Commit 5d8244d4 authored Aug 02, 2022 by Nathan Chancellor Committed by Greg Kroah-Hartman Aug 25, 2022

MIPS: tlbex: Explicitly compare _PAGE_NO_EXEC against 0

[ Upstream commit 74de14fe05dd6b151d73cb0c73c8ec874cbdcde6 ]

When CONFIG_XPA is enabled, Clang warns:

  arch/mips/mm/tlbex.c:629:24: error: converting the result of '<<' to a boolean; did you mean '(1 << _PAGE_NO_EXEC_SHIFT) != 0'? [-Werror,-Wint-in-bool-context]
          if (cpu_has_rixi && !!_PAGE_NO_EXEC) {
                              ^
  arch/mips/include/asm/pgtable-bits.h:174:28: note: expanded from macro '_PAGE_NO_EXEC'
  # define _PAGE_NO_EXEC          (1 << _PAGE_NO_EXEC_SHIFT)
                                     ^
  arch/mips/mm/tlbex.c:2568:24: error: converting the result of '<<' to a boolean; did you mean '(1 << _PAGE_NO_EXEC_SHIFT) != 0'? [-Werror,-Wint-in-bool-context]
          if (!cpu_has_rixi || !_PAGE_NO_EXEC) {
                                ^
  arch/mips/include/asm/pgtable-bits.h:174:28: note: expanded from macro '_PAGE_NO_EXEC'
  # define _PAGE_NO_EXEC          (1 << _PAGE_NO_EXEC_SHIFT)
                                     ^
  2 errors generated.

_PAGE_NO_EXEC can be '0' or '1 << _PAGE_NO_EXEC_SHIFT' depending on the
build and runtime configuration, which is what the negation operators
are trying to convey. To silence the warning, explicitly compare against
0 so the result of the '<<' operator is not implicitly converted to a
boolean.

According to its documentation, GCC enables -Wint-in-bool-context with
-Wall but this warning is not visible when building the same
configuration with GCC. It appears GCC only warns when compiling C++,
not C, although the documentation makes no note of this:
https://godbolt.org/z/x39q3brxf



Reported-by: Sudip Mukherjee (Codethink) <sudipm.mukherjee@gmail.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>

parent 2b7f5591

arch/mips/mm/tlbex.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -629,7 +629,7 @@ static __maybe_unused void build_convert_pte_to_entrylo(u32 **p,
		return;
		}

		if (cpu_has_rixi && !!_PAGE_NO_EXEC) {
		if (cpu_has_rixi && _PAGE_NO_EXEC != 0) {
		if (fill_includes_sw_bits) {
		UASM_i_ROTR(p, reg, reg, ilog2(_PAGE_GLOBAL));
		} else {
		@@ -2568,7 +2568,7 @@ static void check_pabits(void)
		unsigned long entry;
		unsigned pabits, fillbits;

		if (!cpu_has_rixi \|\| !_PAGE_NO_EXEC) {
		if (!cpu_has_rixi \|\| _PAGE_NO_EXEC == 0) {
		/*
		* 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