On Mon, Feb 01, 2021, Dave Hansen wrote: > On 1/31/21 9:40 PM, Kai Huang wrote: > >>> - ret = sgx_drv_init(); > >>> + /* Success if the native *or* virtual EPC driver initialized cleanly. */ > >>> + ret = !!sgx_drv_init() & !!sgx_vepc_init(); > >> If would create more dumb code and just add > >> > >> ret = sgx_vepc_init() > >> if (ret) > >> goto err_kthread; > > Jarkko, I'm not sure I understand this suggestion. > > > Do you mean you want below? > > > > ret = sgx_drv_init(); > > ret = sgx_vepc_init(); > > if (ret) > > goto err_kthread; > > > > This was Sean's original code, but Dave didn't like it. The problem is it's wrong. That snippet would incorrectly bail if drv_init() succeeds but vepc_init() fails. The alternative to the bitwise AND is to snapshot the result in two separate variables: ret = sgx_drv_init(); ret2 = sgx_vepc_init(); if (ret && ret2) goto err_kthread; or check the return from drv_init() _after_ vepc_init(): ret = sgx_drv_init(); if (sgx_vepc_init() && ret) goto err_kthread; As evidenced by this thread, the behavior is subtle and easy to get wrong. I deliberately chose the option that was the weirdest specifically to reduce the probability of someone incorrectly "cleaning up" the code. > Are you sure? I remember the !!&!! abomination being Sean's doing. :) Yep! That 100% functionally correct horror is my doing. > > Sean/Dave, > > > > Please let me know which way you prefer. > > Kai, I don't really know you are saying here. In the end, > sgx_vepc_init() has to run regardless of whether sgx_drv_init() is > successful or not. Also, we only want to 'goto err_kthraed' if *BOTH* > fail. The code you have above will, for instance, 'goto err_kthread' if > sgx_drv_init() succeeds but sgx_vepc_init() fails. It entirely > disregards the sgx_drv_init() error code.
