Re: Compat 32-bit syscall entry from 64-bit task!?

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On 02/08/2012 10:03 PM, Indan Zupancic wrote:

You can check the syscall instruction itself, either before it's executed
or afterwards by checking the IP. Though that's trickier, because the
kernel points the IP to just after int80 for a sysenter call, so you have
to check if there's a sysenter nearby too.


No, that's a total nightmare.  FAIL.

But the kernel is actually changing the registers, so why hide that?

I mean, once user space is aware that the kernel may do swizzling, is there
any actual problem left? Because this sounds like user space was trying to
be clever, but got it wrong. E.g. it knew the kernel was entered not via
int80, but then got confused because of the swizzling.

I would be great if we didn't have an existing compatibility problem. As it is we can't get rid of it easily.

	-hpa

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