* [PATCH] powerpc/mm: fix always true/false warning in slice.c
@ 2018-06-22 13:49 Christophe Leroy
2018-06-22 14:55 ` Mathieu Malaterre
2018-06-29 2:55 ` Michael Ellerman
0 siblings, 2 replies; 5+ messages in thread
From: Christophe Leroy @ 2018-06-22 13:49 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman, malat,
aneesh.kumar
Cc: linux-kernel, linuxppc-dev
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) {
^
arch/powerpc/mm/slice.c:81:20: error: comparison is always false due to limited range of data type [-Werror=type-limits]
if ((start + len) > SLICE_LOW_TOP) {
^
arch/powerpc/mm/slice.c: In function 'slice_mask_for_free':
arch/powerpc/mm/slice.c:136:17: error: comparison is always true due to limited range of data type [-Werror=type-limits]
if (high_limit <= SLICE_LOW_TOP)
^
arch/powerpc/mm/slice.c: In function 'slice_check_range_fits':
arch/powerpc/mm/slice.c:185:12: error: comparison is always true due to limited range of data type [-Werror=type-limits]
if (start < SLICE_LOW_TOP) {
^
arch/powerpc/mm/slice.c:195:39: error: comparison is always false due to limited range of data type [-Werror=type-limits]
if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
^
arch/powerpc/mm/slice.c: In function 'slice_scan_available':
arch/powerpc/mm/slice.c:306:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
if (addr < SLICE_LOW_TOP) {
^
arch/powerpc/mm/slice.c: In function 'get_slice_psize':
arch/powerpc/mm/slice.c:709:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
if (addr < SLICE_LOW_TOP) {
^
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/mm/slice.c | 21 ++++++++++++++-------
1 file changed, 14 insertions(+), 7 deletions(-)
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
@@ -62,6 +62,13 @@ static void slice_print_mask(const char *label, const struct slice_mask *mask) {
#endif
+static inline bool slice_addr_is_low(unsigned long addr)
+{
+ u64 tmp = (u64)addr;
+
+ return tmp < SLICE_LOW_TOP;
+}
+
static void slice_range_to_mask(unsigned long start, unsigned long len,
struct slice_mask *ret)
{
@@ -71,7 +78,7 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
if (SLICE_NUM_HIGH)
bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
- if (start < SLICE_LOW_TOP) {
+ if (slice_addr_is_low(start)) {
unsigned long mend = min(end,
(unsigned long)(SLICE_LOW_TOP - 1));
@@ -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;
@@ -134,7 +141,7 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
if (!slice_low_has_vma(mm, i))
ret->low_slices |= 1u << i;
- if (high_limit <= SLICE_LOW_TOP)
+ if (slice_addr_is_low(high_limit - 1))
return;
for (i = 0; i < GET_HIGH_SLICE_INDEX(high_limit); i++)
@@ -183,7 +190,7 @@ static bool slice_check_range_fits(struct mm_struct *mm,
unsigned long end = start + len - 1;
u64 low_slices = 0;
- if (start < SLICE_LOW_TOP) {
+ if (slice_addr_is_low(start)) {
unsigned long mend = min(end,
(unsigned long)(SLICE_LOW_TOP - 1));
@@ -193,7 +200,7 @@ static bool slice_check_range_fits(struct mm_struct *mm,
if ((low_slices & available->low_slices) != low_slices)
return false;
- if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
+ if (SLICE_NUM_HIGH && !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;
@@ -304,7 +311,7 @@ static bool slice_scan_available(unsigned long addr,
int end, unsigned long *boundary_addr)
{
unsigned long slice;
- if (addr < SLICE_LOW_TOP) {
+ if (slice_addr_is_low(addr)) {
slice = GET_LOW_SLICE_INDEX(addr);
*boundary_addr = (slice + end) << SLICE_LOW_SHIFT;
return !!(available->low_slices & (1u << slice));
@@ -707,7 +714,7 @@ unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
VM_BUG_ON(radix_enabled());
- if (addr < SLICE_LOW_TOP) {
+ if (slice_addr_is_low(addr)) {
psizes = mm->context.low_slices_psize;
index = GET_LOW_SLICE_INDEX(addr);
} else {
--
2.13.3
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc/mm: fix always true/false warning in slice.c
2018-06-22 13:49 [PATCH] powerpc/mm: fix always true/false warning in slice.c Christophe Leroy
@ 2018-06-22 14:55 ` Mathieu Malaterre
2018-06-22 16:17 ` Christophe LEROY
2018-06-29 2:55 ` Michael Ellerman
1 sibling, 1 reply; 5+ messages in thread
From: Mathieu Malaterre @ 2018-06-22 14:55 UTC (permalink / raw)
To: Christophe LEROY
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
Aneesh Kumar K.V, LKML, linuxppc-dev
On Fri, Jun 22, 2018 at 3:49 PM Christophe Leroy
<christophe.leroy@c-s.fr> wrote:
>
> 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) {
> ^
> arch/powerpc/mm/slice.c:81:20: error: comparison is always false due to limited range of data type [-Werror=type-limits]
> if ((start + len) > SLICE_LOW_TOP) {
> ^
> arch/powerpc/mm/slice.c: In function 'slice_mask_for_free':
> arch/powerpc/mm/slice.c:136:17: error: comparison is always true due to limited range of data type [-Werror=type-limits]
> if (high_limit <= SLICE_LOW_TOP)
> ^
> arch/powerpc/mm/slice.c: In function 'slice_check_range_fits':
> arch/powerpc/mm/slice.c:185:12: error: comparison is always true due to limited range of data type [-Werror=type-limits]
> if (start < SLICE_LOW_TOP) {
> ^
> arch/powerpc/mm/slice.c:195:39: error: comparison is always false due to limited range of data type [-Werror=type-limits]
> if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
> ^
> arch/powerpc/mm/slice.c: In function 'slice_scan_available':
> arch/powerpc/mm/slice.c:306:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
> if (addr < SLICE_LOW_TOP) {
> ^
> arch/powerpc/mm/slice.c: In function 'get_slice_psize':
> arch/powerpc/mm/slice.c:709:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
> if (addr < SLICE_LOW_TOP) {
> ^
>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
> ---
> arch/powerpc/mm/slice.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> 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
> @@ -62,6 +62,13 @@ static void slice_print_mask(const char *label, const struct slice_mask *mask) {
>
> #endif
>
> +static inline bool slice_addr_is_low(unsigned long addr)
> +{
> + u64 tmp = (u64)addr;
> +
> + return tmp < SLICE_LOW_TOP;
> +}
> +
> static void slice_range_to_mask(unsigned long start, unsigned long len,
> struct slice_mask *ret)
> {
> @@ -71,7 +78,7 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
> if (SLICE_NUM_HIGH)
> bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
>
> - if (start < SLICE_LOW_TOP) {
> + if (slice_addr_is_low(start)) {
> unsigned long mend = min(end,
> (unsigned long)(SLICE_LOW_TOP - 1));
>
> @@ -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;
> @@ -134,7 +141,7 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
> if (!slice_low_has_vma(mm, i))
> ret->low_slices |= 1u << i;
>
> - if (high_limit <= SLICE_LOW_TOP)
> + if (slice_addr_is_low(high_limit - 1))
Is high_limit ever going to be 0 ?
> return;
>
> for (i = 0; i < GET_HIGH_SLICE_INDEX(high_limit); i++)
> @@ -183,7 +190,7 @@ static bool slice_check_range_fits(struct mm_struct *mm,
> unsigned long end = start + len - 1;
> u64 low_slices = 0;
>
> - if (start < SLICE_LOW_TOP) {
> + if (slice_addr_is_low(start)) {
> unsigned long mend = min(end,
> (unsigned long)(SLICE_LOW_TOP - 1));
>
> @@ -193,7 +200,7 @@ static bool slice_check_range_fits(struct mm_struct *mm,
> if ((low_slices & available->low_slices) != low_slices)
> return false;
>
> - if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
> + if (SLICE_NUM_HIGH && !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;
> @@ -304,7 +311,7 @@ static bool slice_scan_available(unsigned long addr,
> int end, unsigned long *boundary_addr)
> {
> unsigned long slice;
> - if (addr < SLICE_LOW_TOP) {
> + if (slice_addr_is_low(addr)) {
> slice = GET_LOW_SLICE_INDEX(addr);
> *boundary_addr = (slice + end) << SLICE_LOW_SHIFT;
> return !!(available->low_slices & (1u << slice));
> @@ -707,7 +714,7 @@ unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
>
> VM_BUG_ON(radix_enabled());
>
> - if (addr < SLICE_LOW_TOP) {
> + if (slice_addr_is_low(addr)) {
> psizes = mm->context.low_slices_psize;
> index = GET_LOW_SLICE_INDEX(addr);
> } else {
> --
> 2.13.3
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc/mm: fix always true/false warning in slice.c
2018-06-22 14:55 ` Mathieu Malaterre
@ 2018-06-22 16:17 ` Christophe LEROY
0 siblings, 0 replies; 5+ messages in thread
From: Christophe LEROY @ 2018-06-22 16:17 UTC (permalink / raw)
To: Mathieu Malaterre
Cc: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
Aneesh Kumar K.V, LKML, linuxppc-dev
Le 22/06/2018 à 16:55, Mathieu Malaterre a écrit :
> On Fri, Jun 22, 2018 at 3:49 PM Christophe Leroy
> <christophe.leroy@c-s.fr> wrote:
>>
>> 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) {
>> ^
>> arch/powerpc/mm/slice.c:81:20: error: comparison is always false due to limited range of data type [-Werror=type-limits]
>> if ((start + len) > SLICE_LOW_TOP) {
>> ^
>> arch/powerpc/mm/slice.c: In function 'slice_mask_for_free':
>> arch/powerpc/mm/slice.c:136:17: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (high_limit <= SLICE_LOW_TOP)
>> ^
>> arch/powerpc/mm/slice.c: In function 'slice_check_range_fits':
>> arch/powerpc/mm/slice.c:185:12: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (start < SLICE_LOW_TOP) {
>> ^
>> arch/powerpc/mm/slice.c:195:39: error: comparison is always false due to limited range of data type [-Werror=type-limits]
>> if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
>> ^
>> arch/powerpc/mm/slice.c: In function 'slice_scan_available':
>> arch/powerpc/mm/slice.c:306:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (addr < SLICE_LOW_TOP) {
>> ^
>> arch/powerpc/mm/slice.c: In function 'get_slice_psize':
>> arch/powerpc/mm/slice.c:709:11: error: comparison is always true due to limited range of data type [-Werror=type-limits]
>> if (addr < SLICE_LOW_TOP) {
>> ^
>>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>> ---
>> arch/powerpc/mm/slice.c | 21 ++++++++++++++-------
>> 1 file changed, 14 insertions(+), 7 deletions(-)
>>
>> 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
>> @@ -62,6 +62,13 @@ static void slice_print_mask(const char *label, const struct slice_mask *mask) {
>>
>> #endif
>>
>> +static inline bool slice_addr_is_low(unsigned long addr)
>> +{
>> + u64 tmp = (u64)addr;
>> +
>> + return tmp < SLICE_LOW_TOP;
>> +}
>> +
>> static void slice_range_to_mask(unsigned long start, unsigned long len,
>> struct slice_mask *ret)
>> {
>> @@ -71,7 +78,7 @@ static void slice_range_to_mask(unsigned long start, unsigned long len,
>> if (SLICE_NUM_HIGH)
>> bitmap_zero(ret->high_slices, SLICE_NUM_HIGH);
>>
>> - if (start < SLICE_LOW_TOP) {
>> + if (slice_addr_is_low(start)) {
>> unsigned long mend = min(end,
>> (unsigned long)(SLICE_LOW_TOP - 1));
>>
>> @@ -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;
>> @@ -134,7 +141,7 @@ static void slice_mask_for_free(struct mm_struct *mm, struct slice_mask *ret,
>> if (!slice_low_has_vma(mm, i))
>> ret->low_slices |= 1u << i;
>>
>> - if (high_limit <= SLICE_LOW_TOP)
>> + if (slice_addr_is_low(high_limit - 1))
>
> Is high_limit ever going to be 0 ?
See slice_get_unmapped_area(), high_limit will never be 0.
Christophe
>
>> return;
>>
>> for (i = 0; i < GET_HIGH_SLICE_INDEX(high_limit); i++)
>> @@ -183,7 +190,7 @@ static bool slice_check_range_fits(struct mm_struct *mm,
>> unsigned long end = start + len - 1;
>> u64 low_slices = 0;
>>
>> - if (start < SLICE_LOW_TOP) {
>> + if (slice_addr_is_low(start)) {
>> unsigned long mend = min(end,
>> (unsigned long)(SLICE_LOW_TOP - 1));
>>
>> @@ -193,7 +200,7 @@ static bool slice_check_range_fits(struct mm_struct *mm,
>> if ((low_slices & available->low_slices) != low_slices)
>> return false;
>>
>> - if (SLICE_NUM_HIGH && ((start + len) > SLICE_LOW_TOP)) {
>> + if (SLICE_NUM_HIGH && !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;
>> @@ -304,7 +311,7 @@ static bool slice_scan_available(unsigned long addr,
>> int end, unsigned long *boundary_addr)
>> {
>> unsigned long slice;
>> - if (addr < SLICE_LOW_TOP) {
>> + if (slice_addr_is_low(addr)) {
>> slice = GET_LOW_SLICE_INDEX(addr);
>> *boundary_addr = (slice + end) << SLICE_LOW_SHIFT;
>> return !!(available->low_slices & (1u << slice));
>> @@ -707,7 +714,7 @@ unsigned int get_slice_psize(struct mm_struct *mm, unsigned long addr)
>>
>> VM_BUG_ON(radix_enabled());
>>
>> - if (addr < SLICE_LOW_TOP) {
>> + if (slice_addr_is_low(addr)) {
>> psizes = mm->context.low_slices_psize;
>> index = GET_LOW_SLICE_INDEX(addr);
>> } else {
>> --
>> 2.13.3
>>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc/mm: fix always true/false warning in slice.c
2018-06-22 13:49 [PATCH] powerpc/mm: fix always true/false warning in slice.c Christophe Leroy
2018-06-22 14:55 ` Mathieu Malaterre
@ 2018-06-29 2:55 ` Michael Ellerman
2018-08-02 9:30 ` Christophe Leroy
1 sibling, 1 reply; 5+ messages in thread
From: Michael Ellerman @ 2018-06-29 2:55 UTC (permalink / raw)
To: Christophe Leroy, Benjamin Herrenschmidt, Paul Mackerras, malat,
aneesh.kumar
Cc: linux-kernel, linuxppc-dev
Christophe Leroy <christophe.leroy@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 ?
> 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.
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?
cheers
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] powerpc/mm: fix always true/false warning in slice.c
2018-06-29 2:55 ` Michael Ellerman
@ 2018-08-02 9:30 ` Christophe Leroy
0 siblings, 0 replies; 5+ messages in thread
From: Christophe Leroy @ 2018-08-02 9:30 UTC (permalink / raw)
To: Michael Ellerman, Benjamin Herrenschmidt, Paul Mackerras, malat,
aneesh.kumar
Cc: linux-kernel, linuxppc-dev
On 06/29/2018 02:55 AM, Michael Ellerman wrote:
> Christophe Leroy <christophe.leroy@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
>
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2018-08-02 9:30 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2018-06-22 13:49 [PATCH] powerpc/mm: fix always true/false warning in slice.c Christophe Leroy
2018-06-22 14:55 ` Mathieu Malaterre
2018-06-22 16:17 ` Christophe LEROY
2018-06-29 2:55 ` Michael Ellerman
2018-08-02 9:30 ` Christophe Leroy
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