netdev - [PATCH bpf-next 0/3] nfp: bpf: complete shift supports on NFP JIT

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Message-Id: <20180518191211.18670-1-jakub.kicinski@netronome.com>
Date:   Fri, 18 May 2018 12:12:08 -0700
From:   Jakub Kicinski <jakub.kicinski@...ronome.com>
To:     alexei.starovoitov@...il.com, daniel@...earbox.net
Cc:     oss-drivers@...ronome.com, netdev@...r.kernel.org,
        Jakub Kicinski <jakub.kicinski@...ronome.com>
Subject: [PATCH bpf-next 0/3] nfp: bpf: complete shift supports on NFP JIT

Jiong says:

NFP eBPF JIT is missing logic indirect shifts (both left and right) and
arithmetic right shift (both indirect shift and shift by constant).

This patch adds support for them.

For indirect shifts, shift amount is not specified as constant, NFP needs
to get the shift amount through the low 5 bits of source A operand in
PREV_ALU, therefore extra instructions are needed compared with shifts by
constants.

Because NFP is 32-bit, so we are using register pair for 64-bit shifts and
therefore would need different instruction sequences depending on whether
shift amount is less than 32 or not.

NFP branch-on-bit-test instruction emitter is added by this patch set and
is used for efficient runtime check on shift amount. We'd think the shift
amount is less than 32 if bit 5 is clear and greater or equal then 32
otherwise. Shift amount is greater than or equal to 64 will result in
undefined behavior.

This patch also use range info to avoid generating unnecessary runtime code
if we are certain shift amount is less than 32 or not.

Jiong Wang (3):
  nfp: bpf: support logic indirect shifts (BPF_[L|R]SH | BPF_X)
  nfp: bpf: support arithmetic right shift by constant (BPF_ARSH |
    BPF_K)
  nfp: bpf: support arithmetic indirect right shift (BPF_ARSH | BPF_X)

 drivers/net/ethernet/netronome/nfp/bpf/jit.c  | 410 ++++++++++++++++--
 drivers/net/ethernet/netronome/nfp/bpf/main.h |  28 ++
 .../net/ethernet/netronome/nfp/bpf/offload.c  |   2 +
 .../net/ethernet/netronome/nfp/bpf/verifier.c |   8 +
 drivers/net/ethernet/netronome/nfp/nfp_asm.h  |  18 +-
 5 files changed, 435 insertions(+), 31 deletions(-)

-- 
2.17.0