Emulating i486 on i386 (was: TSCs are a no-no on i386)

DISCUSSION Ben Pfaff 1 participant 1 message Jul 31, 2003 11 messages not in the archive

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Ben Pfaff

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2003-07-31 17:35 UTC #11 lore raw

Quoted 13 lines · Jan-Benedict Glaw

On Thu, 2003-07-31 16:12:26 +0100, Jamie Lokier <[email protected]> wrote in message <[email protected]>:
Quoted 11 lines
Quoted 6 lines · Alan Cox
Quoted 2 lines · Jan-Benedict Glaw
See? It's loaded at the "ls" call, but it seems to be not loaded for apt-get.
Remember you need to overload signal setting functions like sigaction. My guess is apt decided to disable your signal and you didnt stop it
An application might install its own SIGILL handler to emulate or trap _other_ instructions. To do it properly, you have to chain the handlers.

Quoted 6 lines

Quoted 2 lines
Not sure how to do this, when you get to the stage of two LD_PRELOAD libraries each wanting to overload sigaction.
That's not (yet) my problem and I think it's not impossible to hook them. _But_ before, I need to get called at all _before_ libstdc++5's _init(). For now, I haven't managed to do that...

One way to get loaded before anything else is to do ELF binary loading by hand in userspace. The kernel exec loads your program, which sets up trap handlers etc., then loads the actual target binary by hand. I did this for an application sandbox. Writing the loader took less than half a day since I was able to use a lot of kernel code from binfmt_elf.c directly, just translating internal kernel calls into open, mmap, etc. system calls.

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