From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Mon, 16 Nov 2015 11:57:40 +0000 Subject: [PATCH] arm64: mm: use correct mapping granularity under DEBUG_RODATA In-Reply-To: <1447669094-31076-1-git-send-email-ard.biesheuvel@linaro.org> References: <1447669094-31076-1-git-send-email-ard.biesheuvel@linaro.org> Message-ID: <20151116115740.GD20696@leverpostej> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi Ard, On Mon, Nov 16, 2015 at 11:18:14AM +0100, Ard Biesheuvel wrote: > 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. I assume for the above that you mean the kernel is loaded TEXT_OFFSET above these addresses. It's only a nit, but it might make things harder for otehrs to reason about in future. Perhaps re-word in terms of PHYS_OFFSET/memstart_addr? e.g. "when PHYS_OFFSET is not a multiple of SECTION_SIZE ...". > ---[ 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 > SWAPPER_BLOCK_SIZE instead of SECTION_SIZE. > > Signed-off-by: Ard Biesheuvel This looks good to me. With or without the rewording above: Acked-by: Mark Rutland Does this need to be backported to stable? Mark. > --- > arch/arm64/mm/mmu.c | 12 ++++++------ > 1 file changed, 6 insertions(+), 6 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index e3f563c81c48..32ddd893da9a 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -362,8 +362,8 @@ static void __init __map_memblock(phys_addr_t start, phys_addr_t end) > * 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), > @@ -451,18 +451,18 @@ static void __init fixup_executable(void) > { > #ifdef CONFIG_DEBUG_RODATA > /* 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), > - SECTION_SIZE); > + SWAPPER_BLOCK_SIZE); > > create_mapping(aligned_start, __phys_to_virt(aligned_start), > __pa(_stext) - aligned_start, > PAGE_KERNEL); > } > > - 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), > - SECTION_SIZE); > + SWAPPER_BLOCK_SIZE); > create_mapping(__pa(__init_end), (unsigned long)__init_end, > aligned_end - __pa(__init_end), > PAGE_KERNEL); > -- > 1.9.1 >