Date: Sun, 09 Nov 2008 00:34:06 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: "David Christensen" <davidch@broadcom.com> Cc: "freebsd-current@freebsd.org" <freebsd-current@freebsd.org> Subject: Re: Dumping Large Binary Buffer Through Sysctl Message-ID: <44713.1226190846@critter.freebsd.dk> In-Reply-To: Your message of "Sat, 08 Nov 2008 16:28:11 PST." <5D267A3F22FD854F8F48B3D2B52381933936483700@IRVEXCHCCR01.corp.ad.broadcom.com>
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In message <5D267A3F22FD854F8F48B3D2B52381933936483700@IRVEXCHCCR01.corp.ad.bro adcom.com>, "David Christensen" writes: >> >I'm looking for a way to dump a large binary debug buffer=3D20 >> >in a driver to a file. I've currently implemented this >> >with SYSCTL_ADD_OPAQUE() and it works fine but running the >> >"sysctl -a" command causes this buffer to be dumped which >> >is something of a pain. Is there a better way to do this? >>=20 >> Much better idea: memory map it, that way your driver does >> not even discover that userland peeks over its shoulder. > >I found the CTLFLAG_SKIP attribute which hides the sysctl and=20 >makes things a lot better. How do I "memory map" the buffer? >Can you give me a function name or point to an example where=20 >this is done so I can look into it further? You implemente a cdevsw->mmap() function that tells the kernel where it is, then in userland, you open the device and call mmap(2). See sys/kern/subr_devstat.c for an example. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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