>From what I've learned building my own XDP loader, it seems like the kernel only takes a bock of eBPF instructions. For any references to maps, the instructions need to have been "fixed up" (if they came from a source like an elf file) to appropriately reference the file descriptors for any maps. As far as I can tell, those file descriptors are the userspace file descriptors for the maps in the loading program > The samples and test cases have examples showing how user space > programs can pin maps and get pinned maps as FDs. However, how would > one access a user-space created pinned map from kernel space, without > having to statically have a 'maps' section defined (and depend on the > elf loader)? You should be able to write a small userspace program that opens the pinned maps and uses those file descriptors to create or fixup an eBPF program from any source (elf or not), so long as you have a way to tell which instructions need to be fixed up. (ELF puts this information into the relocation sections.) samples/bpf/bpf_load.c has an example of how to do the fixing up using the relocation information from an elf file. Take a look at the parse_relo_and_apply() function for how to adjust the eBPF instructions. --Zvi
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