Re: [PATCH] arm64/mm: fix virtual address boundary check
From: Miles Chen
Date: Wed Feb 24 2016 - 20:34:44 EST
On Wed, 2016-02-24 at 16:19 +0000, Catalin Marinas wrote:
> On Thu, Feb 25, 2016 at 12:01:48AM +0800, miles.chen@xxxxxxxxxxxx wrote:
> > From: Miles Chen <miles.chen@xxxxxxxxxxxx>
> > The MODULES_VADDR is not the lowest possible
> > kernel virtual address. TASK_SIZE_64 may be larger than
> > MODULES_VADDR, FIXADDR_TOP, and PCI_IO_START.
> > Fix this by comparing TASK_SIZE_64 (highest user virtual address)
> > with VA_START (lowest kernel virtual address).
> > #define VA_BITS (CONFIG_ARM64_VA_BITS)
> > #define VA_START (UL(0xffffffffffffffff) << VA_BITS)
> > #define PAGE_OFFSET (UL(0xffffffffffffffff) << (VA_BITS - 1))
> > #define MODULES_END (PAGE_OFFSET)
> > #define MODULES_VADDR (MODULES_END - SZ_64M)
> > #define PCI_IO_END (MODULES_VADDR - SZ_2M)
> > #define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)
> > #define FIXADDR_TOP (PCI_IO_START - SZ_2M)
> > #define TASK_SIZE_64 (UL(1) << VA_BITS)
> We should remove these checks altogether. There is a huge gap between
> the user and kernel addresses that they would never overlap (we don't
> have enough levels of page tables to cover 64-bit VA space).
Thanks for your reply. I confirmed that in the ARMv8 documentation.
I'll send another patch to remove these checks.