On Thu, 10 Feb 2022 17:49:15 -0800 Song Liu wrote:
> bpf_prog_pack causes build error with powerpc ppc64_defconfig:
>
> kernel/bpf/core.c:830:23: error: variably modified 'bitmap' at file scope
> 830 | unsigned long bitmap[BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)];
> | ^~~~~~
No idea what this error means but...
> Fix it by turning bitmap into a 0-length array.
>
> Fixes: 57631054fae6 ("bpf: Introduce bpf_prog_pack allocator")
> Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
> Signed-off-by: Song Liu <song@xxxxxxxxxx>
> ---
> kernel/bpf/core.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
> index 42d96549a804..44623c9b5bb1 100644
> --- a/kernel/bpf/core.c
> +++ b/kernel/bpf/core.c
> @@ -827,7 +827,7 @@ int bpf_jit_add_poke_descriptor(struct bpf_prog *prog,
> struct bpf_prog_pack {
> struct list_head list;
> void *ptr;
> - unsigned long bitmap[BITS_TO_LONGS(BPF_PROG_CHUNK_COUNT)];
> + unsigned long bitmap[];
This is really asking to be DECLARE_BITMAP(), does that fix the issue?
> };
>
> #define BPF_PROG_MAX_PACK_PROG_SIZE BPF_PROG_PACK_SIZE
> @@ -840,7 +840,7 @@ static struct bpf_prog_pack *alloc_new_pack(void)
> {
> struct bpf_prog_pack *pack;
>
> - pack = kzalloc(sizeof(*pack), GFP_KERNEL);
> + pack = kzalloc(sizeof(*pack) + BITS_TO_BYTES(BPF_PROG_CHUNK_COUNT), GFP_KERNEL);
Otherwise you may want to use struct_size(pack, bitmap, BITS...).
One of the bots will soon send us a patch to do that.
> if (!pack)
> return NULL;
> pack->ptr = module_alloc(BPF_PROG_PACK_SIZE);
