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

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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: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/159033905529.12355.4368381069655254932.stgit@john-Precision-5820-Tower
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
John Fastabend
2020-05-24 09:50:55 -07:00
committed by Alexei Starovoitov
parent abe3cac870
commit f470378c75
2 changed files with 29 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

24
kernel/bpf/helpers.c
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@@ -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;
}