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

From: Aneesh Kumar K.V
Date: Sat Sep 10 2016 - 12:13:09 EST


Meelis Roos <mroos@xxxxxxxx> 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];