bpf, x64: save 5 bytes in prologue when ebpf insns came from cbpf

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While it's rather cumbersome to reduce prologue for cBPF->eBPF
migrations wrt spill/fill for r15 which is callee saved register
due to bpf_error path in bpf_jit.S that is both used by migrations
as well as native eBPF, we can still trivially save 5 bytes in
prologue for the former since tail calls can never be used there.
cBPF->eBPF migrations also have their own custom prologue in BPF
asm that xors A and X reg anyway, so it's fine we skip this here.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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Daniel Borkmann 2018-02-24 01:08:02 +01:00 • committed by Alexei Starovoitov

parent 4c38e2f386

commit 0869175220

1 changed files with 16 additions and 12 deletions

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arch/x86/net/bpf_jit_comp.c

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