remove CONSTRUCTORS from kernel linker scripts

[emaste]

Summary

The linker script CONSTRUCTORS keyword is only meaningful "when linking object file formats which do not support arbitrary sections, such as ECOFF and XCOFF"[1] and is ignored for other object file formats.

LLVM's lld does not yet accept (and ignore) CONSTRUCTORS, so just remove it from the linker scripts since it has no effect. (Patch in progress upstream so lld will probably accept and ignore CONSTRUCTORS soon, but it seems sensible to me to clean it up.)

[1] https://sourceware.org/binutils/docs/ld/Output-Section-Keywords.html

[kib]

Should it be replaced by *(SORT_BY_NAME(.ctors))'and*(SORT_BY_NAME(.dtors))' constructs, as mentioned in the ld manual ? H, it actually is.

[andrew]

Do we use or support .ctors or .dtors in the kernel? If not I don't see why we would need to add them.

[kib]

In D7343#152828, @andrew wrote:

Do we use or support .ctors or .dtors in the kernel? If not I don't see why we would need to add them.

In principle the answer is yes, we might some day allow the attribute ((constructor)) to work in kernel. E.g. it might occur before the MI sysinit pass. For this reason, I do not see why would it be useful to strip linker script from many features which seems to be unused now.

[emaste]

In D7343#152829, @kib wrote:

In D7343#152828, @andrew wrote:

Do we use or support .ctors or .dtors in the kernel? If not I don't see why we would need to add them.

In principle the answer is yes, we might some day allow the attribute ((constructor)) to work in kernel. E.g. it might occur before the MI sysinit pass. For this reason, I do not see why would it be useful to strip linker script from many features which seems to be unused now.

AFAIK (based on GNU ld's documentation) CONSTRUCTORS has (had) no effect for ELF output, this change would only have an effect on us if we built e.g. ECOFF-format kernels.