netdev - Re: [PATCH v3] net: bnxt_ptp: fix compilation error

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Date:   Mon, 28 Mar 2022 16:01:01 +0900
From:   Damien Le Moal <damien.lemoal@...nsource.wdc.com>
To:     Pavan Chebbi <pavan.chebbi@...adcom.com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: [PATCH v3] net: bnxt_ptp: fix compilation error

On 3/28/22 15:38, Pavan Chebbi wrote:
> On Mon, Mar 28, 2022 at 11:57 AM Damien Le Moal
> <damien.lemoal@...nsource.wdc.com> wrote:
>>
>> The Broadcom bnxt_ptp driver does not compile with GCC 11.2.2 when
>> CONFIG_WERROR is enabled. The following error is generated:
>>
>> drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c: In function ‘bnxt_ptp_enable’:
>> drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c:400:43: error: array
>> subscript 255 is above array bounds of ‘struct pps_pin[4]’
>> [-Werror=array-bounds]
>>   400 |  ptp->pps_info.pins[pin_id].event = BNXT_PPS_EVENT_EXTERNAL;
>>       |  ~~~~~~~~~~~~~~~~~~^~~~~~~~
>> In file included from drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c:20:
>> drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h:75:24: note: while
>> referencing ‘pins’
>>    75 |         struct pps_pin pins[BNXT_MAX_TSIO_PINS];
>>       |                        ^~~~
>> cc1: all warnings being treated as errors
>>
>> This is due to the function ptp_find_pin() returning a pin ID of -1 when
>> a valid pin is not found and this error never being checked.
>> Change the TSIO_PIN_VALID() function to also check that a pin ID is not
>> negative and use this macro in bnxt_ptp_enable() to check the result of
>> the calls to ptp_find_pin() to return an error early for invalid pins.
>> This fixes the compilation error.
>>
>> Fixes: 9e518f25802c ("bnxt_en: 1PPS functions to configure TSIO pins")
>> Cc: <stable@...r.kernel.org>
>> Signed-off-by: Damien Le Moal <damien.lemoal@...nsource.wdc.com>
>> ---
>> Changes from v2:
>> * Restore the improved check in TSIO_PIN_VALID() and use this macro to
>>   return an error early in bnxt_ptp_enable() in case of invalid pin ID.
>> Changes from v1:
>> * No need to change the TSIO_PIN_VALID() macro as pin_id is an unsigned
>>   value.
>>
>>  drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c | 6 +++++-
>>  drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h | 2 +-
>>  2 files changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
>> index a0b321a19361..9c2ad5e67a5d 100644
>> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
>> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.c
>> @@ -382,7 +382,7 @@ static int bnxt_ptp_enable(struct ptp_clock_info *ptp_info,
>>         struct bnxt_ptp_cfg *ptp = container_of(ptp_info, struct bnxt_ptp_cfg,
>>                                                 ptp_info);
>>         struct bnxt *bp = ptp->bp;
>> -       u8 pin_id;
>> +       int pin_id;
>>         int rc;
>>
>>         switch (rq->type) {
>> @@ -390,6 +390,8 @@ static int bnxt_ptp_enable(struct ptp_clock_info *ptp_info,
>>                 /* Configure an External PPS IN */
>>                 pin_id = ptp_find_pin(ptp->ptp_clock, PTP_PF_EXTTS,
>>                                       rq->extts.index);
>> +               if (!TSIO_PIN_VALID(pin_id))
>> +                       return -EOPNOTSUPP;
> 
> Thanks. Could we now remove this check from the function bnxt_ptp_cfg_pin() ?

Having a quick glance at all the call sites, it looks like it would be OK.
But may be in a different patch ?

This patch is not actually fixing any real problem. It is only fixing gcc
not being able to detect that pin_id can never be with an invalid value
since bnxt_ptp_cfg_pin() would fail before pin_id is used in the
assignment in bnxt_ptp_enable().

Thoughts ?

> 
>>                 if (!on)
>>                         break;
>>                 rc = bnxt_ptp_cfg_pin(bp, pin_id, BNXT_PPS_PIN_PPS_IN);
>> @@ -403,6 +405,8 @@ static int bnxt_ptp_enable(struct ptp_clock_info *ptp_info,
>>                 /* Configure a Periodic PPS OUT */
>>                 pin_id = ptp_find_pin(ptp->ptp_clock, PTP_PF_PEROUT,
>>                                       rq->perout.index);
>> +               if (!TSIO_PIN_VALID(pin_id))
>> +                       return -EOPNOTSUPP;
>>                 if (!on)
>>                         break;
>>
>> diff --git a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h
>> index 373baf45884b..530b9922608c 100644
>> --- a/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h
>> +++ b/drivers/net/ethernet/broadcom/bnxt/bnxt_ptp.h
>> @@ -31,7 +31,7 @@ struct pps_pin {
>>         u8 state;
>>  };
>>
>> -#define TSIO_PIN_VALID(pin) ((pin) < (BNXT_MAX_TSIO_PINS))
>> +#define TSIO_PIN_VALID(pin) ((pin) >= 0 && (pin) < (BNXT_MAX_TSIO_PINS))
>>
>>  #define EVENT_DATA2_PPS_EVENT_TYPE(data2)                              \
>>         ((data2) & ASYNC_EVENT_CMPL_PPS_TIMESTAMP_EVENT_DATA2_EVENT_TYPE)
>> --
>> 2.35.1
>>


-- 
Damien Le Moal
Western Digital Research