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@linaro.org 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