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SubjectRe: [PATCH v3 0/6] Static calls
On Fri, Jan 11, 2019 at 01:47:01AM +0000, Nadav Amit wrote:
> Here is an alternative idea (although similar to Steven’s and my code).
>
> Assume that we always clobber R10, R11 on static-calls explicitly, as anyhow
> should be done by the calling convention (and gcc plugin should allow us to
> enforce). Also assume that we hold a table with all source RIP and the
> matching target.
>
> Now, in the int3 handler can you take the faulting RIP and search for it in
> the “static-calls” table, writing the RIP+5 (offset) into R10 (return
> address) and the target into R11. You make the int3 handler to divert the
> code execution by changing pt_regs->rip to point to a new function that does:
>
> push R10
> jmp __x86_indirect_thunk_r11
>
> And then you are done. No?

IIUC, that sounds pretty much like what Steven proposed:

https://lkml.kernel.org/r/20181129122000.7fb4fb04@gandalf.local.home

I liked the idea, BUT, how would it work for callee-saved PV ops? In
that case there's only one clobbered register to work with (rax).

--
Josh

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