UPSTREAM: of/fdt: make memblock minimum physical address arch configurable

By default, early_init_dt_add_memory_arch() ignores memory below
the base of the kernel image since it won't be addressable via the
linear mapping. However, this is not appropriate anymore once we
decouple the kernel text mapping from the linear mapping, so archs
may want to drop the low limit entirely. So allow the minimum to be
overridden by setting MIN_MEMBLOCK_ADDR.

Acked-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Bug: 30369029
Patchset: kaslr-arm64-4.4

(cherry picked from commit 270522a04f7a9911983878fa37da467f9ff1c938)
Signed-off-by: Jeff Vander Stoep <jeffv@google.com>
Change-Id: I4bb2626a87493262a64584b3d808de260129127e

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 86fff625f6d5770ec493a301a30be8d3bfa11831..628f436e16f615c9fa49d2335f645051f9c19ab2 100644 (file)
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -1006,13 +1006,16 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
 }
 
 #ifdef CONFIG_HAVE_MEMBLOCK
+#ifndef MIN_MEMBLOCK_ADDR
+#define MIN_MEMBLOCK_ADDR      __pa(PAGE_OFFSET)
+#endif
 #ifndef MAX_MEMBLOCK_ADDR
 #define MAX_MEMBLOCK_ADDR      ((phys_addr_t)~0)
 #endif
 
 void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
 {
-       const u64 phys_offset = __pa(PAGE_OFFSET);
+       const u64 phys_offset = MIN_MEMBLOCK_ADDR;
 
        if (!PAGE_ALIGNED(base)) {
                if (size < PAGE_SIZE - (base & ~PAGE_MASK)) {