> On Sun, 31 May 2020 23:46:49 +0200
> Lorenzo Bianconi <lorenzo@xxxxxxxxxx> wrote:
>
> > diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
> > index 57402276d8af..24ab0a6b9772 100644
> > --- a/kernel/bpf/cpumap.c
> > +++ b/kernel/bpf/cpumap.c
> > @@ -51,6 +51,10 @@ struct xdp_bulk_queue {
> > /* CPUMAP value */
> > struct bpf_cpumap_val {
> > u32 qsize; /* queue size */
> > + union {
> > + int fd; /* program file descriptor */
> > + u32 id; /* program id */
> > + } prog;
> > };
>
> Please name the union 'bpf_prog' and not 'prog'.
> We should match what David Ahern did for devmap.
Hi Jesper,
ack, I will align the struct to David's one in v2.
Regards,
Lorenzo
>
> Even-though we are NOT exposing this in the UAPI header-file, this still
> becomes a UAPI interface (actually kABI). The struct member names are
> still important, even-though this is a binary layout, because the BTF
> info is basically documenting this API.
>
> Notice when kernel is compiled with BTF info, you (or end-user) can use
> pahole to "reverse" the struct layout (comments don't survive, so we
> need descriptive member names):
>
> $ pahole bpf_devmap_val
> struct bpf_devmap_val {
> __u32 ifindex; /* 0 4 */
> union {
> int fd; /* 4 4 */
> __u32 id; /* 4 4 */
> } bpf_prog; /* 4 4 */
> struct {
> unsigned char data[24]; /* 8 24 */
> } storage; /* 8 24 */
>
> /* size: 32, cachelines: 1, members: 3 */
> /* last cacheline: 32 bytes */
> };
>
> --
> Best regards,
> Jesper Dangaard Brouer
> MSc.CS, Principal Kernel Engineer at Red Hat
> LinkedIn: http://www.linkedin.com/in/brouer
>
>
> $ bpftool btf dump file /sys/kernel/btf/vmlinux format c | grep -A10 'struct bpf_devmap_val {'
> struct bpf_devmap_val {
> __u32 ifindex;
> union {
> int fd;
> __u32 id;
> } bpf_prog;
> struct {
> unsigned char data[24];
> } storage;
> };
>
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