Commit f470378c authored by John Fastabend's avatar John Fastabend Committed by Alexei Starovoitov
Browse files

bpf: Extend bpf_base_func_proto helpers with probe_* and *current_task* 



Often it is useful when applying policy to know something about the
task. If the administrator has CAP_SYS_ADMIN rights then they can
use kprobe + networking hook and link the two programs together to
accomplish this. However, this is a bit clunky and also means we have
to call both the network program and kprobe program when we could just
use a single program and avoid passing metadata through sk_msg/skb->cb,
socket, maps, etc.

To accomplish this add probe_* helpers to bpf_base_func_proto programs
guarded by a perfmon_capable() check. New supported helpers are the
following,

 BPF_FUNC_get_current_task
 BPF_FUNC_probe_read_user
 BPF_FUNC_probe_read_kernel
 BPF_FUNC_probe_read_user_str
 BPF_FUNC_probe_read_kernel_str

Signed-off-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarYonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/159033905529.12355.4368381069655254932.stgit@john-Precision-5820-Tower


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent abe3cac8

kernel/bpf/helpers.c

+24 −0
Original line number Diff line number Diff line
@@ -601,6 +601,12 @@ const struct bpf_func_proto bpf_event_output_data_proto = { 
	.arg5_type      = ARG_CONST_SIZE_OR_ZERO,

};



const struct bpf_func_proto bpf_get_current_task_proto __weak;

const struct bpf_func_proto bpf_probe_read_user_proto __weak;

const struct bpf_func_proto bpf_probe_read_user_str_proto __weak;

const struct bpf_func_proto bpf_probe_read_kernel_proto __weak;

const struct bpf_func_proto bpf_probe_read_kernel_str_proto __weak;



const struct bpf_func_proto *

bpf_base_func_proto(enum bpf_func_id func_id)

{
@@ -647,6 +653,24 @@ bpf_base_func_proto(enum bpf_func_id func_id) 
		return bpf_get_trace_printk_proto();

	case BPF_FUNC_jiffies64:

		return &bpf_jiffies64_proto;

	default:

		break;

	}



	if (!perfmon_capable())

		return NULL;



	switch (func_id) {

	case BPF_FUNC_get_current_task:

		return &bpf_get_current_task_proto;

	case BPF_FUNC_probe_read_user:

		return &bpf_probe_read_user_proto;

	case BPF_FUNC_probe_read_kernel:

		return &bpf_probe_read_kernel_proto;

	case BPF_FUNC_probe_read_user_str:

		return &bpf_probe_read_user_str_proto;

	case BPF_FUNC_probe_read_kernel_str:

		return &bpf_probe_read_kernel_str_proto;

	default:

		return NULL;

	}

kernel/trace/bpf_trace.c

+5 −5
Original line number Diff line number Diff line
@@ -147,7 +147,7 @@ BPF_CALL_3(bpf_probe_read_user, void *, dst, u32, size, 
	return ret;

}



static const struct bpf_func_proto bpf_probe_read_user_proto = {

const struct bpf_func_proto bpf_probe_read_user_proto = {

	.func		= bpf_probe_read_user,

	.gpl_only	= true,

	.ret_type	= RET_INTEGER,
@@ -167,7 +167,7 @@ BPF_CALL_3(bpf_probe_read_user_str, void *, dst, u32, size, 
	return ret;

}



static const struct bpf_func_proto bpf_probe_read_user_str_proto = {

const struct bpf_func_proto bpf_probe_read_user_str_proto = {

	.func		= bpf_probe_read_user_str,

	.gpl_only	= true,

	.ret_type	= RET_INTEGER,
@@ -198,7 +198,7 @@ BPF_CALL_3(bpf_probe_read_kernel, void *, dst, u32, size, 
	return bpf_probe_read_kernel_common(dst, size, unsafe_ptr, false);

}



static const struct bpf_func_proto bpf_probe_read_kernel_proto = {

const struct bpf_func_proto bpf_probe_read_kernel_proto = {

	.func		= bpf_probe_read_kernel,

	.gpl_only	= true,

	.ret_type	= RET_INTEGER,
@@ -253,7 +253,7 @@ BPF_CALL_3(bpf_probe_read_kernel_str, void *, dst, u32, size, 
	return bpf_probe_read_kernel_str_common(dst, size, unsafe_ptr, false);

}



static const struct bpf_func_proto bpf_probe_read_kernel_str_proto = {

const struct bpf_func_proto bpf_probe_read_kernel_str_proto = {

	.func		= bpf_probe_read_kernel_str,

	.gpl_only	= true,

	.ret_type	= RET_INTEGER,
@@ -907,7 +907,7 @@ BPF_CALL_0(bpf_get_current_task) 
	return (long) current;

}



static const struct bpf_func_proto bpf_get_current_task_proto = {

const struct bpf_func_proto bpf_get_current_task_proto = {

	.func		= bpf_get_current_task,

	.gpl_only	= true,

	.ret_type	= RET_INTEGER,

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