[LLVMdev] [RFC] Simple control-flow integrity

[Tom Roeder]

On Sat, Feb 15, 2014 at 7:08 PM, Eric Christopher <echristo at gmail.com> wrote:
> On Tue, Feb 11, 2014 at 9:46 AM, Tom Roeder <tmroeder at google.com> wrote:
>> On Tue, Feb 11, 2014 at 9:12 AM, Reid Kleckner <rnk at google.com> wrote:
>>> On Tue, Feb 11, 2014 at 12:28 AM, Richard Osborne <richard at xmos.com> wrote:
>>>>
>>>>
>>>> On 11 Feb 2014, at 08:15, Eric Christopher <echristo at gmail.com> wrote:
>>>>
>>>> > On Mon, Feb 10, 2014 at 11:51 PM, Reid Kleckner <rnk at google.com> wrote:
>>>> >>
>>>> >>
>>>> >>
>>>> >> IIRC this came up before, and I don't think we expose anything like a
>>>> >> jump
>>>> >> table at the IR level.  As an IR-to-IR transform, I think asm is the
>>>> >> only
>>>> >> way to do it.
>>>> >
>>>> > I'd have to look more at what he's doing, but wouldn't a simple switch
>>>> > statement in IR suffice? Efficiency would be up to the various
>>>> > lowering mechanisms, but it wouldn't require inline asm.
>>
>> I'm not sure I follow how this would work. Could you expand on this, please?
>>
>
> I think you've already rebutted it below, so how about another idea? :)
>
> What about creating a pseudo-plt in the back end that will create this
> jump table for you at object emission time?
>
> Throwing out ideas in an attempt to avoid passes creating inline
> assembly - especially since we're looking at an IR level pass.
>

I'm definitely interested in removing the inline asm bits. I'm not
sure what you mean by a pseudo-plt, though; do you mean hooking into
the code that generates the Procedure Linkage Table? I really don't
know much about the LLVM back end, so I'd have to learn how that all
works in LLVM first.