zlacker

I'm slightly confused after reading about page alignment. Why would a 16k page be less aligned than a 4k page causing assumptions about pointers within those pages to break? The 4k pages on x86 are aligned on 4k boundaries, are the 16k pages on M1 aligned on <4k boundaries?

>>amoss+(OP)
There are more 4k boundaries than 16k boundaries. The issue is code compiled for 4k boundaries running on a 16k system.

>>y1n0+H1
I'm missing something here. Assuming there are pages at 0k, 16k, 32k etc - all of those pages are aligned on 4k boundaries as 4k > 16k. So code written with the assumption that its pages are 4k aligned should have that assumption met when running with 16k pages. It is still early here and I have only had one cup of coffee. Am I misunderstanding something really obvious?

>>amoss+Y8
x86 app might mmap 8kb, then munmap the second 4kb and expect that to work. But not possible on 16k pages.

>>dezgeg+9c
ah ok, so it would not be pointer alignment inside the pages but instead the assumption that page +4k is a page.

>>amoss+hf
I was a little confused by that in the article as well. It being a granularity issue makes more sense to me.