On 29/04/2026 16:23, Ard Biesheuvel wrote: > On Wed, 29 Apr 2026, at 12:54, Kevin Brodsky wrote: >> On 27/04/2026 17:34, Ard Biesheuvel wrote: >>> From: Ard Biesheuvel <[email protected]> >>> >>> Now that the DRAM mapping routines respect existing table mappings and >>> contiguous block and page mappings, it is no longer needed to fiddle >>> with the memblock tables to set and clear the NOMAP attribute in order >>> to omit text and rodata when creating the linear map. >>> >>> Instead, map the kernel text and rodata alias first with the desired >>> attributes, so that they will not be remapped later with different >>> attributes when mapping the memblocks. >>> >>> Signed-off-by: Ard Biesheuvel <[email protected]> >>> --- >>> arch/arm64/mm/mmu.c | 24 +++++++------------- >>> 1 file changed, 8 insertions(+), 16 deletions(-) >>> >>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>> index 5e2348b15783..1a4b4337d29a 100644 >>> --- a/arch/arm64/mm/mmu.c >>> +++ b/arch/arm64/mm/mmu.c >>> @@ -1148,12 +1148,15 @@ static void __init map_mem(void) >>> flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; >>> >>> /* >>> - * Take care not to create a writable alias for the >>> - * read-only text and rodata sections of the kernel image. >>> - * So temporarily mark them as NOMAP to skip mappings in >>> - * the following for-loop >>> + * Map the linear alias of the [_text, __init_begin) interval >>> + * as non-executable now, and remove the write permission in >>> + * mark_linear_text_alias_ro() above (which will be called after >>> + * alternative patching has completed). This makes the contents >>> + * of the region accessible to subsystems such as hibernate, >>> + * but protects it from inadvertent modification or execution. >>> */ >>> - memblock_mark_nomap(kernel_start, kernel_end - kernel_start); >>> + __map_memblock(kernel_start, kernel_end, pgprot_tagged(PAGE_KERNEL), >> Is it now necessary for that mapping to be tagged? If so, it should >> probably be called out in the commit message. >> > As you've pointed out, the initial r/w mapping of the linear alias of rodata > will need to be mapped tagged before moving the zero page there. So this patch > will just preserve that, rather than remapping the region tagged explicitly as > it does now.
Right! I got lost in all the mappings :) - Kevin
