Re: [PATCHv3 perf/core 1/6] tools lib bpf: Add BPF program pinning APIs.

[Joe Stringer <joe@ovn.org>]

On 30 January 2017 at 12:28, Arnaldo Carvalho de Melo <acme@kernel.org> wrote:
> Em Mon, Jan 30, 2017 at 05:25:06PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Thu, Jan 26, 2017 at 01:19:56PM -0800, Joe Stringer escreveu:
>> > Add new APIs to pin a BPF program (or specific instances) to the filesystem.
>> > The user can specify the path full path within a BPF filesystem to pin the
>> > program.
>> >
>> > bpf_program__pin_instance(prog, path, n) will pin the nth instance of
>> > 'prog' to the specified path.
>> > bpf_program__pin(prog, path) will create the directory 'path' (if it
>> > does not exist) and pin each instance within that directory. For
>> > instance, path/0, path/1, path/2.
>> >
>> > Signed-off-by: Joe Stringer <joe@ovn.org>
>>
>> make: Entering directory '/home/acme/git/linux/tools/perf'
>>   BUILD:   Doing 'make -j4' parallel build
>>   CC       /tmp/build/perf/builtin-record.o
>>   CC       /tmp/build/perf/libbpf.o
>>   CC       /tmp/build/perf/util/parse-events.o
>>   INSTALL  trace_plugins
>> libbpf.c: In function ‘make_dir’:
>> libbpf.c:1303:6: error: implicit declaration of function ‘mkdir’ [-Werror=implicit-function-declaration]
>>   if (mkdir(path, 0700) && errno != EEXIST)
>>       ^~~~~
>> libbpf.c:1303:2: error: nested extern declaration of ‘mkdir’ [-Werror=nested-externs]
>>   if (mkdir(path, 0700) && errno != EEXIST)
>>   ^~
>> cc1: all warnings being treated as errors
>> mv: cannot stat '/tmp/build/perf/.libbpf.o.tmp': No such file or directory
>> /home/acme/git/linux/tools/build/Makefile.build:101: recipe for target '/tmp/build/perf/libbpf.o' failed

Not sure why but I didn't see this. Appreciate the fix.

>>
>>
>> And strdup() is not checked for failure, I'm fixing those,
>>
>> +++ b/tools/lib/bpf/libbpf.c
>> @@ -36,6 +36,8 @@
>>  #include <linux/magic.h>
>>  #include <linux/list.h>
>>  #include <linux/limits.h>
>> +#include <sys/stat.h>
>> +#include <sys/types.h>
>>  #include <sys/vfs.h>
>
> This as well:
>
> @@ -1338,7 +1343,7 @@ int bpf_program__pin(struct bpf_program *prog,
> const char *path)
>                 len = snprintf(buf, PATH_MAX, "%s/%d", path, i);
>                 if (len < 0)
>                         return -EINVAL;
> -               else if (len > PATH_MAX)
> +               else if (len >= PATH_MAX)
>                         return -ENAMETOOLONG;
>
>
> See 'man snprintf', return value:
>
> ---
> Thus, a return value of size or more means that the output was
> truncated.
> ---

Good spotting, I looked over the committed versions and tested them,
they seem good to me. Thanks!