Re: listening service without MMU?
On 2022-06-24 11:26 am, johnea wrote: I've run across a number of other references since that timeframe that indicate that dropbear can run on no-MMU platforms using uClibc. Searching hasn't really led to a conclusive answer. So, could you please confirm: Can dropbear run as a listening service on Cortex-M3 with no-MMU? Previously I would say no - usually it would need to run from inetd that executes a separate dropbear server process for each connection. That is required because on a MMUless system the normal fork() doesn't create separate memory spaces for each program, so they interfere with each other. But! In Dropbear 2022.82 it was changed to re-execute itself [1], so it is possible that it would work OK on a MMUless system. You could see if that works - there might be other assumptions that I have missed. Make sure you try a few concurrent connections. Cheers, Matt [1] - Dropbear now re-executes itself rather than just forking for each connection (only on Linux). This allows ASLR to randomise address space for each connection as a security mitigation. It should not have any visible impact - if there are any performance impacts in the wild please report it.
listening service without MMU?
Hello, I'm building dropbear using the buildroot tool, for a SmartFusion2 Cortex-M3 with no MMU. I find in the config file for dropbear on buildroot: ./buildroot/package/dropbear/dropbear.mk ifeq ($(BR2_USE_MMU),y) define DROPBEAR_INSTALL_INIT_SYSV $(INSTALL) -D -m 755 package/dropbear/S50dropbear \ $(TARGET_DIR)/etc/init.d/S50dropbear endef else define DROPBEAR_DISABLE_STANDALONE echo '#define NON_INETD_MODE 0' >> $(@D)/localoptions.h endef DROPBEAR_POST_EXTRACT_HOOKS += DROPBEAR_DISABLE_STANDALONE endif Which disables the standalone NON_INETD_MODE. In searching through the history of the buildroot git repository, this change seems to have been introduced in about 2013. I've run across a number of other references since that timeframe that indicate that dropbear can run on no-MMU platforms using uClibc. Searching hasn't really led to a conclusive answer. So, could you please confirm: Can dropbear run as a listening service on Cortex-M3 with no-MMU? Are there patches that can enable this? Sorry if I'm asking a question that I should have been able to find an answer to. Thank You for your reply... John A dropb...@johnea.net 2022-06-23
