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

Jiri Olsa
2020-04-06T13:00:34Z

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@fc58e82bfba4 ~]$
>
> So I patched it a bit, please ack:

perfect, thanks

Acked-by: Jiri Olsa <jolsa@redhat.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;
>
>