Date: Fri, 9 Nov 2001 13:24:51 +0000 From: Rasputin <rasputin@submonkey.net> To: Anthony Atkielski <anthony@atkielski.com> Cc: security@freebsd.org Subject: Re: FreeBSD and i386 VM hardware Message-ID: <20011109132451.A6163@shikima.mine.nu> In-Reply-To: <01b301c16918$be1763a0$0a00000a@atkielski.com>; from anthony@atkielski.com on Fri, Nov 09, 2001 at 01:19:06PM %2B0100 References: <01b301c16918$be1763a0$0a00000a@atkielski.com>
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* Anthony Atkielski <anthony@atkielski.com> [011109 12:25]: > To what extent does FreeBSD actually use all the fancy virtual-memory features > of latter-day i386 processors? As I recall (it has been several years since I > looked into it), the Intel microprocessors provide some very elaborate features > for management of virtual memory, I/O operations, and security, allowing total > hardware isolation of untrusted processes. How much of this is used by FreeBSD? > I know that UNIX is supposed to isolate users from each other, but how much of > this is done in hardware, and how much of it is simulated in software? Very > tight security usually requires a lot of interdependency between the hardware > and the OS, and since UNIX is supposed to be a multiplatform OS, I'm wondering > how much hardware support for security is actually used by the system. Not much of a hardware guy myself, but I think (from the Daemon Book) most of the UNIX model works via the ability of the kernel to use protected mode features of the CPU, while limiting access to them through system calls to userland (i.e. non-privileged CPU instruction-based) processes. Hence the need for i386 CPUs or higher. Other than that, most of the isolation of processes from each other is based on context switching and (software-based) process structures. I'm sure I read that about 97% of the BSD source tree was platform-independant, the rest being things like MMU hardware-specific code. Any corrections/clarifications to the above are welcome.. -- Rasputin :: Jack of All Trades - Master of Nuns :: To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message
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