From: Michael Ellerman mpe@ellerman.id.au
[ Upstream commit 3b5657ed5b4e27ccf593a41ff3c5aa27dae8df18 ]
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.
But the current logic uses small pages for the entire text section, regardless of whether a larger page size would fit. eg. with the boundary at 16M we could use 2M pages, but instead we use 64K pages up to the 16M boundary:
Mapped 0x0000000000000000-0x0000000001000000 with 64.0 KiB pages Mapped 0x0000000001000000-0x0000000040000000 with 2.00 MiB pages Mapped 0x0000000040000000-0x0000000100000000 with 1.00 GiB pages
This is because the test is checking if addr is < __init_begin and addr + mapping_size is >= _stext. But that is true for all pages between _stext and __init_begin.
Instead what we want to check is if we are crossing the text/data boundary, which is at __init_begin. With that fixed we see:
Mapped 0x0000000000000000-0x0000000000e00000 with 2.00 MiB pages Mapped 0x0000000000e00000-0x0000000001000000 with 64.0 KiB pages Mapped 0x0000000001000000-0x0000000040000000 with 2.00 MiB pages Mapped 0x0000000040000000-0x0000000100000000 with 1.00 GiB pages
ie. we're correctly using 2MB pages below __init_begin, but we still drop down to 64K pages unnecessarily at the boundary.
Signed-off-by: Michael Ellerman mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/mm/pgtable-radix.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/mm/pgtable-radix.c b/arch/powerpc/mm/pgtable-radix.c index 24a2eadc8c21a..b387c7b917b7e 100644 --- a/arch/powerpc/mm/pgtable-radix.c +++ b/arch/powerpc/mm/pgtable-radix.c @@ -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(_stext)) { + (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(_stext)) { + (addr + mapping_size) >= __pa_symbol(__init_begin)) { mapping_size = PAGE_SIZE; psize = mmu_virtual_psize; }