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>,
        KP Singh <kpsingh@...nel.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Shuah Khan <shuah@...nel.org>,
        "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] selftests/bpf: Fix building error when using
 userspace pt_regs



On 2021/12/18 0:45, Andrii Nakryiko wrote:
> On Thu, Dec 16, 2021 at 6:25 PM Pu Lehui <pulehui@...wei.com> wrote:
>>
>>
>>
>> On 2021/12/16 12:06, Andrii Nakryiko wrote:
>>> On Tue, Dec 14, 2021 at 5:54 AM Pu Lehui <pulehui@...wei.com> wrote:
>>>>
>>>> When building bpf selftests on arm64, the following error will 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, which causes build failure when bpf prog use
>>>> macro in bpf_tracing.h. So let's use vmlinux.h directly.
>>>
>>> We could probably also extend bpf_tracing.h to work with
>>> kernel-defined pt_regs, just like we do for x86 (see __KERNEL__ and
>>> __VMLINUX_H__ checks). It's more work, but will benefit other end
>>> users, not just selftests.
>>>
>> It might change a lot. We can use header file directory generated by
>> "make headers_install" to fix it.
> 
> We don't have dependency on "make headers_install" and I'd rather not add it.
> 
> What do you mean by "change a lot"?
> 
Maybe I misunderstood your advice. Your suggestion might be to extend 
bpf_tracing.h to kernel-space pt_regs, while some archs, like arm64, 
only support user-space. So the patch might be like this:

diff --git a/tools/lib/bpf/bpf_tracing.h b/tools/lib/bpf/bpf_tracing.h
index db05a5937105..2c3cb8e9ae92 100644
--- a/tools/lib/bpf/bpf_tracing.h
+++ b/tools/lib/bpf/bpf_tracing.h
@@ -195,9 +195,13 @@ struct pt_regs;

  #elif defined(bpf_target_arm64)

-struct pt_regs;
+#if defined(__KERNEL__)
+#define PT_REGS_ARM64 const volatile struct pt_regs
+#else
  /* arm64 provides struct user_pt_regs instead of struct pt_regs to 
userspace */
  #define PT_REGS_ARM64 const volatile struct user_pt_regs
+#endif
+
  #define PT_REGS_PARM1(x) (((PT_REGS_ARM64 *)(x))->regs[0])
  #define PT_REGS_PARM2(x) (((PT_REGS_ARM64 *)(x))->regs[1])
  #define PT_REGS_PARM3(x) (((PT_REGS_ARM64 *)(x))->regs[2])

>>
>> --- a/tools/testing/selftests/bpf/Makefile
>> +++ b/tools/testing/selftests/bpf/Makefile
>> @@ -294,7 +294,8 @@ 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../../../../usr/include
>>>>
>>>> Signed-off-by: Pu Lehui <pulehui@...wei.com>
>>>> ---
>>>>    tools/testing/selftests/bpf/progs/loop1.c     |  8 ++------
>>>>    tools/testing/selftests/bpf/progs/loop2.c     |  8 ++------
>>>>    tools/testing/selftests/bpf/progs/loop3.c     |  8 ++------
>>>>    tools/testing/selftests/bpf/progs/loop6.c     | 20 ++++++-------------
>>>>    .../selftests/bpf/progs/test_overhead.c       |  8 ++------
>>>>    .../selftests/bpf/progs/test_probe_user.c     |  6 +-----
>>>>    6 files changed, 15 insertions(+), 43 deletions(-)
>>>>
>>>
>>> [...]
>>> .
>>>
> .
>