Commit 39b5be9b authored Jan 05, 2016 by Will Deacon

arm64: mm: move pgd_cache initialisation to pgtable_cache_init



Initialising the suppport for EFI runtime services requires us to
allocate a pgd off the back of an early_initcall. On systems where the
PGD_SIZE is smaller than PAGE_SIZE (e.g. 64k pages and 48-bit VA), the
pgd_cache isn't initialised at this stage, and we panic with a NULL
dereference during boot:

  Unable to handle kernel NULL pointer dereference at virtual address 00000000

  __create_mapping.isra.5+0x84/0x350
  create_pgd_mapping+0x20/0x28
  efi_create_mapping+0x5c/0x6c
  arm_enable_runtime_services+0x154/0x1e4
  do_one_initcall+0x8c/0x190
  kernel_init_freeable+0x84/0x1ec
  kernel_init+0x10/0xe0
  ret_from_fork+0x10/0x50

This patch fixes the problem by initialising the pgd_cache earlier, in
the pgtable_cache_init callback, which sounds suspiciously like what it
was intended for.

Reported-by: Dennis Chen <dennis.chen@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent f9308969

arch/arm64/include/asm/pgtable.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -676,7 +676,8 @@ extern int kern_addr_valid(unsigned long addr);

		#include <asm-generic/pgtable.h>

		#define pgtable_cache_init() do { } while (0)
		void pgd_cache_init(void);
		#define pgtable_cache_init pgd_cache_init

		/*
		* On AArch64, the cache coherency is handled via the set_pte_at() function.

arch/arm64/mm/pgd.c

+6 −6

Original line number	Diff line number	Diff line
		@@ -46,14 +46,14 @@ void pgd_free(struct mm_struct mm, pgd_t pgd)
		kmem_cache_free(pgd_cache, pgd);
		}

		static int __init pgd_cache_init(void)
		void __init pgd_cache_init(void)
		{
		if (PGD_SIZE == PAGE_SIZE)
		return;

		/*
		* Naturally aligned pgds required by the architecture.
		*/
		if (PGD_SIZE != PAGE_SIZE)
		pgd_cache = kmem_cache_create("pgd_cache", PGD_SIZE, PGD_SIZE,
		SLAB_PANIC, NULL);
		return 0;
		}
		core_initcall(pgd_cache_init);