On 06/29/2018 02:55 AM, Michael Ellerman wrote:
Christophe Leroy <christophe.le...@c-s.fr> writes:
This patch fixes the following warnings (obtained with make W=1).
arch/powerpc/mm/slice.c: In function 'slice_range_to_mask':
arch/powerpc/mm/slice.c:73:12: error: comparison is always true due to limited
range of data type [-Werror=type-limits]
if (start < SLICE_LOW_TOP) {
Presumably only on 32-bit ?
Sure
diff --git a/arch/powerpc/mm/slice.c b/arch/powerpc/mm/slice.c
index 9530c6db406a..17c57760e06c 100644
--- a/arch/powerpc/mm/slice.c
+++ b/arch/powerpc/mm/slice.c
@@ -79,7 +86,7 @@ static void slice_range_to_mask(unsigned long start, unsigned
long len,
- (1u << GET_LOW_SLICE_INDEX(start));
}
- if ((start + len) > SLICE_LOW_TOP) {
+ if (!slice_addr_is_low(end)) {
unsigned long start_index = GET_HIGH_SLICE_INDEX(start);
unsigned long align_end = ALIGN(end, (1UL << SLICE_HIGH_SHIFT));
unsigned long count = GET_HIGH_SLICE_INDEX(align_end) -
start_index;
This worries me.
I'll change it in v2 to:
if (SLICE_NUM_HIGH && !slice_addr_is_low(end)) {
By casting before the comparison in the helper you squash the compiler
warning, but the code is still broken if (start + len) overflows.
Presumably that "never happens", but it just seems fishy.
The other similar check in that file does:
if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
Where SLICE_NUM_HIGH == 0 on 32-bit.
Could we fix the less than comparisons with SLICE_LOW_TOP with something
similar, eg:
if (!SLICE_NUM_HIGH || start < SLICE_LOW_TOP) {
ie. limit them to the 64-bit code?
That's not enough to make GCC happy:
arch/powerpc/mm/slice.c: In function ‘slice_range_to_mask’:
arch/powerpc/mm/slice.c:74:31: error: comparison is always true due to
limited range of data type [-Werror=type-limits]
if (!SLICE_NUM_HIGH || start < SLICE_LOW_TOP) {
Christophe
cheers
