+static void check_pabits(void)
+{
+ unsigned long entry;
+ unsigned pabits, fillbits;
+
+ if (!cpu_has_rixi || !_PAGE_NO_EXEC) {
+ /*
+ * We'll only be making use of the fact that we can rotate bits
+ * into the fill if the CPU supports RIXI, so don't bother
+ * probing this for CPUs which don't.
+ */
+ return;
+ }
+
+ write_c0_entrylo0(~0ul);
+ back_to_back_c0_hazard();
+ entry = read_c0_entrylo0();
+
+ /* clear all non-PFN bits */
+ entry &= ~((1 << MIPS_ENTRYLO_PFN_SHIFT) - 1);
+ entry &= ~(MIPS_ENTRYLO_RI | MIPS_ENTRYLO_XI);
+
+ /* find a lower bound on PABITS, and upper bound on fill bits */
+ pabits = fls_long(entry) + 6;
+ fillbits = max_t(int, (int)BITS_PER_LONG - pabits, 0);
+
+ /* minus the RI & XI bits */
+ fillbits -= min_t(unsigned, fillbits, 2);
+
+ if (fillbits >= ilog2(_PAGE_NO_EXEC))
+ fill_includes_sw_bits = true;
+
+ pr_debug("Entry* registers contain %u fill bits\n", fillbits);
+}
+