On 6/21/21 9:11 PM, Michael Ellerman wrote:
> Daniel Axtens <d...@axtens.net> writes:
>> Hi
>>
>>> -static char __init *prom_strcpy(char *dest, const char *src)
>>> +static ssize_t __init prom_strscpy_pad(char *dest, const char *src, size_t
>>> n)
>>> {
>>> - char *tmp = dest;
>>> + ssize_t rc;
>>> + size_t i;
>>>
>>> - while ((*dest++ = *src++) != '\0')
>>> - /* nothing */;
>>> - return tmp;
>>> + if (n == 0 || n > INT_MAX)
>>> + return -E2BIG;
>>> +
>>> + // Copy up to n bytes
>>> + for (i = 0; i < n && src[i] != '\0'; i++)
>>> + dest[i] = src[i];
>>> +
>>> + rc = i;
>>> +
>>> + // If we copied all n then we have run out of space for the nul
>>> + if (rc == n) {
>>> + // Rewind by one character to ensure nul termination
>>> + i--;
>>> + rc = -E2BIG;
>>> + }
>>> +
>>> + for (; i < n; i++)
>>> + dest[i] = '\0';
>>> +
>>> + return rc;
>>> }
>>>
>>
>> This implementation seems good to me.
>>
>> I copied it into a new C file and added the following:
>>
>> int main() {
>> char longstr[255]="abcdefghijklmnopqrstuvwxyz";
>> char shortstr[5];
>> assert(prom_strscpy_pad(longstr, "", 0) == -E2BIG);
>> assert(prom_strscpy_pad(longstr, "hello", 255) == 5);
>> assert(prom_strscpy_pad(shortstr, "hello", 5) == -E2BIG);
>> assert(memcmp(shortstr, "hell", 5) == 0);
>> assert(memcmp(longstr, "hello\0\0\0\0\0\0\0\0\0", 6) == 0);
>> return 0;
>> }
>>
>> All the assertions pass. I believe this covers all the conditions from
>> the strscpy_pad docstring.
>>
>> Reviewed-by: Daniel Axtens <d...@axtens.net>
>
> Thanks.
>
> I'll also drop the explicit nul termination in patch 2, which is a
> leftover from when I was using strncpy().
I guess you can ignore my other email questioning this.
-Tyrel
>
> cheers
>
