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SubjectRe: The disappearing sys_call_table export.
Date

[Alan Cox]
>> 10. kernel patches are impractical, I must be able to do this with std
>> stock, redhat, AND suse kernels.

> So you want every vendor to screw up their kernels and the base kernel
> for an obscure (but fun) corner case. Thats not a rational choice is it.
> You want "performance is everything" you pay the price, don't make
> everyone suffer.

Hmm. sys_call_table is gone? That's sad.

How about a

EXPORT_SYMBOL_GPL_AND_DONT_EVEN_THINK_ABOUT_SENDING_A_BUG_REPORT(sys_call_table);

and displaying a nasty warning message on the console whenever a
module used it?

It is rare that I need to use it, but when I do I need it bad, for instance:

fsync on large files used to have severe performance problems, I was
able to just change sys_fsync to be a call to sys_sync without
rebooting or even restarting the database(Solid) before the problem
got out of hand.

A server for an online internet game had several months of uptime and
I needed to rotate the log-files so I made a module which trapped
sys_write and closed and reopened the file with a new name before
continuing[1].

Even if it is discouraged for normal use it is a very nice thing to
have to fix up various surprises.

I know I can still use the Phrack technique, but somehow I am not
convinced that I can rely on it being available.

--
- Terje
malmedal@usit.uio.no

[1] When I do this kind of thing now I do:
(gdb) attach 9597
(gdb) call close(7)
(gdb) call open("out.txt",0100 | 01, 0666 )
(gdb) cont
This did not work back then however.
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