[PATCH 04/18] perf trace: Fix setting of augmented payload when using eBPF + raw_syscalls

Arnaldo Carvalho de Melo
2018-11-06T12:06:46Z

From: Arnaldo Carvalho de Melo <acme@redhat.com>

For now with BPF raw_augmented we hook into raw_syscalls:sys_enter and
there we get all 6 syscall args plus the tracepoint common fields
(sizeof(long)) and the syscall_nr (another long). So we check if that is
the case and if so don't look after the sc->args_size, but always after
the full raw_syscalls:sys_enter payload, which is fixed.

We'll revisit this later to pass s->args_size to the BPF augmenter (now
tools/perf/examples/bpf/augmented_raw_syscalls.c, so that it copies only
what we need for each syscall, like what happens when we use
syscalls:sys_enter_NAME, so that we reduce the kernel/userspace traffic
to just what is needed for each syscall.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-nlslrg8apxdsobt4pwl3n7ur@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-trace.c | 37 ++++++++++++++++++++++++++++++-------
1 file changed, 30 insertions(+), 7 deletions(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index f582ca575883..835619476370 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -108,6 +108,7 @@ struct trace {
} stats;
unsigned int max_stack;
unsigned int min_stack;
+ bool raw_augmented_syscalls;
bool not_ev_qualifier;
bool live;
bool full_time;
@@ -1724,13 +1725,28 @@ static int trace__fprintf_sample(struct trace *trace, struct perf_evsel *evsel,
return printed;
}

-static void *syscall__augmented_args(struct syscall *sc, struct perf_sample *sample, int *augmented_args_size)
+static void *syscall__augmented_args(struct syscall *sc, struct perf_sample *sample, int *augmented_args_size, bool raw_augmented)
{
void *augmented_args = NULL;
+ /*
+ * For now with BPF raw_augmented we hook into raw_syscalls:sys_enter
+ * and there we get all 6 syscall args plus the tracepoint common
+ * fields (sizeof(long)) and the syscall_nr (another long). So we check
+ * if that is the case and if so don't look after the sc->args_size,
+ * but always after the full raw_syscalls:sys_enter payload, which is
+ * fixed.
+ *
+ * We'll revisit this later to pass s->args_size to the BPF augmenter
+ * (now tools/perf/examples/bpf/augmented_raw_syscalls.c, so that it
+ * copies only what we need for each syscall, like what happens when we
+ * use syscalls:sys_enter_NAME, so that we reduce the kernel/userspace
+ * traffic to just what is needed for each syscall.
+ */
+ int args_size = raw_augmented ? (8 * (int)sizeof(long)) : sc->args_size;

- *augmented_args_size = sample->raw_size - sc->args_size;
+ *augmented_args_size = sample->raw_size - args_size;
if (*augmented_args_size > 0)
- augmented_args = sample->raw_data + sc->args_size;
+ augmented_args = sample->raw_data + args_size;

return augmented_args;
}
@@ -1780,7 +1796,7 @@ static int trace__sys_enter(struct trace *trace, struct perf_evsel *evsel,
* here and avoid using augmented syscalls when the evsel is the raw_syscalls one.
*/
if (evsel != trace->syscalls.events.sys_enter)
- augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size);
+ augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size, trace->raw_augmented_syscalls);
ttrace->entry_time = sample->time;
msg = ttrace->entry_str;
printed += scnprintf(msg + printed, trace__entry_str_size - printed, "%s(", sc->name);
@@ -1833,7 +1849,7 @@ static int trace__fprintf_sys_enter(struct trace *trace, struct perf_evsel *evse
goto out_put;

args = perf_evsel__sc_tp_ptr(evsel, args, sample);
- augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size);
+ augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size, trace->raw_augmented_syscalls);
syscall__scnprintf_args(sc, msg, sizeof(msg), args, augmented_args, augmented_args_size, trace, thread);
fprintf(trace->output, "%s", msg);
err = 0;
@@ -3501,8 +3517,15 @@ int cmd_trace(int argc, const char **argv)
evsel->handler = trace__sys_enter;

evlist__for_each_entry(trace.evlist, evsel) {
- if (strstarts(perf_evsel__name(evsel), "syscalls:sys_exit_") ||
- strcmp(perf_evsel__name(evsel), "raw_syscalls:sys_exit") == 0) {
+ bool raw_syscalls_sys_exit = strcmp(perf_evsel__name(evsel), "raw_syscalls:sys_exit") == 0;
+
+ if (raw_syscalls_sys_exit) {
+ trace.raw_augmented_syscalls = true;
+ goto init_augmented_syscall_tp;
+ }
+
+ if (strstarts(perf_evsel__name(evsel), "syscalls:sys_exit_")) {
+init_augmented_syscall_tp:
perf_evsel__init_augmented_syscall_tp(evsel);
perf_evsel__init_augmented_syscall_tp_ret(evsel);
evsel->handler = trace__sys_exit;
--
2.14.4