Re: [dpdk-dev] [PATCH v3] examples/qos_sched: fix bad bit shift operation

["Dumitrescu, Cristian" <cristian.dumitrescu@intel.com>]

> -----Original Message-----
> From: Jastrzebski, MichalX K
> Sent: Thursday, April 21, 2016 2:08 PM
> To: Dumitrescu, Cristian <cristian.dumitrescu@intel.com>; Zhang, Roy Fan
> <roy.fan.zhang@intel.com>; Singh, Jasvinder <jasvinder.singh@intel.com>
> Cc: dev@dpdk.org; Mrozowicz, SlawomirX
> <slawomirx.mrozowicz@intel.com>
> Subject: [PATCH v3] examples/qos_sched: fix bad bit shift operation
> 
> From: Slawomir Mrozowicz <slawomirx.mrozowicz@intel.com>
> 
> Fix issue reported by Coverity.
> 
> Coverity ID 30690: Bad bit shift operation
> large_shift: In expression 1ULL << i, left shifting by more than 63 bits
> has undefined behavior. The shift amount, i, is as much as 127.
> 
> Fixes: de3cfa2c9823 ("sched: initial import")
> 
> Signed-off-by: Slawomir Mrozowicz <slawomirx.mrozowicz@intel.com>
> ---
>  examples/qos_sched/args.c | 84 +++++++++++++++++++++++++++++------
> ------------
>  1 file changed, 52 insertions(+), 32 deletions(-)
> 
> diff --git a/examples/qos_sched/args.c b/examples/qos_sched/args.c
> index 3e7fd08..cd077ba 100644
> --- a/examples/qos_sched/args.c
> +++ b/examples/qos_sched/args.c
> @@ -53,7 +53,7 @@
> 
>  static uint32_t app_master_core = 1;
>  static uint32_t app_numa_mask;
> -static uint64_t app_used_core_mask = 0;
> +static int app_used_core_mask[RTE_MAX_LCORE];
>  static uint64_t app_used_port_mask = 0;
>  static uint64_t app_used_rx_port_mask = 0;
>  static uint64_t app_used_tx_port_mask = 0;
> @@ -115,22 +115,23 @@ static inline int str_is(const char *str, const char *is)
>  	return strcmp(str, is) == 0;
>  }
> 
> -/* returns core mask used by DPDK */
> -static uint64_t
> -app_eal_core_mask(void)
> +/* compare used core with eal configuration,
> +	returns:
> +		1 if equal
> +		0 if differ */
> +static int
> +app_eal_core_check(void)
>  {
> -	uint32_t i;
> -	uint64_t cm = 0;
> +	uint16_t i;
> +	int ret = 1;
>  	struct rte_config *cfg = rte_eal_get_configuration();
> 
> -	for (i = 0; i < RTE_MAX_LCORE; i++) {
> -		if (cfg->lcore_role[i] == ROLE_RTE)
> -			cm |= (1ULL << i);
> +	for (i = 0; i < RTE_MAX_LCORE && ret; i++) {
> +		if ((cfg->lcore_role[i] == ROLE_RTE) !=
> app_used_core_mask[i])
> +			ret = 0;
>  	}
> 
> -	cm |= (1ULL << cfg->master_lcore);
> -
> -	return cm;
> +	return ret;
>  }
> 
> 
> @@ -292,14 +293,9 @@ app_parse_flow_conf(const char *conf_str)
>  	app_used_tx_port_mask |= mask;
>  	app_used_port_mask |= mask;
> 
> -	mask = 1lu << pconf->rx_core;
> -	app_used_core_mask |= mask;
> -
> -	mask = 1lu << pconf->wt_core;
> -	app_used_core_mask |= mask;
> -
> -	mask = 1lu << pconf->tx_core;
> -	app_used_core_mask |= mask;
> +	app_used_core_mask[pconf->rx_core] = 1;
> +	app_used_core_mask[pconf->wt_core] = 1;
> +	app_used_core_mask[pconf->tx_core] = 1;
> 
>  	nb_pfc++;
> 
> @@ -335,7 +331,7 @@ app_parse_args(int argc, char **argv)
>  	int option_index;
>  	const char *optname;
>  	char *prgname = argv[0];
> -	uint32_t i, nb_lcores;
> +	uint16_t i, j, k, nb_lcores;
> 
>  	static struct option lgopts[] = {
>  		{ "pfc", 1, 0, 0 },
> @@ -349,6 +345,9 @@ app_parse_args(int argc, char **argv)
>  		{ NULL,  0, 0, 0 }
>  	};
> 
> +	for (i = 0; i < RTE_MAX_LCORE; i++)
> +		app_used_core_mask[i] = 0;
> +
>  	/* initialize EAL first */
>  	ret = rte_eal_init(argc, argv);
>  	if (ret < 0)
> @@ -436,19 +435,40 @@ app_parse_args(int argc, char **argv)
>  	}
> 
>  	/* check master core index validity */
> -	for(i = 0; i <= app_master_core; i++) {
> -		if (app_used_core_mask & (1u << app_master_core)) {
> -			RTE_LOG(ERR, APP, "Master core index is not
> configured properly\n");
> -			app_usage(prgname);
> -			return -1;
> -		}
> +	if (app_used_core_mask[app_master_core] == 1) {
> +		RTE_LOG(ERR, APP,
> +			"Master core index is not configured properly\n");
> +		app_usage(prgname);
> +		return -1;
>  	}
> -	app_used_core_mask |= 1u << app_master_core;
> +	app_used_core_mask[app_master_core] = 1;
> +
> +	if ((app_eal_core_check() == 0) ||
> +		(app_master_core != rte_get_master_lcore())) {
> +
> +		char used_hexstr[RTE_MAX_LCORE/4+1];
> +		char conf_hexstr[RTE_MAX_LCORE/4+1];
> +		int used_byte, conf_byte;
> +		struct rte_config *cfg = rte_eal_get_configuration();
> +
> +		for (i = 0; i < RTE_MAX_LCORE/4; i++) {
> +			used_byte = 0;
> +			conf_byte = 0;
> +			for (j = 0; j < 3; j++) {
> +				k = 4 * (RTE_MAX_LCORE/4 - i - 1) + j;
> +				used_byte += app_used_core_mask[k] << j;
> +				conf_byte +=
> +					((cfg->lcore_role[k] ==
> +					ROLE_RTE)?1:0) << j;
> +			}
> +			sprintf(&used_hexstr[i], "%1x", used_byte);
> +			sprintf(&conf_hexstr[i], "%1x", used_byte);
> +		}
> +
> +		RTE_LOG(ERR, APP, "EAL core mask not configured
> properly\n");
> +		RTE_LOG(ERR, APP, "  must be   : %s\n", used_hexstr);
> +		RTE_LOG(ERR, APP, "  instead of: %s\n", conf_hexstr);
> 
> -	if ((app_used_core_mask != app_eal_core_mask()) ||
> -			(app_master_core != rte_get_master_lcore())) {
> -		RTE_LOG(ERR, APP, "EAL core mask not configured properly,
> must be %" PRIx64
> -				" instead of %" PRIx64 "\n" ,
> app_used_core_mask, app_eal_core_mask());
>  		return -1;
>  	}
> 
> --
> 1.9.1


Can you please explain the root issue?

This patch contains way too much code for fixing a shift overflow issue, it is basically a rework without explaining the issue or reason/benefit for the rework.

This approach does not look right to me, I am sure there is a better and quicker way to fix the potential issue once we all understand it.