* [PATCH] arm:fix negation of -2147483648 warning with UBSASN
[not found] <CGME20171012104401epcas5p3c707a85cc3a6b35bf34a710f435736cd@epcas5p3.samsung.com>
@ 2017-10-12 10:40 ` Manjeet Pawar
2017-10-12 10:51 ` Russell King - ARM Linux
0 siblings, 1 reply; 2+ messages in thread
From: Manjeet Pawar @ 2017-10-12 10:40 UTC (permalink / raw)
To: linux-arm-kernel
From: Rohit Thapliyal <r.thapliyal@samsung.com>
Using gcc-6 and UBSAN enabled, we get the following warning:
=========================================================
[1-1.4604] UBSAN: Undefined behaviour in ./arch/arm/include/asm/bitops.h:296:17
[1-1.4604] negation of -2147483648 cannot be represented in type 'int':
[1-1.4605] CPU: 1 PID: 189 Comm: sync Tainted: GO 4.1.10 #1 PPID: 166 PComm: init
[1-1.4605] SCHED_NORMAL (p:120, static_p:120, normal_p:120, rt_p:0)
[1-1.4605] Backtrace:
[1-1.4605] [<c0016050>] (dump_backtrace) from [<c0016fac>] (show_stack+0x18/0x20)
[1-1.4605] r7:c098196c r6:00000000 r5:60040093 r4:c0a177f4
[1-1.4605] [<c0016f94>] (show_stack) from [<c06f36d8>] (dump_stack+0xf4/0x148)
[1-1.4605] [<c06f35e4>] (dump_stack) from [<c03b8b94>] (ubsan_epilogue+0x14/0x54)
[1-1.4605] r10:00000101 r9:00000120 r8:00000100 r7:00001000 r6:80000000 r5:c0a18b00
[1-1.4605] r4:d8099c00
[1-1.4605] [<c03b8b80>] (ubsan_epilogue) from [<c03b941c>] (__ubsan_handle_negate_overflow+0x88/0x90)
[1-1.4605] r5:c0a18b00 r4:c098148c
[1-1.4605] [<c03b9394>] (__ubsan_handle_negate_overflow) from [<c03823c4>] (radix_tree_next_chunk+0x380/0x470)
[1-1.4605] r6:e1b88d20 r5:00000006 r4:00000020
[1-1.4606] [<c0382044>] (radix_tree_next_chunk) from [<c0158f10>] (find_get_pages_tag+0x158/0x1e8)
[1-1.4606] r10:00000004 r9:0000000e r8:00000101 r7:ffffffff r6:00000000 r5:e1b91cb4
[1-1.4606] r4:00000001
[1-1.4606] [<c0158db8>] (find_get_pages_tag) from [<c016e160>] (pagevec_lookup_tag+0x30/0x3c)
[1-1.4606] r10:0000000e r9:27f662e4 r8:00000000 r7:ffffffff r6:e50da320 r5:d8099d60
=========================================================
In order to remove these warnings, it seems harmless to modify
the signed ints with unsigned long as a fix of negation of -2147483648 in signed int.
Signed-off-by: Rohit Thapliyal <r.thapliyal@samsung.com>
Signed-off-by: Manjeet Pawar <manjeet.p@samsung.com>
---
arch/arm/include/asm/bitops.h | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/bitops.h b/arch/arm/include/asm/bitops.h
index 5638099..95028db 100644
--- a/arch/arm/include/asm/bitops.h
+++ b/arch/arm/include/asm/bitops.h
@@ -222,7 +222,7 @@ extern int _find_next_bit_be(const unsigned long *p, int size, int offset);
#else
-static inline int constant_fls(int x)
+static inline int constant_fls(unsigned long x)
{
int r = 32;
@@ -270,7 +270,7 @@ static inline unsigned int __clz(unsigned int x)
* fls() returns zero if the input is zero, otherwise returns the bit
* position of the last set bit, where the LSB is 1 and MSB is 32.
*/
-static inline int fls(int x)
+static inline int fls(unsigned long x)
{
if (__builtin_constant_p(x))
return constant_fls(x);
@@ -291,7 +291,7 @@ static inline unsigned long __fls(unsigned long x)
* ffs() returns zero if the input was zero, otherwise returns the bit
* position of the first set bit, where the LSB is 1 and MSB is 32.
*/
-static inline int ffs(int x)
+static inline int ffs(unsigned long x)
{
return fls(x & -x);
}
--
1.9.1
^ permalink raw reply related [flat|nested] 2+ messages in thread
* [PATCH] arm:fix negation of -2147483648 warning with UBSASN
2017-10-12 10:40 ` [PATCH] arm:fix negation of -2147483648 warning with UBSASN Manjeet Pawar
@ 2017-10-12 10:51 ` Russell King - ARM Linux
0 siblings, 0 replies; 2+ messages in thread
From: Russell King - ARM Linux @ 2017-10-12 10:51 UTC (permalink / raw)
To: linux-arm-kernel
On Thu, Oct 12, 2017 at 04:10:58PM +0530, Manjeet Pawar wrote:
> From: Rohit Thapliyal <r.thapliyal@samsung.com>
>
> Using gcc-6 and UBSAN enabled, we get the following warning:
>
> =========================================================
> [1-1.4604] UBSAN: Undefined behaviour in ./arch/arm/include/asm/bitops.h:296:17
> [1-1.4604] negation of -2147483648 cannot be represented in type 'int':
> [1-1.4605] CPU: 1 PID: 189 Comm: sync Tainted: GO 4.1.10 #1 PPID: 166 PComm: init
> [1-1.4605] SCHED_NORMAL (p:120, static_p:120, normal_p:120, rt_p:0)
> [1-1.4605] Backtrace:
> [1-1.4605] [<c0016050>] (dump_backtrace) from [<c0016fac>] (show_stack+0x18/0x20)
> [1-1.4605] r7:c098196c r6:00000000 r5:60040093 r4:c0a177f4
> [1-1.4605] [<c0016f94>] (show_stack) from [<c06f36d8>] (dump_stack+0xf4/0x148)
> [1-1.4605] [<c06f35e4>] (dump_stack) from [<c03b8b94>] (ubsan_epilogue+0x14/0x54)
> [1-1.4605] r10:00000101 r9:00000120 r8:00000100 r7:00001000 r6:80000000 r5:c0a18b00
> [1-1.4605] r4:d8099c00
> [1-1.4605] [<c03b8b80>] (ubsan_epilogue) from [<c03b941c>] (__ubsan_handle_negate_overflow+0x88/0x90)
> [1-1.4605] r5:c0a18b00 r4:c098148c
> [1-1.4605] [<c03b9394>] (__ubsan_handle_negate_overflow) from [<c03823c4>] (radix_tree_next_chunk+0x380/0x470)
> [1-1.4605] r6:e1b88d20 r5:00000006 r4:00000020
> [1-1.4606] [<c0382044>] (radix_tree_next_chunk) from [<c0158f10>] (find_get_pages_tag+0x158/0x1e8)
> [1-1.4606] r10:00000004 r9:0000000e r8:00000101 r7:ffffffff r6:00000000 r5:e1b91cb4
> [1-1.4606] r4:00000001
> [1-1.4606] [<c0158db8>] (find_get_pages_tag) from [<c016e160>] (pagevec_lookup_tag+0x30/0x3c)
> [1-1.4606] r10:0000000e r9:27f662e4 r8:00000000 r7:ffffffff r6:e50da320 r5:d8099d60
> =========================================================
>
> In order to remove these warnings, it seems harmless to modify
> the signed ints with unsigned long as a fix of negation of -2147483648 in signed int.
>
> Signed-off-by: Rohit Thapliyal <r.thapliyal@samsung.com>
> Signed-off-by: Manjeet Pawar <manjeet.p@samsung.com>
> ---
> arch/arm/include/asm/bitops.h | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm/include/asm/bitops.h b/arch/arm/include/asm/bitops.h
> index 5638099..95028db 100644
> --- a/arch/arm/include/asm/bitops.h
> +++ b/arch/arm/include/asm/bitops.h
> @@ -222,7 +222,7 @@ extern int _find_next_bit_be(const unsigned long *p, int size, int offset);
>
> #else
>
> -static inline int constant_fls(int x)
> +static inline int constant_fls(unsigned long x)
> {
> int r = 32;
>
> @@ -270,7 +270,7 @@ static inline unsigned int __clz(unsigned int x)
> * fls() returns zero if the input is zero, otherwise returns the bit
> * position of the last set bit, where the LSB is 1 and MSB is 32.
> */
> -static inline int fls(int x)
> +static inline int fls(unsigned long x)
> {
> if (__builtin_constant_p(x))
> return constant_fls(x);
> @@ -291,7 +291,7 @@ static inline unsigned long __fls(unsigned long x)
> * ffs() returns zero if the input was zero, otherwise returns the bit
> * position of the first set bit, where the LSB is 1 and MSB is 32.
> */
> -static inline int ffs(int x)
> +static inline int ffs(unsigned long x)
> {
> return fls(x & -x);
> }
Every other architecture, including asm-generic, uses 'int' for fls()
and ffs(). If we're going to change the prototype, it needs to be
changed everwhere, not just one implementation.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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2017-10-12 10:40 ` [PATCH] arm:fix negation of -2147483648 warning with UBSASN Manjeet Pawar
2017-10-12 10:51 ` Russell King - ARM Linux
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