netdev - Re: [PATCH 13/15] perf tools: Synthesize bpf_trampoline/dispatcher ksymbol event

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Date:   Mon, 6 Apr 2020 15:00:21 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Song Liu <songliubraving@...com>, netdev@...r.kernel.org,
        bpf@...r.kernel.org, Andrii Nakryiko <andriin@...com>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        Jakub Kicinski <kuba@...nel.org>,
        David Miller <davem@...hat.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        John Fastabend <john.fastabend@...il.com>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        Song Liu <song@...nel.org>
Subject: Re: [PATCH 13/15] perf tools: Synthesize bpf_trampoline/dispatcher
 ksymbol event

On Mon, Apr 06, 2020 at 09:54:12AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Thu, Mar 12, 2020 at 08:56:08PM +0100, Jiri Olsa escreveu:
> > +static int
> > +process_bpf_image(char *name, u64 addr, struct kallsyms_parse *data)
> > +{
> > +	struct machine *machine = data->machine;
> > +	union perf_event *event = data->event;
> > +	struct perf_record_ksymbol *ksymbol;
> > +
> > +	ksymbol = &event->ksymbol;
> > +
> > +	*ksymbol = (struct perf_record_ksymbol) {
> > +		.header = {
> > +			.type = PERF_RECORD_KSYMBOL,
> > +			.size = offsetof(struct perf_record_ksymbol, name),
> > +		},
> > +		.addr      = addr,
> > +		.len       = page_size,
> > +		.ksym_type = PERF_RECORD_KSYMBOL_TYPE_BPF,
> > +		.flags     = 0,
> > +	};
> > +
> > +	strncpy(ksymbol->name, name, KSYM_NAME_LEN);
> > +	ksymbol->header.size += PERF_ALIGN(strlen(name) + 1, sizeof(u64));
> > +	memset((void *) event + event->header.size, 0, machine->id_hdr_size);
> > +	event->header.size += machine->id_hdr_size;
> > +
> > +	return perf_tool__process_synth_event(data->tool, event, machine,
> > +					      data->process);
> 
> This explodes in fedora 32 and rawhide and in openmandriva:cooker:
> 
>   GEN      /tmp/build/perf/python/perf.so
>   CC       /tmp/build/perf/util/bpf-event.o
> In file included from /usr/include/string.h:495,
>                  from /git/perf/tools/lib/bpf/libbpf_common.h:12,
>                  from /git/perf/tools/lib/bpf/bpf.h:31,
>                  from util/bpf-event.c:4:
> In function ‘strncpy’,
>     inlined from ‘process_bpf_image’ at util/bpf-event.c:323:2,
>     inlined from ‘kallsyms_process_symbol’ at util/bpf-event.c:358:9:
> /usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ specified bound 256 equals destination size [-Werror=stringop-truncation]
>   106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos (__dest));
>       |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> mv: cannot stat '/tmp/build/perf/util/.bpf-event.o.tmp': No such file or directory
> make[4]: *** [/git/perf/tools/build/Makefile.build:97: /tmp/build/perf/util/bpf-event.o] Error 1
> make[3]: *** [/git/perf/tools/build/Makefile.build:139: util] Error 2
> make[2]: *** [Makefile.perf:617: /tmp/build/perf/perf-in.o] Error 2
> make[1]: *** [Makefile.perf:225: sub-make] Error 2
> make: *** [Makefile:70: all] Error 2
> make: Leaving directory '/git/perf/tools/perf'
> [perfbuilder@...8e82bfba4 ~]$
> 
> So I patched it a bit, please ack:

perfect, thanks

Acked-by: Jiri Olsa <jolsa@...hat.com>

jirka

> 
> 
> diff --git a/tools/perf/util/bpf-event.c b/tools/perf/util/bpf-event.c
> index 3728db98981e..0cd41a862952 100644
> --- a/tools/perf/util/bpf-event.c
> +++ b/tools/perf/util/bpf-event.c
> @@ -306,6 +306,7 @@ process_bpf_image(char *name, u64 addr, struct kallsyms_parse *data)
>  	struct machine *machine = data->machine;
>  	union perf_event *event = data->event;
>  	struct perf_record_ksymbol *ksymbol;
> +	int len;
>  
>  	ksymbol = &event->ksymbol;
>  
> @@ -320,8 +321,8 @@ process_bpf_image(char *name, u64 addr, struct kallsyms_parse *data)
>  		.flags     = 0,
>  	};
>  
> -	strncpy(ksymbol->name, name, KSYM_NAME_LEN);
> -	ksymbol->header.size += PERF_ALIGN(strlen(name) + 1, sizeof(u64));
> +	len = scnprintf(ksymbol->name, KSYM_NAME_LEN, "%s", name);
> +	ksymbol->header.size += PERF_ALIGN(len + 1, sizeof(u64));
>  	memset((void *) event + event->header.size, 0, machine->id_hdr_size);
>  	event->header.size += machine->id_hdr_size;
>  
>