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net: filter: BPF 'JIT' compiler for PPC64
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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 <matt@ozlabs.org>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Matt Evans authored and David S. Miller committed Jul 21, 2011
1 parent 3aeb7d2 commit 0ca87f0
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1 change: 1 addition & 0 deletions arch/powerpc/Kconfig
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Expand Up @@ -134,6 +134,7 @@ config PPC
select GENERIC_IRQ_SHOW_LEVEL
select HAVE_RCU_TABLE_FREE if SMP
select HAVE_SYSCALL_TRACEPOINTS
select HAVE_BPF_JIT if PPC64

config EARLY_PRINTK
bool
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3 changes: 2 additions & 1 deletion arch/powerpc/Makefile
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Expand Up @@ -154,7 +154,8 @@ core-y += arch/powerpc/kernel/ \
arch/powerpc/lib/ \
arch/powerpc/sysdev/ \
arch/powerpc/platforms/ \
arch/powerpc/math-emu/
arch/powerpc/math-emu/ \
arch/powerpc/net/
core-$(CONFIG_XMON) += arch/powerpc/xmon/
core-$(CONFIG_KVM) += arch/powerpc/kvm/

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40 changes: 40 additions & 0 deletions arch/powerpc/include/asm/ppc-opcode.h
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Expand Up @@ -71,6 +71,42 @@
#define PPC_INST_ERATSX 0x7c000126
#define PPC_INST_ERATSX_DOT 0x7c000127

/* Misc instructions for BPF compiler */
#define PPC_INST_LD 0xe8000000
#define PPC_INST_LHZ 0xa0000000
#define PPC_INST_LWZ 0x80000000
#define PPC_INST_STD 0xf8000000
#define PPC_INST_STDU 0xf8000001
#define PPC_INST_MFLR 0x7c0802a6
#define PPC_INST_MTLR 0x7c0803a6
#define PPC_INST_CMPWI 0x2c000000
#define PPC_INST_CMPDI 0x2c200000
#define PPC_INST_CMPLW 0x7c000040
#define PPC_INST_CMPLWI 0x28000000
#define PPC_INST_ADDI 0x38000000
#define PPC_INST_ADDIS 0x3c000000
#define PPC_INST_ADD 0x7c000214
#define PPC_INST_SUB 0x7c000050
#define PPC_INST_BLR 0x4e800020
#define PPC_INST_BLRL 0x4e800021
#define PPC_INST_MULLW 0x7c0001d6
#define PPC_INST_MULHWU 0x7c000016
#define PPC_INST_MULLI 0x1c000000
#define PPC_INST_DIVWU 0x7c0003d6
#define PPC_INST_RLWINM 0x54000000
#define PPC_INST_RLDICR 0x78000004
#define PPC_INST_SLW 0x7c000030
#define PPC_INST_SRW 0x7c000430
#define PPC_INST_AND 0x7c000038
#define PPC_INST_ANDDOT 0x7c000039
#define PPC_INST_OR 0x7c000378
#define PPC_INST_ANDI 0x70000000
#define PPC_INST_ORI 0x60000000
#define PPC_INST_ORIS 0x64000000
#define PPC_INST_NEG 0x7c0000d0
#define PPC_INST_BRANCH 0x48000000
#define PPC_INST_BRANCH_COND 0x40800000

/* macros to insert fields into opcodes */
#define __PPC_RA(a) (((a) & 0x1f) << 16)
#define __PPC_RB(b) (((b) & 0x1f) << 11)
Expand All @@ -83,6 +119,10 @@
#define __PPC_T_TLB(t) (((t) & 0x3) << 21)
#define __PPC_WC(w) (((w) & 0x3) << 21)
#define __PPC_WS(w) (((w) & 0x1f) << 11)
#define __PPC_SH(s) __PPC_WS(s)
#define __PPC_MB(s) (((s) & 0x1f) << 6)
#define __PPC_ME(s) (((s) & 0x1f) << 1)
#define __PPC_BI(s) (((s) & 0x1f) << 16)

/*
* Only use the larx hint bit on 64bit CPUs. e500v1/v2 based CPUs will treat a
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4 changes: 4 additions & 0 deletions arch/powerpc/net/Makefile
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@@ -0,0 +1,4 @@
#
# Arch-specific network modules
#
obj-$(CONFIG_BPF_JIT) += bpf_jit_64.o bpf_jit_comp.o
227 changes: 227 additions & 0 deletions arch/powerpc/net/bpf_jit.h
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/* bpf_jit.h: BPF JIT compiler for PPC64
*
* Copyright 2011 Matt Evans <matt@ozlabs.org>, IBM Corporation
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; version 2
* of the License.
*/
#ifndef _BPF_JIT_H
#define _BPF_JIT_H

#define BPF_PPC_STACK_LOCALS 32
#define BPF_PPC_STACK_BASIC (48+64)
#define BPF_PPC_STACK_SAVE (18*8)
#define BPF_PPC_STACKFRAME (BPF_PPC_STACK_BASIC+BPF_PPC_STACK_LOCALS+ \
BPF_PPC_STACK_SAVE)
#define BPF_PPC_SLOWPATH_FRAME (48+64)

/*
* Generated code register usage:
*
* As normal PPC C ABI (e.g. r1=sp, r2=TOC), with:
*
* skb r3 (Entry parameter)
* A register r4
* X register r5
* addr param r6
* r7-r10 scratch
* skb->data r14
* skb headlen r15 (skb->len - skb->data_len)
* m[0] r16
* m[...] ...
* m[15] r31
*/
#define r_skb 3
#define r_ret 3
#define r_A 4
#define r_X 5
#define r_addr 6
#define r_scratch1 7
#define r_D 14
#define r_HL 15
#define r_M 16

#ifndef __ASSEMBLY__

/*
* Assembly helpers from arch/powerpc/net/bpf_jit.S:
*/
extern u8 sk_load_word[], sk_load_half[], sk_load_byte[], sk_load_byte_msh[];

#define FUNCTION_DESCR_SIZE 24

/*
* 16-bit immediate helper macros: HA() is for use with sign-extending instrs
* (e.g. LD, ADDI). If the bottom 16 bits is "-ve", add another bit into the
* top half to negate the effect (i.e. 0xffff + 1 = 0x(1)0000).
*/
#define IMM_H(i) ((uintptr_t)(i)>>16)
#define IMM_HA(i) (((uintptr_t)(i)>>16) + \
(((uintptr_t)(i) & 0x8000) >> 15))
#define IMM_L(i) ((uintptr_t)(i) & 0xffff)

#define PLANT_INSTR(d, idx, instr) \
do { if (d) { (d)[idx] = instr; } idx++; } while (0)
#define EMIT(instr) PLANT_INSTR(image, ctx->idx, instr)

#define PPC_NOP() EMIT(PPC_INST_NOP)
#define PPC_BLR() EMIT(PPC_INST_BLR)
#define PPC_BLRL() EMIT(PPC_INST_BLRL)
#define PPC_MTLR(r) EMIT(PPC_INST_MTLR | __PPC_RT(r))
#define PPC_ADDI(d, a, i) EMIT(PPC_INST_ADDI | __PPC_RT(d) | \
__PPC_RA(a) | IMM_L(i))
#define PPC_MR(d, a) PPC_OR(d, a, a)
#define PPC_LI(r, i) PPC_ADDI(r, 0, i)
#define PPC_ADDIS(d, a, i) EMIT(PPC_INST_ADDIS | \
__PPC_RS(d) | __PPC_RA(a) | IMM_L(i))
#define PPC_LIS(r, i) PPC_ADDIS(r, 0, i)
#define PPC_STD(r, base, i) EMIT(PPC_INST_STD | __PPC_RS(r) | \
__PPC_RA(base) | ((i) & 0xfffc))

#define PPC_LD(r, base, i) EMIT(PPC_INST_LD | __PPC_RT(r) | \
__PPC_RA(base) | IMM_L(i))
#define PPC_LWZ(r, base, i) EMIT(PPC_INST_LWZ | __PPC_RT(r) | \
__PPC_RA(base) | IMM_L(i))
#define PPC_LHZ(r, base, i) EMIT(PPC_INST_LHZ | __PPC_RT(r) | \
__PPC_RA(base) | IMM_L(i))
/* Convenience helpers for the above with 'far' offsets: */
#define PPC_LD_OFFS(r, base, i) do { if ((i) < 32768) PPC_LD(r, base, i); \
else { PPC_ADDIS(r, base, IMM_HA(i)); \
PPC_LD(r, r, IMM_L(i)); } } while(0)

#define PPC_LWZ_OFFS(r, base, i) do { if ((i) < 32768) PPC_LWZ(r, base, i); \
else { PPC_ADDIS(r, base, IMM_HA(i)); \
PPC_LWZ(r, r, IMM_L(i)); } } while(0)

#define PPC_LHZ_OFFS(r, base, i) do { if ((i) < 32768) PPC_LHZ(r, base, i); \
else { PPC_ADDIS(r, base, IMM_HA(i)); \
PPC_LHZ(r, r, IMM_L(i)); } } while(0)

#define PPC_CMPWI(a, i) EMIT(PPC_INST_CMPWI | __PPC_RA(a) | IMM_L(i))
#define PPC_CMPDI(a, i) EMIT(PPC_INST_CMPDI | __PPC_RA(a) | IMM_L(i))
#define PPC_CMPLWI(a, i) EMIT(PPC_INST_CMPLWI | __PPC_RA(a) | IMM_L(i))
#define PPC_CMPLW(a, b) EMIT(PPC_INST_CMPLW | __PPC_RA(a) | __PPC_RB(b))

#define PPC_SUB(d, a, b) EMIT(PPC_INST_SUB | __PPC_RT(d) | \
__PPC_RB(a) | __PPC_RA(b))
#define PPC_ADD(d, a, b) EMIT(PPC_INST_ADD | __PPC_RT(d) | \
__PPC_RA(a) | __PPC_RB(b))
#define PPC_MUL(d, a, b) EMIT(PPC_INST_MULLW | __PPC_RT(d) | \
__PPC_RA(a) | __PPC_RB(b))
#define PPC_MULHWU(d, a, b) EMIT(PPC_INST_MULHWU | __PPC_RT(d) | \
__PPC_RA(a) | __PPC_RB(b))
#define PPC_MULI(d, a, i) EMIT(PPC_INST_MULLI | __PPC_RT(d) | \
__PPC_RA(a) | IMM_L(i))
#define PPC_DIVWU(d, a, b) EMIT(PPC_INST_DIVWU | __PPC_RT(d) | \
__PPC_RA(a) | __PPC_RB(b))
#define PPC_AND(d, a, b) EMIT(PPC_INST_AND | __PPC_RA(d) | \
__PPC_RS(a) | __PPC_RB(b))
#define PPC_ANDI(d, a, i) EMIT(PPC_INST_ANDI | __PPC_RA(d) | \
__PPC_RS(a) | IMM_L(i))
#define PPC_AND_DOT(d, a, b) EMIT(PPC_INST_ANDDOT | __PPC_RA(d) | \
__PPC_RS(a) | __PPC_RB(b))
#define PPC_OR(d, a, b) EMIT(PPC_INST_OR | __PPC_RA(d) | \
__PPC_RS(a) | __PPC_RB(b))
#define PPC_ORI(d, a, i) EMIT(PPC_INST_ORI | __PPC_RA(d) | \
__PPC_RS(a) | IMM_L(i))
#define PPC_ORIS(d, a, i) EMIT(PPC_INST_ORIS | __PPC_RA(d) | \
__PPC_RS(a) | IMM_L(i))
#define PPC_SLW(d, a, s) EMIT(PPC_INST_SLW | __PPC_RA(d) | \
__PPC_RS(a) | __PPC_RB(s))
#define PPC_SRW(d, a, s) EMIT(PPC_INST_SRW | __PPC_RA(d) | \
__PPC_RS(a) | __PPC_RB(s))
/* slwi = rlwinm Rx, Ry, n, 0, 31-n */
#define PPC_SLWI(d, a, i) EMIT(PPC_INST_RLWINM | __PPC_RA(d) | \
__PPC_RS(a) | __PPC_SH(i) | \
__PPC_MB(0) | __PPC_ME(31-(i)))
/* srwi = rlwinm Rx, Ry, 32-n, n, 31 */
#define PPC_SRWI(d, a, i) EMIT(PPC_INST_RLWINM | __PPC_RA(d) | \
__PPC_RS(a) | __PPC_SH(32-(i)) | \
__PPC_MB(i) | __PPC_ME(31))
/* sldi = rldicr Rx, Ry, n, 63-n */
#define PPC_SLDI(d, a, i) EMIT(PPC_INST_RLDICR | __PPC_RA(d) | \
__PPC_RS(a) | __PPC_SH(i) | \
__PPC_MB(63-(i)) | (((i) & 0x20) >> 4))
#define PPC_NEG(d, a) EMIT(PPC_INST_NEG | __PPC_RT(d) | __PPC_RA(a))

/* Long jump; (unconditional 'branch') */
#define PPC_JMP(dest) EMIT(PPC_INST_BRANCH | \
(((dest) - (ctx->idx * 4)) & 0x03fffffc))
/* "cond" here covers BO:BI fields. */
#define PPC_BCC_SHORT(cond, dest) EMIT(PPC_INST_BRANCH_COND | \
(((cond) & 0x3ff) << 16) | \
(((dest) - (ctx->idx * 4)) & \
0xfffc))
#define PPC_LI32(d, i) do { PPC_LI(d, IMM_L(i)); \
if ((u32)(uintptr_t)(i) >= 32768) { \
PPC_ADDIS(d, d, IMM_HA(i)); \
} } while(0)
#define PPC_LI64(d, i) do { \
if (!((uintptr_t)(i) & 0xffffffff00000000ULL)) \
PPC_LI32(d, i); \
else { \
PPC_LIS(d, ((uintptr_t)(i) >> 48)); \
if ((uintptr_t)(i) & 0x0000ffff00000000ULL) \
PPC_ORI(d, d, \
((uintptr_t)(i) >> 32) & 0xffff); \
PPC_SLDI(d, d, 32); \
if ((uintptr_t)(i) & 0x00000000ffff0000ULL) \
PPC_ORIS(d, d, \
((uintptr_t)(i) >> 16) & 0xffff); \
if ((uintptr_t)(i) & 0x000000000000ffffULL) \
PPC_ORI(d, d, (uintptr_t)(i) & 0xffff); \
} } while (0);

static inline bool is_nearbranch(int offset)
{
return (offset < 32768) && (offset >= -32768);
}

/*
* The fly in the ointment of code size changing from pass to pass is
* avoided by padding the short branch case with a NOP. If code size differs
* with different branch reaches we will have the issue of code moving from
* one pass to the next and will need a few passes to converge on a stable
* state.
*/
#define PPC_BCC(cond, dest) do { \
if (is_nearbranch((dest) - (ctx->idx * 4))) { \
PPC_BCC_SHORT(cond, dest); \
PPC_NOP(); \
} else { \
/* Flip the 'T or F' bit to invert comparison */ \
PPC_BCC_SHORT(cond ^ COND_CMP_TRUE, (ctx->idx+2)*4); \
PPC_JMP(dest); \
} } while(0)

/* To create a branch condition, select a bit of cr0... */
#define CR0_LT 0
#define CR0_GT 1
#define CR0_EQ 2
/* ...and modify BO[3] */
#define COND_CMP_TRUE 0x100
#define COND_CMP_FALSE 0x000
/* Together, they make all required comparisons: */
#define COND_GT (CR0_GT | COND_CMP_TRUE)
#define COND_GE (CR0_LT | COND_CMP_FALSE)
#define COND_EQ (CR0_EQ | COND_CMP_TRUE)
#define COND_NE (CR0_EQ | COND_CMP_FALSE)
#define COND_LT (CR0_LT | COND_CMP_TRUE)

#define SEEN_DATAREF 0x10000 /* might call external helpers */
#define SEEN_XREG 0x20000 /* X reg is used */
#define SEEN_MEM 0x40000 /* SEEN_MEM+(1<<n) = use mem[n] for temporary
* storage */
#define SEEN_MEM_MSK 0x0ffff

struct codegen_context {
unsigned int seen;
unsigned int idx;
int pc_ret0; /* bpf index of first RET #0 instruction (if any) */
};

#endif

#endif
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