Re: [gentoo-user] _syscallX isn't in linux-headers-2.6.20 ??

[Boyd Stephen Smith Jr.]

On Wednesday 07 February 2007 18:53, Iain Buchanan wrote:
> Hi all,
>
> I'm trying to use:
>
> _syscall3(int, ioprio_set, int, which, int, who, int, ioprio);
> _syscall2(int, ioprio_get, int, which, int, who);
>
> and supposedly I just
>
> #include <linux/unistd.h>
>
> but I'm getting these error from gcc:
>
> error: syntax error before "ioprio_set"
> warning: data definition has no type or storage class
> error: syntax error before "ioprio_get"
> warning: data definition has no type or storage class
>
> so I had a look in /usr/include/linux/unistd.h and it doesn't even have
> _syscall in there!! It's in /usr/src/linux though...

That means that the kernel devs have decided that API is not userland safe.  
In recent kernels, there's a specific 'headers' (or somesuch) make target, 
that generates .h files that are appropriate to use in userland.

If you need access to APIs that aren't in those headers, you should be 
writing 
a kernel module, or convincing the kernel developers to expose these APIs 
to 
userland.  Your kernel module may need be only a tiny stub, just something 
to 
go between your userland and the non-userland-safe APIs.

> Am I doing something wrong?

It's possible you just need another header.  It also possible that there's 
a 
different entry point now. I seem to remember the location of the syscall 
table is recently changed to something like randomized per-process at some 
point in the 2.6.1x line.  That may have changed how you need to be calling 
things.

-- 
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