Hi Shreyansh,
> >
> > Furthermore the virtual field in the page structure coresponds to this
> > kernel logical address and it never changes if the page belongs to
> > ZONE_NORMAL?
>
> IMHO, yes.
Does that also mean that the kernel image is loaded in the RAM memory
region corresponding to ZONE_DMA?
I am concluding this from the fact that the kernel image (bzImage) is
loaded at the *physical location* 0x100000 (which corresponds to
1048576 or 1 MB). - as mentioned in Understanding the Linux Kernel
(Booting process).
This seems to be very much the case. A quick objdump of the kernel
image reveals the kernel is indeed expecting to be loaded at an
address of C0100000:
Sections:
Idx Name Size VMA LMA File off Algn
0 .text 00114254 c0100000 c0100000 00001000 2**4
CONTENTS, ALLOC, LOAD, READONLY, CODE
1 .text.lock 0000279e c0214254 c0214254 00115254 2**2
CONTENTS, ALLOC, LOAD, READONLY, CODE
2 .rodata 0000d3c0 c0216a00 c0216a00 00117a00 2**5
If that is right, does this effect any DMA'able devices' way of
addressing the 16MB of dedicated DMA zone
Ummm ... I do not think that the drivers should be affected by this. I
expect kmalloc (and other memory allocation functions) to be smart
enough - so they will allocate a and return memory ONLY if it is not
occupied by the kernel (Obviously!).
So IMHO, there is no potential danger of corrupting the kernel image
if your driver restricts its access to only the memory it got from
kmalloc().
Thanks,
Rajat
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