Date: Thu, 12 Jul 2001 06:58:09 -0500 From: y-carden@uniandes.edu.co To: questions@freebsd.org Subject: Some questions about kernel programming Message-ID: <M2001071206580901828@Ayax.uniandes.edu.co>
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Dear Friends
I have some questions about kernel programming:
1. Why I can call some system calls functions into the kernel but
another not?, for example: I can call printf(), but I can't call
socket().
2. Into kernel I can call the socket "low level" functions
that this system calls invoke sosocket(), soconnect(), etc.
but, How I do replace the send() system call? Perhaps, Can I call
write() into kernel with same parameters?
For example :
/* res = send(skt, buf, buflen, 0); */
res = write (skt, buf, buflen);
3. How I can copy a pointer string ( character array ) from user space to
kernel space using copyin() without the following problem (I can't
pass the length the explicitly from user land):
struct MySystemCall_args {
char * address;
};
int MySystemCall( p,uap)
struct proc *p;
register struct MySystemCall_args *uap;
{
char *the_address;
printf(" ---> uap->address : %s\n", uap->address );
printf(" ---> (strlen (uap->address) * sizeof(char)) : %d \n",
(strlen (uap->address) * sizeof(char)) );
copyin(uap->address, the_address, (strlen (uap->address) * sizeof(char))
);
printf("the_address: %s \n", the_address );
printf("strlen (the_address): %d \n", strlen (the_address) );
When this code run in mode kernel:
---> uap->address : 127.0.0.1
---> (strlen (uap->address) * sizeof(char)) : 9
the_address : 127.0.0.1\M-"\M-Y\M-GX\M-p+\M-@@\M-_\M-*\M-@
strlen (the_address): 20
This crash the kernel later...
Thanks for your help.
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