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

Arnaldo Carvalho de Melo
2020-04-06T12:54:17Z

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:

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;