Date: Tue, 2 May 1995 16:43:35 -0700 (PDT) From: Julian Elischer <julian@ref.tfs.com> To: dufault@hda.com (Peter Dufault) Cc: hackers@FreeBSD.org Subject: Re: what's in ioctl flag arg? Message-ID: <199505022343.QAA09824@ref.tfs.com> In-Reply-To: <199505022207.SAA00880@hda.com> from "Peter Dufault" at May 2, 95 06:07:12 pm
next in thread | previous in thread | raw e-mail | index | archive | help
>
> What's in the ioctl flag arg? I hope it is a copy of the
> flag passed in to the open(), but I can't find where it gets
> set up and I'm not sure if it gets translated into an "F_"
> thing instead.
>
> Is this how I verify that you can't write to a file in the ioctl call:
>
> (flag & O_ACCMODE) == O_RDONLY
>
> Peter
>
> --
> Peter Dufault Real Time Machine Control and Simulation
> HD Associates, Inc. Voice: 508 433 6936
> dufault@hda.com Fax: 508 433 5267
>
hmmmmmmmm
/*
* Ioctl system call
*/
struct ioctl_args {
int fd;
int com;
caddr_t data;
};
calls
error = (*fp->f_ops->fo_ioctl)(fp, com, data, p);
which is in fact....
/*
* File table vnode ioctl routine.
*/
int
vn_ioctl(fp, com, data, p)
struct file *fp;
int com;
caddr_t data;
struct proc *p;
which in turn calls
case VCHR:
case VBLK:
error = VOP_IOCTL(vp, com, data, fp->f_flag, p->p_ucred, p);
which is in fact:
/*
* Device ioctl operation.
*/
/* ARGSUSED */
int
spec_ioctl(ap)
struct vop_ioctl_args /* {
struct vnode *a_vp;
int a_command;
caddr_t a_data;
int a_fflag;
struct ucred *a_cred;
struct proc *a_p;
} */ *ap;
{
which calls:
case VCHR:
return ((*cdevsw[major(dev)].d_ioctl)(dev, ap->a_command,
ap->a_data, ap->a_fflag, ap->a_p));
thus the flag comes from:
fp->f_flag, which is the flags in the file table..
/*
* Kernel descriptor table.
* One entry for each open kernel vnode and socket.
*/
struct file {
struct file *f_filef; /* list of active files */
struct file **f_fileb; /* list of active files */
short f_flag; /* see fcntl.h */
#define DTYPE_VNODE 1 /* file */
#define DTYPE_SOCKET 2 /* communications endpoint */
short f_type; /* descriptor type */
short f_count; /* reference count */
short f_msgcount; /* references from message queue */
struct ucred *f_cred; /* credentials associated with descriptor */
struct fileops {
int (*fo_read) __P((struct file *fp, struct uio *uio,
struct ucred *cred));
int (*fo_write) __P((struct file *fp, struct uio *uio,
struct ucred *cred));
int (*fo_ioctl) __P((struct file *fp, int com,
caddr_t data, struct proc *p));
int (*fo_select) __P((struct file *fp, int which,
struct proc *p));
int (*fo_close) __P((struct file *fp, struct proc *p));
} *f_ops;
off_t f_offset;
caddr_t f_data; /* vnode or socket */
};
..
following to fcntl.h
/*
* Kernel encoding of open mode; separate read and write bits that are
* independently testable: 1 greater than the above.
*
* XXX
* FREAD and FWRITE are excluded from the #ifdef KERNEL so that TIOCFLUSH,
* which was documented to use FREAD/FWRITE, continues to work.
*/
#ifndef _POSIX_SOURCE
#define FREAD 0x0001
#define FWRITE 0x0002
#endif
#define O_NONBLOCK 0x0004 /* no delay */
#define O_APPEND 0x0008 /* set append mode */
#ifndef _POSIX_SOURCE
#define O_SHLOCK 0x0010 /* open with shared file lock */
#define O_EXLOCK 0x0020 /* open with exclusive file lock */
#define O_ASYNC 0x0040 /* signal pgrp when data ready */
#define O_FSYNC 0x0080 /* synchronous writes */
#endif
#define O_CREAT 0x0200 /* create if nonexistant */
#define O_TRUNC 0x0400 /* truncate to zero length */
#define O_EXCL 0x0800 /* error if already exists */
#ifdef KERNEL
#define FMARK 0x1000 /* mark during gc() */
#define FDEFER 0x2000 /* defer for next gc pass */
#define FHASLOCK 0x4000 /* descriptor holds advisory lock */
#endif
/* defined by POSIX 1003.1; BSD default, so no bit required */
#define O_NOCTTY 0 /* don't assign controlling terminal */
#ifdef KERNEL
/* convert from open() flags to/from fflags; convert O_RD/WR to FREAD/FWRITE */
#define FFLAGS(oflags) ((oflags) + 1)
#define OFLAGS(fflags) ((fflags) - 1)
/* bits to save after open */
#define FMASK (FREAD|FWRITE|FAPPEND|FASYNC|FFSYNC|FNONBLOCK)
/* bits settable by fcntl(F_SETFL, ...) */
#define FCNTLFLAGS (FAPPEND|FASYNC|FFSYNC|FNONBLOCK)
#endif
/*
* The O_* flags used to have only F* names, which were used in the kernel
* and by fcntl. We retain the F* names for the kernel f_flags field
* and for backward compatibility for fcntl.
*/
#ifndef _POSIX_SOURCE
#define FAPPEND O_APPEND /* kernel/compat */
#define FASYNC O_ASYNC /* kernel/compat */
#define FFSYNC O_FSYNC /* kernel */
#define FNONBLOCK O_NONBLOCK /* kernel */
#define FNDELAY O_NONBLOCK /* compat */
#define O_NDELAY O_NONBLOCK /* compat */
#endif
:)
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?199505022343.QAA09824>