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>
Kind regards,
Daniel
> static int __init prom_strncmp(const char *cs, const char *ct, size_t count)
> @@ -2701,7 +2719,7 @@ static void __init flatten_device_tree(void)
>
> /* Add "phandle" in there, we'll need it */
> namep = make_room(&mem_start, &mem_end, 16, 1);
> - prom_strcpy(namep, "phandle");
> + prom_strscpy_pad(namep, "phandle", sizeof("phandle"));
> mem_start = (unsigned long)namep + prom_strlen(namep) + 1;
>
> /* Build string array */
> --
> 2.25.1
