If TRACE_SESSION exists, we will use extra 8-bytes in the stack of the trampoline to store the flags that we needed, and the 8-bytes lie before the function argument count, which means ctx[-2]. And we will store the flag "is_exit" to the first bit of it.
Introduce the kfunc bpf_tracing_is_exit(), which is used to tell if it is fexit currently. Signed-off-by: Menglong Dong <[email protected]> Co-developed-by: Leon Hwang <[email protected]> Signed-off-by: Leon Hwang <[email protected]> --- kernel/bpf/verifier.c | 5 ++++- kernel/trace/bpf_trace.c | 43 +++++++++++++++++++++++++++++++++++++--- 2 files changed, 44 insertions(+), 4 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 40e3274e8bc2..a1db11818d01 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12284,6 +12284,7 @@ enum special_kfunc_type { KF___bpf_trap, KF_bpf_task_work_schedule_signal, KF_bpf_task_work_schedule_resume, + KF_bpf_tracing_is_exit, }; BTF_ID_LIST(special_kfunc_list) @@ -12356,6 +12357,7 @@ BTF_ID(func, bpf_res_spin_unlock_irqrestore) BTF_ID(func, __bpf_trap) BTF_ID(func, bpf_task_work_schedule_signal) BTF_ID(func, bpf_task_work_schedule_resume) +BTF_ID(func, bpf_tracing_is_exit) static bool is_task_work_add_kfunc(u32 func_id) { @@ -12410,7 +12412,8 @@ get_kfunc_ptr_arg_type(struct bpf_verifier_env *env, struct bpf_reg_state *reg = ®s[regno]; bool arg_mem_size = false; - if (meta->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx]) + if (meta->func_id == special_kfunc_list[KF_bpf_cast_to_kern_ctx] || + meta->func_id == special_kfunc_list[KF_bpf_tracing_is_exit]) return KF_ARG_PTR_TO_CTX; /* In this function, we verify the kfunc's BTF as per the argument type, diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 4f87c16d915a..6dde48b9d27f 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -3356,12 +3356,49 @@ static const struct btf_kfunc_id_set bpf_kprobe_multi_kfunc_set = { .filter = bpf_kprobe_multi_filter, }; -static int __init bpf_kprobe_multi_kfuncs_init(void) +__bpf_kfunc_start_defs(); + +__bpf_kfunc bool bpf_tracing_is_exit(void *ctx) +{ + /* ctx[-2] is the session flags, and the last bit is is_exit */ + return ((u64 *)ctx)[-2] & 1; +} + +__bpf_kfunc_end_defs(); + +BTF_KFUNCS_START(tracing_kfunc_set_ids) +BTF_ID_FLAGS(func, bpf_tracing_is_exit) +BTF_KFUNCS_END(tracing_kfunc_set_ids) + +static int bpf_tracing_filter(const struct bpf_prog *prog, u32 kfunc_id) +{ + if (!btf_id_set8_contains(&tracing_kfunc_set_ids, kfunc_id)) + return 0; + + if (prog->type != BPF_PROG_TYPE_TRACING || + prog->expected_attach_type != BPF_TRACE_SESSION) + return -EINVAL; + + return 0; +} + +static const struct btf_kfunc_id_set bpf_tracing_kfunc_set = { + .owner = THIS_MODULE, + .set = &tracing_kfunc_set_ids, + .filter = bpf_tracing_filter, +}; + +static int __init bpf_trace_kfuncs_init(void) { - return register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, &bpf_kprobe_multi_kfunc_set); + int err = 0; + + err = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_KPROBE, &bpf_kprobe_multi_kfunc_set); + err = err ?: register_btf_kfunc_id_set(BPF_PROG_TYPE_TRACING, &bpf_tracing_kfunc_set); + + return err; } -late_initcall(bpf_kprobe_multi_kfuncs_init); +late_initcall(bpf_trace_kfuncs_init); typedef int (*copy_fn_t)(void *dst, const void *src, u32 size, struct task_struct *tsk); -- 2.51.0
