On Mon, Sep 17, 2018 at 12:43:30PM +0800, Jun Yao wrote:
> Create the initial page table in the init_pg_dir. And update the
> init_mm.pgd to make sure that pgd_offset_k() works correctly. When
> the final page table is created, we redirect the init_mm.pgd to the
> swapper_pg_dir.
>
> Signed-off-by: Jun Yao <[email protected]>
> ---
> arch/arm64/include/asm/pgtable.h | 2 ++
> arch/arm64/kernel/asm-offsets.c | 1 +
> arch/arm64/kernel/head.S | 9 +++++++--
> arch/arm64/mm/mmu.c | 1 +
> 4 files changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/pgtable.h
> b/arch/arm64/include/asm/pgtable.h
> index 2ab2031b778c..b11d6fc62a62 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -718,6 +718,8 @@ static inline pmd_t pmdp_establish(struct vm_area_struct
> *vma,
> }
> #endif
>
> +extern pgd_t init_pg_dir[PTRS_PER_PGD];
> +extern pgd_t init_pg_end[];
> extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
> extern pgd_t swapper_pg_end[];
> extern pgd_t idmap_pg_dir[PTRS_PER_PGD];
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index 323aeb5f2fe6..43f52cfdfad4 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -82,6 +82,7 @@ int main(void)
> DEFINE(S_FRAME_SIZE, sizeof(struct pt_regs));
> BLANK();
> DEFINE(MM_CONTEXT_ID, offsetof(struct mm_struct,
> context.id.counter));
> + DEFINE(MM_PGD, offsetof(struct mm_struct, pgd));
> BLANK();
> DEFINE(VMA_VM_MM, offsetof(struct vm_area_struct, vm_mm));
> DEFINE(VMA_VM_FLAGS, offsetof(struct vm_area_struct,
> vm_flags));
> diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
> index de2aaea00bd2..cf8a58211b80 100644
> --- a/arch/arm64/kernel/head.S
> +++ b/arch/arm64/kernel/head.S
> @@ -376,7 +376,7 @@ __create_page_tables:
> /*
> * Map the kernel image (starting with PHYS_OFFSET).
> */
> - adrp x0, swapper_pg_dir
> + adrp x0, init_pg_dir
> mov_q x5, KIMAGE_VADDR + TEXT_OFFSET // compile time __va(_text)
> add x5, x5, x23 // add KASLR displacement
> mov x4, PTRS_PER_PGD
> @@ -439,6 +439,11 @@ __primary_switched:
> bl __pi_memset
> dsb ishst // Make zero page visible to PTW
>
> + // Update init_mm.pgd
> + adrp x0, init_pg_dir
> + adr_l x1, init_mm
> + str x0, [x1, #MM_PGD]
> +
We should be able to set this up statically with INIT_MM_CONTEXT(). i.e.
in <asm/mmu.h> have:
#define INIT_MM_CONTEXT(name) \
.pgd = init_pg_dir
Thanks,
Mark.
> #ifdef CONFIG_KASAN
> bl kasan_early_init
> #endif
> @@ -833,7 +838,7 @@ __primary_switch:
> mrs x20, sctlr_el1 // preserve old SCTLR_EL1 value
> #endif
>
> - adrp x1, swapper_pg_dir
> + adrp x1, init_pg_dir
> bl __enable_mmu
> #ifdef CONFIG_RELOCATABLE
> bl __relocate_kernel
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 65f86271f02b..af80dca335ce 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -646,6 +646,7 @@ void __init paging_init(void)
> cpu_replace_ttbr1(__va(pgd_phys));
> memcpy(swapper_pg_dir, pgdp, PGD_SIZE);
> cpu_replace_ttbr1(lm_alias(swapper_pg_dir));
> + init_mm.pgd = swapper_pg_dir;
>
> pgd_clear_fixmap();
> memblock_free(pgd_phys, PAGE_SIZE);
> --
> 2.17.1
>
