Date: Thu, 11 Aug 2005 16:21:02 -0700 (PDT) From: Doug Ambrisko <ambrisko@ambrisko.com> To: John Baldwin <jhb@freebsd.org> Cc: freebsd-hackers@freebsd.org, Dan Nelson <dnelson@allantgroup.com> Subject: Re: Checking sysctl values from within the kernel. Message-ID: <200508112321.j7BNL2rf001303@ambrisko.com> In-Reply-To: <200508051101.33927.jhb@FreeBSD.org>
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John Baldwin writes: | On Friday 05 August 2005 10:50 am, Dan Nelson wrote: | > In the last episode (Aug 05), Thordur I. Bjornsson said: | > > If I want to check a sysctl value from within the kernel (e.g. an | > > KLD), should I use the system calls described in sysctl(3) ? | > > | > > If not, what is the propper way to do so ? | > | > Since most sysctls are direct mappings onto integer variables in the | > kernel, just check the variable directly. | | There's also a kernel_sysctl() function available in the kernel for in-kernel | access to sysctls. You might have to lookup the OID for a given name | yourself though. Actually, there's a kernel_sysctlbyname() as well. This could be a fragile interface though. I used this scheme to do "soft-linking" between modules that could be kldloaded into the kernel or static. We called it several times every few seconds. Over time the system would wedge on a setjmp or something like that. We changed it to a function call since in a static kernel then the problem went away. Doug A.
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