Le lundi 18 juillet 2011 à 17:50 +1000, Matt Evans a écrit : > An implementation of a code generator for BPF programs to speed up packet > filtering on PPC64, inspired by Eric Dumazet's x86-64 version. > > Filter code is generated as an ABI-compliant function in module_alloc()'d mem > with stackframe & prologue/epilogue generated if required (simple filters > don't > need anything more than an li/blr). The filter's local variables, M[], live > in > registers. Supports all BPF opcodes, although "complicated" loads from > negative > packet offsets (e.g. SKF_LL_OFF) are not yet supported. > > There are a couple of further optimisations left for future work; many-pass > assembly with branch-reach reduction and a register allocator to push M[] > variables into volatile registers would improve the code quality further. > > This currently supports big-endian 64-bit PowerPC only (but is fairly simple > to port to PPC32 or LE!). > > Enabled in the same way as x86-64: > > echo 1 > /proc/sys/net/core/bpf_jit_enable > > Or, enabled with extra debug output: > > echo 2 > /proc/sys/net/core/bpf_jit_enable > > Signed-off-by: Matt Evans <[email protected]> > --- > > Since the RFC post, this has incorporated the bugfixes/tidies from review > plus a > couple more found in further testing, plus some general/comment tidies.
Hi Matt A small note about SEEN_XREG usage in PPC against x86_64 : In x86_64, XREG is stored in EBX : I had to save/restore it in function prologue epilogue. And set it to zero in prologue to avoid leak of kernel information. In PPC, you chose a scratch register, so you only have to zero it in function prologue, if X is ever read. So in PPC SEEN_XREG only is to be set of X is read, not if written. So you dont have to set SEEN_XREG bit in this part : > + case BPF_S_MISC_TAX: /* X = A */ > + ctx->seen |= SEEN_XREG; > + PPC_MR(r_X, r_A); > + break; and in this part : > + case BPF_S_LDX_IMM: /* X = K */ > + ctx->seen |= SEEN_XREG; > + PPC_LI32(r_X, K); > + break; and : > + case BPF_S_LDX_MEM: /* X = mem[K] */ > + PPC_MR(r_X, r_M + (K & 0xf)); > + ctx->seen |= SEEN_XREG | SEEN_MEM | (1<<(K & 0xf)); > + break; and : > + case BPF_S_LDX_W_LEN: /* X = skb->len; */ > + ctx->seen |= SEEN_XREG; > + PPC_LWZ_OFFS(r_X, r_skb, offsetof(struct sk_buff, len)); > + break; > + _______________________________________________ Linuxppc-dev mailing list [email protected] https://lists.ozlabs.org/listinfo/linuxppc-dev
