Re: [PATCH bpf-next 11/11] tools: bpftool: allow reuse of maps with bpftool prog load

[Daniel Borkmann <daniel@iogearbox.net>]

On 07/04/2018 04:54 AM, Jakub Kicinski wrote:
> Add map parameter to prog load which will allow reuse of existing
> maps instead of creating new ones.
> 
> Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
> Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
[...]
> +
> +			fd = map_parse_fd(&argc, &argv);
> +			if (fd < 0)
> +				goto err_free_reuse_maps;
> +
> +			map_replace = reallocarray(map_replace, old_map_fds + 1,
> +						   sizeof(*map_replace));
> +			if (!map_replace) {
> +				p_err("mem alloc failed");
> +				goto err_free_reuse_maps;

Series in general looks good to me. However, above reallocarray() doesn't
exist and hence build fails, please see below. Is that from newest glibc?

You probably need some fallback implementation or in general have something
bpftool internal that doesn't make a bet on its availability.

# make

Auto-detecting system features:
...                        libbfd: [ on  ]
...        disassembler-four-args: [ OFF ]

  CC       bpf_jit_disasm.o
  LINK     bpf_jit_disasm
  CC       bpf_dbg.o
  LINK     bpf_dbg
  CC       bpf_asm.o
  BISON    bpf_exp.yacc.c
  CC       bpf_exp.yacc.o
  FLEX     bpf_exp.lex.c
  CC       bpf_exp.lex.o
  LINK     bpf_asm
  DESCEND  bpftool

Auto-detecting system features:
...                        libbfd: [ on  ]
...        disassembler-four-args: [ OFF ]

  CC       map_perf_ring.o
  CC       xlated_dumper.o
  CC       perf.o
  CC       prog.o
prog.c: In function ‘do_load’:
prog.c:785:18: warning: implicit declaration of function ‘reallocarray’ [-Wimplicit-function-declaration]
    map_replace = reallocarray(map_replace, old_map_fds + 1,
                  ^~~~~~~~~~~~
prog.c:785:16: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
    map_replace = reallocarray(map_replace, old_map_fds + 1,
                ^
  CC       common.o
  CC       cgroup.o
  CC       main.o
  CC       json_writer.o
  CC       cfg.o
  CC       map.o
  CC       jit_disasm.o
  CC       disasm.o

Auto-detecting system features:
...                        libelf: [ on  ]
...                           bpf: [ on  ]

Warning: Kernel ABI header at 'tools/include/uapi/linux/bpf.h' differs from latest version at 'include/uapi/linux/bpf.h'
  CC       libbpf.o
  CC       bpf.o
  CC       nlattr.o
  CC       btf.o
  LD       libbpf-in.o
  LINK     libbpf.a
  LINK     bpftool
prog.o: In function `do_load':
prog.c:(.text+0x23d): undefined reference to `reallocarray'
collect2: error: ld returned 1 exit status
Makefile:89: recipe for target 'bpftool' failed
make[1]: *** [bpftool] Error 1
Makefile:99: recipe for target 'bpftool' failed
make: *** [bpftool] Error 2

Thanks,
Daniel