Once the JITed images for each function in a multi-function program
are generated after the first three JIT passes, we only need to fix
the target address for the branch instruction corresponding to each
bpf-to-bpf function call.
This introduces the following optimizations for reducing the work
done by the JIT compiler when handling multi-function programs:
[1] Instead of doing two extra passes to fix the bpf function calls,
do just one as that would be sufficient.
[2] During the extra pass, only overwrite the instruction sequences
for the bpf-to-bpf function calls as everything else would still
remain exactly the same. This also reduces the number of writes
to the JITed image.
[3] Do not regenerate the prologue and the epilogue during the extra
pass as that would be redundant.
Signed-off-by: Sandipan Das <sandipan@linux.ibm.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
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