Re: [PATCH v3 2/6] x86/mm/KASLR: Open code unnecessary function get_padding

[Kees Cook]

On Sat, Feb 16, 2019 at 6:02 AM Baoquan He  wrote:
>
> It's used only twice and we do bit shifts in the parent function
> anyway so it's not like it's hiding some uninteresting detail.
>
> Suggested-by: Ingo Molnar 
> Signed-off-by: Baoquan He 

Acked-by: Kees Cook 

-Kees

> ---
>  arch/x86/mm/kaslr.c | 10 ++
>  1 file changed, 2 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
> index d7c6e4e8e48e..bf680929fe26 100644
> --- a/arch/x86/mm/kaslr.c
> +++ b/arch/x86/mm/kaslr.c
> @@ -104,12 +104,6 @@ static __initdata struct kaslr_memory_region {
> { _base, 1 },
>  };
>
> -/* Get size in bytes used by the memory region */
> -static inline unsigned long get_padding(struct kaslr_memory_region *region)
> -{
> -   return (region->size_tb << TB_SHIFT);
> -}
> -
>  /*
>   * Apply no randomization if KASLR was disabled at boot or if KASAN
>   * is enabled. KASAN shadow mappings rely on regions being PGD aligned.
> @@ -161,7 +155,7 @@ void __init kernel_randomize_memory(void)
> /* Calculate entropy available between regions */
> remain_entropy = vaddr_end - vaddr_start;
> for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++)
> -   remain_entropy -= get_padding(_regions[i]);
> +   remain_entropy -= kaslr_regions[i].size_tb << TB_SHIFT;
>
> prandom_seed_state(_state, kaslr_get_random_long("Memory"));
>
> @@ -185,7 +179,7 @@ void __init kernel_randomize_memory(void)
>  * Jump the region and add a minimum padding based on
>  * randomization alignment.
>  */
> -   vaddr += get_padding(_regions[i]);
> +   vaddr += kaslr_regions[i].size_tb << TB_SHIFT;
> if (pgtable_l5_enabled())
> vaddr = round_up(vaddr + 1, P4D_SIZE);
> else
> --
> 2.17.2
>


-- 
Kees Cook

[PATCH v3 2/6] x86/mm/KASLR: Open code unnecessary function get_padding

[Baoquan He]

It's used only twice and we do bit shifts in the parent function
anyway so it's not like it's hiding some uninteresting detail.

Suggested-by: Ingo Molnar 
Signed-off-by: Baoquan He 
---
 arch/x86/mm/kaslr.c | 10 ++
 1 file changed, 2 insertions(+), 8 deletions(-)

diff --git a/arch/x86/mm/kaslr.c b/arch/x86/mm/kaslr.c
index d7c6e4e8e48e..bf680929fe26 100644
--- a/arch/x86/mm/kaslr.c
+++ b/arch/x86/mm/kaslr.c
@@ -104,12 +104,6 @@ static __initdata struct kaslr_memory_region {
{ _base, 1 },
 };
 
-/* Get size in bytes used by the memory region */
-static inline unsigned long get_padding(struct kaslr_memory_region *region)
-{
-   return (region->size_tb << TB_SHIFT);
-}
-
 /*
  * Apply no randomization if KASLR was disabled at boot or if KASAN
  * is enabled. KASAN shadow mappings rely on regions being PGD aligned.
@@ -161,7 +155,7 @@ void __init kernel_randomize_memory(void)
/* Calculate entropy available between regions */
remain_entropy = vaddr_end - vaddr_start;
for (i = 0; i < ARRAY_SIZE(kaslr_regions); i++)
-   remain_entropy -= get_padding(_regions[i]);
+   remain_entropy -= kaslr_regions[i].size_tb << TB_SHIFT;
 
prandom_seed_state(_state, kaslr_get_random_long("Memory"));
 
@@ -185,7 +179,7 @@ void __init kernel_randomize_memory(void)
 * Jump the region and add a minimum padding based on
 * randomization alignment.
 */
-   vaddr += get_padding(_regions[i]);
+   vaddr += kaslr_regions[i].size_tb << TB_SHIFT;
if (pgtable_l5_enabled())
vaddr = round_up(vaddr + 1, P4D_SIZE);
else
-- 
2.17.2