Hi Pierre,
On Mon, Mar 18, 2024 at 4:35 PM Pierre-Clément Tosi ptosi@google.com wrote:
The implementation of map_range() creates the requested mapping by walking the page tables, iterating over multiple PTEs and/or descending into existing table mappings as needed. When doing so, it assumes any pre-existing valid PTE to be a table mapping. This assumption is wrong if the platform code attempts to successively map two overlapping ranges where the latter intersects a block mapping created for the former.
As a result, map_range() treats the existing block mapping as a table mapping and descends into it i.e. starts interpreting the previously-mapped range as an array of PTEs, writing to them and potentially even descending further (extra fun with MMIO ranges!).
Instead, pass any valid non-table mapping to split_block(), which ensures that it actually was a block mapping (calls panic() otherwise) before splitting it.
Fixes: 41e2787f5ec4 ("arm64: Reduce add_map() complexity") Signed-off-by: Pierre-Clément Tosi ptosi@google.com
This fixes the boot regression on colibri-imx8x.
Thanks a lot for your fix!
Tested-by: Fabio Estevam festevam@gmail.com