[U-Boot] [PATCH v2 07/13] x86: Fix signed shift overflow in MSR_IA32_APICBASE_BASE

[Bin Meng]

Hi Eugeniu,

On Mon, Aug 27, 2018 at 7:19 AM Eugeniu Rosca <roscaeugeniu at gmail.com> wrote:
>
> Fix the following UBSAN report:
>  ======================================================================
>  UBSAN: Undefined behaviour in arch/x86/cpu/lapic.c:73:14
>  left shift of 1048575 by 12 places cannot be represented in type 'int'
>  ======================================================================
>
> Steps to reproduce the above:
> * echo CONFIG_UBSAN=y >> configs/qemu-x86_defconfig
> * make ARCH=x86 qemu-x86_defconfig all
> * qemu-system-i386 --version
>   QEMU emulator version 2.5.0 (Debian 1:2.5+dfsg-5ubuntu10.31)
> * qemu-system-i386 --nographic -bios u-boot.rom
>
> Fixes: 98568f0fa96b ("x86: Import MSR/MTRR code from Linux")
> Signed-off-by: Eugeniu Rosca <erosca at de.adit-jv.com>
> ---
>
> Changes in v2:
>  - None. Newly pushed.
> ---
>  arch/x86/include/asm/msr-index.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/include/asm/msr-index.h b/arch/x86/include/asm/msr-index.h
> index 9c1dbe61d596..d8b7b8013c74 100644
> --- a/arch/x86/include/asm/msr-index.h
> +++ b/arch/x86/include/asm/msr-index.h
> @@ -370,7 +370,7 @@
>  #define MSR_IA32_APICBASE              0x0000001b
>  #define MSR_IA32_APICBASE_BSP          (1<<8)
>  #define MSR_IA32_APICBASE_ENABLE       (1<<11)
> -#define MSR_IA32_APICBASE_BASE         (0xfffff<<12)
> +#define MSR_IA32_APICBASE_BASE         (0xfffffUL << 12)

I don't understand why such warnings is emitted: "left shift of
1048575 by 12 places cannot be represented in type 'int'"

Compilers don't complain this code and Linux kernel has the same
definition here.

Regards,
Bin