Commit b43c5287 authored Aug 14, 2018 by Michael Ellerman Committed by Greg Kroah-Hartman Dec 01, 2019

powerpc/mm/radix: Fix small page at boundary when splitting



[ Upstream commit 81d1b54dec95209ab5e5be2cf37182885f998753 ]

When we have CONFIG_STRICT_KERNEL_RWX enabled, we want to split the
linear mapping at the text/data boundary so we can map the kernel
text read only.

Currently we always use a small page at the text/data boundary, even
when that's not necessary:

  Mapped 0x0000000000000000-0x0000000000e00000 with 2.00 MiB pages
  Mapped 0x0000000000e00000-0x0000000001000000 with 64.0 KiB pages
  Mapped 0x0000000001000000-0x0000000040000000 with 2.00 MiB pages

This is because the check that the mapping crosses the __init_begin
boundary is too strict, it also returns true when we map exactly up to
the boundary.

So fix it to check that the mapping would actually map past
__init_begin, and with that we see:

  Mapped 0x0000000000000000-0x0000000040000000 with 2.00 MiB pages
  Mapped 0x0000000040000000-0x0000000100000000 with 1.00 GiB pages

Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent b499fa07

arch/powerpc/mm/pgtable-radix.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -295,14 +295,14 @@ static int __meminit create_physical_mapping(unsigned long start,

		if (split_text_mapping && (mapping_size == PUD_SIZE) &&
		(addr < __pa_symbol(__init_begin)) &&
		(addr + mapping_size) >= __pa_symbol(__init_begin)) {
		(addr + mapping_size) > __pa_symbol(__init_begin)) {
		max_mapping_size = PMD_SIZE;
		goto retry;
		}

		if (split_text_mapping && (mapping_size == PMD_SIZE) &&
		(addr < __pa_symbol(__init_begin)) &&
		(addr + mapping_size) >= __pa_symbol(__init_begin)) {
		(addr + mapping_size) > __pa_symbol(__init_begin)) {
		mapping_size = PAGE_SIZE;
		psize = mmu_virtual_psize;
		}