Hi Ben, Vladimir,


*dusts off very thick PPC cobwebs*  Sorry for the delay as I'm =
travelling, didn't get to this until now.

On 02/09/2013, at 9:45 PM, Benjamin Herrenschmidt wrote:

On Mon, 2013-09-02 at 19:48 +0200, Vladimir Murzin wrote:

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Ping
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On Wed, Aug 28, 2013 at 02:49:52AM +0400, Vladimir Murzin wrote:

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commit b6069a9570 (filter: add MOD operation) added generic
support for modulus operation in BPF.
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Sorry, nobody got a chance to review that yet. Unfortunately Matt
doesn't work for us anymore and none of us has experience with the
BPF code, so somebody (possibly me) will need to spend a bit of time
figuring it out before verifying that is correct.
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Do you have a test case/suite by any chance ?
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Ben.
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This patch brings JIT support for PPC64
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Signed-off-by: Vladimir Murzin <redacted>
---
arch/powerpc/net/bpf_jit_comp.c | 22 ++++++++++++++++++++++
1 file changed, 22 insertions(+)
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diff --git a/arch/powerpc/net/bpf_jit_comp.c =

b/arch/powerpc/net/bpf_jit_comp.c

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index bf56e33..96f24dc 100644

--- a/arch/powerpc/net/bpf_jit_comp.c
+++ b/arch/powerpc/net/bpf_jit_comp.c

@@ -193,6 +193,28 @@ static int bpf_jit_build_body(struct sk_filter =

*fp, u32 *image,

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				PPC_MUL(r_A, r_A, r_scratch1);
			}
			break;
+		case BPF_S_ALU_MOD_X: /* A %=3D X; */
+			ctx->seen |=3D SEEN_XREG;
+			PPC_CMPWI(r_X, 0);
+			if (ctx->pc_ret0 !=3D -1) {
+				PPC_BCC(COND_EQ, addrs[ctx->pc_ret0]);
+			} else {
+				PPC_BCC_SHORT(COND_NE, (ctx->idx*4)+12);
+				PPC_LI(r_ret, 0);
+				PPC_JMP(exit_addr);
+			}
+			PPC_DIVWU(r_scratch1, r_A, r_X);
+			PPC_MUL(r_scratch1, r_X, r_scratch1);
+			PPC_SUB(r_A, r_A, r_scratch1);
+			break;

Without having compiled & tested this, it looks fine to me (especially =
with the corrected DIVWU opcode in the other patch, oops...).

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+		case BPF_S_ALU_MOD_K: /* A %=3D K; */
+#define r_scratch2 (r_scratch1 + 1)
+			PPC_LI32(r_scratch2, K);
+			PPC_DIVWU(r_scratch1, r_A, r_scratch2);
+			PPC_MUL(r_scratch1, r_scratch2, r_scratch1);
+			PPC_SUB(r_A, r_A, r_scratch1);
+#undef r_scratch2
+			break;

If you need another scratch register, it should really be defined in =
bpf_jit.h instead.

Once you define r_scratch2 in there,

Acked-by: Matt Evans <redacted>


Thanks!


Matt

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		case BPF_S_ALU_DIV_X: /* A /=3D X; */
			ctx->seen |=3D SEEN_XREG;
			PPC_CMPWI(r_X, 0);
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1.8.1.5
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