Messages in this thread Patch in this message | | | Date | Wed, 06 Jan 2016 16:35:34 +0000 | From | James Morse <> | Subject | Re: [PATCH v2 04/13] arm64: decouple early fixmap init from linear mapping |
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Hi Ard!
On 30/12/15 15:26, Ard Biesheuvel wrote: > Since the early fixmap page tables are populated using pages that are > part of the static footprint of the kernel, they are covered by the > initial kernel mapping, and we can refer to them without using __va/__pa > translations, which are tied to the linear mapping. > > Instead, let's introduce __phys_to_kimg, which will be tied to the kernel > virtual mapping, regardless of whether or not it intersects with the linear > mapping. This will allow us to move the kernel out of the linear mapping in > a subsequent patch. >
I gave your arm64-kaslr-v2 branch a go on juno r1, currently with ARM64_RELOCATABLE_KERNEL=n, to find it didn't boot.
git bisect pointed to this patch. From the debugger it looks like rubbish is ending up the page tables after early_fixmap_init(), printing bits of bm_pmd and friends shows these aren't zeroed.
I think this is because the section(".pgdir") is dragging these outside the __bss_start/__bss_stop range that is zeroed in head.S:__mmap_switched().
The following inelegant patch fixes this problem for me: ----------------------------%<---------------------------- diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index a78fc5a882da..15fc9712ddc1 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -559,6 +559,7 @@ void __init early_fixmap_init(void) if (pgd_none(*pgd)) { static pud_t bm_pud[PTRS_PER_PUD] __pgdir;
+ memset(bm_pud, 0, sizeof(bm_pud)); pgd_populate(&init_mm, pgd, bm_pud); memblock_reserve(__pa(bm_pud), sizeof(bm_pud)); } @@ -570,6 +571,7 @@ void __init early_fixmap_init(void) if (pud_none(*pud)) { static pmd_t bm_pmd[PTRS_PER_PMD] __pgdir;
+ memset(bm_pmd, 0, sizeof(bm_pmd)); pud_populate(&init_mm, pud, bm_pmd); memblock_reserve(__pa(bm_pmd), sizeof(bm_pmd)); } @@ -580,6 +582,7 @@ void __init early_fixmap_init(void) if (pmd_none(*pmd)) { static pte_t bm_pte[PTRS_PER_PTE] __pgdir;
+ memset(bm_pte, 0, sizeof(bm_pte)); pmd_populate_kernel(&init_mm, pmd, bm_pte); memblock_reserve(__pa(bm_pte), sizeof(bm_pte)); } ----------------------------%<---------------------------- I'm sure there is a better way!
Thanks,
James
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