Re: UBSAN: Undefined behaviour in arch/powerpc/kernel/cputable.c

From	"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: UBSAN: Undefined behaviour in arch/powerpc/kernel/cputable.c
Date	2016-09-10 18:20 +0200
Message-ID	<sfTay-2uE-3@gated-at.bofh.it> (permalink)
References	<sfsk2-2dK-17@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Meelis Roos <mroos@linux.ee> writes:

> Got this on my PowerPC G4 (533 MHz, PowerPC 7410, PowerMac3,4 platform), 
> with gcc version 5.3.1 20160509 (Debian 5.3.1-19):
>
> [    0.000000] ================================================================================
> [    0.000000] UBSAN: Undefined behaviour in arch/powerpc/kernel/cputable.c:2240:25
> [    0.000000] shift exponent 32 is too large for 32-bit type 'long unsigned int'
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.8.0-rc5-00075-gd71f058 #106
> [    0.000000] Call Trace:
> [    0.000000] [c0a5ff10] [c03aa588] ubsan_epilogue+0x18/0x4c (unreliable)
> [    0.000000] [c0a5ff20] [c03aab38] __ubsan_handle_shift_out_of_bounds+0xe8/0x13c
> [    0.000000] [c0a5ffa0] [c07c42d0] cpu_feature_keys_init+0xa0/0xb8
> [    0.000000] [c0a5ffd0] [c07ca1fc] setup_feature_keys+0x14/0x24
> [    0.000000] [c0a5ffe0] [c07c6c74] machine_init+0x18/0x58
> [    0.000000] [c0a5fff0] [c000341c] start_here+0x38/0x78
> [    0.000000] ================================================================================
>
>

Can you try

diff --git a/arch/powerpc/include/asm/cpu_has_feature.h b/arch/powerpc/include/asm/cpu_has_feature.h
index 2ef55f8968a2..b312b152461b 100644
--- a/arch/powerpc/include/asm/cpu_has_feature.h
+++ b/arch/powerpc/include/asm/cpu_has_feature.h
@@ -15,7 +15,7 @@ static inline bool early_cpu_has_feature(unsigned long feature)
 #ifdef CONFIG_JUMP_LABEL_FEATURE_CHECKS
 #include <linux/jump_label.h>
 
-#define NUM_CPU_FTR_KEYS	64
+#define NUM_CPU_FTR_KEYS	BITS_PER_LONG
 
 extern struct static_key_true cpu_feature_keys[NUM_CPU_FTR_KEYS];

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Re: UBSAN: Undefined behaviour in arch/powerpc/kernel/cputable.c "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> - 2016-09-10 18:20 +0200

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