On Fri, Jun 3, 2022 at 2:21 AM Jiri Olsa <jolsa@xxxxxxxxxx> wrote:
>
> Some functions we use for bpf prologue generation are going to be
> deprecated. This change reworks current code not to use them.
>
> We need to replace following functions/struct:
> bpf_program__set_prep
> bpf_program__nth_fd
> struct bpf_prog_prep_result
>
> Currently we use bpf_program__set_prep to hook perf callback before
> program is loaded and provide new instructions with the prologue.
>
> We replace this function/ality by taking instructions for specific
> program, attaching prologue to them and load such new ebpf programs
> with prologue using separate bpf_prog_load calls (outside libbpf
> load machinery).
>
> Before we can take and use program instructions, we need libbpf to
> actually load it. This way we get the final shape of its instructions
> with all relocations and verifier adjustments).
>
> There's one glitch though.. perf kprobe program already assumes
> generated prologue code with proper values in argument registers,
> so loading such program directly will fail in the verifier.
>
> That's where the fallback pre-load handler fits in and prepends
> the initialization code to the program. Once such program is loaded
> we take its instructions, cut off the initialization code and prepend
> the prologue.
>
> I know.. sorry ;-)
>
> Suggested-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> Signed-off-by: Jiri Olsa <jolsa@xxxxxxxxxx>
> ---
> tools/perf/util/bpf-loader.c | 128 ++++++++++++++++++++++++++++++-----
> 1 file changed, 110 insertions(+), 18 deletions(-)
>
> diff --git a/tools/perf/util/bpf-loader.c b/tools/perf/util/bpf-loader.c
> index e7992a0eb477..2ce5f9684863 100644
> --- a/tools/perf/util/bpf-loader.c
> +++ b/tools/perf/util/bpf-loader.c
> @@ -9,6 +9,7 @@
> #include <linux/bpf.h>
> #include <bpf/libbpf.h>
> #include <bpf/bpf.h>
> +#include <linux/filter.h>
> #include <linux/err.h>
> #include <linux/kernel.h>
> #include <linux/string.h>
> @@ -49,6 +50,7 @@ struct bpf_prog_priv {
> struct bpf_insn *insns_buf;
> int nr_types;
> int *type_mapping;
> + int *proglogue_fds;
massively copy/pasted typo? prologue_fds?
Other than that looks good to me, but we'll need Arnaldo's ack before
merging into bpf-next.
> };
>
> struct bpf_perf_object {
> @@ -56,6 +58,11 @@ struct bpf_perf_object {
> struct bpf_object *obj;
> };
>
[...]
