reproduce (this is a W=1 build):
        git checkout 203e3beb73e53584ca90bc2a6d8240b9b12b9bcf
        b4 shazam https://lore.kernel.org/r/20250926-scratch-bobbyeshleman-devmem-tcp-token-upstream-v4-2-39156563c3ea@meta.com
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash net/ipv4/