On 04/17/2017 05:38 AM, David Miller wrote:
There are a bunch of things I want to do still, and I know that I have
to attend to sparc32 more cleanly, but I wanted to post this now that
I have it passing the BPF testsuite completely:
[24174.315421] test_bpf: Summary: 305 PASSED, 0 FAILED, [297/297 JIT'ed]
Awesome, thanks for working on it! :)
Only major unimplemented feature is tail calls, which I am very sure I
can do simply but until something easy to use like test_bpf can
exercise it I probably won't do it.
There is samples/bpf/sockex3_kern.c, which exercises it. To
run it, it would be (clang/llvm needed due to BPF backend not
available in gcc):
# cd samples/bpf
# make
# ./sockex3
IP src.port -> dst.port bytes packets
127.0.0.1.12865 -> 127.0.0.1.49711 148 2
127.0.0.1.49711 -> 127.0.0.1.12865 108 2
[...]
Inside parse_eth_proto(), it will do tail calls based on the
eth protocol. Over time, we'll move such C based tests over to
tools/testing/selftests/bpf/.
From my side, what I need to do to turn this into a non-RFC is to sort
out sparc32. My plan is to take the existing cBPF JIT, rip out all of
the sparc64 specific bits, and have sparc32 use that. And do it in
such a way that git bisection is not broken.
Makes sense. That would follow the same model as ppc32/64.
As a future optimization I'd like to add support for emitting cbcond
instructions on newer chips.
This implementation grabs a register window all the time, and we could
avoid that and use a leaf function in certatin situations. The
register layout is also not optimal, and one side effect is that we
have to move the argument registers over during function calls.
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[...]
+/* Map BPF registers to SPARC registers */
+static const int bpf2sparc[] = {
+ /* return value from in-kernel function, and exit value from eBPF */
+ [BPF_REG_0] = I5,
+
+ /* arguments from eBPF program to in-kernel function */
+ [BPF_REG_1] = I0,
+ [BPF_REG_2] = I1,
+ [BPF_REG_3] = I2,
+ [BPF_REG_4] = I3,
+ [BPF_REG_5] = I4,
+
+ /* callee saved registers that in-kernel function will preserve */
+ [BPF_REG_6] = L0,
+ [BPF_REG_7] = L1,
+ [BPF_REG_8] = L2,
+ [BPF_REG_9] = L3,
+
+ /* read-only frame pointer to access stack */
+ [BPF_REG_FP] = FP,
On a quick initial glance, you also need to map BPF_REG_AX. If
I understand the convention correctly, you could use L7 for that.
You can test for it through tools/testing/selftests/bpf/test_kmod.sh
which exercises the test_bpf.ko under various sysctl combinations as
part of the BPF selftest suite.
+ /* temporary register for internal BPF JIT */
+ [TMP_REG_1] = G1,
+ [TMP_REG_2] = G3,
+ [TMP_REG_3] = L6,
+
+ [SKB_HLEN_REG] = L4,
+ [SKB_DATA_REG] = L5,
+};
Thanks a lot!
Daniel
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