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([2620:10d:c092:500::5:6287]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4255d8a6c49sm20657717f8f.3.2025.10.06.04.50.19 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 06 Oct 2025 04:50:20 -0700 (PDT) Message-ID: <62376422-6d60-42b9-b09e-393396fb7302@gmail.com> Date: Mon, 6 Oct 2025 12:50:19 +0100 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 10/10] selftests/bpf: add file dynptr tests To: Andrii Nakryiko Cc: bpf@vger.kernel.org, ast@kernel.org, andrii@kernel.org, daniel@iogearbox.net, kafai@meta.com, kernel-team@meta.com, eddyz87@gmail.com, memxor@gmail.com, Mykyta Yatsenko References: <20251003160416.585080-1-mykyta.yatsenko5@gmail.com> <20251003160416.585080-11-mykyta.yatsenko5@gmail.com> Content-Language: en-US From: Mykyta Yatsenko In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 10/3/25 21:02, Andrii Nakryiko wrote: > On Fri, Oct 3, 2025 at 9:04 AM Mykyta Yatsenko > wrote: >> From: Mykyta Yatsenko >> >> Introducing selftests for validating file-backed dynptr works as >> expected. >> * validate implementation supports dynptr slice and read operations >> * validate destructors should be paired with initializers >> >> Signed-off-by: Mykyta Yatsenko >> --- >> .../selftests/bpf/prog_tests/file_reader.c | 81 ++++++ >> .../testing/selftests/bpf/progs/file_reader.c | 241 ++++++++++++++++++ >> .../selftests/bpf/progs/file_reader_fail.c | 57 +++++ >> 3 files changed, 379 insertions(+) >> create mode 100644 tools/testing/selftests/bpf/prog_tests/file_reader.c >> create mode 100644 tools/testing/selftests/bpf/progs/file_reader.c >> create mode 100644 tools/testing/selftests/bpf/progs/file_reader_fail.c > Non-sleepable file dynptr can fail to read, so this test is a bit > fragile. Let's have a sleepable test (fentry.s or something like > that?) This is sleepable, because it runs in task work callback. > > Plus, can you please add a test that validates that we do page in file > contents even if it was not physically in memory? see madvise(addr, > page_sz, MADV_PAGEOUT) in selftests I tried to tell kernel to evict those pages via: posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED); I'll rework to madvise(addr, page_sz, MADV_PAGEOUT) > >> +int err; >> +void *user_ptr; >> +char buf[1024]; >> +char *user_buf; >> +volatile const __u32 user_buf_sz; >> +volatile const __s32 test_type = -1; >> + >> +static int process_vma(struct task_struct *task, struct vm_area_struct *vma, void *data); >> +static int search_elf(struct file *file); >> +static int validate_large_file_read(struct file *file); >> +static int task_work_callback(struct bpf_map *map, void *key, void *value); >> + >> +SEC("raw_tp/sys_enter") >> +int on_getpid(void *ctx) >> +{ >> + struct task_struct *task = bpf_get_current_task_btf(); >> + struct elem *work; >> + int key = 0; > this will be called for every syscall in the system, regardless of the > process, so you probably need to filter this by process ID? > >> + >> + work = bpf_map_lookup_elem(&arrmap, &key); >> + if (!work) { >> + err = 1; >> + return 0; >> + } >> + bpf_task_work_schedule_signal(task, &work->tw, &arrmap, task_work_callback, NULL); >> + return 0; >> +} >> + > [...] > >> +static long process_vma_unreleased_ref(struct task_struct *task, struct vm_area_struct *vma, >> + void *data) >> +{ >> + struct bpf_dynptr dynptr; >> + >> + if (!vma->vm_file) >> + return 1; >> + >> + err = bpf_dynptr_from_file(vma->vm_file, 0, &dynptr); >> + return err ? 1 : 0; >> +} >> + >> +SEC("fentry.s/" SYS_PREFIX "sys_nanosleep") >> +__failure __msg("Unreleased reference id=") int on_nanosleep_unreleased_ref(void *ctx) > nit: keep annotations on separate line from the function itself > >> +{ >> + struct task_struct *task = bpf_get_current_task_btf(); >> + >> + bpf_find_vma(task, (unsigned long)user_ptr, process_vma_unreleased_ref, NULL, 0); >> + return 0; >> +} >> + >> +SEC("xdp") >> +__failure __msg("Expected a dynptr of type file as arg #0") >> +int xdp_wrong_dynptr_type(struct xdp_md *xdp) >> +{ >> + struct bpf_dynptr dynptr; >> + >> + bpf_dynptr_from_xdp(xdp, 0, &dynptr); >> + bpf_dynptr_file_discard(&dynptr); >> + return 0; >> +} >> + >> +SEC("xdp") >> +__failure __msg("Expected an initialized dynptr as arg #0") >> +int xdp_no_dynptr_type(struct xdp_md *xdp) >> +{ >> + struct bpf_dynptr dynptr; >> + >> + bpf_dynptr_file_discard(&dynptr); >> + return 0; >> +} >> -- >> 2.51.0 >>