Re: [PATCH] IBM zSystems: Fix left-shifting negative PCRel32 values (PR gas/29152)

[Andreas Krebbel <krebbel@linux.ibm.com>]

On 5/16/22 20:35, Ilya Leoshkevich wrote:
> s390_insert_operand ()'s val, min and max are encoded PCRel32 values
> and need to be left-shifted by 1 before being shown to the user.
> Left-shifting negative values is undefined behavior in C, but the
> current code does not try to prevent it, causing UBSan to complain.
> 
> Fix by casting the values to their unsigned equivalents before
> shifting.
> ---
>  gas/config/tc-s390.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/gas/config/tc-s390.c b/gas/config/tc-s390.c
> index fb452f8a986..04a3c059c91 100644
> --- a/gas/config/tc-s390.c
> +++ b/gas/config/tc-s390.c
> @@ -622,9 +622,9 @@ s390_insert_operand (unsigned char *insn,
>  
>  	  if (operand->flags & S390_OPERAND_PCREL)
>  	    {
> -	      val <<= 1;
> -	      min <<= 1;
> -	      max <<= 1;
> +	      val = (offsetT) ((addressT) val << 1);
> +	      min = (offsetT) ((addressT) min << 1);
> +	      max = (offsetT) ((addressT) max << 1);
>  	    }
>  	  if (file == (char *) NULL)
>  	    as_bad (err, (int64_t) val, (int64_t) min, (int64_t) max);

Committed to master. Thanks!

Andreas