On Mon, 2019-12-09 at 16:06 -0800, James Bottomley wrote:
> +/**
> + * asn1_encode_integer - encode positive integer to ASN.1
> + * @_data: pointer to the pointer to the data
> + * @integer: integer to be encoded
> + * @len: length of buffer
> + *
> + * This is a simplified encoder: it only currently does
> + * positive integers, but it should be simple enough to add the
> + * negative case if a use comes along.
> + */
> +void asn1_encode_integer(unsigned char **_data, s64 integer, int len)
> +{
> + unsigned char *data = *_data, *d = &data[2];
> + int i;
> + bool found = false;
> +
> + if (WARN(integer < 0,
> + "BUG: asn1_encode_integer only supports positive integers"))
> + return;
> +
> + if (WARN(len < 3,
> + "BUG: buffer for integers must have at least 3 bytes"))
> + return;
> +
> + len =- 2;
> +
> + data[0] = _tag(UNIV, PRIM, INT);
> + if (integer == 0) {
> + *d++ = 0;
> + goto out;
> + }
> + for (i = sizeof(integer); i > 0 ; i--) {
> + int byte = integer >> (8*(i-1));
> +
> + if (!found && byte == 0)
> + continue;
> + found = true;
> + if (byte & 0x80) {
> + /*
> + * no check needed here, we already know we
> + * have len >= 1
> + */
> + *d++ = 0;
> + len--;
> + }
> + if (WARN(len == 0,
> + "BUG buffer too short in asn1_encode_integer"))
> + return;
> + *d++ = byte;
> + len--;
> + }
> + out:
> + data[1] = d - data - 2;
> + *_data = d;
> +}
> +EXPORT_SYMBOL_GPL(asn1_encode_integer);
Didn't you say you were going to make it return an error when it ran
out of space or was asked to encode a negative number?
There are other encoding functions which you haven't yet added the
buffer length field to, and they'll want to be able to return -ENOSPC
too.
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