On some architectures certain values of splashimage will lead to a data abort exception. Document the problem, and implement a callback for splashimage to reject such values. Cc: Anatolij Gustschin <agust@denx.de> Cc: Wolfgang Denk <wd@denx.de> Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il> Acked-by: Igor Grinberg <grinberg@compulab.co.il>master
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If you are experiencing hangups/data-aborts when trying to display a BMP image, |
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the following might be relevant to your situation... |
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Some architectures cannot handle unaligned memory accesses, and an attempt to |
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perform one will lead to a data abort. On such architectures it is necessary to |
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make sure all data is properly aligned, and in many situations simply choosing |
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a 32 bit aligned address is enough to ensure proper alignment. This is not |
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always the case when dealing with data that has an internal layout such as a |
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BMP image: |
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BMP images have a header that starts with 2 byte-size fields followed by mostly |
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32 bit fields. The packed struct that represents this header can be seen below: |
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typedef struct bmp_header { |
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/* Header */ |
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char signature[2]; |
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__u32 file_size; |
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__u32 reserved; |
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__u32 data_offset; |
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... etc |
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} __attribute__ ((packed)) bmp_header_t; |
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When placed in an aligned address such as 0x80a00000, char signature offsets |
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the __u32 fields into unaligned addresses (in our example 0x80a00002, |
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0x80a00006, and so on...). When these fields are accessed by U-Boot, a 32 bit |
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access is generated at a non-32-bit-aligned address, causing a data abort. |
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The proper alignment for BMP images is therefore: 32-bit-aligned-address + 2. |
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