Messages in this thread | | | From | Linus Torvalds <> | Date | Thu, 19 Jan 2012 11:37:50 -0800 | Subject | Re: Compat 32-bit syscall entry from 64-bit task!? |
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On Thu, Jan 19, 2012 at 11:30 AM, Andrew Lutomirski <luto@mit.edu> wrote: > > Unless you're writing a debugger and you want to disassemble the code > that's being executed (i.e. normal code, not a system call). I wonder > how gdb guesses whether the cpu is in long mode.
Yes, if you need to disassemble user space you would need to figure out the mode.
I would suggest looking at 'rip/rsp' first, though, and just say that if it's >32-bit, it's flat mode. Only if both rsp and rip fit in 32 bits should you even bother start guessing.
Because technically I suspect you really do need to look it up in the segment descriptors, and I don't think we have that kind of interface (nor do I think we really want to expose one).
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