Re: The disappearing sys_call_table export.

Yoav Weiss
2003-05-06T08:33:20Z

> But how? When some global will not be exported, it would not be listed
> in /proc/ksyms.

So what ?
You just find the right address (in this case by getting the addresses of
exported syscalls and finding a list in memory, containing them in the
right order), and cast it to be the syscall table. If you want it to work
with a binary-only driver, you can even insmod a small module that does
that and adds the result to the symbol table for other modules to use.

We've been doing that for years on closed-source systems like AIX. The
above is just one way to locate a struct in memory. A faster way is to
find some exported structs which are known to point to the unexported
symbol from some offset, extract the symbol's address, and "re-export" it.

In fact, in linux which is opensource, you can probably write a script
that extracts any unexported symbol from the source code, find a path to
it from some exported symbol, and automagically create a module that
re-exports this symbol for your legacy driver to use.

If you write the script, don't forget to GPL it :)

Yoav Weiss