Date: Wed, 10 Aug 2005 15:09:28 +0200 From: alexander <arundel@h3c.de> To: freebsd-hackers@freebsd.org Subject: Re: Using sysarch specific syscalls in assembly? Message-ID: <20050810130928.GA2027@skatecity> In-Reply-To: <20050809192530.GA19230@skatecity> References: <20050809133109.GA15300@skatecity> <20050809154541.C057243D45@mx1.FreeBSD.org> <20050809192530.GA19230@skatecity>
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I tried to write a little C app that uses sysarch and i386_set_ioperm to gain
access to certain ports and after a bit of testing I'm pretty sure that there
is a bug or better a timing issue with the sysarch syscall or the
i386_set_ioperm procedure. Please have a look at the following code:
//CODE START
#include <machine/sysarch.h>
int main (void) {
unsigned int port = 0x378;
unsigned char val = 'A';
int number = 4;
static inline void outb (unsigned short int port, unsigned char val) {
__asm__ volatile ("outb %0,%1\n"::"a" (val), "d" (port) );
}
struct i386_ioperm_args {
unsigned int start;
unsigned int length;
int enable;
};
struct i386_ioperm_args *args;
struct i386_ioperm_args arg;
args = &arg;
args->start = 0x378;
args->length = 1;
args->enable = 1;
if(sysarch(number,args) == 0) {
/* int i;
for(i=0; i < 100; i++) {
printf("DELAY\n");
}
*/
outb(0x378,0xF);
exit(0);
}
else {
printf("Error during syscall");
exit(1);
}
}
//eof
//CODE END
On my PC this code will cause a core dump (Bus error: 10). If I however add a
delay (the code that's commented out) the app will end without any errors.
It seems FBSD needs some time to set the I/O permissions for an app. Can
somebody test this code on his computer? Maybe this is a bug in RELENG_6. I'm
running:
FreeBSD 6.0-BETA1 #0: Mon Jul 18 03:00:45 CEST 2005
Thx a bunch.
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