lkml.org 
[lkml]   [2019]   [Apr]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v3 07/11] arm: Use generic mmap top-down layout
From
Date
On 4/18/19 1:28 AM, Kees Cook wrote:
> On Wed, Apr 17, 2019 at 12:30 AM Alexandre Ghiti <alex@ghiti.fr> wrote:
>> arm uses a top-down mmap layout by default that exactly fits the generic
>> functions, so get rid of arch specific code and use the generic version
>> by selecting ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT.
>>
>> Signed-off-by: Alexandre Ghiti <alex@ghiti.fr>
> Acked-by: Kees Cook <keescook@chromium.org>


Thanks !


>
> -Kees
>
>> ---
>> arch/arm/Kconfig | 1 +
>> arch/arm/include/asm/processor.h | 2 --
>> arch/arm/mm/mmap.c | 62 --------------------------------
>> 3 files changed, 1 insertion(+), 64 deletions(-)
>>
>> diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
>> index 850b4805e2d1..f8f603da181f 100644
>> --- a/arch/arm/Kconfig
>> +++ b/arch/arm/Kconfig
>> @@ -28,6 +28,7 @@ config ARM
>> select ARCH_SUPPORTS_ATOMIC_RMW
>> select ARCH_USE_BUILTIN_BSWAP
>> select ARCH_USE_CMPXCHG_LOCKREF
>> + select ARCH_WANT_DEFAULT_TOPDOWN_MMAP_LAYOUT if MMU
>> select ARCH_WANT_IPC_PARSE_VERSION
>> select BUILDTIME_EXTABLE_SORT if MMU
>> select CLONE_BACKWARDS
>> diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
>> index 57fe73ea0f72..944ef1fb1237 100644
>> --- a/arch/arm/include/asm/processor.h
>> +++ b/arch/arm/include/asm/processor.h
>> @@ -143,8 +143,6 @@ static inline void prefetchw(const void *ptr)
>> #endif
>> #endif
>>
>> -#define HAVE_ARCH_PICK_MMAP_LAYOUT
>> -
>> #endif
>>
>> #endif /* __ASM_ARM_PROCESSOR_H */
>> diff --git a/arch/arm/mm/mmap.c b/arch/arm/mm/mmap.c
>> index 0b94b674aa91..b8d912ac9e61 100644
>> --- a/arch/arm/mm/mmap.c
>> +++ b/arch/arm/mm/mmap.c
>> @@ -17,43 +17,6 @@
>> ((((addr)+SHMLBA-1)&~(SHMLBA-1)) + \
>> (((pgoff)<<PAGE_SHIFT) & (SHMLBA-1)))
>>
>> -/* gap between mmap and stack */
>> -#define MIN_GAP (128*1024*1024UL)
>> -#define MAX_GAP ((STACK_TOP)/6*5)
>> -#define STACK_RND_MASK (0x7ff >> (PAGE_SHIFT - 12))
>> -
>> -static int mmap_is_legacy(struct rlimit *rlim_stack)
>> -{
>> - if (current->personality & ADDR_COMPAT_LAYOUT)
>> - return 1;
>> -
>> - if (rlim_stack->rlim_cur == RLIM_INFINITY)
>> - return 1;
>> -
>> - return sysctl_legacy_va_layout;
>> -}
>> -
>> -static unsigned long mmap_base(unsigned long rnd, struct rlimit *rlim_stack)
>> -{
>> - unsigned long gap = rlim_stack->rlim_cur;
>> - unsigned long pad = stack_guard_gap;
>> -
>> - /* Account for stack randomization if necessary */
>> - if (current->flags & PF_RANDOMIZE)
>> - pad += (STACK_RND_MASK << PAGE_SHIFT);
>> -
>> - /* Values close to RLIM_INFINITY can overflow. */
>> - if (gap + pad > gap)
>> - gap += pad;
>> -
>> - if (gap < MIN_GAP)
>> - gap = MIN_GAP;
>> - else if (gap > MAX_GAP)
>> - gap = MAX_GAP;
>> -
>> - return PAGE_ALIGN(STACK_TOP - gap - rnd);
>> -}
>> -
>> /*
>> * We need to ensure that shared mappings are correctly aligned to
>> * avoid aliasing issues with VIPT caches. We need to ensure that
>> @@ -181,31 +144,6 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
>> return addr;
>> }
>>
>> -unsigned long arch_mmap_rnd(void)
>> -{
>> - unsigned long rnd;
>> -
>> - rnd = get_random_long() & ((1UL << mmap_rnd_bits) - 1);
>> -
>> - return rnd << PAGE_SHIFT;
>> -}
>> -
>> -void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
>> -{
>> - unsigned long random_factor = 0UL;
>> -
>> - if (current->flags & PF_RANDOMIZE)
>> - random_factor = arch_mmap_rnd();
>> -
>> - if (mmap_is_legacy(rlim_stack)) {
>> - mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
>> - mm->get_unmapped_area = arch_get_unmapped_area;
>> - } else {
>> - mm->mmap_base = mmap_base(random_factor, rlim_stack);
>> - mm->get_unmapped_area = arch_get_unmapped_area_topdown;
>> - }
>> -}
>> -
>> /*
>> * You really shouldn't be using read() or write() on /dev/mem. This
>> * might go away in the future.
>> --
>> 2.20.1
>>
>

\
 
 \ /
  Last update: 2019-04-18 08:06    [W:0.087 / U:1.988 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site