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

From: Yafang Shao
Date: Mon Oct 25 2021 - 04:34:19 EST


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@xxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <arnaldo.melo@xxxxxxxxx>
Cc: Andrii Nakryiko <andrii.nakryiko@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: Petr Mladek <pmladek@xxxxxxxx>
---
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