[PATCH] fs: semihosting: Use correct variable for error check

[Heinrich Schuchardt]

On 10/2/25 13:00, Andrew Goodbody wrote:
> On 02/10/2025 10:52, Heinrich Schuchardt wrote:
>> On 10/2/25 11:39, Andrew Goodbody wrote:
>>> After calling a function that can return an error, the test to detect
>>> that error should use the return value not a different variable. Fix it.
>>>
>>> This issue was found by Smatch.
>>>
>>
>> Fixes: f676b45151c3 ("fs: Add semihosting filesystem")
>>
>>> Signed-off-by: Andrew Goodbody <andrew.goodbody at linaro.org>
>>> ---
>>>   fs/semihostingfs.c | 2 +-
>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/fs/semihostingfs.c b/fs/semihostingfs.c
>>> index 
>>> 77e39ca407e4d240a1fd573497c5b6b908816454..9d7a136b9ba9b035545b34b31df58e2d65de7db9 100644
>>> --- a/fs/semihostingfs.c
>>> +++ b/fs/semihostingfs.c
>>> @@ -35,7 +35,7 @@ static int smh_fs_read_at(const char *filename, 
>>> loff_t pos, void *buffer,
>>>       }
>>>       if (!maxsize) {
>>>           size = smh_flen(fd);
>>> -        if (ret < 0) {
>>> +        if (size < 0) {
>>
>> The ARM specification (https://developer.arm.com/documentation/ 
>> dui0203/ j/semihosting/semihosting-operations/sys-flen--0x0c-) has:
>>
>> SYS_FLEN (0x0C)
>>
>> Returns the length of a specified file.
>> On exit, R0 contains:
>>      the current length of the file object, if the call is successful
>>      -1 if an error occurs.
>>
>> Please, consider that the file length on 32bit systems may exceed 2^31 
>> You must not consider this as an error.

How about changing the smh_flen() interface to:

int smh_flen(int fd, size_t *size)

Best regards

Heinrich

>>
>> %s/if (size < 0)/if (size == -1L)/
> 
> Unfortunately that is not sufficient with the current code. smh_flen() 
> and others will call smh_errno() if the sys call returns -1 so other 
> error codes may possibly be returned. [1]
> This seems to be going well beyond the scope of my patch.
> 
> Andrew
> 
> 1. 80e62ccfa63 arm: smh: Return errno on error
> 
>> Best regards
>>
>> Heinrich
>>
>>>               smh_close(fd);
>>>               return size;
>>>           }
>>>
>>> ---
>>> base-commit: da47ddebd16a7e1047da8537fbf01558d2a89fcf
>>> change-id: 20251002-fs_semihosting-85d697fbfcad
>>>
>>> Best regards,
>>
>