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

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

[Iain Buchanan]

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...

Am I doing something wrong?  I'm following
http://www.die.net/doc/linux/man/man2/ioprio_set.2.html

I know this is a C-ish question, only loosely related to gentoo but I'd
really appreciate any help!!

TIA,
-- 
Iain Buchanan <iaindb at netspace dot net dot au>

The groundhog is like most other prophets; it delivers its message and then
disappears.

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

[Christian Marie]

On Thu, Feb 08, 2007 at 10:23:09AM +0930, 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

Hi,

It would be helpful to provide us with the failing code as we have no
clue what you could be doing wrong.
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Re: [gentoo-user] Re: _syscallX isn't in linux-headers-2.6.20 ??

[Iain Buchanan]

On Thu, 2007-02-08 at 16:10 +1100, Christian Marie wrote:
> On Thu, Feb 08, 2007 at 10:23:09AM +0930, 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
> 
> Hi,
> 
> It would be helpful to provide us with the failing code as we have no
> clue what you could be doing wrong.

sure - my question was more "where has the define for _syscall2 gone?",
but here is the code.  It comes
from /usr/src/linux/Documentation/block/ioprio.txt.  I compile it with:
$ gcc -o ionice ionice.c 
ionice.c:36: error: syntax error before "ioprio_set"
ionice.c:36: warning: data definition has no type or storage class
ionice.c:37: error: syntax error before "ioprio_get"
ionice.c:37: warning: data definition has no type or storage class

------begin ionice.c------
//
// Sample ionice utility copied from
// /usr/src/linux/Documentation/block/ioprio.txt from gentoo kernel version
// 2.6.19-suspend2-r1.  Probably (C) Jens Axboe <axboe@suse.de> and GPL'd?
//

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <getopt.h>
#include <unistd.h>
#include <sys/ptrace.h>

extern int sys_ioprio_set(int, int, int);
extern int sys_ioprio_get(int, int);

#if defined(__i386__)
#define __NR_ioprio_set		289
#define __NR_ioprio_get		290
#elif defined(__ppc__)
#define __NR_ioprio_set		273
#define __NR_ioprio_get		274
#elif defined(__x86_64__)
#define __NR_ioprio_set		251
#define __NR_ioprio_get		252
#elif defined(__ia64__)
#define __NR_ioprio_set		1274
#define __NR_ioprio_get		1275
#else
#error "Unsupported arch"
#endif

int ioprio_get(int which, int who);
int ioprio_set(int which, int who, int ioprio);

_syscall3(int, ioprio_set, int, which, int, who, int, ioprio);
_syscall2(int, ioprio_get, int, which, int, who);

enum {
	IOPRIO_CLASS_NONE,
	IOPRIO_CLASS_RT,
	IOPRIO_CLASS_BE,
	IOPRIO_CLASS_IDLE,
};

enum {
	IOPRIO_WHO_PROCESS = 1,
	IOPRIO_WHO_PGRP,
	IOPRIO_WHO_USER,
};

#define IOPRIO_CLASS_SHIFT	13

const char *to_prio[] = { "none", "realtime", "best-effort", "idle", };

int main(int argc, char *argv[])
{
	int ioprio = 4, set = 0, ioprio_class = IOPRIO_CLASS_BE;
	int c, pid = 0;

	while ((c = getopt(argc, argv, "+n:c:p:")) != EOF) {
		switch (c) {
		case 'n':
			ioprio = strtol(optarg, NULL, 10);
			set = 1;
			break;
		case 'c':
			ioprio_class = strtol(optarg, NULL, 10);
			set = 1;
			break;
		case 'p':
			pid = strtol(optarg, NULL, 10);
			break;
		}
	}

	switch (ioprio_class) {
		case IOPRIO_CLASS_NONE:
			ioprio_class = IOPRIO_CLASS_BE;
			break;
		case IOPRIO_CLASS_RT:
		case IOPRIO_CLASS_BE:
			break;
		case IOPRIO_CLASS_IDLE:
			ioprio = 7;
			break;
		default:
			printf("bad prio class %d\n", ioprio_class);
			return 1;
	}

	if (!set) {
		if (!pid && argv[optind])
			pid = strtol(argv[optind], NULL, 10);

		ioprio = ioprio_get(IOPRIO_WHO_PROCESS, pid);

		printf("pid=%d, %d\n", pid, ioprio);

		if (ioprio == -1)
			perror("ioprio_get");
		else {
			ioprio_class = ioprio >> IOPRIO_CLASS_SHIFT;
			ioprio = ioprio & 0xff;
			printf("%s: prio %d\n", to_prio[ioprio_class], ioprio);
		}
	} else {
		if (ioprio_set(IOPRIO_WHO_PROCESS, pid, ioprio | ioprio_class << IOPRIO_CLASS_SHIFT) == -1) {
			perror("ioprio_set");
			return 1;
		}

		if (argv[optind])
			execvp(argv[optind], &argv[optind]);
	}

	return 0;
}

------end ionice.c------

thanks,
-- 
Iain Buchanan <iaindb at netspace dot net dot au>

Progress might have been all right once, but it's gone on too long.
		-- Ogden Nash

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

[Boyd Stephen Smith Jr.]

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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.

-- 
Boyd Stephen Smith Jr.                     ,= ,-_-. =. 
bss03@volumehost.net                      ((_/)o o(\_))
ICQ: 514984 YM/AIM: DaTwinkDaddy           `-'(. .)`-' 
http://iguanasuicide.org/                      \_/     
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