On Mon, Sep 02, 2024 at 03:31:43PM +0100, Mark Rutland wrote:
> ssize_t __kernel_getrandom(void *buffer, size_t len, unsigned int flags,
> void *opaque_state, size_t opaque_len)
> {
> if (alternative_has_cap_likely(ARM64_HAS_FPSIMD)) {
> return __cvdso_getrandom(buffer, len, flags,
> opaque_state, opaque_len);
> }
>
> if (unlikely(opaque_len == ~0UL && !buffer && !len && !flags))
> return -ENOSYS;
>
> return getrandom_syscall(buffer, len, flags);
> }
>
> ... though the conditions for returning -ENOSYS look very odd to me; why
> do we care about fast-pathing that specific case rather than forwarding
> that to the kernel, and does __cvdso_getrandom() handle that correctly?
Adhemerval's code here is fine and correct. The opaque_len==~0UL thing
is a special vDSO case for getting the param struct back, not something
related to the kernel. See __cvdso_getrandom_data() for details.
