linux-kernel - Re: [PATCH 2/2] uprobes: add speculative lockless VMA-to-inode-to-uprobe resolution

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Message-ID: <20240915150429.GC27726@redhat.com>
Date: Sun, 15 Sep 2024 17:04:30 +0200
From: Oleg Nesterov <oleg@...hat.com>
To: Andrii Nakryiko <andrii@...nel.org>
Cc: linux-trace-kernel@...r.kernel.org, peterz@...radead.org,
	rostedt@...dmis.org, mhiramat@...nel.org, bpf@...r.kernel.org,
	linux-kernel@...r.kernel.org, jolsa@...nel.org, paulmck@...nel.org,
	willy@...radead.org, surenb@...gle.com, akpm@...ux-foundation.org,
	linux-mm@...ck.org, mjguzik@...il.com, brauner@...nel.org,
	jannh@...gle.com
Subject: Re: [PATCH 2/2] uprobes: add speculative lockless
 VMA-to-inode-to-uprobe resolution

On 09/05, Andrii Nakryiko wrote:
>
> +static struct uprobe *find_active_uprobe_speculative(unsigned long bp_vaddr)
> +{
> +	const vm_flags_t flags = VM_HUGETLB | VM_MAYEXEC | VM_MAYSHARE;
...
> +	if (!vm_file || (vma->vm_flags & flags) != VM_MAYEXEC)
> +		goto bail;

Not that this can really simplify your patch, feel free to ignore, but I don't
think you need to check vma->vm_flags.

Yes, find_active_uprobe_rcu() does the same valid_vma(vma, false) check, but it
too can/should be removed, afaics.

valid_vma(vma, false) makes sense in, say, unapply_uprobe() to quickly filter
out vma's which can't have this bp installed, but not in the handle_swbp() paths.

Oleg.