svn commit: r355611 - head/sys/kern

[Konstantin Belousov]

On Wed, Dec 11, 2019 at 03:52:30PM +0000, Andriy Gapon wrote:
> Author: avg
> Date: Wed Dec 11 15:52:29 2019
> New Revision: 355611
> URL: https://svnweb.freebsd.org/changeset/base/355611
> 
> Log:
>   add a sanity check to the system call registration code
>   
>   A system call number should be at least reserved.
>   We do not expect an attempt to register a fixed number system call
>   when nothing at all is known about it.
>   
>   MFC after:	3 weeks
>   Sponsored by:	Panzura
> 
> Modified:
>   head/sys/kern/kern_syscalls.c
> 
> Modified: head/sys/kern/kern_syscalls.c
> ==============================================================================
> --- head/sys/kern/kern_syscalls.c	Wed Dec 11 15:15:21 2019	(r355610)
> +++ head/sys/kern/kern_syscalls.c	Wed Dec 11 15:52:29 2019	(r355611)
> @@ -120,11 +120,14 @@ kern_syscall_register(struct sysent *sysents, int *off
>  		if (i == SYS_MAXSYSCALL)
>  			return (ENFILE);
>  		*offset = i;
> -	} else if (*offset < 0 || *offset >= SYS_MAXSYSCALL)
> +	} else if (*offset < 0 || *offset >= SYS_MAXSYSCALL) {
>  		return (EINVAL);
> -	else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys &&
> -	    sysents[*offset].sy_call != (sy_call_t *)lkmressys)
> +	} else if (sysents[*offset].sy_call != (sy_call_t *)lkmnosys &&
> +	    sysents[*offset].sy_call != (sy_call_t *)lkmressys) {
> +		KASSERT(sysents[*offset].sy_call != NULL,
> +		    ("undefined syscall %d", *offset));
I do not think that the assert is very useful.  On debug kernels, where
the development would most likely take place, its only function is to annoy
developer by requiring him to reboot the host if he did not guessed a
free syscall number right.

I suggest to convert this into printf, might be also under bootverbose.

Also, why do you say that the syscall is undefined ?  I would state that
it is not reusable for dynamically loaded syscall, instead.

>  		return (EEXIST);
> +	}
>  
>  	KASSERT(sysents[*offset].sy_thrcnt == SY_THR_ABSENT,
>  	    ("dynamic syscall is not protected"));