On Tue, Sep 20, 2022 at 10:01 AM Roberto Sassu roberto.sassu@huaweicloud.com wrote:
From: Roberto Sassu roberto.sassu@huawei.com
eBPF dynamic pointers is a new feature recently added to upstream. It binds together a pointer to a memory area and its size. The internal kernel structure bpf_dynptr_kern is not accessible by eBPF programs in user space. They instead see bpf_dynptr, which is then translated to the internal kernel structure by the eBPF verifier.
The problem is that it is not possible to include at the same time the uapi include linux/bpf.h and the vmlinux BTF vmlinux.h, as they both contain the definition of some structures/enums. The compiler complains saying that the structures/enums are redefined.
As bpf_dynptr is defined in the uapi include linux/bpf.h, this makes it impossible to include vmlinux.h. However, in some cases, e.g. when using kfuncs, vmlinux.h has to be included. The only option until now was to include vmlinux.h and add the definition of bpf_dynptr directly in the eBPF program source code from linux/bpf.h.
Solve the problem by using the same approach as for bpf_timer (which also follows the same scheme with the _kern suffix for the internal kernel structure).
Add the following line in one of the dynamic pointer helpers, bpf_dynptr_from_mem():
BTF_TYPE_EMIT(struct bpf_dynptr);
Cc: stable@vger.kernel.org Cc: Joanne Koong joannelkoong@gmail.com Fixes: 97e03f521050c ("bpf: Add verifier support for dynptrs") Signed-off-by: Roberto Sassu roberto.sassu@huawei.com Acked-by: Yonghong Song yhs@fb.com
I tested this out and it works, however for the BPF signing use case where "bpf_dynptr_kern" is added to struct bpf_prog_aux one still ends up defining the __ksym extern with bpf_dynptr_kern.
But let's discuss that when the series is posted.
Tested-by: KP Singh kpsingh@kernel.org