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SubjectRE: QUESTION: modifying kernel functions in a running kernel
Date
> > Is it possible to change a function (not a syscall) which is public
> > (i.e shown in /proc/ksyms) from a module? Something like changing the
> > address to the function so my function will be called instead of the
> > public one?

> There was a comment about this a few months ago. Basically
> someone wanted to change a basic function. They changed all references to
> the function to be calls to a function address. The function address was
set
> at init time to the common usage. From a module, they could reach in an
put a
> different address, which everyone would then call. john

This is starting to remind me of a function call that existed in AmigaOS
called
SetFunction(). It allowed runtime patching of operating system functions,
which
was all well and good. The only problem with it was that would be perhaps
many
different patches for the same routine. One fixes one bug, one fixes another
etc..
The only way around this problem is nesting patches (ie, calling the
previous
function) This can be real ugly, and in many cases caused crashes as patches
were
not written to comply with each other.

So the end result is that if you have >1 bug fix patch you'd need to reboot
anyway, nullifying the reason for the whole mechanism.

I'm aware that there were some 'managers' that handled patch nesting better
than
the default, but I never saw a perfect one in the many years that I used an
Amiga.

(The machine may be a memory, but the OS lives on in my mind :-)

regards,

Dave.

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