Re: [PATCH v1 6/7] perf trace: 5sec fix libbpf 1.0+ compatibility

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Em Wed, Nov 02, 2022 at 09:54:36PM -0700, Ian Rogers escreveu:
> Avoid use of tools/perf/include/bpf/bpf.h and use the more regular BPF
> headers.
> 
> Note, on testing the probe was unable to attach and the program failed.

Humm, trying to test:

[root@quaco ~]# perf trace -e /home/acme/git/perf/tools/perf/examples/bpf/5sec.c |& head -15
In file included from /home/acme/git/perf/tools/perf/examples/bpf/5sec.c:42:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/bpf.h:9:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/workqueue.h:9:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/timer.h:6:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/ktime.h:24:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/time.h:6:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/math64.h:6:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/math.h:6:
/lib/modules/5.19.16-200.fc36.x86_64/build/./arch/x86/include/asm/div64.h:85:28: error: invalid output constraint '=a' in asm
        asm ("mulq %2; divq %3" : "=a" (q)
                                  ^
In file included from /home/acme/git/perf/tools/perf/examples/bpf/5sec.c:42:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/bpf.h:9:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/workqueue.h:9:
In file included from /lib/modules/5.19.16-200.fc36.x86_64/build/./include/linux/timer.h:6:
[root@quaco ~]#

So I go and try to remove that <linux/bpf.h>:

[acme@quaco perf]$ git diff
diff --git a/tools/perf/examples/bpf/5sec.c b/tools/perf/examples/bpf/5sec.c
index 3bd7fc17631f0440..e0d5525c6a1374ae 100644
--- a/tools/perf/examples/bpf/5sec.c
+++ b/tools/perf/examples/bpf/5sec.c
@@ -39,7 +39,6 @@
    Copyright (C) 2018 Red Hat, Inc., Arnaldo Carvalho de Melo <acme@redhat.com>
 */

-#include <linux/bpf.h>
 #include <bpf/bpf_helpers.h>

 #define NSEC_PER_SEC   1000000000L
[acme@quaco perf]$

[root@quaco ~]# perf trace -e /home/acme/git/perf/tools/perf/examples/bpf/5sec.c
/home/acme/git/perf/tools/perf/examples/bpf/5sec.c:42:10: fatal error: 'bpf/bpf_helpers.h' file not found
#include <bpf/bpf_helpers.h>
         ^~~~~~~~~~~~~~~~~~~
1 error generated.
ERROR:	unable to compile /home/acme/git/perf/tools/perf/examples/bpf/5sec.c
Hint:	Check error message shown above.
Hint:	You can also pre-compile it into .o using:
     		clang -target bpf -O2 -c /home/acme/git/perf/tools/perf/examples/bpf/5sec.c
     	with proper -I and -D options.
event syntax error: '/home/acme/git/perf/tools/perf/examples/bpf/5sec.c'
                     \___ Failed to load /home/acme/git/perf/tools/perf/examples/bpf/5sec.c from source: Error when compiling BPF scriptlet

(add -v to see detail)
Run 'perf list' for a list of valid events

 Usage: perf trace [<options>] [<command>]
    or: perf trace [<options>] -- <command> [<options>]
    or: perf trace record [<options>] [<command>]
    or: perf trace record [<options>] -- <command> [<options>]

    -e, --event <event>   event/syscall selector. use 'perf list' to list available events
[root@quaco ~]#

It is not even finding it, in this machine I have libbpf 0.7.0, so there
is a /usr/include/bpf/bpf_helpers.h, but probably that isn't in the
include path set up to build the tools/perf/examples/bpf/ files, perhaps
it should use:

-Itools/lib/  so that it gets tools/lib/bpf_helpers.h?

Trying to get this tested...

- Arnaldo
 
> Signed-off-by: Ian Rogers <irogers@google.com>
> ---
>  tools/perf/examples/bpf/5sec.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/perf/examples/bpf/5sec.c b/tools/perf/examples/bpf/5sec.c
> index e6b6181c6dc6..f22312c64713 100644
> --- a/tools/perf/examples/bpf/5sec.c
> +++ b/tools/perf/examples/bpf/5sec.c
> @@ -39,13 +39,15 @@
>     Copyright (C) 2018 Red Hat, Inc., Arnaldo Carvalho de Melo <acme@redhat.com>
>  */
>  
> -#include <bpf.h>
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
>  
>  #define NSEC_PER_SEC	1000000000L
>  
> -int probe(hrtimer_nanosleep, rqtp)(void *ctx, int err, long long sec)
> +SEC("hrtimer_nanosleep=hrtimer_nanosleep rqtp")
> +int hrtimer_nanosleep(void *ctx, int err, long long sec)
>  {
>  	return sec / NSEC_PER_SEC == 5ULL;
>  }
> +char _license[] SEC("license") = "GPL";
>  
> -license(GPL);
> -- 
> 2.38.1.273.g43a17bfeac-goog

-- 

- Arnaldo