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 :)
> +{
> + 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"))
> --
> 2.29.2
>
