bpf, riscv: add BPF JIT for RV64G
authorBjörn Töpel <bjorn.topel@gmail.com>
Tue, 5 Feb 2019 12:41:22 +0000 (13:41 +0100)
committerDaniel Borkmann <daniel@iogearbox.net>
Tue, 5 Feb 2019 15:56:10 +0000 (16:56 +0100)
commit2353ecc6f91fd15b893fa01bf85a1c7a823ee4f2
tree309a4f88c91f36813f16d88cc8627a737779b4fe
parent31de389707c8842ce71eaa8eff1eb74a43d5ef30
bpf, riscv: add BPF JIT for RV64G

This commit adds a BPF JIT for RV64G.

The JIT is a two-pass JIT, and has a dynamic prolog/epilogue (similar
to the MIPS64 BPF JIT) instead of static ones (e.g. x86_64).

At the moment the RISC-V Linux port does not support
CONFIG_HAVE_KPROBES, which means that CONFIG_BPF_EVENTS is not
supported. Thus, no tests involving BPF_PROG_TYPE_TRACEPOINT,
BPF_PROG_TYPE_PERF_EVENT, BPF_PROG_TYPE_KPROBE and
BPF_PROG_TYPE_RAW_TRACEPOINT passes.

The implementation does not support "far branching" (>4KiB).

Test results:
  # modprobe test_bpf
  test_bpf: Summary: 378 PASSED, 0 FAILED, [366/366 JIT'ed]

  # echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
  # ./test_verifier
  ...
  Summary: 761 PASSED, 507 SKIPPED, 2 FAILED

Note that "test_verifier" was run with one build with
CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y and one without, otherwise
many of the the tests that require unaligned access were skipped.

CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS=y:
  # echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
  # ./test_verifier | grep -c 'NOTE.*unknown align'
  0

No CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS:
  # echo 1 > /proc/sys/kernel/unprivileged_bpf_disabled
  # ./test_verifier | grep -c 'NOTE.*unknown align'
  59

The two failing test_verifier tests are:
  "ld_abs: vlan + abs, test 1"
  "ld_abs: jump around ld_abs"

This is due to that "far branching" involved in those tests.

All tests where done on QEMU (QEMU emulator version 3.1.50
(v3.1.0-688-g8ae951fbc106)).

Signed-off-by: Björn Töpel <bjorn.topel@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
arch/riscv/Kconfig
arch/riscv/Makefile
arch/riscv/net/Makefile [new file with mode: 0644]
arch/riscv/net/bpf_jit_comp.c [new file with mode: 0644]