linux-kernel - [PATCH v6 06/12] samples/bpf/test_overhead_kprobe_kern: make it adopt to task comm size change

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Message-Id: <20211025083315.4752-7-laoar.shao@gmail.com>
Date:   Mon, 25 Oct 2021 08:33:09 +0000
From:   Yafang Shao <laoar.shao@...il.com>
To:     akpm@...ux-foundation.org, keescook@...omium.org,
        rostedt@...dmis.org, mathieu.desnoyers@...icios.com,
        arnaldo.melo@...il.com, pmladek@...e.com, peterz@...radead.org,
        viro@...iv.linux.org.uk, valentin.schneider@....com,
        qiang.zhang@...driver.com, robdclark@...omium.org,
        christian@...uner.io, dietmar.eggemann@....com, mingo@...hat.com,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        davem@...emloft.net, kuba@...nel.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, kafai@...com,
        songliubraving@...com, yhs@...com, john.fastabend@...il.com,
        kpsingh@...nel.org, dennis.dalessandro@...nelisnetworks.com,
        mike.marciniszyn@...nelisnetworks.com, dledford@...hat.com,
        jgg@...pe.ca
Cc:     linux-rdma@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-perf-users@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, oliver.sang@...el.com, lkp@...el.com,
        Yafang Shao <laoar.shao@...il.com>,
        Andrii Nakryiko <andrii.nakryiko@...il.com>
Subject: [PATCH v6 06/12] samples/bpf/test_overhead_kprobe_kern: make it adopt to task comm size change

bpf_probe_read_kernel_str() will add a nul terminator to the dst, then
we don't care about if the dst size is big enough. This patch also
replaces the hard-coded 16 with TASK_COMM_LEN to make it adopt to task
comm size change.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@...il.com>
Cc: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Kees Cook <keescook@...omium.org>
Cc: Petr Mladek <pmladek@...e.com>
---
 samples/bpf/test_overhead_kprobe_kern.c | 11 ++++++-----
 samples/bpf/test_overhead_tp_kern.c     |  5 +++--
 2 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/samples/bpf/test_overhead_kprobe_kern.c b/samples/bpf/test_overhead_kprobe_kern.c
index f6d593e47037..8fdd2c9c56b2 100644
--- a/samples/bpf/test_overhead_kprobe_kern.c
+++ b/samples/bpf/test_overhead_kprobe_kern.c
@@ -6,6 +6,7 @@
  */
 #include <linux/version.h>
 #include <linux/ptrace.h>
+#include <linux/sched.h>
 #include <uapi/linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
@@ -22,17 +23,17 @@ int prog(struct pt_regs *ctx)
 {
 	struct signal_struct *signal;
 	struct task_struct *tsk;
-	char oldcomm[16] = {};
-	char newcomm[16] = {};
+	char oldcomm[TASK_COMM_LEN] = {};
+	char newcomm[TASK_COMM_LEN] = {};
 	u16 oom_score_adj;
 	u32 pid;
 
 	tsk = (void *)PT_REGS_PARM1(ctx);
 
 	pid = _(tsk->pid);
-	bpf_probe_read_kernel(oldcomm, sizeof(oldcomm), &tsk->comm);
-	bpf_probe_read_kernel(newcomm, sizeof(newcomm),
-			      (void *)PT_REGS_PARM2(ctx));
+	bpf_probe_read_kernel_str(oldcomm, sizeof(oldcomm), &tsk->comm);
+	bpf_probe_read_kernel_str(newcomm, sizeof(newcomm),
+				  (void *)PT_REGS_PARM2(ctx));
 	signal = _(tsk->signal);
 	oom_score_adj = _(signal->oom_score_adj);
 	return 0;
diff --git a/samples/bpf/test_overhead_tp_kern.c b/samples/bpf/test_overhead_tp_kern.c
index eaa32693f8fc..80edadacb692 100644
--- a/samples/bpf/test_overhead_tp_kern.c
+++ b/samples/bpf/test_overhead_tp_kern.c
@@ -4,6 +4,7 @@
  * modify it under the terms of version 2 of the GNU General Public
  * License as published by the Free Software Foundation.
  */
+#include <linux/sched.h>
 #include <uapi/linux/bpf.h>
 #include <bpf/bpf_helpers.h>
 
@@ -11,8 +12,8 @@
 struct task_rename {
 	__u64 pad;
 	__u32 pid;
-	char oldcomm[16];
-	char newcomm[16];
+	char oldcomm[TASK_COMM_LEN];
+	char newcomm[TASK_COMM_LEN];
 	__u16 oom_score_adj;
 };
 SEC("tracepoint/task/task_rename")
-- 
2.17.1