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Subject[PATCH v5 07/15] samples/bpf/kern: use TASK_COMM_LEN instead of hard-coded 16
Date
The linux/sched.h is visible to the bpf kernel modules, so we can use
TASK_COMM_LEN_16 to replace the hard-coded 16 in these bpf kernel
modules to make it more grepable.

In these bpf modules, someone gets task comm via bpf_get_current_comm(),
which always get a nul terminated string. While someone gets task comm via
bpf_probe_read_kernel(), which is unsafe, we should use
bpf_probe_read_kernel_str() instead.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Petr Mladek <pmladek@suse.com>
---
samples/bpf/offwaketime_kern.c | 10 +++++-----
samples/bpf/test_overhead_kprobe_kern.c | 11 ++++++-----
samples/bpf/test_overhead_tp_kern.c | 5 +++--
samples/bpf/tracex2_kern.c | 3 ++-
4 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/samples/bpf/offwaketime_kern.c b/samples/bpf/offwaketime_kern.c
index 4866afd054da..c0fd04497eea 100644
--- a/samples/bpf/offwaketime_kern.c
+++ b/samples/bpf/offwaketime_kern.c
@@ -23,8 +23,8 @@
#define MAX_ENTRIES 10000

struct key_t {
- char waker[TASK_COMM_LEN];
- char target[TASK_COMM_LEN];
+ char waker[TASK_COMM_LEN_16];
+ char target[TASK_COMM_LEN_16];
u32 wret;
u32 tret;
};
@@ -44,7 +44,7 @@ struct {
} start SEC(".maps");

struct wokeby_t {
- char name[TASK_COMM_LEN];
+ char name[TASK_COMM_LEN_16];
u32 ret;
};

@@ -113,11 +113,11 @@ static inline int update_counts(void *ctx, u32 pid, u64 delta)
/* 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_16];
int prev_pid;
int prev_prio;
long long prev_state;
- char next_comm[16];
+ char next_comm[TASK_COMM_LEN_16];
int next_pid;
int next_prio;
};
diff --git a/samples/bpf/test_overhead_kprobe_kern.c b/samples/bpf/test_overhead_kprobe_kern.c
index f6d593e47037..31e8c5ee0cdc 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_16] = {};
+ char newcomm[TASK_COMM_LEN_16] = {};
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..a6d5b3301af2 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_16];
+ char newcomm[TASK_COMM_LEN_16];
__u16 oom_score_adj;
};
SEC("tracepoint/task/task_rename")
diff --git a/samples/bpf/tracex2_kern.c b/samples/bpf/tracex2_kern.c
index 5bc696bac27d..d70ce59055cb 100644
--- a/samples/bpf/tracex2_kern.c
+++ b/samples/bpf/tracex2_kern.c
@@ -7,6 +7,7 @@
#include <linux/skbuff.h>
#include <linux/netdevice.h>
#include <linux/version.h>
+#include <linux/sched.h>
#include <uapi/linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>
@@ -65,7 +66,7 @@ static unsigned int log2l(unsigned long v)
}

struct hist_key {
- char comm[16];
+ char comm[TASK_COMM_LEN_16];
u64 pid_tgid;
u64 uid_gid;
u64 index;
--
2.17.1
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