Andreas Schwab wrote:
> "H. Peter Anvin" <[EMAIL PROTECTED]> writes:
>
>> No, that would be bad. If compat_u64 is used to carry 32-bit ABIs
>> forward into 64-bit space without needing compatibility hacks, then this
>> would actually introduce ABI incompatibilities depending on CONFIG_COMPAT!
>
> But without CONFIG_COMPAT there is no 32-bit ABI, thus no need for
> compat_u64 in the first place.
>
You're missing the point.
Someone introduces an interface, which uses a structure:
struct foo {
u32 bar;
u64 baz;
u32 quux;
};
Now, we want to port that to 64 bits. We can either introduce a
thunking function to mangle the argument, or we can redefine the structure:
struct foo {
u32 bar;
compat_u64 baz;
u32 quux;
};
... which is still ABI compatible on 32 bits, but doesn't require thunking.
Obviously, this is not a panacea; if the original "struct foo" has also
been introduced on 64 bits before the bug is caught, then you're screwed.
-hpa
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