[PATCH 22/63] perf trace: Implement syscall filtering in augmented_syscalls

Arnaldo Carvalho de Melo
2018-12-18T22:09:51Z

Just another map, this time an BPF_MAP_TYPE_ARRAY, stating with
one bool per syscall, stating if it should be filtered or not.

So, with a pre-built augmented_raw_syscalls.o file, we use:

# perf trace -e open*,augmented_raw_syscalls.o
0.000 ( 0.016 ms): DNS Res~er #37/29652 openat(dfd: CWD, filename: /etc/hosts, flags: CLOEXEC ) = 138
187.039 ( 0.048 ms): gsd-housekeepi/2436 openat(dfd: CWD, filename: /etc/fstab, flags: CLOEXEC ) = 11
187.348 ( 0.041 ms): gsd-housekeepi/2436 openat(dfd: CWD, filename: /proc/self/mountinfo, flags: CLOEXEC ) = 11
188.793 ( 0.036 ms): gsd-housekeepi/2436 openat(dfd: CWD, filename: /proc/self/mountinfo, flags: CLOEXEC ) = 11
189.803 ( 0.029 ms): gsd-housekeepi/2436 openat(dfd: CWD, filename: /proc/self/mountinfo, flags: CLOEXEC ) = 11
190.774 ( 0.027 ms): gsd-housekeepi/2436 openat(dfd: CWD, filename: /proc/self/mountinfo, flags: CLOEXEC ) = 11
284.620 ( 0.149 ms): DataStorage/3076 openat(dfd: CWD, filename: /home/acme/.mozilla/firefox/ina67tev.default/SiteSecurityServiceState.txt, flags: CREAT|TRUNC|WRONLY, mode: IRUGO|IWUSR|IWGRP) = 167
^C#

What is it that this gsd-housekeeping thingy needs to open
/proc/self/mountinfo four times periodically? :-)

This map will be extended to tell per-syscall parameters, i.e. how many
bytes to copy per arg, using the function signature to get the types and
then the size of those types, via BTF.

Cc: Adrian Hunter <adrian.hunter@intel.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-cy222g9ucvnym3raqvxp0hpg@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
---
tools/perf/builtin-trace.c | 66 +++++++++++++++++++
.../examples/bpf/augmented_raw_syscalls.c | 26 +++++++-
2 files changed, 91 insertions(+), 1 deletion(-)

diff --git a/tools/perf/builtin-trace.c b/tools/perf/builtin-trace.c
index f9eb5bc4fefb..de81918c7ad4 100644
--- a/tools/perf/builtin-trace.c
+++ b/tools/perf/builtin-trace.c
@@ -76,6 +76,7 @@ struct trace {
struct {
int max;
struct syscall *table;
+ struct bpf_map *map;
struct {
struct perf_evsel *sys_enter,
*sys_exit,
@@ -2578,8 +2579,64 @@ static int trace__set_ev_qualifier_tp_filter(struct trace *trace)
goto out;
}

+#ifdef HAVE_LIBBPF_SUPPORT
+static int trace__set_ev_qualifier_bpf_filter(struct trace *trace)
+{
+ int fd = bpf_map__fd(trace->syscalls.map);
+ bool value = !trace->not_ev_qualifier;
+ int err = 0;
+ size_t i;
+
+ for (i = 0; i < trace->ev_qualifier_ids.nr; ++i) {
+ int key = trace->ev_qualifier_ids.entries[i];
+
+ err = bpf_map_update_elem(fd, &key, &value, BPF_EXIST);
+ if (err)
+ break;
+ }
+
+ return err;
+}
+
+static int __trace__init_syscalls_bpf_map(struct trace *trace, bool enabled)
+{
+ int fd = bpf_map__fd(trace->syscalls.map);
+ int err = 0, key;
+
+ for (key = 0; key < trace->sctbl->syscalls.nr_entries; ++key) {
+ err = bpf_map_update_elem(fd, &key, &enabled, BPF_ANY);
+ if (err)
+ break;
+ }
+
+ return err;
+}
+
+static int trace__init_syscalls_bpf_map(struct trace *trace)
+{
+ bool enabled = true;
+
+ if (trace->ev_qualifier_ids.nr)
+ enabled = trace->not_ev_qualifier;
+
+ return __trace__init_syscalls_bpf_map(trace, enabled);
+}
+#else
+static int trace__set_ev_qualifier_bpf_filter(struct trace *trace __maybe_unused)
+{
+ return 0;
+}
+
+static int trace__init_syscalls_bpf_map(struct trace *trace __maybe_unused)
+{
+ return 0;
+}
+#endif // HAVE_LIBBPF_SUPPORT
+
static int trace__set_ev_qualifier_filter(struct trace *trace)
{
+ if (trace->syscalls.map)
+ return trace__set_ev_qualifier_bpf_filter(trace);
return trace__set_ev_qualifier_tp_filter(trace);
}

@@ -2822,6 +2879,9 @@ static int trace__run(struct trace *trace, int argc, const char **argv)
if (err < 0)
goto out_error_mem;

+ if (trace->syscalls.map)
+ trace__init_syscalls_bpf_map(trace);
+
if (trace->ev_qualifier_ids.nr > 0) {
err = trace__set_ev_qualifier_filter(trace);
if (err < 0)
@@ -3449,6 +3509,11 @@ static void trace__set_bpf_map_filtered_pids(struct trace *trace)
trace->filter_pids.map = bpf__find_map_by_name("pids_filtered");
}

+static void trace__set_bpf_map_syscalls(struct trace *trace)
+{
+ trace->syscalls.map = bpf__find_map_by_name("syscalls");
+}
+
int cmd_trace(int argc, const char **argv)
{
const char *trace_usage[] = {
@@ -3589,6 +3654,7 @@ int cmd_trace(int argc, const char **argv)
if (evsel) {
trace.syscalls.events.augmented = evsel;
trace__set_bpf_map_filtered_pids(&trace);
+ trace__set_bpf_map_syscalls(&trace);
}

err = bpf__setup_stdout(trace.evlist);
diff --git a/tools/perf/examples/bpf/augmented_raw_syscalls.c b/tools/perf/examples/bpf/augmented_raw_syscalls.c
index 74ce7574073d..bb3dcc4ec256 100644
--- a/tools/perf/examples/bpf/augmented_raw_syscalls.c
+++ b/tools/perf/examples/bpf/augmented_raw_syscalls.c
@@ -26,6 +26,13 @@ struct bpf_map SEC("maps") __augmented_syscalls__ = {
.max_entries = __NR_CPUS__,
};

+struct bpf_map SEC("maps") syscalls = {
+ .type = BPF_MAP_TYPE_ARRAY,
+ .key_size = sizeof(int),
+ .value_size = sizeof(bool),
+ .max_entries = 512,
+};
+
struct syscall_enter_args {
unsigned long long common_tp_fields;
long syscall_nr;
@@ -56,6 +63,7 @@ int sys_enter(struct syscall_enter_args *args)
struct syscall_enter_args args;
struct augmented_filename filename;
} augmented_args;
+ bool *enabled;
unsigned int len = sizeof(augmented_args);
const void *filename_arg = NULL;

@@ -63,6 +71,10 @@ int sys_enter(struct syscall_enter_args *args)
return 0;

probe_read(&augmented_args.args, sizeof(augmented_args.args), args);
+
+ enabled = bpf_map_lookup_elem(&syscalls, &augmented_args.args.syscall_nr);
+ if (enabled == NULL || !*enabled)
+ return 0;
/*
* Yonghong and Edward Cree sayz:
*
@@ -131,7 +143,19 @@ int sys_enter(struct syscall_enter_args *args)
SEC("raw_syscalls:sys_exit")
int sys_exit(struct syscall_exit_args *args)
{
- return !pid_filter__has(&pids_filtered, getpid());
+ struct syscall_exit_args exit_args;
+ bool *enabled;
+
+ if (pid_filter__has(&pids_filtered, getpid()))
+ return 0;
+
+ probe_read(&exit_args, sizeof(exit_args), args);
+
+ enabled = bpf_map_lookup_elem(&syscalls, &exit_args.syscall_nr);
+ if (enabled == NULL || !*enabled)
+ return 0;
+
+ return 1;
}

license(GPL);
--
2.19.2