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[79.242.62.232]) by smtp.gmail.com with ESMTPSA id g18sm2436886wrv.42.2021.11.11.02.07.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 11 Nov 2021 02:07:46 -0800 (PST) Message-ID: <8be53ae6-b3f9-f3da-afc7-23c8232a7a0a@redhat.com> Date: Thu, 11 Nov 2021 11:07:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.2.0 Subject: Re: [PATCH 5/7] samples/bpf/test_overhead_kprobe_kern: make it adopt to task comm size change Content-Language: en-US To: Yafang Shao , akpm@linux-foundation.org Cc: 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, Kees Cook , Mathieu Desnoyers , Arnaldo Carvalho de Melo , Alexei Starovoitov , Andrii Nakryiko , Michal Miroslaw , Peter Zijlstra , Steven Rostedt , Matthew Wilcox , Al Viro , Petr Mladek References: <20211108083840.4627-1-laoar.shao@gmail.com> <20211108083840.4627-6-laoar.shao@gmail.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20211108083840.4627-6-laoar.shao@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08.11.21 09:38, Yafang Shao wrote: > 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 > Reviewed-by: Kees Cook > Cc: Mathieu Desnoyers > Cc: Arnaldo Carvalho de Melo > Cc: Alexei Starovoitov > Cc: Andrii Nakryiko > Cc: Michal Miroslaw > Cc: Peter Zijlstra > Cc: Steven Rostedt > Cc: Matthew Wilcox > Cc: David Hildenbrand > Cc: Al Viro > Cc: Kees Cook > Cc: Petr Mladek > --- > samples/bpf/offwaketime_kern.c | 4 ++-- > samples/bpf/test_overhead_kprobe_kern.c | 11 ++++++----- > samples/bpf/test_overhead_tp_kern.c | 5 +++-- > 3 files changed, 11 insertions(+), 9 deletions(-) > > diff --git a/samples/bpf/offwaketime_kern.c b/samples/bpf/offwaketime_kern.c > index 4866afd054da..eb4d94742e6b 100644 > --- a/samples/bpf/offwaketime_kern.c > +++ b/samples/bpf/offwaketime_kern.c > @@ -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]; > 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/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 > #include > +#include > #include > #include > #include > @@ -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)); It's a shame we have to do a manual copy here ... Changes LGTM Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb