Messages in this thread |  | | Date | Wed, 18 Apr 2018 17:49:09 +0800 | From | Wang YanQing <> | Subject | Re: [PATCH] bpf, x86_32: add eBPF JIT compiler for ia32 (x86_32) |
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On Wed, Apr 18, 2018 at 05:31:18PM +0800, Wang YanQing wrote: > The JIT compiler emits ia32 bit instructions. Currently, It supports > eBPF only. Classic BPF is supported because of the conversion by BPF core. > > Almost all instructions from eBPF ISA supported except the following: > BPF_ALU64 | BPF_DIV | BPF_K > BPF_ALU64 | BPF_DIV | BPF_X > BPF_ALU64 | BPF_MOD | BPF_K > BPF_ALU64 | BPF_MOD | BPF_X > BPF_STX | BPF_XADD | BPF_W > BPF_STX | BPF_XADD | BPF_DW > > It doesn't support BPF_JMP|BPF_CALL with BPF_PSEUDO_CALL too. > > IA32 has few general purpose registers, EAX|EDX|ECX|EBX|ESI|EDI, > and for these six registers, we can't treat all of them as real > general purpose registers: > MUL instructions need EAX:EDX, shift instructions need ECX, ESI|EDI > for string manipulation instructions. > > So I decide to use stack to emulate all eBPF 64 registers, this will > simplify the implementation very much, because we don't need to face > the flexible memory address modes on ia32, for example, we don't need > to write below codes for one BPF_ADD instruction: > if (src_reg is a register && dst_reg is a register) > { > //one instruction encoding for ADD instruction > } else if (only src is a register) > { > //another different instruction encoding for ADD instruction > } else if (only dst is a register) > { > //another different instruction encoding for ADD instruction > } else > { > //src and dst are all on stack. > //another different instruction encoding for ADD instruction > } > > If you think above if-else-else-else isn't so painful, try to think > it for BPF_ALU64|BPF_*SHIFT* instruction:) > > Tested on my PC(Intel(R) Core(TM) i5-5200U CPU) and virtualbox. > > Testing results on i5-5200U: > > 1) test_bpf: Summary: 349 PASSED, 0 FAILED, [319/341 JIT'ed] > 2) test_progs: Summary: 81 PASSED, 2 FAILED. > test_progs report "libbpf: incorrect bpf_call opcode" for > test_l4lb_noinline and test_xdp_noinline, because there is > no llvm-6.0 on my machine, and current implementation doesn't > support BPF_CALL, so I think we can ignore it. > 3) test_lpm: OK > 4) test_lru_map: OK > 5) test_verifier: Summary: 823 PASSED, 5 FAILED > test_verifier report "invalid bpf_context access off=68 size=1/2/4/8" > for all the 5 FAILED testcases, and test_verifier report them when > we turn off the jit, so I think the jit can do nothing to fix them. > > Above tests are all done with following flags enabled discretely: > bpf_jit_enable=1 and bpf_jit_harden=2 > > Below are some numbers for this jit implementation: > Note: > I run test_progs 100 times in loop for every testcase, the numbers > are in format: total/times=avg. The numbers that test_bpf report > almost show the same relation. > > a:jit_enable=0 and jit_harden=0 b:jit_enable=1 and jit_harden=0 > test_pkt_access:PASS:ipv4:15622/100=156 test_pkt_access:PASS:ipv4:10057/100=100 > test_pkt_access:PASS:ipv6:9130/100=91 test_pkt_access:PASS:ipv6:5055/100=50 > test_xdp:PASS:ipv4:240198/100=2401 test_xdp:PASS:ipv4:145945/100=1459 > test_xdp:PASS:ipv6:137326/100=1373 test_xdp:PASS:ipv6:67337/100=673 > test_l4lb:PASS:ipv4:61100/100=611 test_l4lb:PASS:ipv4:38137/100=381 > test_l4lb:PASS:ipv6:101000/100=1010 test_l4lb:PASS:ipv6:57779/100=577 > > c:jit_enable=0 and jit_harden=2 b:jit_enable=1 and jit_harden=2 > test_pkt_access:PASS:ipv4:15214/100=152 test_pkt_access:PASS:ipv4:12650/100=126 > test_pkt_access:PASS:ipv6:9132/100=91 test_pkt_access:PASS:ipv6:7074/100=70 > test_xdp:PASS:ipv4:237252/100=2372 test_xdp:PASS:ipv4:147211/100=1472 > test_xdp:PASS:ipv6:135977/100=1359 test_xdp:PASS:ipv6:85783/100=857 > test_l4lb:PASS:ipv4:61324/100=613 test_l4lb:PASS:ipv4:53222/100=532 > test_l4lb:PASS:ipv6:100833/100=1008 test_l4lb:PASS:ipv6:76322/100=763 > > Yes, the numbers are pretty without turn on jit_harden, if we want to speedup > jit_harden, then we need to move BPF_REG_AX to *real* register instead of stack > emulation, but If we do it, we need to face all the pain I describe above. We > can do it in next step. > > See Documentation/networking/filter.txt for more information. > > Signed-off-by: Wang YanQing <udknight@gmail.com> > --- > arch/x86/Kconfig | 2 +- > arch/x86/include/asm/nospec-branch.h | 26 +- > arch/x86/net/Makefile | 10 +- > arch/x86/net/bpf_jit32.S | 147 +++ > arch/x86/net/bpf_jit_comp32.c | 2239 ++++++++++++++++++++++++++++++++++ > 5 files changed, 2419 insertions(+), 5 deletions(-) > create mode 100644 arch/x86/net/bpf_jit32.S > create mode 100644 arch/x86/net/bpf_jit_comp32.c Add CC to davem@davemloft.net
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