[PATCH 1/2] arm: use generic fixmap.h
Kees Cook
keescook at chromium.org
Fri Jul 25 12:56:46 PDT 2014
On Fri, Jul 18, 2014 at 7:33 AM, Leif Lindholm <leif.lindholm at linaro.org> wrote:
> On Wed, Jul 09, 2014 at 04:49:02PM -0400, Mark Salter wrote:
>> On Wed, 2014-07-09 at 10:39 +0100, Leif Lindholm wrote:
>> > diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
>> > index 45aeaac..3c59cdf 100644
>> > --- a/arch/arm/mm/highmem.c
>> > +++ b/arch/arm/mm/highmem.c
>> > @@ -20,16 +20,19 @@
>> >
>> > pte_t *fixmap_page_table;
>> >
>> > +#define __kmap_fix_to_virt(x) (__fix_to_virt(FIX_KMAP_NR_PTES - 1 - (x)))
>>
>> FIX_KMAP_END - (x) ?
>>
>> > +#define __kmap_virt_to_fix(x) (FIX_KMAP_NR_PTES - 1 - __fix_to_virt(x))
>>
>> shouldn't this use __virt_to_fix(x)?
>
> Err, clearly.
> Good thing I managed to mess up the end of the interface that actually
> isn't used anywhere in the kernel(!).
>
> Fixed in the below.
>
> /
> Leif
>
> From d0a82cd19000139d32232f415bcf46f476c16561 Mon Sep 17 00:00:00 2001
> From: Mark Salter <msalter at redhat.com>
> Date: Thu, 14 Nov 2013 11:37:32 -0500
> Subject: [PATCH 1/2] arm: use generic fixmap.h
>
> ARM is different from other architectures in that fixmap pages are
> indexed with a positive offset from FIXADDR_START. Other architectures
> index with a negative offset from FIXADDR_TOP. In order to use the
> generic fixmap.h definitions, this patch redefines FIXADDR_TOP to be
> inclusive of the useable range. That is, FIXADDR_TOP is the virtual
> address of the topmost fixed page. The newly defined FIXADDR_END is
> the first virtual address past the fixed mappings.
>
> The patch also introduces local helper macros in highmem.c to reverse
> the iteration order of fixmap pages.
>
> Signed-off-by: Mark Salter <msalter at redhat.com>
> [Rebased to 3.16-rc4, reverse kmap fixmap traversal]
> Signed-off-by: Leif Lindholm <leif.lindholm at linaro.org>
> ---
> arch/arm/include/asm/fixmap.h | 45 ++++++++++++++++++++++++++---------------
> arch/arm/mm/highmem.c | 13 +++++++-----
> arch/arm/mm/init.c | 2 +-
> 3 files changed, 38 insertions(+), 22 deletions(-)
>
> diff --git a/arch/arm/include/asm/fixmap.h b/arch/arm/include/asm/fixmap.h
> index 74124b0..8992431 100644
> --- a/arch/arm/include/asm/fixmap.h
> +++ b/arch/arm/include/asm/fixmap.h
> @@ -1,28 +1,41 @@
> #ifndef _ASM_FIXMAP_H
> #define _ASM_FIXMAP_H
>
> +#include <asm/pgtable.h>
> +
> #define FIXADDR_START 0xffc00000UL
> -#define FIXADDR_TOP 0xffe00000UL
> -#define FIXADDR_SIZE (FIXADDR_TOP - FIXADDR_START)
> +#define FIXADDR_END 0xffe00000UL
> +#define FIXADDR_SIZE (FIXADDR_END - FIXADDR_START)
> +#define FIXADDR_TOP (FIXADDR_END - PAGE_SIZE)
>
> #define FIX_KMAP_NR_PTES (FIXADDR_SIZE >> PAGE_SHIFT)
>
> -#define __fix_to_virt(x) (FIXADDR_START + ((x) << PAGE_SHIFT))
> -#define __virt_to_fix(x) (((x) - FIXADDR_START) >> PAGE_SHIFT)
> +enum fixed_addresses {
> + FIX_KMAP_BEGIN,
> + FIX_KMAP_END = FIX_KMAP_NR_PTES - 1,
> + __end_of_fixed_addresses
> +};
> +
> +/*
> + * Temporary boot-time mappings, used by early_ioremap(),
> + * before ioremap() is functional.
> + *
> + * (P)re-using the last pmd of the FIXADDR region, which is used for
> + * highmem later on, and statically aligned to 1MB.
> + * Growing down from FIXADDR_TOP
> + */
> +#define NR_FIX_BTMAPS 32
> +#define FIX_BTMAPS_SLOTS (PTRS_PER_PTE / NR_FIX_BTMAPS)
> +#define TOTAL_FIX_BTMAPS (NR_FIX_BTMAPS * FIX_BTMAPS_SLOTS)
> +#define FIX_BTMAP_END FIX_KMAP_BEGIN
> +#define FIX_BTMAP_BEGIN (FIX_BTMAP_END + TOTAL_FIX_BTMAPS - 1)
>
> -extern void __this_fixmap_does_not_exist(void);
> +#define FIXMAP_PAGE_NORMAL (L_PTE_MT_WRITEBACK | L_PTE_YOUNG | L_PTE_PRESENT)
> +#define FIXMAP_PAGE_IO (L_PTE_MT_DEV_NONSHARED | L_PTE_YOUNG | L_PTE_PRESENT)
>
> -static inline unsigned long fix_to_virt(const unsigned int idx)
> -{
> - if (idx >= FIX_KMAP_NR_PTES)
> - __this_fixmap_does_not_exist();
> - return __fix_to_virt(idx);
> -}
> +extern void __early_set_fixmap(enum fixed_addresses idx,
> + phys_addr_t phys, pgprot_t flags);
>
> -static inline unsigned int virt_to_fix(const unsigned long vaddr)
> -{
> - BUG_ON(vaddr >= FIXADDR_TOP || vaddr < FIXADDR_START);
> - return __virt_to_fix(vaddr);
> -}
> +#include <asm-generic/fixmap.h>
>
> #endif
> diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
> index 45aeaac..2e5b773 100644
> --- a/arch/arm/mm/highmem.c
> +++ b/arch/arm/mm/highmem.c
> @@ -20,16 +20,19 @@
>
> pte_t *fixmap_page_table;
>
> +#define __kmap_fix_to_virt(x) (__fix_to_virt(FIX_KMAP_NR_PTES - 1 - (x)))
> +#define __kmap_virt_to_fix(x) (FIX_KMAP_NR_PTES - 1 - __virt_to_fix(x))
> +
> static inline void set_fixmap_pte(int idx, pte_t pte)
> {
> - unsigned long vaddr = __fix_to_virt(idx);
> + unsigned long vaddr = __kmap_fix_to_virt(idx);
> set_pte_ext(fixmap_page_table + idx, pte, 0);
> local_flush_tlb_kernel_page(vaddr);
> }
>
> static inline pte_t get_fixmap_pte(unsigned long vaddr)
> {
> - unsigned long idx = __virt_to_fix(vaddr);
> + unsigned long idx = __kmap_virt_to_fix(vaddr);
> return *(fixmap_page_table + idx);
> }
>
> @@ -78,7 +81,7 @@ void *kmap_atomic(struct page *page)
> type = kmap_atomic_idx_push();
>
> idx = type + KM_TYPE_NR * smp_processor_id();
> - vaddr = __fix_to_virt(idx);
> + vaddr = __kmap_fix_to_virt(idx);
> #ifdef CONFIG_DEBUG_HIGHMEM
> /*
> * With debugging enabled, kunmap_atomic forces that entry to 0.
> @@ -109,7 +112,7 @@ void __kunmap_atomic(void *kvaddr)
> if (cache_is_vivt())
> __cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
> #ifdef CONFIG_DEBUG_HIGHMEM
> - BUG_ON(vaddr != __fix_to_virt(idx));
> + BUG_ON(vaddr != __kmap_fix_to_virt(idx));
> set_fixmap_pte(idx, __pte(0));
> #else
> (void) idx; /* to kill a warning */
> @@ -132,7 +135,7 @@ void *kmap_atomic_pfn(unsigned long pfn)
>
> type = kmap_atomic_idx_push();
> idx = type + KM_TYPE_NR * smp_processor_id();
> - vaddr = __fix_to_virt(idx);
> + vaddr = __kmap_fix_to_virt(idx);
> #ifdef CONFIG_DEBUG_HIGHMEM
> BUG_ON(!pte_none(*(fixmap_page_table + idx)));
> #endif
> diff --git a/arch/arm/mm/init.c b/arch/arm/mm/init.c
> index 659c75d..ad82c05 100644
> --- a/arch/arm/mm/init.c
> +++ b/arch/arm/mm/init.c
> @@ -570,7 +570,7 @@ void __init mem_init(void)
> MLK(DTCM_OFFSET, (unsigned long) dtcm_end),
> MLK(ITCM_OFFSET, (unsigned long) itcm_end),
> #endif
> - MLK(FIXADDR_START, FIXADDR_TOP),
> + MLK(FIXADDR_START, FIXADDR_END),
> MLM(VMALLOC_START, VMALLOC_END),
> MLM(PAGE_OFFSET, (unsigned long)high_memory),
> #ifdef CONFIG_HIGHMEM
> --
> 1.7.10.4
>
>
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel at lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
I'd like to use this for kernel RO text handling too (kprobes and
kgdb). Is this patch alone in good enough shape for landing in -next?
I would want this added as well:
https://patchwork.kernel.org/patch/3941001/
Thoughts?
-Kees
--
Kees Cook
Chrome OS Security
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