On 29/05/2026 17:02, Ard Biesheuvel wrote: > From: Ard Biesheuvel <[email protected]> > > Now that the linear region 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 > initial attributes and granularity, so that the loop iterating over the > memblocks will not remap it in a manner that prevents it from being > remapped with updated attributes later. > > Signed-off-by: Ard Biesheuvel <[email protected]>
Reviewed-by: Kevin Brodsky <[email protected]> > --- > arch/arm64/mm/mmu.c | 26 ++++++++------------ > 1 file changed, 10 insertions(+), 16 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 971996e46fd1..dcfca5667e5c 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -1164,12 +1164,17 @@ 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 first > + * so that its write permissions can be removed later without the need > + * to split any block mappings created by the loop below. > + * > + * Write permissions are needed for alternatives patching, and will be > + * removed later by mark_linear_text_alias_ro() above. 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), > + flags); > > /* map all the memory banks */ > for_each_mem_range(i, &start, &end) { > @@ -1181,17 +1186,6 @@ static void __init map_mem(void) > __map_memblock(start, end, pgprot_tagged(PAGE_KERNEL), > flags); > } > - > - /* > - * 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() below (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. > - */ > - __map_memblock(kernel_start, kernel_end, PAGE_KERNEL, 0); > - memblock_clear_nomap(kernel_start, kernel_end - kernel_start); > } > > void mark_rodata_ro(void)
