[bacescuandrei]

UC_M68K_REG_CR_VBR is declared in m68k.h, but neither reg_read nor reg_write in qemu/target/m68k/unicorn.c handled it. Accesses were a no-op that printed the deprecation warning ("Your register accessing on id 21 is deprecated…"). Setting the vector base therefore had no effect: exceptions and movec %vbr used whatever env->vbr held, and the value could not be read back. Both accessors now map it to env->vbr, unmasked, which is how QEMU's movec helpers treat it.

test_vbr in tests/unit/test_m68k.c runs on an M68040 in supervisor mode. It writes VBR through the API and reads it back. It then runs movec %vbr, %d0 to check that the CPU sees that value, and movec %d1, %vbr to check that a value the CPU writes can be read through the API.

Without the change, all three checks fail (and the warning is printed). With it, test_m68k passes. Built with UNICORN_ARCH=m68k.

I found this with a scan that round-trips every UC_*_REG_* id of each architecture through uc_reg_write/uc_reg_read on current dev. Apart from register fields that are masked by design, VBR was the m68k register that didn't round-trip.