On Mon, Feb 12, 2018 at 11:33 AM, Shilpasri G Bhat
<shilpa.b...@linux.vnet.ibm.com> wrote:
> Hi,
>
> On 02/12/2018 03:59 PM, Viresh Kumar wrote:
>> On 12-02-18, 15:51, Shilpasri G Bhat wrote:
>>> This patch fixes the below Coverity warning:
>>>
>>> *** CID 182816: Memory - illegal accesses (NEGATIVE_RETURNS)
>>> /drivers/cpufreq/powernv-cpufreq.c: 1008 in powernv_fast_switch()
>>> 1002 unsigned int target_freq)
>>> 1003 {
>>> 1004 int index;
>>> 1005 struct powernv_smp_call_data freq_data;
>>> 1006
>>> 1007 index = cpufreq_table_find_index_dl(policy, target_freq);
>>>>>> CID 182816: Memory - illegal accesses (NEGATIVE_RETURNS)
>>>>>> Using variable "index" as an index to array "powernv_freqs".
>>> 1008 freq_data.pstate_id = powernv_freqs[index].driver_data;
>>> 1009 freq_data.gpstate_id = powernv_freqs[index].driver_data;
>>> 1010 set_pstate(&freq_data);
>>> 1011
>>> 1012 return powernv_freqs[index].frequency;
>>> 1013 }
>>>
>>> Signed-off-by: Shilpasri G Bhat <shilpa.b...@linux.vnet.ibm.com>
>>> ---
>>> drivers/cpufreq/powernv-cpufreq.c | 3 +++
>>> 1 file changed, 3 insertions(+)
>>>
>>> diff --git a/drivers/cpufreq/powernv-cpufreq.c
>>> b/drivers/cpufreq/powernv-cpufreq.c
>>> index 29cdec1..69edfe9 100644
>>> --- a/drivers/cpufreq/powernv-cpufreq.c
>>> +++ b/drivers/cpufreq/powernv-cpufreq.c
>>> @@ -1005,6 +1005,9 @@ static unsigned int powernv_fast_switch(struct
>>> cpufreq_policy *policy,
>>> struct powernv_smp_call_data freq_data;
>>>
>>> index = cpufreq_table_find_index_dl(policy, target_freq);
>>> + if (unlikely(index < 0))
>>> + index = get_nominal_index();
>>> +
>>
>> AFAICT, you will get -1 here only if the freq table had no valid
>> frequencies (or the freq table is empty). Why would that happen ?
>
> I agree too. There is no way we can get -1 with initialized cpu frequency
> table.
> We don't initialize powernv-cpufreq if we don't have valid CPU frequency
> entries. Is there any other way to suppress the Coverity tool warning apart
> from
> ignoring it?
In principle you could use BUG_ON(something_impossible) to annotate
that kind of thing to the static analysis tools, but that would
generate extra code.
