linux-kernel - Re: [PATCH bpf-next] bpf: Allow bpf_d_path in perf_event

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Message-ID: <20211028224653.qhuwkp75fridkzpw@kafai-mbp.dhcp.thefacebook.com>
Date:   Thu, 28 Oct 2021 15:46:53 -0700
From:   Martin KaFai Lau <kafai@...com>
To:     Florent Revest <revest@...omium.org>
CC:     <bpf@...r.kernel.org>, <ast@...nel.org>, <daniel@...earbox.net>,
        <andrii@...nel.org>, <kpsingh@...nel.org>, <jackmanb@...gle.com>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] bpf: Allow bpf_d_path in perf_event_mmap

On Thu, Oct 28, 2021 at 06:43:57PM +0200, Florent Revest wrote:
> Allow the helper to be called from the perf_event_mmap hook. This is
> convenient to lookup vma->vm_file and implement a similar logic as
> perf_event_mmap_event in BPF.
>From struct vm_area_struct:
	struct file * vm_file;          /* File we map to (can be NULL). */

Under perf_event_mmap, vm_file won't be NULL or bpf_d_path can handle it?

> 
> Signed-off-by: Florent Revest <revest@...omium.org>
> ---
>  kernel/trace/bpf_trace.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index cbcd0d6fca7c..f6e301c775a5 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -922,6 +922,9 @@ BTF_ID(func, vfs_fallocate)
>  BTF_ID(func, dentry_open)
>  BTF_ID(func, vfs_getattr)
>  BTF_ID(func, filp_close)
> +#ifdef CONFIG_PERF_EVENTS
> +BTF_ID(func, perf_event_mmap)
> +#endif
>  BTF_SET_END(btf_allowlist_d_path)
>  
>  static bool bpf_d_path_allowed(const struct bpf_prog *prog)
> -- 
> 2.33.0.1079.g6e70778dc9-goog
>