Commit 2353ecc6 authored Feb 05, 2019 by Björn Töpel Committed by Daniel Borkmann Feb 05, 2019

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>

parent 31de3897

arch/riscv/Kconfig

+1 −0

Original line number	Diff line number	Diff line
		@@ -49,6 +49,7 @@ config RISCV
		select RISCV_TIMER
		select GENERIC_IRQ_MULTI_HANDLER
		select ARCH_HAS_PTE_SPECIAL
		select HAVE_EBPF_JIT if 64BIT

		config MMU
		def_bool y

arch/riscv/Makefile

+1 −1

Original line number	Diff line number	Diff line
		@@ -77,7 +77,7 @@ KBUILD_IMAGE := $(boot)/Image.gz

		head-y := arch/riscv/kernel/head.o

		core-y += arch/riscv/kernel/ arch/riscv/mm/
		core-y += arch/riscv/kernel/ arch/riscv/mm/ arch/riscv/net/

		libs-y += arch/riscv/lib/

arch/riscv/net/Makefile

0 → 100644

+1 −0

Original line number	Diff line number	Diff line
		obj-$(CONFIG_BPF_JIT) += bpf_jit_comp.o

arch/riscv/net/bpf_jit_comp.c

0 → 100644

+1602 −0

File added.

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