Fix preprocessor error on non-RHEL kernels >= 7.0

[sergiobaiao]

Problem

Building on non-RHEL kernels >= 7.0 (e.g. Ubuntu mainline) fails with:

gasket_interrupt.c:162:88: error: missing binary operator before token '('
    (defined RHEL_RELEASE_CODE && RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(9, 5))

gasket_core.c:1849:76: error: missing binary operator before token '('
    (defined RHEL_RELEASE_CODE && RHEL_RELEASE_CODE >= RHEL_RELEASE_VERSION(9, 4))

RHEL_RELEASE_VERSION is a function-like macro defined only on RHEL kernels. When used in a compound #if expression on non-RHEL kernels, GCC expands all macros before evaluating logical operators — there is no short-circuit at expansion time. The undefined RHEL_RELEASE_VERSION expands to 0, and the trailing (9, x) argument list then produces the "missing binary operator" syntax error, even though defined RHEL_RELEASE_CODE is false.

Fix

Restructure both affected guards into nested #ifdef blocks so RHEL_RELEASE_VERSION() is only reached by the preprocessor on kernels where it is defined:

• gasket_interrupt.c: eventfd_signal() arity guard (>= 6.8.0 / RHEL 9.5 backport)
• gasket_core.c: class_create() arity guard (>= 6.4.0 / RHEL 9.4 backport)

The logic is equivalent to the original intent — RHEL backport paths are preserved — but the preprocessor no longer encounters RHEL_RELEASE_VERSION() on kernels where it is undefined.

Test

Verified build and dpkg -i install on Ubuntu kernel 7.0.0-15-generic. Both gasket.ko and apex.ko compile, sign, and install via DKMS successfully.

🤖 Generated with Claude Code

[bennydiamond]

Confirmed working on Promox 9 with kernel 7.0.6-2-pve

[sergiobaiao]

please merge this, and also put the commands to build the packages back on the README:

debuild -us -uc -tc -b (for debian/ubuntu at least)