Messages in this thread | | | Subject | Shared memory usage | Date | Mon, 16 Jan 2006 09:15:16 -0500 | From | "linux-os \(Dick Johnson\)" <> |
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Hello,
I have an embedded system in which there are about 18.4 megabytes of shared libraries using shared memory, plus 12 pages of shared memory, memory-mapped into user-space. This all works fine.
But the customer complained during certification testing that shared memory in use is not measured and therefore cannot be verified. This means that there may be rogue communications channels, using shared memory, in the system. I need to prove that there are no such channels by metering the shared memory and then accounting for every bit shown.
/proc/meminfo does not show any shared memory in use!
total: used: free: shared: buffers: cached: Mem: 255332352 7806976 247525376 0 94208 2764800 Swap: 0 0 0 MemTotal: 249348 kB MemFree: 241724 kB MemShared: 0 kB <---------- Buffers: 92 kB Cached: 2700 kB SwapCached: 0 kB Active: 608 kB Inactive: 4348 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 249348 kB LowFree: 241724 kB SwapTotal: 0 kB SwapFree: 0 kB
This used Linux version 2.4.26. In attempting to troubleshoot this, I found that current kernel versions don't even have a shared memory entry in /proc/meminfo.
So, how do I find the total amount of shared memory in use on a system? This does not need to be in /proc. I could write a driver that finds all the shared memory and reports it, but I need to know how. Also, anybody certifying systems for secure use needs to know the amount of shared memory in use so it would be a real good idea if that information was available in /proc as it was in the past before it was removed.
Cheers, Dick Johnson Penguin : Linux version 2.6.13.4 on an i686 machine (5589.54 BogoMips). Warning : 98.36% of all statistics are fiction. .
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