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: 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>

diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 886949f..bb4fb63 100644 (file)
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -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)
 {
@@ -648,6 +654,24 @@ bpf_base_func_proto(enum bpf_func_id func_id)
        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;
        }
 }

diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 9531f54..187cd69 100644 (file)
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -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,