[DTrace-devel] [PATCH 2/5] libproc: fix mapping names low in the address space

[Kris Van Hees]

On Mon, Apr 24, 2023 at 08:08:13PM +0100, Nick Alcock via DTrace-devel wrote:
> For reasons which escape my understanding, address ranges in
> /proc/$pid/maps are zero-padded up to eight digits, but filenames in
> /proc/$pid/map_files are not zero-padded at all.  Strip the zeroes off
> when deriving the latter from the former.
> 
> (Only observable with non-PIE executables, since only they are ever that
> low in the address space.)
> 
> Signed-off-by: Nick Alcock <nick.alcock at oracle.com>

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

> ---
>  libproc/Psymtab.c | 25 ++++++++++++++++++++++++-
>  1 file changed, 24 insertions(+), 1 deletion(-)
> 
> diff --git a/libproc/Psymtab.c b/libproc/Psymtab.c
> index cd55b8cf1678a..a95161884c27a 100644
> --- a/libproc/Psymtab.c
> +++ b/libproc/Psymtab.c
> @@ -53,6 +53,19 @@ static int Pxlookup_by_name_internal(struct ps_prochandle *P, Lmid_t lmid,
>  	(1 << STT_COMMON) | (1 << STT_TLS))
>  #define	IS_DATA_TYPE(tp)	(((1 << (tp)) & DATA_TYPES) != 0)
>  
> +static char *
> +dezerostr(char *str)
> +{
> +	size_t i;
> +
> +	if (str[0] != '0')
> +		return str;
> +
> +	i = strspn(str, "0");
> +	memmove(str, str + i, strlen(str) - i + 1);
> +
> +	return str;
> +}
>  
>  static ulong_t
>  string_hash(const char *key)
> @@ -527,6 +540,7 @@ Pupdate_maps(struct ps_prochandle *P)
>  		unsigned int minor;
>  		char	perms[5];
>  		const char *first_space;
> +		char *dash;
>  		map_info_t *mptr;
>  		prmap_file_t *prf;
>  		prmap_t *pmptr;
> @@ -545,10 +559,19 @@ Pupdate_maps(struct ps_prochandle *P)
>  
>  		/*
>  		 * Skip anonymous mappings, and special mappings like the stack,
> -		 * heap, and vdso; also skip on OOM.
> +		 * heap, and vdso; also skip on OOM.  Drop leading zeroes from
> +		 * the addresses as well (map_files entries lack them).
>  		 */
>  		first_space = strchr(line, ' ');
>  		mapaddrname = strndup(line, first_space - line);
> +		dezerostr(mapaddrname);
> +
> +		dash = strchr(mapaddrname, '-');
> +		if (dash) {
> +			dash++;
> +			dezerostr(dash);
> +		}
> +
>  		if ((fn == NULL) || (mapaddrname == NULL) || (fn[0] == '[')) {
>  			free(fn);
>  			free(mapaddrname);
> -- 
> 2.39.1.268.g9de2f9a303
> 
> 
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