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

[Pu Lehui]

On 2021/12/23 7:17, Andrii Nakryiko wrote:
> On Tue, Dec 21, 2021 at 5:33 PM Pu Lehui <pulehui@xxxxxxxxxx> wrote:
> > On 2021/12/22 7:52, Andrii Nakryiko wrote:
> > > On Mon, Dec 20, 2021 at 4:58 PM Pu Lehui <pulehui@xxxxxxxxxx> 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@xxxxxxxxxx> wrote:
> > > > > > > On 2021/12/16 12:06, Andrii Nakryiko wrote:
> > > > > > > > On Tue, Dec 14, 2021 at 5:54 AM Pu Lehui <pulehui@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > > > > > > > ---
> > > > > > > > >      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(-)
> > > > > > > >
> > > > > > > > [...]
> > > > > > > > .
> > > > > > .
> > > > > .
> > > .
> .