[DTrace-devel] [PATCH] Write 0 rather than '\0' in *.S files

[Kris Van Hees]

On Thu, Dec 02, 2021 at 01:44:52PM -0500, eugene.loh--- via DTrace-devel wrote:
> From: Eugene Loh <eugene.loh at oracle.com>
> 
> Apparently, when one uses stb in a bpf/*.S file to write a '\0',
> one writes a literal '0'.  This problem was not seen until the
> basename/dirname patches were combined with
>         cf1e9df28b95  Optimize dt_cg_store_val() for string values
> Prior to that, we trusted the string-length prefix and truncated the
> string before the literal '0'.
> 
> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>

Reviewed-by: Kris Van Hees <kris.van.hees at oracle.com>

> ---
>  bpf/basename.S | 4 ++--
>  bpf/dirname.S  | 4 ++--
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/bpf/basename.S b/bpf/basename.S
> index 3ddb3bbf..2839614c 100644
> --- a/bpf/basename.S
> +++ b/bpf/basename.S
> @@ -107,7 +107,7 @@ dt_basename :
>  	 */
>  	mov	LEN, 1
>  	stb	[DST+DT_STRLEN_BYTES], '.'
> -	stb	[DST+(DT_STRLEN_BYTES+1)], '\0'
> +	stb	[DST+(DT_STRLEN_BYTES+1)], 0
>  	ja	.Lcoda
>  
>  .Lslash:
> @@ -116,7 +116,7 @@ dt_basename :
>  	 */
>  	mov	LEN, 1
>  	stb	[DST+DT_STRLEN_BYTES], '/'
> -	stb	[DST+(DT_STRLEN_BYTES+1)], '\0'
> +	stb	[DST+(DT_STRLEN_BYTES+1)], 0
>  	ja	.Lcoda
>  #undef SRC
>  #undef DST
> diff --git a/bpf/dirname.S b/bpf/dirname.S
> index 1ab676ce..908fa68a 100644
> --- a/bpf/dirname.S
> +++ b/bpf/dirname.S
> @@ -123,7 +123,7 @@ dt_dirname :
>  	 */
>  	mov	LEN, 1
>  	stb	[DST+DT_STRLEN_BYTES], '.'
> -	stb	[DST+(DT_STRLEN_BYTES+1)], '\0'
> +	stb	[DST+(DT_STRLEN_BYTES+1)], 0
>  	ja	.Lcoda
>  
>  .Lslash:
> @@ -132,7 +132,7 @@ dt_dirname :
>  	 */
>  	mov	LEN, 1
>  	stb	[DST+DT_STRLEN_BYTES], '/'
> -	stb	[DST+(DT_STRLEN_BYTES+1)], '\0'
> +	stb	[DST+(DT_STRLEN_BYTES+1)], 0
>  	ja	.Lcoda
>  #undef SRC
>  #undef DST
> -- 
> 2.18.4
> 
> 
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