[PATCH 1/2] arm64: mm: dump: make page table dumping reusable

[Huang Shijie]

On Tue, May 31, 2016 at 02:49:01PM +0100, Mark Rutland wrote:
> For debugging purposes, it would be nice if we could export page tables
> other than the swapper_pg_dir to userspace. To enable this, this patch
> refactors the arm64 page table dumping code such that multiple tables
> may be registered with the framework, and exported under debugfs.
>
> Signed-off-by: Mark Rutland <mark.rutland at arm.com>
> Signed-off-by: Ard Biesheuvel <ard.biesheuvel at linaro.org>
> Cc: Catalin Marinas <catalin.marinas at arm.com>
> Cc: Laura Abbott <labbott at fedoraproject.org>
> Cc: Will Deacon <will.deacon at arm.com>
> ---
>  arch/arm64/include/asm/ptdump.h | 44 +++++++++++++++++++++++++++++++++++++++++
>  arch/arm64/mm/dump.c            | 32 +++++++++++++++++++-----------
>  2 files changed, 64 insertions(+), 12 deletions(-)
>  create mode 100644 arch/arm64/include/asm/ptdump.h
>
> diff --git a/arch/arm64/include/asm/ptdump.h b/arch/arm64/include/asm/ptdump.h
> new file mode 100644
> index 0000000..07b8ed0
> --- /dev/null
> +++ b/arch/arm64/include/asm/ptdump.h
> @@ -0,0 +1,44 @@
> +/*
> + * Copyright (C) 2014 ARM Ltd.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +#ifndef __ASM_PTDUMP_H
> +#define __ASM_PTDUMP_H
> +
> +#ifdef CONFIG_ARM64_PTDUMP
> +
> +#include <linux/mm_types.h>
> +
> +struct addr_marker {
> +     unsigned long start_address;
> +     char *name;
> +};
> +
> +struct ptdump_info {
> +     struct mm_struct                *mm;
> +     const struct addr_marker        *markers;
> +     unsigned long                   base_addr;
> +     unsigned long                   max_addr;
> +};
> +
> +int ptdump_register(struct ptdump_info *info, const char *name);
Since we export this to other page tables,  I guess the @base_addr in the ptdump_info{} may not equal to
the VA_START. But the current dump.c does _NOT_ use the @start address been
passed in, it use the 0 as the start address for the walk_pgd/walk_pud/walk_pmd/walk_pte.
It is wrong in logic, since the start address is VA_START, the code gets
the right result coincidentally.

thanks
Huang Shijie
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