On Sat, May 7, 2022 at 8:21 PM Kui-Feng Lee <kuifeng@xxxxxx> wrote:
>
> Pass a cookie along with BPF_LINK_CREATE requests.
>
> Add a bpf_cookie field to struct bpf_tracing_link to attach a cookie.
> The cookie of a bpf_tracing_link is available by calling
> bpf_get_attach_cookie when running the BPF program of the attached
> link.
>
> The value of a cookie will be set at bpf_tramp_run_ctx by the
> trampoline of the link.
>
> Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxx>
> ---
> arch/x86/net/bpf_jit_comp.c | 12 ++++++++++--
> include/linux/bpf.h | 1 +
> include/uapi/linux/bpf.h | 9 +++++++++
> kernel/bpf/bpf_lsm.c | 17 +++++++++++++++++
> kernel/bpf/syscall.c | 12 ++++++++----
> kernel/bpf/trampoline.c | 7 +++++--
> kernel/trace/bpf_trace.c | 17 +++++++++++++++++
> tools/include/uapi/linux/bpf.h | 9 +++++++++
> 8 files changed, 76 insertions(+), 8 deletions(-)
>
LGTM with a suggestion for some follow up clean up.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> diff --git a/arch/x86/net/bpf_jit_comp.c b/arch/x86/net/bpf_jit_comp.c
> index bf4576a6938c..52a5eba2d5e8 100644
> --- a/arch/x86/net/bpf_jit_comp.c
> +++ b/arch/x86/net/bpf_jit_comp.c
> @@ -1764,13 +1764,21 @@ static int invoke_bpf_prog(const struct btf_func_model *m, u8 **pprog,
> struct bpf_tramp_link *l, int stack_size,
> bool save_ret)
> {
> + u64 cookie = 0;
> u8 *prog = *pprog;
> u8 *jmp_insn;
> int ctx_cookie_off = offsetof(struct bpf_tramp_run_ctx, bpf_cookie);
> struct bpf_prog *p = l->link.prog;
>
> - /* mov rdi, 0 */
> - emit_mov_imm64(&prog, BPF_REG_1, 0, 0);
> + if (l->link.type == BPF_LINK_TYPE_TRACING) {
It would probably be nicer to put cookie field into struct
bpf_tramp_link instead so that the JIT compiler doesn't have to do
this special handling. It also makes sense that struct bpf_trampoline
*trampoline is moved into struct bpf_tramp_link itself (given
trampoline is always there for bpf_tramp_link).
> + struct bpf_tracing_link *tr_link =
> + container_of(l, struct bpf_tracing_link, link);
> +
> + cookie = tr_link->cookie;
> + }
> +
> + /* mov rdi, cookie */
> + emit_mov_imm64(&prog, BPF_REG_1, (long) cookie >> 32, (u32) (long) cookie);
>
> /* Prepare struct bpf_tramp_run_ctx.
> *
[...]
