Dmitry Torokhov <dtor@xxxxxxxxxx> writes:
But why is it aligned on 2-byte boundary and why m64k is not happy with
module_version_attribute but is happy with kernel_param which is also
aligned similarly?
struct kernel_parm doesn't contain internal padding on 32 bit
architectures (it does on 64bit architectures though).
If we unroll module_version_attribute it woud look like this:
struct module_version_attribute {
struct module_attribute {
struct attribute {
const char *name;
mode_t mode;
} attr;
...
} mattr;
const char *module_name;
const char *version;
};
So I would expect it be aligned on (char *) boundary which should be the
same as (void *).
mode_t is a 16 bit type, thus any following member becomes aligned on an
odd 2 byte boundary. On 32bit architectures with 4 byte alignment and
16 bit mode_t struct attribute contains 2 bytes of internal padding.
(64bit architectures typically have a 32bit mode_t, and there are 4
bytes of padding.)
Will it help if we rearrange module_version_attribute definition to
explicitly have first field being a pointer so it is more like
kernel_param, like this:
struct module_version_attribute {
const char *module_name;
const char *version;
struct module_attribute mattr;
};
That won't change the total size of the structure.
Andreas.
--
Andreas Schwab, schwab@xxxxxxxxxxxxxx
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."
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