metag: copy devicetree to non-init memory

Make a copy of the device tree blob in non-init memory. It is required
when using built-in device tree files that the platform code copies the
blob to non-init memory prior to calling unflatten_device_tree(),
otherwise the strings that the device tree refer to will get poisoned
and potentially reused, breaking later reading of the device tree
post-init (such as compatible matching in modules, debugfs, and the
procfs interface).

Signed-off-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: Vineet Gupta <vgupta@synopsys.com>

3 files changed, 20 insertions, 0 deletions

diff --git a/arch/metag/include/asm/prom.h b/arch/metag/include/asm/prom.h
index d881396c392c..ccac97e865d0 100644
--- a/arch/metag/include/asm/prom.h
+++ b/arch/metag/include/asm/prom.h
@@ -18,6 +18,7 @@
 #define HAVE_ARCH_DEVTREE_FIXUPS
 
 extern struct machine_desc *setup_machine_fdt(void *dt);
+extern void copy_fdt(void);
 extern void metag_dt_memblock_reserve(void);
 
 #endif /* __ASM_METAG_PROM_H */
diff --git a/arch/metag/kernel/devtree.c b/arch/metag/kernel/devtree.c
index 5b6b1d855492..7cd02529636e 100644
--- a/arch/metag/kernel/devtree.c
+++ b/arch/metag/kernel/devtree.c
@@ -95,3 +95,20 @@ struct machine_desc * __init setup_machine_fdt(void *dt)
 
         return mdesc_best;
 }
+
+/**
+ * copy_fdt - Copy device tree into non-init memory.
+ *
+ * We must copy the flattened device tree blob into non-init memory because the
+ * unflattened device tree will reference the strings in it directly.
+ */
+void __init copy_fdt(void)
+{
+        void *alloc = early_init_dt_alloc_memory_arch(
+                        be32_to_cpu(initial_boot_params->totalsize), 0x40);
+        if (alloc) {
+                memcpy(alloc, initial_boot_params,
+                       be32_to_cpu(initial_boot_params->totalsize));
+                initial_boot_params = alloc;
+        }
+}
diff --git a/arch/metag/kernel/setup.c b/arch/metag/kernel/setup.c
index dd6c5ad73917..879246170aec 100644
--- a/arch/metag/kernel/setup.c
+++ b/arch/metag/kernel/setup.c
@@ -406,6 +406,8 @@ void __init setup_arch(char **cmdline_p)
         cpu_2_hwthread_id[smp_processor_id()] = hard_processor_id();
         hwthread_id_2_cpu[hard_processor_id()] = smp_processor_id();
 
+        /* Copy device tree blob into non-init memory before unflattening */
+        copy_fdt();
         unflatten_device_tree();
 
 #ifdef CONFIG_SMP