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SubjectRe: [PATCH v3 1/2] kaslr: shift linear region randomization ahead of memory_limit
hi will and all:
>
> The following is schematic diagram of the program before and after the
> modification.
>
> Before:
> if (memstart_addr + linear_region_size < memblock_end_of_DRAM()) {} --(a)
> if (memory_limit != PHYS_ADDR_MAX) {} --(b)
> if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {} --(c)
> if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {} --(d)*
>
> After:
> if (memstart_addr + linear_region_size < memblock_end_of_DRAM()) {} --(a)
> if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {} --(d)*
> if (memory_limit != PHYS_ADDR_MAX) {} --(b)
> if (IS_ENABLED(CONFIG_BLK_DEV_INITRD) && phys_initrd_size) {} --(c)
>
> After grouping modification of memstart_address by moving linear region
> randomization ahead of memory_init, driver can safely using macro,
> __phys_to_virt, in (b) or (c), if necessary.
>
> Signed-off-by: pierre Kuo <vichy.kuo@gmail.com>
> ---
> Changes in v2:
> - add Fixes tag
>
> Changes in v3:
> - adding patch of shifting linear region randomization ahead of
> memory_limit
>
> arch/arm64/mm/init.c | 33 +++++++++++++++++----------------
> 1 file changed, 17 insertions(+), 16 deletions(-)
>
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 7205a9085b4d..5142020fc146 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -389,6 +389,23 @@ void __init arm64_memblock_init(void)
> memblock_remove(0, memstart_addr);
> }
>
> + if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
> + extern u16 memstart_offset_seed;
> + u64 range = linear_region_size -
> + (memblock_end_of_DRAM() - memblock_start_of_DRAM());
> +
> + /*
> + * If the size of the linear region exceeds, by a sufficient
> + * margin, the size of the region that the available physical
> + * memory spans, randomize the linear region as well.
> + */
> + if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
> + range /= ARM64_MEMSTART_ALIGN;
> + memstart_addr -= ARM64_MEMSTART_ALIGN *
> + ((range * memstart_offset_seed) >> 16);
> + }
> + }
> +
> /*
> * Apply the memory limit if it was set. Since the kernel may be loaded
> * high up in memory, add back the kernel region that must be accessible
> @@ -428,22 +445,6 @@ void __init arm64_memblock_init(void)
> }
> }
>
> - if (IS_ENABLED(CONFIG_RANDOMIZE_BASE)) {
> - extern u16 memstart_offset_seed;
> - u64 range = linear_region_size -
> - (memblock_end_of_DRAM() - memblock_start_of_DRAM());
> -
> - /*
> - * If the size of the linear region exceeds, by a sufficient
> - * margin, the size of the region that the available physical
> - * memory spans, randomize the linear region as well.
> - */
> - if (memstart_offset_seed > 0 && range >= ARM64_MEMSTART_ALIGN) {
> - range /= ARM64_MEMSTART_ALIGN;
> - memstart_addr -= ARM64_MEMSTART_ALIGN *
> - ((range * memstart_offset_seed) >> 16);
> - }
> - }
>
> /*
> * Register the kernel text, kernel data, initrd, and initial

Would you mind to give some comment and suggestion for these v3 patches?
https://lkml.org/lkml/2019/4/8/682
https://lkml.org/lkml/2019/4/8/683

Sincerely appreciate your kind help,

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