Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
From:   Yafang Shao <laoar.shao@gmail.com>
To:     akpm@linux-foundation.org, keescook@chromium.org,
        rostedt@goodmis.org, mathieu.desnoyers@efficios.com,
        arnaldo.melo@gmail.com, pmladek@suse.com, peterz@infradead.org,
        viro@zeniv.linux.org.uk, valentin.schneider@arm.com,
        qiang.zhang@windriver.com, robdclark@chromium.org,
        christian@brauner.io, dietmar.eggemann@arm.com, mingo@redhat.com,
        juri.lelli@redhat.com, vincent.guittot@linaro.org,
        davem@davemloft.net, kuba@kernel.org, ast@kernel.org,
        daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com,
        songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com,
        kpsingh@kernel.org, dennis.dalessandro@cornelisnetworks.com,
        mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com,
        jgg@ziepe.ca
Cc:     linux-rdma@vger.kernel.org, netdev@vger.kernel.org,
        bpf@vger.kernel.org, linux-perf-users@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, oliver.sang@intel.com, lkp@intel.com,
        Yafang Shao <laoar.shao@gmail.com>,
        Andrii Nakryiko <andrii.nakryiko@gmail.com>
Subject: [PATCH v6 10/12] tools/testing/selftests/bpf: make it adopt to task comm size change
Date:   Mon, 25 Oct 2021 08:33:13 +0000
Message-Id: <20211025083315.4752-11-laoar.shao@gmail.com>
In-Reply-To: <20211025083315.4752-1-laoar.shao@gmail.com>
References: <20211025083315.4752-1-laoar.shao@gmail.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The hard-coded 16 is used in various bpf progs. These progs get task
comm either via bpf_get_current_comm() or prctl() or
bpf_core_read_str(), all of which can work well even if the task comm size
is changed.

In these BPF programs, one thing to be improved is the
sched:sched_switch tracepoint args. As the tracepoint args are derived
from the kernel, we'd better make it same with the kernel. So the macro
TASK_COMM_LEN is converted to type enum, then all the BPF programs can
get it through BTF.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Petr Mladek <pmladek@suse.com>
---
 include/linux/sched.h                                   | 9 +++++++--
 tools/testing/selftests/bpf/progs/test_stacktrace_map.c | 6 +++---
 tools/testing/selftests/bpf/progs/test_tracepoint.c     | 6 +++---
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index c1a927ddec64..124538db792c 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -274,8 +274,13 @@ struct task_group;
 
 #define get_current_state()	READ_ONCE(current->__state)
 
-/* Task command name length: */
-#define TASK_COMM_LEN			16
+/*
+ * Define the task command name length as enum, then it can be visible to
+ * BPF programs.
+ */
+enum {
+	TASK_COMM_LEN = 16,
+};
 
 extern void scheduler_tick(void);
 
diff --git a/tools/testing/selftests/bpf/progs/test_stacktrace_map.c b/tools/testing/selftests/bpf/progs/test_stacktrace_map.c
index 00ed48672620..e9b602a6dc1b 100644
--- a/tools/testing/selftests/bpf/progs/test_stacktrace_map.c
+++ b/tools/testing/selftests/bpf/progs/test_stacktrace_map.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (c) 2018 Facebook
 
-#include <linux/bpf.h>
+#include <vmlinux.h>
 #include <bpf/bpf_helpers.h>
 
 #ifndef PERF_MAX_STACK_DEPTH
@@ -41,11 +41,11 @@ struct {
 /* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
 struct sched_switch_args {
 	unsigned long long pad;
-	char prev_comm[16];
+	char prev_comm[TASK_COMM_LEN];
 	int prev_pid;
 	int prev_prio;
 	long long prev_state;
-	char next_comm[16];
+	char next_comm[TASK_COMM_LEN];
 	int next_pid;
 	int next_prio;
 };
diff --git a/tools/testing/selftests/bpf/progs/test_tracepoint.c b/tools/testing/selftests/bpf/progs/test_tracepoint.c
index 4b825ee122cf..f21982681e28 100644
--- a/tools/testing/selftests/bpf/progs/test_tracepoint.c
+++ b/tools/testing/selftests/bpf/progs/test_tracepoint.c
@@ -1,17 +1,17 @@
 // SPDX-License-Identifier: GPL-2.0
 // Copyright (c) 2017 Facebook
 
-#include <linux/bpf.h>
+#include <vmlinux.h>
 #include <bpf/bpf_helpers.h>
 
 /* taken from /sys/kernel/debug/tracing/events/sched/sched_switch/format */
 struct sched_switch_args {
 	unsigned long long pad;
-	char prev_comm[16];
+	char prev_comm[TASK_COMM_LEN];
 	int prev_pid;
 	int prev_prio;
 	long long prev_state;
-	char next_comm[16];
+	char next_comm[TASK_COMM_LEN];
 	int next_pid;
 	int next_prio;
 };
-- 
2.17.1