On 2/5/19 2:50 PM, Rick Edgecombe wrote: > This introduces a new capability for BPF program JIT's to be located in > vmalloc > space on x86_64. This can serve as a backup area for CONFIG_BPF_JIT_ALWAYS_ON > in > case an unprivileged app uses all of the module space allowed by > bpf_jit_limit. > > In order to allow for calls from the increased distance of vmalloc from > kernel/module space, relative calls are emitted as full indirect calls if the > maximum relative call distance is exceeded. So the resulting performance of > call > BPF instructions in this case is similar to the BPF interpreter.
If I read this correctly the patches introduce retpoline overhead to direct function call because JITed progs are more than 32-bit apart and they're far away only because of dubious security concern ? Nack.
