On Thu, Sep 02, 2021 at 12:13:40PM -0700, Alexei Starovoitov wrote:
> On Thu, Sep 2, 2021 at 2:08 AM Jean-Philippe Brucker
> <jean-philippe@xxxxxxxxxx> wrote:
> >
> > struct pt_regs is not exported to userspace on all archs. arm64 and s390
> > export "user_pt_regs" instead, which causes build failure at the moment:
> >
> > progs/test_task_pt_regs.c:8:16: error: variable has incomplete type 'struct pt_regs'
> > struct pt_regs current_regs = {};
>
> Right, which is 'bpf_user_pt_regs_t'.
> It's defined for all archs and arm64/s390/ppc/risv define it
> differently from pt_regs.
>
> >
> > Use the multi-arch macros defined by tools/lib/bpf/bpf_tracing.h to copy
> > the pt_regs into a locally-defined struct.
> >
> > Copying the user_pt_regs struct on arm64 wouldn't work because the
> > struct is too large and the compiler complains about using too much
> > stack.
>
> That's a different issue.
It does work when doing an implicit copy (current_regs = *regs) rather
than using __builtin_memcpy(). Don't know why but I'll take it.
> I think the cleaner fix would be to make the test use
> bpf_user_pt_regs_t instead.
Right, although that comes with another complication. We end up including
tools/include/uapi/asm/bpf_perf_event.h which requires the compiler
builtins "__aarch64__", "__s390__", etc. Those are not defined with
"clang -target bpf" so I have to add them to the command line.
I'll resend with your suggestion but this patch is simpler.
Thanks,
Jean
