On Fri, Mar 5, 2021 at 5:42 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 plus instruction check stolen from ppc_function_entry
> function pointed out and explained by Michael and Naveen.
>
> Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
> Cc: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> .../selftests/bpf/prog_tests/attach_probe.c | 40 ++++++++++++++++++-
> 1 file changed, 39 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..9dc4e3dfbcf3 100644
> --- a/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> +++ b/tools/testing/selftests/bpf/prog_tests/attach_probe.c
> @@ -2,6 +2,44 @@
> #include <test_progs.h>
> #include "test_attach_probe.skel.h"
>
> +#if defined(__powerpc64__) && defined(_CALL_ELF) && _CALL_ELF == 2
> +
> +#define OP_RT_RA_MASK 0xffff0000UL
> +#define LIS_R2 0x3c400000UL
> +#define ADDIS_R2_R12 0x3c4c0000UL
> +#define ADDI_R2_R2 0x38420000UL
> +
> +static ssize_t get_offset(ssize_t addr, ssize_t base)
> +{
> + u32 *insn = (u32 *) addr;
> +
> + /*
> + * A PPC64 ABIv2 function may have a local and a global entry
> + * point. We need to use the local entry point when patching
> + * functions, so identify and step over the global entry point
> + * sequence.
> + *
> + * The global entry point sequence is always of the form:
> + *
> + * addis r2,r12,XXXX
> + * addi r2,r2,XXXX
> + *
> + * A linker optimisation may convert the addis to lis:
> + *
> + * lis r2,XXXX
> + * addi r2,r2,XXXX
> + */
> + if ((((*insn & OP_RT_RA_MASK) == ADDIS_R2_R12) ||
> + ((*insn & OP_RT_RA_MASK) == LIS_R2)) &&
> + ((*(insn + 1) & OP_RT_RA_MASK) == ADDI_R2_R2))
> + return (ssize_t)(insn + 2) - base;
> + else
> + return addr - base;
> +}
> +#else
> +#define get_offset(addr, base) (addr - base)
I turned this into a static function, not sure why you preferred
#define here. Applied to bpf-next.
> +#endif
> +
> ssize_t get_base_addr() {
> size_t start, offset;
> char buf[256];
> @@ -36,7 +74,7 @@ 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"))
> --
> 2.27.0
>
