Re: [RFC PATCH 0/8] uprobe/x86: Add support to optimize prologue

[Oleg Nesterov]

On 11/17, Jiri Olsa wrote:
>
> This patchset adds support to optimize uprobe on top of instruction
> that could be emulated and also adds support to emulate particular
> versions of mov and sub instructions to cover some of the user space
> functions prologues, like:
>
>   pushq %rbp
>   movq  %rsp,%rbp
>   subq  $0xb0,%rsp

...

> There's an additional issue that single instruction replacement does
> not have and it's the possibility of the user space code to jump in the
> middle of those 5 bytes. I think it's unlikely to happen at the function
> prologue, but uprobe could be placed anywhere. I'm not sure how to
> mitigate this other than having some enable/disable switch or config
> option, which is unfortunate.

plus this breaks single-stepping... Although perhaps we don't really care.

Oleg.