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Date: Fri, 24 Mar 2017 15:54:48 -0700
From: Kees Cook <keescook@...omium.org>
To: Russell King <linux@...linux.org.uk>
Cc: Mark Rutland <mark.rutland@....com>, Afzal Mohammed <afzal.mohd.ma@...il.com>, 
	"linux-arm-kernel@...ts.infradead.org" <linux-arm-kernel@...ts.infradead.org>, LKML <linux-kernel@...r.kernel.org>, 
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v2] ARM: ptdump: Add domain to output

On Thu, Mar 2, 2017 at 4:30 PM, Kees Cook <keescook@...omium.org> wrote:
> This adds the memory domain (on non-LPAE) to the PMD and PTE dumps. This
> isn't in the regular PMD bit struct because I couldn't find a clean way to
> fall back to retain some of the PMD bits when reporting PTE. So this is
> special-cased for now.
>
> New output example:
>
> ---[ Modules ]---
> 0x7f000000-0x7f001000       4K DOMAIN_KERNEL      ro x  SHD MEM/CACHED/WBWA
> 0x7f001000-0x7f002000       4K DOMAIN_KERNEL      ro NX SHD MEM/CACHED/WBWA
> 0x7f002000-0x7f004000       8K DOMAIN_KERNEL      RW NX SHD MEM/CACHED/WBWA
> ---[ Kernel Mapping ]---
> 0x80000000-0x80100000       1M DOMAIN_KERNEL      RW NX SHD
> 0x80100000-0x80800000       7M DOMAIN_KERNEL      ro x  SHD
> 0x80800000-0x80b00000       3M DOMAIN_KERNEL      ro NX SHD
> 0x80b00000-0xa0000000     501M DOMAIN_KERNEL      RW NX SHD
> ...
> ---[ Vectors ]---
> 0xffff0000-0xffff1000       4K DOMAIN_VECTORS USR ro x  SHD MEM/CACHED/WBWA
> 0xffff1000-0xffff2000       4K DOMAIN_VECTORS     ro x  SHD MEM/CACHED/WBWA
>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> This actually works correctly now (tested by forcing different domains on
> portions of the Kernel Mapping. I really wanted to find a way to use the
> existing bit structs, but I couldn't make anything work... I'm open to ideas.

Any feedback on this? Should I submit this to the ARM patch tracker?

Thanks!

-Kees

> ---
>  arch/arm/mm/dump.c | 54 ++++++++++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 44 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm/mm/dump.c b/arch/arm/mm/dump.c
> index 21192d6eda40..3770d9f83bdc 100644
> --- a/arch/arm/mm/dump.c
> +++ b/arch/arm/mm/dump.c
> @@ -17,6 +17,7 @@
>  #include <linux/mm.h>
>  #include <linux/seq_file.h>
>
> +#include <asm/domain.h>
>  #include <asm/fixmap.h>
>  #include <asm/memory.h>
>  #include <asm/pgtable.h>
> @@ -43,6 +44,7 @@ struct pg_state {
>         unsigned long start_address;
>         unsigned level;
>         u64 current_prot;
> +       const char *current_domain;
>  };
>
>  struct prot_bits {
> @@ -216,7 +218,8 @@ static void dump_prot(struct pg_state *st, const struct prot_bits *bits, size_t
>         }
>  }
>
> -static void note_page(struct pg_state *st, unsigned long addr, unsigned level, u64 val)
> +static void note_page(struct pg_state *st, unsigned long addr, unsigned level,
> +                     u64 val, const char *domain)
>  {
>         static const char units[] = "KMGTPE";
>         u64 prot = val & pg_level[level].mask;
> @@ -224,8 +227,10 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level, u
>         if (!st->level) {
>                 st->level = level;
>                 st->current_prot = prot;
> +               st->current_domain = domain;
>                 seq_printf(st->seq, "---[ %s ]---\n", st->marker->name);
>         } else if (prot != st->current_prot || level != st->level ||
> +                  domain != st->current_domain ||
>                    addr >= st->marker[1].start_address) {
>                 const char *unit = units;
>                 unsigned long delta;
> @@ -240,6 +245,8 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level, u
>                                 unit++;
>                         }
>                         seq_printf(st->seq, "%9lu%c", delta, *unit);
> +                       if (st->current_domain)
> +                               seq_printf(st->seq, " %s", st->current_domain);
>                         if (pg_level[st->level].bits)
>                                 dump_prot(st, pg_level[st->level].bits, pg_level[st->level].num);
>                         seq_printf(st->seq, "\n");
> @@ -251,11 +258,13 @@ static void note_page(struct pg_state *st, unsigned long addr, unsigned level, u
>                 }
>                 st->start_address = addr;
>                 st->current_prot = prot;
> +               st->current_domain = domain;
>                 st->level = level;
>         }
>  }
>
> -static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start)
> +static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start,
> +                    const char *domain)
>  {
>         pte_t *pte = pte_offset_kernel(pmd, 0);
>         unsigned long addr;
> @@ -263,25 +272,50 @@ static void walk_pte(struct pg_state *st, pmd_t *pmd, unsigned long start)
>
>         for (i = 0; i < PTRS_PER_PTE; i++, pte++) {
>                 addr = start + i * PAGE_SIZE;
> -               note_page(st, addr, 4, pte_val(*pte));
> +               note_page(st, addr, 4, pte_val(*pte), domain);
>         }
>  }
>
> +static const char *get_domain_name(pmd_t *pmd)
> +{
> +#ifndef CONFIG_ARM_LPAE
> +       switch (pmd_val(*pmd) & PMD_DOMAIN_MASK) {
> +       case PMD_DOMAIN(DOMAIN_KERNEL):
> +               return "DOMAIN_KERNEL ";
> +       case PMD_DOMAIN(DOMAIN_USER):
> +               return "DOMAIN_USER   ";
> +       case PMD_DOMAIN(DOMAIN_IO):
> +               return "DOMAIN_IO     ";
> +       case PMD_DOMAIN(DOMAIN_VECTORS):
> +               return "DOMAIN_VECTORS";
> +       default:
> +               return "DOMAIN_unknown";
> +       }
> +#endif
> +       return NULL;
> +}
> +
>  static void walk_pmd(struct pg_state *st, pud_t *pud, unsigned long start)
>  {
>         pmd_t *pmd = pmd_offset(pud, 0);
>         unsigned long addr;
>         unsigned i;
> +       const char *domain;
>
>         for (i = 0; i < PTRS_PER_PMD; i++, pmd++) {
>                 addr = start + i * PMD_SIZE;
> +               domain = get_domain_name(pmd);
>                 if (pmd_none(*pmd) || pmd_large(*pmd) || !pmd_present(*pmd))
> -                       note_page(st, addr, 3, pmd_val(*pmd));
> +                       note_page(st, addr, 3, pmd_val(*pmd), domain);
>                 else
> -                       walk_pte(st, pmd, addr);
> +                       walk_pte(st, pmd, addr, domain);
>
> -               if (SECTION_SIZE < PMD_SIZE && pmd_large(pmd[1]))
> -                       note_page(st, addr + SECTION_SIZE, 3, pmd_val(pmd[1]));
> +               if (SECTION_SIZE < PMD_SIZE && pmd_large(pmd[1])) {
> +                       addr += SECTION_SIZE;
> +                       pmd++;
> +                       domain = get_domain_name(pmd);
> +                       note_page(st, addr, 3, pmd_val(*pmd), domain);
> +               }
>         }
>  }
>
> @@ -296,7 +330,7 @@ static void walk_pud(struct pg_state *st, pgd_t *pgd, unsigned long start)
>                 if (!pud_none(*pud)) {
>                         walk_pmd(st, pud, addr);
>                 } else {
> -                       note_page(st, addr, 2, pud_val(*pud));
> +                       note_page(st, addr, 2, pud_val(*pud), NULL);
>                 }
>         }
>  }
> @@ -317,11 +351,11 @@ static void walk_pgd(struct seq_file *m)
>                 if (!pgd_none(*pgd)) {
>                         walk_pud(&st, pgd, addr);
>                 } else {
> -                       note_page(&st, addr, 1, pgd_val(*pgd));
> +                       note_page(&st, addr, 1, pgd_val(*pgd), NULL);
>                 }
>         }
>
> -       note_page(&st, 0, 0, 0);
> +       note_page(&st, 0, 0, 0, NULL);
>  }
>
>  static int ptdump_show(struct seq_file *m, void *v)
> --
> 2.7.4
>
>
> --
> Kees Cook
> Pixel Security



-- 
Kees Cook
Pixel Security

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