Re: [PATCH v5 bpf-next 3/4] bpf: Add kernel module with user mode driver that populates bpffs.

On Mon, Aug 3, 2020 at 10:41 AM Daniel Borkmann [off-list ref] wrote:

On 8/3/20 7:34 PM, Daniel Borkmann wrote:

quoted

On 8/3/20 7:15 PM, Daniel Borkmann wrote:

quoted

On 8/3/20 12:29 AM, Alexei Starovoitov wrote:

quoted

From: Alexei Starovoitov <ast@kernel.org>

Add kernel module with user mode driver that populates bpffs with
BPF iterators.

[...]

   CC      kernel/events/ring_buffer.o
   CC [U]  kernel/bpf/preload/./../../../tools/lib/bpf/bpf.o
   CC [U]  kernel/bpf/preload/./../../../tools/lib/bpf/libbpf.o
In file included from kernel/bpf/preload/./../../../tools/lib/bpf/libbpf.c:47:0:
./tools/include/tools/libc_compat.h:11:21: error: static declaration of ‘reallocarray’ follows non-static declaration
  static inline void *reallocarray(void *ptr, size_t nmemb, size_t size)
                      ^~~~~~~~~~~~
In file included from kernel/bpf/preload/./../../../tools/lib/bpf/libbpf.c:16:0:
/usr/include/stdlib.h:558:14: note: previous declaration of ‘reallocarray’ was here
  extern void *reallocarray (void *__ptr, size_t __nmemb, size_t __size)
               ^~~~~~~~~~~~

A bit offtopic. reallocarray and related feature detection causes so
much hassle, that I'm strongly tempted to just get rid of it in the
entire libbpf. Or just unconditionally implement libbpf-specific
reallocarray function. Any objections?

   CC      kernel/user-return-notifier.o
scripts/Makefile.userprogs:43: recipe for target 'kernel/bpf/preload/./../../../tools/lib/bpf/libbpf.o' failed
make[3]: *** [kernel/bpf/preload/./../../../tools/lib/bpf/libbpf.o] Error 1
scripts/Makefile.build:497: recipe for target 'kernel/bpf/preload' failed
make[2]: *** [kernel/bpf/preload] Error 2
scripts/Makefile.build:497: recipe for target 'kernel/bpf' failed
make[1]: *** [kernel/bpf] Error 2
make[1]: *** Waiting for unfinished jobs....
[...]