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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id r25sm16507932pge.61.2021.10.25.14.29.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 25 Oct 2021 14:29:43 -0700 (PDT) Date: Mon, 25 Oct 2021 14:29:43 -0700 From: Kees Cook To: Yafang Shao Cc: akpm@linux-foundation.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, arnaldo.melo@gmail.com, pmladek@suse.com, peterz@infradead.org, viro@zeniv.linux.org.uk, valentin.schneider@arm.com, qiang.zhang@windriver.com, robdclark@chromium.org, christian@brauner.io, dietmar.eggemann@arm.com, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, davem@davemloft.net, kuba@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, kpsingh@kernel.org, dennis.dalessandro@cornelisnetworks.com, mike.marciniszyn@cornelisnetworks.com, dledford@redhat.com, jgg@ziepe.ca, linux-rdma@vger.kernel.org, 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, Andrii Nakryiko Subject: Re: [PATCH v6 10/12] tools/testing/selftests/bpf: make it adopt to task comm size change Message-ID: <202110251428.B891AD6ACB@keescook> References: <20211025083315.4752-1-laoar.shao@gmail.com> <20211025083315.4752-11-laoar.shao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211025083315.4752-11-laoar.shao@gmail.com> Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Mon, Oct 25, 2021 at 08:33:13AM +0000, Yafang Shao wrote: > The hard-coded 16 is used in various bpf progs. These progs get task > comm either via bpf_get_current_comm() or prctl() or > bpf_core_read_str(), all of which can work well even if the task comm size > is changed. > > In these BPF programs, one thing to be improved is the > sched:sched_switch tracepoint args. As the tracepoint args are derived > from the kernel, we'd better make it same with the kernel. So the macro > TASK_COMM_LEN is converted to type enum, then all the BPF programs can > get it through BTF. > > Signed-off-by: Yafang Shao > Cc: Mathieu Desnoyers > Cc: Arnaldo Carvalho de Melo > Cc: Andrii Nakryiko > Cc: Peter Zijlstra > Cc: Steven Rostedt > Cc: Al Viro > Cc: Kees Cook > Cc: Petr Mladek > --- > include/linux/sched.h | 9 +++++++-- > tools/testing/selftests/bpf/progs/test_stacktrace_map.c | 6 +++--- > tools/testing/selftests/bpf/progs/test_tracepoint.c | 6 +++--- > 3 files changed, 13 insertions(+), 8 deletions(-) > > diff --git a/include/linux/sched.h b/include/linux/sched.h > index c1a927ddec64..124538db792c 100644 > --- a/include/linux/sched.h > +++ b/include/linux/sched.h > @@ -274,8 +274,13 @@ struct task_group; > > #define get_current_state() READ_ONCE(current->__state) > > -/* Task command name length: */ > -#define TASK_COMM_LEN 16 > +/* > + * Define the task command name length as enum, then it can be visible to > + * BPF programs. > + */ > +enum { > + TASK_COMM_LEN = 16, > +}; > > extern void scheduler_tick(void); > > diff --git a/tools/testing/selftests/bpf/progs/test_stacktrace_map.c b/tools/testing/selftests/bpf/progs/test_stacktrace_map.c > index 00ed48672620..e9b602a6dc1b 100644 > --- a/tools/testing/selftests/bpf/progs/test_stacktrace_map.c > +++ b/tools/testing/selftests/bpf/progs/test_stacktrace_map.c > @@ -1,7 +1,7 @@ > // SPDX-License-Identifier: GPL-2.0 > // Copyright (c) 2018 Facebook > > -#include > +#include Why is this change needed here and below? > #include > > #ifndef PERF_MAX_STACK_DEPTH > @@ -41,11 +41,11 @@ struct { > /* 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/tools/testing/selftests/bpf/progs/test_tracepoint.c b/tools/testing/selftests/bpf/progs/test_tracepoint.c > index 4b825ee122cf..f21982681e28 100644 > --- a/tools/testing/selftests/bpf/progs/test_tracepoint.c > +++ b/tools/testing/selftests/bpf/progs/test_tracepoint.c > @@ -1,17 +1,17 @@ > // SPDX-License-Identifier: GPL-2.0 > // Copyright (c) 2017 Facebook > > -#include > +#include > #include > > /* 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; > }; > -- > 2.17.1 > -- Kees Cook