2021-10-21 03:48:40

by Yafang Shao

Subject: [PATCH v5 11/15] tools/bpf/bpftool: use TASK_COMM_LEN_16 instead of hard-coded 16

Use TASK_COMM_LEN_16 instead of hard-coded 16 to make it more grepable.
It uses bpf_probe_read_kernel() to get task comm, which may return a
string without nul terminator. We should use bpf_probe_read_kernel_str()
instead.

Signed-off-by: Yafang Shao <[email protected]>
Cc: Mathieu Desnoyers <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Steven Rostedt <[email protected]>
Cc: Kees Cook <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Petr Mladek <[email protected]>
---
tools/bpf/bpftool/Makefile | 1 +
tools/bpf/bpftool/main.h | 3 ++-
tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 4 ++--
tools/bpf/bpftool/skeleton/pid_iter.h | 4 +++-
4 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index d73232be1e99..33fbde84993c 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -164,6 +164,7 @@ $(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF)
$(QUIET_CLANG)$(CLANG) \
-I$(if $(OUTPUT),$(OUTPUT),.) \
-I$(srctree)/tools/include/uapi/ \
+ -I$(srctree)/tools/include/ \
-I$(LIBBPF_PATH) \
-I$(srctree)/tools/lib \
-g -O2 -Wall -target bpf -c $< -o $@ && $(LLVM_STRIP) -g $@
diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
index 90caa42aac4c..5efa27188f68 100644
--- a/tools/bpf/bpftool/main.h
+++ b/tools/bpf/bpftool/main.h
@@ -12,6 +12,7 @@
#include <linux/compiler.h>
#include <linux/kernel.h>
#include <linux/hashtable.h>
+#include <linux/sched/task.h>
#include <tools/libc_compat.h>

#include <bpf/libbpf.h>
@@ -124,7 +125,7 @@ struct obj_refs_table {

struct obj_ref {
int pid;
- char comm[16];
+ char comm[TASK_COMM_LEN_16];
};

struct obj_refs {
diff --git a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
index d9b420972934..f70702fcb224 100644
--- a/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
+++ b/tools/bpf/bpftool/skeleton/pid_iter.bpf.c
@@ -71,8 +71,8 @@ int iter(struct bpf_iter__task_file *ctx)

e.pid = task->tgid;
e.id = get_obj_id(file->private_data, obj_type);
- bpf_probe_read_kernel(&e.comm, sizeof(e.comm),
- task->group_leader->comm);
+ bpf_probe_read_kernel_str(&e.comm, sizeof(e.comm),
+ task->group_leader->comm);
bpf_seq_write(ctx->meta->seq, &e, sizeof(e));

return 0;
diff --git a/tools/bpf/bpftool/skeleton/pid_iter.h b/tools/bpf/bpftool/skeleton/pid_iter.h
index 5692cf257adb..675b2916567e 100644
--- a/tools/bpf/bpftool/skeleton/pid_iter.h
+++ b/tools/bpf/bpftool/skeleton/pid_iter.h
@@ -3,10 +3,12 @@
#ifndef __PID_ITER_H
#define __PID_ITER_H

+#include <linux/sched/task.h>
+
struct pid_iter_entry {
__u32 id;
int pid;
- char comm[16];
+ char comm[TASK_COMM_LEN_16];
};

#endif
--
2.17.1

2021-10-21 22:41:21

by Andrii Nakryiko

Subject: Re: [PATCH v5 11/15] tools/bpf/bpftool: use TASK_COMM_LEN_16 instead of hard-coded 16

On Wed, Oct 20, 2021 at 8:46 PM Yafang Shao <[email protected]> wrote:
>
> Use TASK_COMM_LEN_16 instead of hard-coded 16 to make it more grepable.
> It uses bpf_probe_read_kernel() to get task comm, which may return a
> string without nul terminator. We should use bpf_probe_read_kernel_str()
> instead.
>
> Signed-off-by: Yafang Shao <[email protected]>
> Cc: Mathieu Desnoyers <[email protected]>
> Cc: Arnaldo Carvalho de Melo <[email protected]>
> Cc: Peter Zijlstra <[email protected]>
> Cc: Steven Rostedt <[email protected]>
> Cc: Kees Cook <[email protected]>
> Cc: Al Viro <[email protected]>
> Cc: Petr Mladek <[email protected]>
> ---
> tools/bpf/bpftool/Makefile | 1 +
> tools/bpf/bpftool/main.h | 3 ++-
> tools/bpf/bpftool/skeleton/pid_iter.bpf.c | 4 ++--
> tools/bpf/bpftool/skeleton/pid_iter.h | 4 +++-
> 4 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index d73232be1e99..33fbde84993c 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -164,6 +164,7 @@ $(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF)
> $(QUIET_CLANG)$(CLANG) \
> -I$(if $(OUTPUT),$(OUTPUT),.) \
> -I$(srctree)/tools/include/uapi/ \
> + -I$(srctree)/tools/include/ \

bpftool shouldn't rely on internal kernel headers for compilation. If
you want to have TASK_COMM_LEN_16 constant for grep-ability, just
#define it where appropriate

> -I$(LIBBPF_PATH) \
> -I$(srctree)/tools/lib \
> -g -O2 -Wall -target bpf -c $< -o $@ && $(LLVM_STRIP) -g $@
> diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h
> index 90caa42aac4c..5efa27188f68 100644
> --- a/tools/bpf/bpftool/main.h
> +++ b/tools/bpf/bpftool/main.h
> @@ -12,6 +12,7 @@
> #include <linux/compiler.h>
> #include <linux/kernel.h>
> #include <linux/hashtable.h>
> +#include <linux/sched/task.h>
> #include <tools/libc_compat.h>
>

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