Fix booting on arm64

[andrew]

Summary

Fix booting on some arm64 systems after r327879 by fixing the call to
utf8_to_ucs2 in boot1.efi. We need to initialise the ucs2 output string
so it will allocate space, and use the return value to determine if the
call was successful.

[imp]

stand/efi/boot1/boot1.c

93 ↗

(On Diff #37968)

Why isn't testing uv == NULL sufficient? We always don't change it when there's an error. The bug here is that uv wasn't initialized to NULL like efi_setenv_freebsd_wcs was.

109–111 ↗

(On Diff #37968)

We have the same code here.

[andrew]

stand/efi/boot1/boot1.c

93 ↗

(On Diff #37968)

It's allocated at the start of utf8_to_ucs2. I don't see where it's then set to NULL.

109–111 ↗

(On Diff #37968)

That also looks wrong, however as utf8_to_ucs2 only seems to fail when the input string is bad I think the error case in either function is unlikely.

[imp]

stand/efi/boot1/boot1.c

93 ↗

(On Diff #37968)

Yea, you're right.... Other code I've written sets it to null and I'd assumed this did too. It should, but doesn't, so this check is right.

109–111 ↗

(On Diff #37968)

We should do the same check here of the return value.

[imp]

See also https://reviews.freebsd.org/D13917, but I think checking the return values is better in both places.