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

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

Em Thu, Nov 03, 2022 at 12:36:36PM -0300, Arnaldo Carvalho de Melo escreveu:
> 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...

Running with -v:

llvm compiling command : /usr/lib64/ccache/clang -D__KERNEL__ -D__NR_CPUS__=8 -DLINUX_VERSION_CODE=0x51310 -g -I/home/acme/lib/perf/include/bpf -nostdinc -I./arch/x86/include -I./arch/x86/include/generated  -I./include -I./arch/x86/include/uapi -I./arch/x86/include/generated/uapi -I./include/uapi -I./include/generated/uapi -include ./include/linux/compiler-version.h -include ./include/linux/kconfig.h  -Wno-unused-value -Wno-pointer-sign -working-directory /lib/modules/5.19.16-200.fc36.x86_64/build -c /home/acme/git/perf/tools/perf/examples/bpf/5sec.c -target bpf  -g -O2 -o -
/home/acme/git/perf/tools/perf/examples/bpf/5sec.c:42:10: fatal error: 'bpf/bpf_helpers.h' file not found

There is still that -I/home/acme/lib/perf/include/bpf, I'll remove it
from the include path and try to replace it with the libbpf path...

- Arnaldo