[PATCH v2] Fix data abort caused by mis-aligning FIT data

Reuben Dowle
2020-09-01T21:32:01Z

Attempting to place device tree immediately after an image in memory can lead
to mis-aligned data accesses if that image size is not divisible by the
alignment requirements of the architecture.

Data aborts caused by this were observed on a custom Marvel A388 based system,
where the image was a uboot FIT file. The total size varies depending on the
uboot device tree size, which does not always lead to correct alignment.

The minimum alignment specified for ARM [1] and ARM64 [2] linux booting has been
used

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/booting.rst#n126
[2] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm64/booting.rst#n45

Signed-off-by: Reuben Dowle <reuben.dowle@4rf.com>
---
common/spl/spl_fit.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/common/spl/spl_fit.c b/common/spl/spl_fit.c
index 365104f..a8bfd38 100644
--- a/common/spl/spl_fit.c
+++ b/common/spl/spl_fit.c
@@ -349,9 +349,12 @@ static int spl_fit_append_fdt(struct spl_image_info *spl_image,

/*
* Use the address following the image as target address for the
- * device tree.
+ * device tree. Load address is aligned to 8 bytes to match the required
+ * alignment specified for linux arm [1] and arm 64 [2] booting
+ * [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm/booting.rst#n126
+ * [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/arm64/booting.rst#n45
*/
- image_info.load_addr = spl_image->load_addr + spl_image->size;
+ image_info.load_addr = ALIGN(spl_image->load_addr + spl_image->size, 8);

/* Figure out which device tree the board wants to use */
node = spl_fit_get_image_node(fit, images, FIT_FDT_PROP, index++);
--
2.7.4