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bpf: Implement get_current_task_btf and RET_PTR_TO_BTF_ID

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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@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20201106103747.2780972-6-kpsingh@chromium.org
This commit is contained in:
KP Singh
2020-11-06 10:37:43 +00:00
committed by Alexei Starovoitov
parent 864ab0616d
commit 3ca1032ab7
5 changed files with 40 additions and 2 deletions
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9
include/uapi/linux/bpf.h
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@@ -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