On Mon, Mar 01, 2021 at 02:58:53PM -0800, Yonghong Song wrote:
>
>
> On 3/1/21 11:04 AM, Jiri Olsa 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).
>
> Any documentation in the kernel about this behavior? This will
> help to validate the change without trying with powerpc64 qemu...
we got similar fix in perf:
7b6ff0bdbf4f perf probe ppc64le: Fixup function entry if using kallsyms lookup
CC-ing few other folks from ppc land for more info
jirka
>
> > + */
> > +#define LEP_OFFSET 8
> > +
> > +static ssize_t get_offset(ssize_t offset)
> > +{
> > + return offset + LEP_OFFSET;
> > +}
> > +#else
> > +#define get_offset(offset) (offset)
> > +#endif
> > +
> > ssize_t get_base_addr() {
> > size_t start, offset;
> > char buf[256];
> > @@ -36,7 +52,7 @@ void test_attach_probe(void)
> > if (CHECK(base_addr < 0, "get_base_addr",
> > "failed to find base addr: %zd", base_addr))
> > return;
> > - uprobe_offset = (size_t)&get_base_addr - base_addr;
> > + uprobe_offset = get_offset((size_t)&get_base_addr - base_addr);
> > skel = test_attach_probe__open_and_load();
> > if (CHECK(!skel, "skel_open", "failed to open skeleton\n"))
> >
>
