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

    > >>>
    > >>> --- 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(-)
    > >>>>>
    > >>>>
    > >>>> [...]
    > >>>> .
    > >>>>
    > >> .
    > >>
    > > .

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