UPSTREAM: arm64/mm: ensure memstart_addr remains sufficiently aligned

After choosing memstart_addr to be the highest multiple of
ARM64_MEMSTART_ALIGN less than or equal to the first usable physical memory
address, we clip the memblocks to the maximum size of the linear region.
Since the kernel may be high up in memory, we take care not to clip the
kernel itself, which means we have to clip some memory from the bottom if
this occurs, to ensure that the distance between the first and the last
usable physical memory address can be covered by the linear region.

However, we fail to update memstart_addr if this clipping from the bottom
occurs, which means that we may still end up with virtual addresses that
wrap into the userland range. So increment memstart_addr as appropriate to
prevent this from happening.

Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Change-Id: I72306207cc46a30b780f5e00b9ef23aa8409867e
(cherry picked from commit 2958987f5da2ebcf6a237c5f154d7e3340e60945)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 08aa45ff05b642d09c3a71a4a729c396cf765a8e..0db12e9e8765adee7d71b5a19660d23596fbebc7 100644 (file)
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -192,8 +192,12 @@ void __init arm64_memblock_init(void)
         */
        memblock_remove(max_t(u64, memstart_addr + linear_region_size, __pa(_end)),
                        ULLONG_MAX);
-       if (memblock_end_of_DRAM() > linear_region_size)
-               memblock_remove(0, memblock_end_of_DRAM() - linear_region_size);
+       if (memstart_addr + linear_region_size < memblock_end_of_DRAM()) {
+               /* ensure that memstart_addr remains sufficiently aligned */
+               memstart_addr = round_up(memblock_end_of_DRAM() - linear_region_size,
+                                        ARM64_MEMSTART_ALIGN);
+               memblock_remove(0, memstart_addr);
+       }
 
        /*
         * Apply the memory limit if it was set. Since the kernel may be loaded