powerpc/kasan: fix early boot failure on PPC32

Due to commit 4a6d8cf90017 ("powerpc/mm: don't use pte_alloc_kernel()
until slab is available on PPC32"), pte_alloc_kernel() cannot be used
during early KASAN init.

Fix it by using memblock_alloc() instead.

Fixes: 2edb16efc899 ("powerpc/32: Add KASAN support")
Cc: stable@vger.kernel.org # v5.2+
Reported-by: Erhard F. <erhard_f@mailbox.org>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/da89670093651437f27d2975224712e0a130b055.1564552796.git.christophe.leroy@c-s.fr

1 files changed, 5 insertions, 2 deletions

diff --git a/arch/powerpc/mm/kasan/kasan_init_32.c b/arch/powerpc/mm/kasan/kasan_init_32.c
index 0d62be3cba47..74f4555a62ba 100644
--- a/arch/powerpc/mm/kasan/kasan_init_32.c
+++ b/arch/powerpc/mm/kasan/kasan_init_32.c
@@ -21,7 +21,7 @@ static void kasan_populate_pte(pte_t *ptep, pgprot_t prot)
                 __set_pte_at(&init_mm, va, ptep, pfn_pte(PHYS_PFN(pa), prot), 0);
 }
 
-static int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end)
+static int __ref kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_end)
 {
         pmd_t *pmd;
         unsigned long k_cur, k_next;
@@ -35,7 +35,10 @@ static int kasan_init_shadow_page_tables(unsigned long k_start, unsigned long k_
                 if ((void *)pmd_page_vaddr(*pmd) != kasan_early_shadow_pte)
                         continue;
 
-                new = pte_alloc_one_kernel(&init_mm);
+                if (slab_is_available())
+                        new = pte_alloc_one_kernel(&init_mm);
+                else
+                        new = memblock_alloc(PTE_FRAG_SIZE, PTE_FRAG_SIZE);
 
                 if (!new)
                         return -ENOMEM;