Messages in this thread | | | From | "Khimenko Victor" <> | Date | Wed, 26 Jul 2000 17:31:14 +0400 (MSD) | Subject | Re: Direct access to hardware |
| |
In <Pine.LNX.4.10.10007261155410.17041-100000@dax.joh.cam.ac.uk> James Sutherland (jas88@cam.ac.uk) wrote: > On 25 Jul 2000, Krzysztof Halasa wrote:
>> James Sutherland <jas88@cam.ac.uk> writes: >> >> > On Tue, 25 Jul 2000, Stuart MacDonald wrote: >> > >> > > Which is exactly the point. The hard drives should be checking for >> > > invalid ATA commands in hardware, right in the drive, preventing >> > > damage from bad commands. Putting a filter into the kernel is not >> > > the right fix. >> > >> > As with some of the Intel CPU bugs, the problem is NOT "invalid ATA >> > commands" - it's a matter of VALID commands which are dangerous. FDIV on >> > early Pentiums isn't an invalid instruction - it just produces the wrong >> > results at times. So the SOFTWARE must do something to avoid this - either >> > that, or you need to replace the hardware, which isn't desirable. You do >> > something in the OS to prevent these problem commands being used. >> >> So what does the kernel (can) do to prevent this problem on defective >> pentiums?
> Trap the defective instructions, and implement a replacement instruction > in software. On later Intel CPUs, you can sometimes use a microcode update > to fix it - this also requires OS intervention.
> Either way, essentially you tell the OS to block the duff instructions, > and it does so.
Exactly. You are ONLY blocking "duff instructions" to workaround bug in hardware. You are not trying to standardtize life.
Why not add filters in fs/exec.c so only "good commands" can be executed ? And when new program is developed you "only" need to get approval in "linux-programs committee": kernel only need to know that it's now safe to execute gcj - it's safe "GNU Java Compiler", not some malicious code. What's the difference ? There are exist "standard" commands (see POSIX) and there are conutless "vendor-specific extensions". Why not limit itself to standard commands and to not change standard when new program is wanted ? You can destroy not only HDD but a lot more with malicious or buggy setuid program in typical system.
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu Please read the FAQ at http://www.tux.org/lkml/
| |