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

[Pu Lehui <pulehui@huawei.com>]

On 2021/12/23 7:17, Andrii Nakryiko wrote:
> On Tue, Dec 21, 2021 at 5:33 PM Pu Lehui <pulehui@huawei.com> wrote:
>>
>>
>>
>> On 2021/12/22 7:52, Andrii Nakryiko wrote:
>>> On Mon, Dec 20, 2021 at 4:58 PM Pu Lehui <pulehui@huawei.com> wrote:
>>>>
>>>>
>>>>
>>>> On 2021/12/20 22:02, Pu Lehui wrote:
>>>>>
>>>>>
>>>>> On 2021/12/18 0:45, Andrii Nakryiko wrote:
>>>>>> On Thu, Dec 16, 2021 at 6:25 PM Pu Lehui <pulehui@huawei.com> wrote:
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> On 2021/12/16 12:06, Andrii Nakryiko wrote:
>>>>>>>> On Tue, Dec 14, 2021 at 5:54 AM Pu Lehui <pulehui@huawei.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,
>>>
>>> yes
>>>
>>>>> 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])
>>>>>
>>>> Please ignore the last reply. User-space pt_regs of arm64/s390 is the
>>>> first part of the kernel-space's, it should has covered both kernel and
>>>> userspace.
>>>
>>> Alright, so is there still a problem or not? Looking at the definition
>>> of struct pt_regs for arm64, just casting struct pt_regs to struct
>>> user_pt_regs will indeed just work. So in that case, what was your
>>> original issue?
>>>
>> Thanks for your reply. The original issue is, when arm64 bpf selftests
>> cross compiling in x86_64 host, clang cannot find the arch specific uapi
>> ptrace.h, and then the above error occur. Of course it works when
>> compiling in arm64 host for it owns the corresponding uapi ptrace.h. So
>> my suggestion is to add arch specific use header file directory
>> generated by "make headers_install" for the cross compiling issue.
> 
> I see. Can you try adding something like:
> 
> ARCH_APIDIR := $(abspath ../../../../arch/$(SRCARCH)/include/uapi)
> 
> and then add -I$(ARCH_APIDIR) to BPF_CFLAGS?
> 
> Please let me know if that works for your cross-compilation case.
> 
It works, thanks. I will add it to v2.
>>>>>>>
>>>>>>> --- a/tools/testing/selftests/bpf/Makefile
>>>>>>> +++ b/tools/testing/selftests/bpf/Makefile
>>>>>>> @@ -294,7 +294,8 @@ MENDIAN=$(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@huawei.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(-)
>>>>>>>>>
>>>>>>>>
>>>>>>>> [...]
>>>>>>>> .
>>>>>>>>
>>>>>> .
>>>>>>
>>>>> .
>>> .
>>>
> .
>