Turning a SIGSEGV into a regular function call under Linux, allowing throw

[FeepingCreature]

On 03/13/12 23:24, Vladimir Panteleev wrote:
> On Tuesday, 13 March 2012 at 10:09:55 UTC, FeepingCreature wrote:
>> However, there is a method to turn a signal handler into a regular function call that you can throw from.
> 
> Very nice!
> 
> The only similarity with a buffer overflow exploit is that we're overriding the continuation address. There is no execution of data, so it's closer to a "return-to-libc" attack.
> 

Argh. Yeah, that's the one I was thinking of.

> Here's a D implementation without inline assembler. It's DMD-specific due to a weirdness of its codegen.
> http://dump.thecybershadow.net/20f792fa05c020e561137cfaf3d65d7a/sigthrow_32.d
> 
> The 64-bit version is a hack, in that it clobbers the last word on the stack. If the exception was thrown right after a stack frame was created, things might go ugly. The same trick as in my 32-bit implementation (creating a new stack frame with an extern(C) helper) won't work here, and I don't know enough about x64 exception handling to know how to fix it.
> http://dump.thecybershadow.net/121efc460a01fb4597926ec76352a674/sigthrow_64.d
> 

Sweet. Yeah, I think you need to use naked and reconstruct the stackframe. Not sure how it'd look; I'm not familiar with the x86_64 ABI.
> I think something like this needs to end up in Druntime, at least for Linux x86 and x64.

Would be nice. I mean, Windows already has segfault-as-exception, doesn't it? It's only fair :)