MMU related code
Hi, Where do I find the code in the kernel related to the MMU and resolving memory addresses? I am trying to understand what the implications are if code like this has bugs and the impact on the various functions that return chunks of memory for use via pointers (either as pages or kmalloc chunks) etc. Regards, Carter
On Mon, 29 Oct 2018 00:08:12 +0800, Carter Cheng said:
Where do I find the code in the kernel related to the MMU and resolving memory addresses? I am trying to understand what the implications are if code like this has bugs and the impact on the various functions that return chunks of memory for use via pointers (either as pages or kmalloc chunks) etc.
The results are easy enough to predict even without looking at the code. If your memory allocations are buggy, you get random memory overlays and corruption, attempts to access non-mapped physical or virtual memory addresses, and so on. Basically, all the same sorts of issues beginning C programmers encounter before they understand pointers.
Hi, A BUGGY MMU may also have some security implications, like flawed protection of one process against another one. MMU may work fine without any performance or functionality issue. But it might reveal one's address space to the others. I'm not sure if what I have told is true but let me know if it is wrong pls! Thanks On Mon, Oct 29, 2018 at 9:50 AM <valdis.kletnieks@vt.edu> wrote:
On Mon, 29 Oct 2018 00:08:12 +0800, Carter Cheng said:
Where do I find the code in the kernel related to the MMU and resolving memory addresses? I am trying to understand what the implications are if code like this has bugs and the impact on the various functions that return chunks of memory for use via pointers (either as pages or kmalloc chunks) etc.
The results are easy enough to predict even without looking at the code. If your memory allocations are buggy, you get random memory overlays and corruption, attempts to access non-mapped physical or virtual memory addresses, and so on.
Basically, all the same sorts of issues beginning C programmers encounter before they understand pointers. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Is the /mm directory the correct place to look? It seems to contain memory related code but from what little I have read it seems at a higher level building in some cases at least on kmalloc. I am just curious about a point raised by the SVA dissertation(by John Criswell). Another point he does raise but I am uncertain about how true it is in general is that to do static analysis/dynamic instrumentation properly on the kernel one needs some method to assess what the inline assembly fragments do and to deal with this particular problem he replaced all this code with custom bitcode instructions.
Hi Carter, On Mon, Oct 29, 2018 at 03:33:02PM +0800, Carter Cheng wrote:
Is the /mm directory the correct place to look? It seems to contain memory related code but from what little I have read it seems at a higher level building in some cases at least on kmalloc.
Most if the paging/MMU code is also architecture specific which means that it resides in the arch/mm subfolders. I saw that there was a MM 101 presentation last week at the Open Source Summit [1], Unfortunatetly, it is quite high-level and most likelt uninterestting to you. But there is also a huge subsection in the official kernel documentation which has many references to the mm/ and arch/mm code [2]. Cheers, Steffen [1] https://events.linuxfoundation.org/wp-content/uploads/2017/12/MM-101-Introdu... [2] https://www.kernel.org/doc/html/latest/vm/index.html
Thanks, I'll check it out. On Mon, Oct 29, 2018 at 3:45 PM Steffen Vogel <post@steffenvogel.de> wrote:
Hi Carter,
On Mon, Oct 29, 2018 at 03:33:02PM +0800, Carter Cheng wrote:
Is the /mm directory the correct place to look? It seems to contain memory related code but from what little I have read it seems at a higher level building in some cases at least on kmalloc.
Most if the paging/MMU code is also architecture specific which means that it resides in the arch/mm subfolders.
I saw that there was a MM 101 presentation last week at the Open Source Summit [1], Unfortunatetly, it is quite high-level and most likelt uninterestting to you.
But there is also a huge subsection in the official kernel documentation which has many references to the mm/ and arch/mm code [2].
Cheers, Steffen
[1] https://events.linuxfoundation.org/wp-content/uploads/2017/12/MM-101-Introdu... [2] https://www.kernel.org/doc/html/latest/vm/index.html
participants (4)
-
Carter Cheng -
SeyedAlireza Sanaee -
Steffen Vogel -
valdis.kletnieks＠vt.edu