From: KP Singh <kpsingh@xxxxxxxxxx>
The currently available bpf_get_current_task returns an unsigned integer
which can be used along with BPF_CORE_READ to read data from
the task_struct but still cannot be used as an input argument to a
helper that accepts an ARG_PTR_TO_BTF_ID of type task_struct.
In order to implement this helper a new return type, RET_PTR_TO_BTF_ID,
is added. This is similar to RET_PTR_TO_BTF_ID_OR_NULL but does not
require checking the nullness of returned pointer.
Signed-off-by: KP Singh <kpsingh@xxxxxxxxxx>
---
include/linux/bpf.h | 1 +
include/uapi/linux/bpf.h | 9 +++++++++
kernel/bpf/verifier.c | 10 +++++++---
kernel/trace/bpf_trace.c | 16 ++++++++++++++++
tools/include/uapi/linux/bpf.h | 9 +++++++++
5 files changed, 42 insertions(+), 3 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 2b16bf48aab6..05ea8c55d893 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -310,6 +310,7 @@ enum bpf_return_type {
RET_PTR_TO_BTF_ID_OR_NULL, /* returns a pointer to a btf_id or NULL */
RET_PTR_TO_MEM_OR_BTF_ID_OR_NULL, /* returns a pointer to a valid memory or a btf_id or NULL */
RET_PTR_TO_MEM_OR_BTF_ID, /* returns a pointer to a valid memory or a btf_id */
+ RET_PTR_TO_BTF_ID, /* returns a pointer to a btf_id */
};
/* eBPF function prototype used by verifier to allow BPF_CALLs from eBPF programs
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index bb443c4f3637..05c997913872 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3779,6 +3779,14 @@ union bpf_attr {
* 0 on success.
*
* **-ENOENT** if the bpf_local_storage cannot be found.
+ *
+ * struct task_struct *bpf_get_current_task_btf(void)
+ * Description
+ * Return a BTF pointer to the "current" task.
+ * This pointer can also be used in helpers that accept an
+ * *ARG_PTR_TO_BTF_ID* of type *task_struct*.
+ * Return
+ * Pointer to the current task.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3939,6 +3947,7 @@ union bpf_attr {
FN(redirect_peer), \
FN(task_storage_get), \
FN(task_storage_delete), \
+ FN(get_current_task_btf), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index b0790876694f..eb0aef85fc11 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -493,7 +493,8 @@ static bool is_ptr_cast_function(enum bpf_func_id func_id)
func_id == BPF_FUNC_skc_to_tcp6_sock ||
func_id == BPF_FUNC_skc_to_udp6_sock ||
func_id == BPF_FUNC_skc_to_tcp_timewait_sock ||
- func_id == BPF_FUNC_skc_to_tcp_request_sock;
+ func_id == BPF_FUNC_skc_to_tcp_request_sock ||
+ func_id == BPF_FUNC_get_current_task_btf;
}
/* string representation of 'enum bpf_reg_type' */
@@ -5186,11 +5187,14 @@ static int check_helper_call(struct bpf_verifier_env *env, int func_id, int insn
PTR_TO_BTF_ID : PTR_TO_BTF_ID_OR_NULL;
regs[BPF_REG_0].btf_id = meta.ret_btf_id;
}
- } else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL) {
+ } else if (fn->ret_type == RET_PTR_TO_BTF_ID_OR_NULL ||
+ fn->ret_type == RET_PTR_TO_BTF_ID) {
int ret_btf_id;
mark_reg_known_zero(env, regs, BPF_REG_0);
- regs[BPF_REG_0].type = PTR_TO_BTF_ID_OR_NULL;
+ regs[BPF_REG_0].type = fn->ret_type == RET_PTR_TO_BTF_ID ?
+ PTR_TO_BTF_ID :
+ PTR_TO_BTF_ID_OR_NULL;
ret_btf_id = *fn->ret_btf_id;
if (ret_btf_id == 0) {
verbose(env, "invalid return type %d of func %s#%d\n",
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 4517c8b66518..7b48aa1c695a 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -1022,6 +1022,20 @@ const struct bpf_func_proto bpf_get_current_task_proto = {
.ret_type = RET_INTEGER,
};
+BPF_CALL_0(bpf_get_current_task_btf)
+{
+ return (unsigned long) current;
+}
+
+BTF_ID_LIST_SINGLE(bpf_get_current_btf_ids, struct, task_struct)
+
+const struct bpf_func_proto bpf_get_current_task_btf_proto = {
+ .func = bpf_get_current_task_btf,
+ .gpl_only = true,
+ .ret_type = RET_PTR_TO_BTF_ID,
+ .ret_btf_id = &bpf_get_current_btf_ids[0],
+};
+
BPF_CALL_2(bpf_current_task_under_cgroup, struct bpf_map *, map, u32, idx)
{
struct bpf_array *array = container_of(map, struct bpf_array, map);
@@ -1265,6 +1279,8 @@ bpf_tracing_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
return &bpf_get_current_pid_tgid_proto;
case BPF_FUNC_get_current_task:
return &bpf_get_current_task_proto;
+ case BPF_FUNC_get_current_task_btf:
+ return &bpf_get_current_task_btf_proto;
case BPF_FUNC_get_current_uid_gid:
return &bpf_get_current_uid_gid_proto;
case BPF_FUNC_get_current_comm:
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index bb443c4f3637..05c997913872 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3779,6 +3779,14 @@ union bpf_attr {
* 0 on success.
*
* **-ENOENT** if the bpf_local_storage cannot be found.
+ *
+ * struct task_struct *bpf_get_current_task_btf(void)
+ * Description
+ * Return a BTF pointer to the "current" task.
+ * This pointer can also be used in helpers that accept an
+ * *ARG_PTR_TO_BTF_ID* of type *task_struct*.
+ * Return
+ * Pointer to the current task.
*/
#define __BPF_FUNC_MAPPER(FN) \
FN(unspec), \
@@ -3939,6 +3947,7 @@ union bpf_attr {
FN(redirect_peer), \
FN(task_storage_get), \
FN(task_storage_delete), \
+ FN(get_current_task_btf), \
/* */
/* integer value in 'imm' field of BPF_CALL instruction selects which helper
--
2.29.0.rc2.309.g374f81d7ae-goog
