linux-kernel - Re: [PATCHv5 bpf-next 6/8] x86/shstk: Add return uprobe support

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Date: Thu, 9 May 2024 16:24:37 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "olsajiri@...il.com" <olsajiri@...il.com>
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Subject: Re: [PATCHv5 bpf-next 6/8] x86/shstk: Add return uprobe support

On Thu, 2024-05-09 at 10:30 +0200, Jiri Olsa wrote:
> > Per the earlier discussion, this cannot be reached unless uretprobes are in
> > use,
> > which cannot happen without something with privileges taking an action. But
> > are
> > uretprobes ever used for monitoring applications where security is
> > important? Or
> > is it strictly a debug-time thing?
> 
> sorry, I don't have that level of detail, but we do have customers
> that use uprobes in general or want to use it and complain about
> the speed
> 
> there are several tools in bcc [1] that use uretprobes in scripts,
> like:
>   memleak, sslsniff, trace, bashreadline, gethostlatency, argdist,
>   funclatency

Is it possible to have shadow stack only use the non-syscall solution? It seems
it exposes a more limited compatibility in that it only allows writing the
specific trampoline address. (IIRC) Then shadow stack users could still use
uretprobes, but just not the new optimized solution. There are already
operations that are slower with shadow stack, like longjmp(), so this could be
ok maybe.