arm64: vmemmap: use virtual projection of linear region

[ Upstream commit dfd55ad85e4a7fbaa82df12467515ac3c81e8a3e ]

Commit dd006da21646 ("arm64: mm: increase VA range of identity map") made
some changes to the memory mapping code to allow physical memory to reside
at an offset that exceeds the size of the virtual mapping.

However, since the size of the vmemmap area is proportional to the size of
the VA area, but it is populated relative to the physical space, we may
end up with the struct page array being mapped outside of the vmemmap
region. For instance, on my Seattle A0 box, I can see the following output
in the dmesg log.

   vmemmap : 0xffffffbdc0000000 - 0xffffffbfc0000000   (     8 GB maximum)
             0xffffffbfc0000000 - 0xffffffbfd0000000   (   256 MB actual)

We can fix this by deciding that the vmemmap region is not a projection of
the physical space, but of the virtual space above PAGE_OFFSET, i.e., the
linear region. This way, we are guaranteed that the vmemmap region is of
sufficient size, and we can even reduce the size by half.

Cc: <stable@vger.kernel.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Sasha Levin <sasha.levin@oracle.com>

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index cf731942276817344a642b309e8638555c90e982..514fb0c9e6f9e7a3564217d090a535f52ea6988d 100644 (file)
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -33,17 +33,18 @@
 /*
  * VMALLOC and SPARSEMEM_VMEMMAP ranges.
  *
- * VMEMAP_SIZE: allows the whole VA space to be covered by a struct page array
+ * VMEMAP_SIZE: allows the whole linear region to be covered by a struct page array
  *     (rounded up to PUD_SIZE).
  * VMALLOC_START: beginning of the kernel VA space
  * VMALLOC_END: extends to the available space below vmmemmap, PCI I/O space,
  *     fixed mappings and modules
  */
-#define VMEMMAP_SIZE           ALIGN((1UL << (VA_BITS - PAGE_SHIFT)) * sizeof(struct page), PUD_SIZE)
+#define VMEMMAP_SIZE           ALIGN((1UL << (VA_BITS - PAGE_SHIFT - 1)) * sizeof(struct page), PUD_SIZE)
 #define VMALLOC_START          (UL(0xffffffffffffffff) << VA_BITS)
 #define VMALLOC_END            (PAGE_OFFSET - PUD_SIZE - VMEMMAP_SIZE - SZ_64K)
 
-#define vmemmap                        ((struct page *)(VMALLOC_END + SZ_64K))
+#define VMEMMAP_START          (VMALLOC_END + SZ_64K)
+#define vmemmap                        ((struct page *)VMEMMAP_START - (memstart_addr >> PAGE_SHIFT))
 
 #define FIRST_USER_ADDRESS     0UL
 

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index ad87ce826cce45ec0ac710c4dc1b721d8aaa8f97..ae8f940152aa801f883d439b29158007c3b9e0e0 100644 (file)
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -312,8 +312,8 @@ void __init mem_init(void)
                  "      .data : 0x%p" " - 0x%p" "   (%6ld KB)\n",
                  MLG(VMALLOC_START, VMALLOC_END),
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
-                 MLG((unsigned long)vmemmap,
-                     (unsigned long)vmemmap + VMEMMAP_SIZE),
+                 MLG(VMEMMAP_START,
+                     VMEMMAP_START + VMEMMAP_SIZE),
                  MLM((unsigned long)virt_to_page(PAGE_OFFSET),
                      (unsigned long)virt_to_page(high_memory)),
 #endif