Messages in this thread | | | Subject | Re: [PATCH] x86/cpu: fix undefined behavior in bit shift for intel_detect_tlb | From | cuigaosheng <> | Date | Tue, 1 Nov 2022 19:48:07 +0800 |
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We don't need to add UBSAN calltrace, so I have merged the patch with another patch("x86/cpu: replacing the open-coded shift with BIT(x)"), please ignore this patch,thanks for review this patch!
On 2022/10/31 20:32, Peter Zijlstra wrote: > On Mon, Oct 31, 2022 at 01:30:57PM +0100, Peter Zijlstra wrote: >> On Mon, Oct 31, 2022 at 07:43:40PM +0800, Gaosheng Cui wrote: >>> Shifting signed 32-bit value by 31 bits is undefined, so changing >>> significant bit to unsigned. The UBSAN warning calltrace like below: >>> >>> UBSAN: shift-out-of-bounds in arch/x86/kernel/cpu/intel.c:948:21 >>> left shift of 1 by 31 places cannot be represented in type 'int' >> Is it really? Shouldn't -fstrict-overflow define this case? > -fno-strict-overflow that is, which implies -fwrapv which ensures 2s > complement, at which point shifting signed numbers is fully defined. > > .
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