Hi James,
On Wednesday 20 February 2013 08:22 PM, James Hogan wrote:
> 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).
While the patch conceptually looks correct, I'm not sure why any user of DT -
post-init would refer to DT bindings using of_fdt_* API which use the flat tree,
instead of the binary tree (more efficient in space/usage). Is this to support
some in-transition drivers and other code.
And if this is a general problem, then it is probably better done in DT core.
I'm sure I'm missing something here.
> Signed-off-by: James Hogan <james.ho...@imgtec.com>
> ---
> arch/metag/include/asm/prom.h | 1 +
> arch/metag/kernel/devtree.c | 17 +++++++++++++++++
> arch/metag/kernel/setup.c | 2 ++
> 3 files changed, 20 insertions(+)
>
> diff --git a/arch/metag/include/asm/prom.h b/arch/metag/include/asm/prom.h
> index d881396..ccac97e 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 5b6b1d85..7cd0252 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 dd6c5ad..8792461 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
--
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