[PATCH 4.3 136/157] arm64: mm: use correct mapping granularity under DEBUG_RODATA

From: Greg Kroah-Hartman
Date: Wed Jan 27 2016 - 13:33:25 EST

4.3-stable review patch. If anyone has any objections, please let me know.


From: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>

commit 4fee9f364b9b99f76732f2a6fd6df679a237fa74 upstream.

When booting a 64k pages kernel that is built with CONFIG_DEBUG_RODATA
and resides at an offset that is not a multiple of 512 MB, the rounding
that occurs in __map_memblock() and fixup_executable() results in
incorrect regions being mapped.

The following snippet from /sys/kernel/debug/kernel_page_tables shows
how, when the kernel is loaded 2 MB above the base of DRAM at 0x40000000,
the first 2 MB of memory (which may be inaccessible from non-secure EL1
or just reserved by the firmware) is inadvertently mapped into the end of
the module region.

---[ Modules start ]---
0xfffffdffffe00000-0xfffffe0000000000 2M RW NX ... UXN MEM/NORMAL
---[ Modules end ]---
---[ Kernel Mapping ]---
0xfffffe0000000000-0xfffffe0000090000 576K RW NX ... UXN MEM/NORMAL
0xfffffe0000090000-0xfffffe0000200000 1472K ro x ... UXN MEM/NORMAL
0xfffffe0000200000-0xfffffe0000800000 6M ro x ... UXN MEM/NORMAL
0xfffffe0000800000-0xfffffe0000810000 64K ro x ... UXN MEM/NORMAL
0xfffffe0000810000-0xfffffe0000a00000 1984K RW NX ... UXN MEM/NORMAL
0xfffffe0000a00000-0xfffffe00ffe00000 4084M RW NX ... UXN MEM/NORMAL

The same issue is likely to occur on 16k pages kernels whose load
address is not a multiple of 32 MB (i.e., SECTION_SIZE). So round to

Fixes: da141706aea5 ("arm64: add better page protections to arm64")
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
Acked-by: Mark Rutland <mark.rutland@xxxxxxx>
Acked-by: Laura Abbott <labbott@xxxxxxxxxx>
Signed-off-by: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

arch/arm64/mm/mmu.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -308,8 +308,8 @@ static void __init __map_memblock(phys_a
* for now. This will get more fine grained later once all memory
* is mapped
- unsigned long kernel_x_start = round_down(__pa(_stext), SECTION_SIZE);
- unsigned long kernel_x_end = round_up(__pa(__init_end), SECTION_SIZE);
+ unsigned long kernel_x_start = round_down(__pa(_stext), SWAPPER_BLOCK_SIZE);
+ unsigned long kernel_x_end = round_up(__pa(__init_end), SWAPPER_BLOCK_SIZE);

if (end < kernel_x_start) {
create_mapping(start, __phys_to_virt(start),
@@ -397,18 +397,18 @@ void __init fixup_executable(void)
/* now that we are actually fully mapped, make the start/end more fine grained */
- if (!IS_ALIGNED((unsigned long)_stext, SECTION_SIZE)) {
+ if (!IS_ALIGNED((unsigned long)_stext, SWAPPER_BLOCK_SIZE)) {
unsigned long aligned_start = round_down(__pa(_stext),

create_mapping(aligned_start, __phys_to_virt(aligned_start),
__pa(_stext) - aligned_start,

- if (!IS_ALIGNED((unsigned long)__init_end, SECTION_SIZE)) {
+ if (!IS_ALIGNED((unsigned long)__init_end, SWAPPER_BLOCK_SIZE)) {
unsigned long aligned_end = round_up(__pa(__init_end),
create_mapping(__pa(__init_end), (unsigned long)__init_end,
aligned_end - __pa(__init_end),