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31 lines
830 B
31 lines
830 B
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Decoding an IOCTL Magic Number |
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To decode a hex IOCTL code: |
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Most architectures use this generic format, but check |
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include/ARCH/ioctl.h for specifics, e.g. powerpc |
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uses 3 bits to encode read/write and 13 bits for size. |
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====== ================================== |
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bits meaning |
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31-30 00 - no parameters: uses _IO macro |
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10 - read: _IOR |
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01 - write: _IOW |
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11 - read/write: _IOWR |
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29-16 size of arguments |
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15-8 ascii character supposedly |
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unique to each driver |
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7-0 function # |
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====== ================================== |
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So for example 0x82187201 is a read with arg length of 0x218, |
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character 'r' function 1. Grepping the source reveals this is:: |
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#define VFAT_IOCTL_READDIR_BOTH _IOR('r', 1, struct dirent [2])
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