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From: Grant Likely on 11 Mar 2010 12:40
This patch makes unflatten_device_tree() safe to call from any arch
setup code with the following changes:
- Make sure initial_boot_params actually points to a device tree blob
before unflattening
- Make sure the initial_boot_params->magic field is correct
- If CONFIG_OF_FLATTREE is not set, then make unflatten_device_tree()
an empty #define.

This patch also adds some additional debug output to the top of
unflatten_device_tree().

Signed-off-by: Grant Likely <grant.likely(a)secretlab.ca>
---

drivers/of/fdt.c | 15 +++++++++++++++
include/linux/of_fdt.h | 2 ++
2 files changed, 17 insertions(+), 0 deletions(-)

diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
index 406757a..5ce7bd5 100644
--- a/drivers/of/fdt.c
+++ b/drivers/of/fdt.c
@@ -553,6 +553,21 @@ void __init unflatten_device_tree(void)

pr_debug(" -> unflatten_device_tree()\n");

+ if (!initial_boot_params) {
+ pr_debug("No device tree pointer\n");
+ return;
+ }
+
+ pr_debug("Unflattening device tree:\n");
+ pr_debug("magic: %08x\n", be32_to_cpu(initial_boot_params->magic));
+ pr_debug("size: %08x\n", be32_to_cpu(initial_boot_params->totalsize));
+ pr_debug("version: %08x\n", be32_to_cpu(initial_boot_params->version));
+
+ if (be32_to_cpu(initial_boot_params->magic) != OF_DT_HEADER) {
+ pr_err("Invalid device tree blob header\n");
+ return;
+ }
+
/* First pass, scan for size */
start = ((unsigned long)initial_boot_params) +
be32_to_cpu(initial_boot_params->off_dt_struct);
diff --git a/include/linux/of_fdt.h b/include/linux/of_fdt.h
index f0fdd1f..54399f1 100644
--- a/include/linux/of_fdt.h
+++ b/include/linux/of_fdt.h
@@ -99,6 +99,8 @@ extern int early_init_dt_scan_root(unsigned long node, const char *uname,
/* Other Prototypes */
extern void unflatten_device_tree(void);
extern void early_init_devtree(void *);
+#else /* CONFIG_OF_FLATTREE */
+static inline void define unflatten_device_tree(void) {}
#endif /* CONFIG_OF_FLATTREE */

#endif /* __ASSEMBLY__ */

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Prev: [RFC] kmemleak: Is DMI supported ?
Next: [PATCH 0/3] Various OF cleanups