[PATCH v18 02/13] btf: Export bpf_dynptr definition

[Yonghong Song]

On 9/19/22 7:27 AM, Roberto Sassu wrote:
> From: Roberto Sassu <roberto.sassu at 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 at vger.kernel.org
> Cc: Joanne Koong <joannelkoong at gmail.com>
> Fixes: 97e03f521050c ("bpf: Add verifier support for dynptrs")
> Signed-off-by: Roberto Sassu <roberto.sassu at huawei.com>

Acked-by: Yonghong Song <yhs at fb.com>