Date: Thu, 29 Apr 2010 19:52:45 +0200 (CEST) From: "=?ISO-8859-15?Q?Luk=E1=A8_Czerner?=" <czerner.lukas@gmail.com> To: freebsd-hackers@freebsd.org Cc: czerner.lukas@gmail.com Subject: ioctl, copy string from user Message-ID: <alpine.DEB.1.10.1004291938210.30007@a04-0215a.kn.vutbr.cz>
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Hi,
I know that there are plenty of examples in the kernel code, but I
just can not get it working, so maybe I am doing some stupid mistake
I am not aware of. Please give me a hint if you can.
What I want to do is simply call the ioctl from the userspace with
(char *) argument. Then, in kernel ioctl handling function copy the
string argument into the kernel space. I have tried it various ways,
everything without any success.
*** Userspace ***
char name[MAXLEN];
strncpy(name, argv[1], MAXLEN);
fprintf(stdout,"Name: %s\n",name);
if (ioctl(fd, MYIOCTL, name)) {
...
*** Kernel ***
case MYIOCTL: {
char buffer[MAXLEN]; /* Yes I can allocate it dynamically,
byt just for simplicity */
retval = copyinstr(ap->a_data, buffer, MAXLEN - 1, NULL);
uprintf("In kerne - name : %s\n", buffer)
...
The output is still the same at userspace app it prints out the name
properly (obviously), but in kernel space it just prints out
nothing. So I want to ask what is the proper way to do this ??
And the second question. I have commented that I can allocate buffer
dynamically, but I suppose that there will be some locks involved so
I think I can not just use M_WAITOK, am I right ?
Thanks!
-Lukas.
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