Subject: Re: [PATCH bpf-next v2] libbpf: Print hint about ulimit when getting permission denied error

From: Toke Høiland-Jørgensen <[email-masked]>
Date: Wed, 18 Dec 2019 12:08:34 +0100

Naresh Kamboju <[email-masked]> writes:

> On Tue, 17 Dec 2019 at 00:00, Toke Høiland-Jørgensen <[email-masked]> wrote:
>> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
>> index a2cc7313763a..3fe42d6b0c2f 100644
>> --- a/tools/lib/bpf/libbpf.c
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -41,6 +41,7 @@
>>  #include <sys/types.h>
>>  #include <sys/vfs.h>
>>  #include <sys/utsname.h>
>> +#include <sys/resource.h>
>>  #include <tools/libc_compat.h>
>>  #include <libelf.h>
>>  #include <gelf.h>
>> @@ -100,6 +101,32 @@ void libbpf_print(enum libbpf_print_level level, const char *format, ...)
>>         va_end(args);
>>  }
>>
>> +static void pr_perm_msg(int err)
>> +{
>> +       struct rlimit limit;
>> +       char buf[100];
>> +
>> +       if (err != -EPERM || geteuid() != 0)
>> +               return;
>> +
>> +       err = getrlimit(RLIMIT_MEMLOCK, &limit);
>> +       if (err)
>> +               return;
>> +
>> +       if (limit.rlim_cur == RLIM_INFINITY)
>> +               return;
>> +
>> +       if (limit.rlim_cur < 1024)
>> +               snprintf(buf, sizeof(buf), "%lu bytes", limit.rlim_cur);
>
>  libbpf.c: In function 'pr_perm_msg':
>  libbpf.c:120:33: error: format '%lu' expects argument of type 'long
> unsigned int', but argument 4 has type 'rlim_t {aka long long unsigned
> int}' [-Werror=format=]
>     snprintf(buf, sizeof(buf), "%lu bytes", limit.rlim_cur);
>                                 ~~^         ~~~~~~~~~~~~~~
>                                 %llu
>

Ah, guess this needs PRIu64. Will send a follow-up, thanks for the
report :)

-Toke