UPSTREAM: arm64: vmemmap: use virtual projection of linear region

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>
Bug: 30369029
Patchset: kaslr-arm64-4.4

(cherry picked from commit dfd55ad85e4a7fbaa82df12467515ac3c81e8a3e)
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Change-Id: I8112d910f9659941dab6de5b3791f395150c77f1

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 9bf72b72b76d868ba84dc47ab60ac41c32a5b0c4..d48ea8fc789d8ad48fd5ff26f906c6c619b9ee7c 100644 (file)
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -34,18 +34,19 @@
 /*
  * 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 vmalloc 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          (MODULES_END)
 #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 e333f7f0b4f25a0637373338b6935401299df70a..04c7e8ba47ce47692d4996898a9adca8b062ff44 100644 (file)
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -365,8 +365,8 @@ void __init mem_init(void)
                  MLK_ROUNDUP(_text, _etext),
                  MLK_ROUNDUP(_sdata, _edata),
 #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