On 2021/03/02 09:19AM, Yonghong Song wrote: > > > On 3/2/21 3:14 AM, Jiri Olsa wrote: > > On Mon, Mar 01, 2021 at 04:34:24PM -0800, Andrii Nakryiko wrote: > > > On Mon, Mar 1, 2021 at 11:11 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote: > > > > > > > > When testing uprobes we the test gets GEP (Global Entry Point) > > > > address from kallsyms, but then the function is called locally > > > > so the uprobe is not triggered. > > > > > > > > Fixing this by adjusting the address to LEP (Local Entry Point) > > > > for powerpc arch. > > > > > > > > Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx> > > > > --- > > > > .../selftests/bpf/prog_tests/attach_probe.c | 18 +++++++++++++++++- > > > > 1 file changed, 17 insertions(+), 1 deletion(-) > > > > > > > > diff --git a/tools/testing/selftests/bpf/prog_tests/attach_probe.c b/tools/testing/selftests/bpf/prog_tests/attach_probe.c > > > > index a0ee87c8e1ea..c3cfb48d3ed0 100644 > > > > --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c > > > > +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c > > > > @@ -2,6 +2,22 @@ > > > > #include <test_progs.h> > > > > #include "test_attach_probe.skel.h" > > > > > > > > +#if defined(__powerpc64__) > > > > +/* > > > > + * We get the GEP (Global Entry Point) address from kallsyms, > > > > + * but then the function is called locally, so we need to adjust > > > > + * the address to get LEP (Local Entry Point). > > > > + */ > > > > +#define LEP_OFFSET 8 > > > > + > > > > +static ssize_t get_offset(ssize_t offset) > > > > > > if we mark this function __weak global, would it work as is? Would it > > > get an address of a global entry point? I know nothing about this GEP > > > vs LEP stuff, interesting :) > > > > you mean get_base_addr? it's already global > > > > all the calls to get_base_addr within the object are made > > to get_base_addr+0x8 > > > > 00000000100350c0 <test_attach_probe>: > > ... > > 100350e0: 59 fd ff 4b bl 10034e38 <get_base_addr+0x8> > > ... > > 100358a8: 91 f5 ff 4b bl 10034e38 <get_base_addr+0x8> > > > > > > I'm following perf fix we had for similar issue: > > 7b6ff0bdbf4f perf probe ppc64le: Fixup function entry if using kallsyms lookup > > > > I'll get more info on that > > Thanks. The patch > 7b6ff0bdbf4f perf probe ppc64le: Fixup function entry if using kallsyms > lookup > talked about offset + 8 for kernel symbols. > I guess uprobe symbol might be in the same situation if using the > same compilation mechanism as kernel. But it would be good > to get confirmation from ppc people. Yes, this is part of the ELF V2 ABI, so it applies to both kernel and userspace. - Naveen
