Linux doesn't exist in the 1980s, Linus started this work in the 1990s.

But yes, the string slice type should have existed in C89 and it's very obvious from here that not having something of this sort - maybe what Rust would call &[u8] the reference to a slice of bytes - was a big problem for C.

The correct way to represent this is what's called a "fat pointer". A pair of values, one is a conventional "thin" pointer to the start of the slice, and the other is a count. Your register pressure increases in the compiler backend but problems are significantly reduced because you have fewer bounds misses.