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linux/arch/mips/net/bpf_jit.c
Markos Chandras 266a88e220 MIPS: BPF: Introduce BPF ASM helpers 
This commit introduces BPF ASM helpers for MIPS and MIPS64 kernels.
The purpose of this patch is to twofold:

1) We are now able to handle negative offsets instead of either
falling back to the interpreter or to simply not do anything and
bail out.

2) Optimize reads from the packet header instead of calling the C
helpers

Because of this patch, we are now able to get rid of quite a bit of
code in the JIT generation process by using MIPS optimized assembly
code. The new assembly code makes the test_bpf testsuite happy with
all 60 test passing successfully compared to the previous
implementation where 2 tests were failing.
Doing some basic analysis in the results between the old
implementation and the new one we can obtain the following
summary running current mainline on an ER8 board (+/- 30us delta is
ignored to prevent noise from kernel scheduling or IRQ latencies):

Summary: 22 tests are faster, 7 are slower and 47 saw no improvement

with the most notable improvement being the tcpdump tests. The 7 tests
that seem to be a bit slower is because they all follow the slow path
(bpf_internal_load_pointer_neg_helper) which is meant to be slow so
that's not a problem.

Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Cc: netdev@vger.kernel.org
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: linux-kernel@vger.kernel.org
Cc: linux-mips@linux-mips.org
Cc: netdev@vger.kernel.org
Patchwork: http://patchwork.linux-mips.org/patch/10530/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
2015-06-21 21:54:25 +02:00

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/*
* Just-In-Time compiler for BPF filters on MIPS
*
* Copyright (c) 2014 Imagination Technologies Ltd.
* Author: Markos Chandras <markos.chandras@imgtec.com>
*
* 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.
*/
#include <linux/bitops.h>
#include <linux/compiler.h>
#include <linux/errno.h>
#include <linux/filter.h>
#include <linux/if_vlan.h>
#include <linux/kconfig.h>
#include <linux/moduleloader.h>
#include <linux/netdevice.h>
#include <linux/string.h>
#include <linux/slab.h>
#include <linux/types.h>
#include <asm/asm.h>
#include <asm/bitops.h>
#include <asm/cacheflush.h>
#include <asm/cpu-features.h>
#include <asm/uasm.h>
#include "bpf_jit.h"
/* ABI
* r_skb_hl SKB header length
* r_data SKB data pointer
* r_off Offset
* r_A BPF register A
* r_X BPF register X
* r_skb *skb
* r_M *scratch memory
* r_skb_len SKB length
*
* On entry (*bpf_func)(*skb, *filter)
* a0 = MIPS_R_A0 = skb;
* a1 = MIPS_R_A1 = filter;
*
* Stack
* ...
* M[15]
* M[14]
* M[13]
* ...
* M[0] <-- r_M
* saved reg k-1
* saved reg k-2
* ...
* saved reg 0 <-- r_sp
* <no argument area>
*
* Packet layout
*
* <--------------------- len ------------------------>
* <--skb-len(r_skb_hl)-->< ----- skb->data_len ------>
* ----------------------------------------------------
* | skb->data |
* ----------------------------------------------------
*/
#define ptr typeof(unsigned long)
#define SCRATCH_OFF(k) (4 * (k))
/* JIT flags */
#define SEEN_CALL (1 << BPF_MEMWORDS)
#define SEEN_SREG_SFT (BPF_MEMWORDS + 1)
#define SEEN_SREG_BASE (1 << SEEN_SREG_SFT)
#define SEEN_SREG(x) (SEEN_SREG_BASE << (x))
#define SEEN_OFF SEEN_SREG(2)
#define SEEN_A SEEN_SREG(3)
#define SEEN_X SEEN_SREG(4)
#define SEEN_SKB SEEN_SREG(5)
#define SEEN_MEM SEEN_SREG(6)
/* SEEN_SK_DATA also implies skb_hl an skb_len */
#define SEEN_SKB_DATA (SEEN_SREG(7) | SEEN_SREG(1) | SEEN_SREG(0))
/* Arguments used by JIT */
#define ARGS_USED_BY_JIT 2 /* only applicable to 64-bit */
#define SBIT(x) (1 << (x)) /* Signed version of BIT() */
/**
* struct jit_ctx - JIT context
* @skf: The sk_filter
* @prologue_bytes: Number of bytes for prologue
* @idx: Instruction index
* @flags: JIT flags
* @offsets: Instruction offsets
* @target: Memory location for the compiled filter
*/
struct jit_ctx {
const struct bpf_prog *skf;
unsigned int prologue_bytes;
u32 idx;
u32 flags;
u32 *offsets;
u32 *target;
};
static inline int optimize_div(u32 *k)
{
/* power of 2 divides can be implemented with right shift */
if (!(*k & (*k-1))) {
*k = ilog2(*k);
return 1;
}
return 0;
}
static inline void emit_jit_reg_move(ptr dst, ptr src, struct jit_ctx *ctx);
/* Simply emit the instruction if the JIT memory space has been allocated */
#define emit_instr(ctx, func, ...) \
do { \
if ((ctx)->target != NULL) { \
u32 *p = &(ctx)->target[ctx->idx]; \
uasm_i_##func(&p, ##__VA_ARGS__); \
} \
(ctx)->idx++; \
} while (0)
/*
* Similar to emit_instr but it must be used when we need to emit
* 32-bit or 64-bit instructions
*/
#define emit_long_instr(ctx, func, ...) \
do { \
if ((ctx)->target != NULL) { \
u32 *p = &(ctx)->target[ctx->idx]; \
UASM_i_##func(&p, ##__VA_ARGS__); \
} \
(ctx)->idx++; \
} while (0)
/* Determine if immediate is within the 16-bit signed range */
static inline bool is_range16(s32 imm)
{
return !(imm >= SBIT(15) || imm < -SBIT(15));
}
static inline void emit_addu(unsigned int dst, unsigned int src1,
unsigned int src2, struct jit_ctx *ctx)
{
emit_instr(ctx, addu, dst, src1, src2);
}
static inline void emit_nop(struct jit_ctx *ctx)
{
emit_instr(ctx, nop);
}
/* Load a u32 immediate to a register */
static inline void emit_load_imm(unsigned int dst, u32 imm, struct jit_ctx *ctx)
{
if (ctx->target != NULL) {
/* addiu can only handle s16 */
if (!is_range16(imm)) {
u32 *p = &ctx->target[ctx->idx];
uasm_i_lui(&p, r_tmp_imm, (s32)imm >> 16);
p = &ctx->target[ctx->idx + 1];
uasm_i_ori(&p, dst, r_tmp_imm, imm & 0xffff);
} else {
u32 *p = &ctx->target[ctx->idx];
uasm_i_addiu(&p, dst, r_zero, imm);
}
}
ctx->idx++;
if (!is_range16(imm))
ctx->idx++;
}
static inline void emit_or(unsigned int dst, unsigned int src1,
unsigned int src2, struct jit_ctx *ctx)
{
emit_instr(ctx, or, dst, src1, src2);
}
static inline void emit_ori(unsigned int dst, unsigned src, u32 imm,
struct jit_ctx *ctx)
{
if (imm >= BIT(16)) {
emit_load_imm(r_tmp, imm, ctx);
emit_or(dst, src, r_tmp, ctx);
} else {
emit_instr(ctx, ori, dst, src, imm);
}
}
static inline void emit_daddiu(unsigned int dst, unsigned int src,
int imm, struct jit_ctx *ctx)
{
/*
* Only used for stack, so the imm is relatively small
* and it fits in 15-bits
*/
emit_instr(ctx, daddiu, dst, src, imm);
}
static inline void emit_addiu(unsigned int dst, unsigned int src,
u32 imm, struct jit_ctx *ctx)
{
if (!is_range16(imm)) {
emit_load_imm(r_tmp, imm, ctx);
emit_addu(dst, r_tmp, src, ctx);
} else {
emit_instr(ctx, addiu, dst, src, imm);
}
}
static inline void emit_and(unsigned int dst, unsigned int src1,
unsigned int src2, struct jit_ctx *ctx)
{
emit_instr(ctx, and, dst, src1, src2);
}
static inline void emit_andi(unsigned int dst, unsigned int src,
u32 imm, struct jit_ctx *ctx)
{
/* If imm does not fit in u16 then load it to register */
if (imm >= BIT(16)) {
emit_load_imm(r_tmp, imm, ctx);
emit_and(dst, src, r_tmp, ctx);
} else {
emit_instr(ctx, andi, dst, src, imm);
}
}
static inline void emit_xor(unsigned int dst, unsigned int src1,
unsigned int src2, struct jit_ctx *ctx)
{
emit_instr(ctx, xor, dst, src1, src2);
}
static inline void emit_xori(ptr dst, ptr src, u32 imm, struct jit_ctx *ctx)
{
/* If imm does not fit in u16 then load it to register */
if (imm >= BIT(16)) {
emit_load_imm(r_tmp, imm, ctx);
emit_xor(dst, src, r_tmp, ctx);
} else {
emit_instr(ctx, xori, dst, src, imm);
}
}
static inline void emit_stack_offset(int offset, struct jit_ctx *ctx)
{
emit_long_instr(ctx, ADDIU, r_sp, r_sp, offset);
}
static inline void emit_subu(unsigned int dst, unsigned int src1,
unsigned int src2, struct jit_ctx *ctx)
{
emit_instr(ctx, subu, dst, src1, src2);
}
static inline void emit_neg(unsigned int reg, struct jit_ctx *ctx)
{
emit_subu(reg, r_zero, reg, ctx);
}
static inline void emit_sllv(unsigned int dst, unsigned int src,
unsigned int sa, struct jit_ctx *ctx)
{
emit_instr(ctx, sllv, dst, src, sa);
}
static inline void emit_sll(unsigned int dst, unsigned int src,
unsigned int sa, struct jit_ctx *ctx)
{
/* sa is 5-bits long */
if (sa >= BIT(5))
/* Shifting >= 32 results in zero */
emit_jit_reg_move(dst, r_zero, ctx);
else
emit_instr(ctx, sll, dst, src, sa);
}
static inline void emit_srlv(unsigned int dst, unsigned int src,
unsigned int sa, struct jit_ctx *ctx)
{
emit_instr(ctx, srlv, dst, src, sa);
}
static inline void emit_srl(unsigned int dst, unsigned int src,
unsigned int sa, struct jit_ctx *ctx)
{
/* sa is 5-bits long */
if (sa >= BIT(5))
/* Shifting >= 32 results in zero */
emit_jit_reg_move(dst, r_zero, ctx);
else
emit_instr(ctx, srl, dst, src, sa);
}
static inline void emit_slt(unsigned int dst, unsigned int src1,
unsigned int src2, struct jit_ctx *ctx)
{
emit_instr(ctx, slt, dst, src1, src2);
}
static inline void emit_sltu(unsigned int dst, unsigned int src1,
unsigned int src2, struct jit_ctx *ctx)
{
emit_instr(ctx, sltu, dst, src1, src2);
}
static inline void emit_sltiu(unsigned dst, unsigned int src,
unsigned int imm, struct jit_ctx *ctx)
{
/* 16 bit immediate */
if (!is_range16((s32)imm)) {
emit_load_imm(r_tmp, imm, ctx);
emit_sltu(dst, src, r_tmp, ctx);
} else {
emit_instr(ctx, sltiu, dst, src, imm);
}
}
/* Store register on the stack */
static inline void emit_store_stack_reg(ptr reg, ptr base,
unsigned int offset,
struct jit_ctx *ctx)
{
emit_long_instr(ctx, SW, reg, offset, base);
}
static inline void emit_store(ptr reg, ptr base, unsigned int offset,
struct jit_ctx *ctx)
{
emit_instr(ctx, sw, reg, offset, base);
}
static inline void emit_load_stack_reg(ptr reg, ptr base,
unsigned int offset,
struct jit_ctx *ctx)
{
emit_long_instr(ctx, LW, reg, offset, base);
}
static inline void emit_load(unsigned int reg, unsigned int base,
unsigned int offset, struct jit_ctx *ctx)
{
emit_instr(ctx, lw, reg, offset, base);
}
static inline void emit_load_byte(unsigned int reg, unsigned int base,
unsigned int offset, struct jit_ctx *ctx)
{
emit_instr(ctx, lb, reg, offset, base);
}
static inline void emit_half_load(unsigned int reg, unsigned int base,
unsigned int offset, struct jit_ctx *ctx)
{
emit_instr(ctx, lh, reg, offset, base);
}
static inline void emit_mul(unsigned int dst, unsigned int src1,
unsigned int src2, struct jit_ctx *ctx)
{
emit_instr(ctx, mul, dst, src1, src2);
}
static inline void emit_div(unsigned int dst, unsigned int src,
struct jit_ctx *ctx)
{
if (ctx->target != NULL) {
u32 *p = &ctx->target[ctx->idx];
uasm_i_divu(&p, dst, src);
p = &ctx->target[ctx->idx + 1];
uasm_i_mflo(&p, dst);
}
ctx->idx += 2; /* 2 insts */
}
static inline void emit_mod(unsigned int dst, unsigned int src,
struct jit_ctx *ctx)
{
if (ctx->target != NULL) {
u32 *p = &ctx->target[ctx->idx];
uasm_i_divu(&p, dst, src);
p = &ctx->target[ctx->idx + 1];
uasm_i_mfhi(&p, dst);
}
ctx->idx += 2; /* 2 insts */
}
static inline void emit_dsll(unsigned int dst, unsigned int src,
unsigned int sa, struct jit_ctx *ctx)
{
emit_instr(ctx, dsll, dst, src, sa);
}
static inline void emit_dsrl32(unsigned int dst, unsigned int src,
unsigned int sa, struct jit_ctx *ctx)
{
emit_instr(ctx, dsrl32, dst, src, sa);
}
static inline void emit_wsbh(unsigned int dst, unsigned int src,
struct jit_ctx *ctx)
{
emit_instr(ctx, wsbh, dst, src);
}
/* load pointer to register */
static inline void emit_load_ptr(unsigned int dst, unsigned int src,
int imm, struct jit_ctx *ctx)
{
/* src contains the base addr of the 32/64-pointer */
emit_long_instr(ctx, LW, dst, imm, src);
}
/* load a function pointer to register */
static inline void emit_load_func(unsigned int reg, ptr imm,
struct jit_ctx *ctx)
{
if (config_enabled(CONFIG_64BIT)) {
/* At this point imm is always 64-bit */
emit_load_imm(r_tmp, (u64)imm >> 32, ctx);
emit_dsll(r_tmp_imm, r_tmp, 16, ctx); /* left shift by 16 */
emit_ori(r_tmp, r_tmp_imm, (imm >> 16) & 0xffff, ctx);
emit_dsll(r_tmp_imm, r_tmp, 16, ctx); /* left shift by 16 */
emit_ori(reg, r_tmp_imm, imm & 0xffff, ctx);
} else {
emit_load_imm(reg, imm, ctx);
}
}
/* Move to real MIPS register */
static inline void emit_reg_move(ptr dst, ptr src, struct jit_ctx *ctx)
{
emit_long_instr(ctx, ADDU, dst, src, r_zero);
}
/* Move to JIT (32-bit) register */
static inline void emit_jit_reg_move(ptr dst, ptr src, struct jit_ctx *ctx)
{
emit_addu(dst, src, r_zero, ctx);
}
/* Compute the immediate value for PC-relative branches. */
static inline u32 b_imm(unsigned int tgt, struct jit_ctx *ctx)
{
if (ctx->target == NULL)
return 0;
/*
* We want a pc-relative branch. We only do forward branches
* so tgt is always after pc. tgt is the instruction offset
* we want to jump to.
* Branch on MIPS:
* I: target_offset <- sign_extend(offset)
* I+1: PC += target_offset (delay slot)
*
* ctx->idx currently points to the branch instruction
* but the offset is added to the delay slot so we need
* to subtract 4.
*/
return ctx->offsets[tgt] -
(ctx->idx * 4 - ctx->prologue_bytes) - 4;
}
static inline void emit_bcond(int cond, unsigned int reg1, unsigned int reg2,
unsigned int imm, struct jit_ctx *ctx)
{
if (ctx->target != NULL) {
u32 *p = &ctx->target[ctx->idx];
switch (cond) {
case MIPS_COND_EQ:
uasm_i_beq(&p, reg1, reg2, imm);
break;
case MIPS_COND_NE:
uasm_i_bne(&p, reg1, reg2, imm);
break;
case MIPS_COND_ALL:
uasm_i_b(&p, imm);
break;
default:
pr_warn("%s: Unhandled branch conditional: %d\n",
__func__, cond);
}
}
ctx->idx++;
}
static inline void emit_b(unsigned int imm, struct jit_ctx *ctx)
{
emit_bcond(MIPS_COND_ALL, r_zero, r_zero, imm, ctx);
}
static inline void emit_jalr(unsigned int link, unsigned int reg,
struct jit_ctx *ctx)
{
emit_instr(ctx, jalr, link, reg);
}
static inline void emit_jr(unsigned int reg, struct jit_ctx *ctx)
{
emit_instr(ctx, jr, reg);
}
static inline u16 align_sp(unsigned int num)
{
/* Double word alignment for 32-bit, quadword for 64-bit */
unsigned int align = config_enabled(CONFIG_64BIT) ? 16 : 8;
num = (num + (align - 1)) & -align;
return num;
}
static bool is_load_to_a(u16 inst)
{
switch (inst) {
case BPF_LD | BPF_W | BPF_LEN:
case BPF_LD | BPF_W | BPF_ABS:
case BPF_LD | BPF_H | BPF_ABS:
case BPF_LD | BPF_B | BPF_ABS:
return true;
default:
return false;
}
}
static void save_bpf_jit_regs(struct jit_ctx *ctx, unsigned offset)
{
int i = 0, real_off = 0;
u32 sflags, tmp_flags;
/* Adjust the stack pointer */
emit_stack_offset(-align_sp(offset), ctx);
tmp_flags = sflags = ctx->flags >> SEEN_SREG_SFT;
/* sflags is essentially a bitmap */
while (tmp_flags) {
if ((sflags >> i) & 0x1) {
emit_store_stack_reg(MIPS_R_S0 + i, r_sp, real_off,
ctx);
real_off += SZREG;
}
i++;
tmp_flags >>= 1;
}
/* save return address */
if (ctx->flags & SEEN_CALL) {
emit_store_stack_reg(r_ra, r_sp, real_off, ctx);
real_off += SZREG;
}
/* Setup r_M leaving the alignment gap if necessary */
if (ctx->flags & SEEN_MEM) {
if (real_off % (SZREG * 2))
real_off += SZREG;
emit_long_instr(ctx, ADDIU, r_M, r_sp, real_off);
}
}
static void restore_bpf_jit_regs(struct jit_ctx *ctx,
unsigned int offset)
{
int i, real_off = 0;
u32 sflags, tmp_flags;
tmp_flags = sflags = ctx->flags >> SEEN_SREG_SFT;
/* sflags is a bitmap */
i = 0;
while (tmp_flags) {
if ((sflags >> i) & 0x1) {
emit_load_stack_reg(MIPS_R_S0 + i, r_sp, real_off,
ctx);
real_off += SZREG;
}
i++;
tmp_flags >>= 1;
}
/* restore return address */
if (ctx->flags & SEEN_CALL)
emit_load_stack_reg(r_ra, r_sp, real_off, ctx);
/* Restore the sp and discard the scrach memory */
emit_stack_offset(align_sp(offset), ctx);
}
static unsigned int get_stack_depth(struct jit_ctx *ctx)
{
int sp_off = 0;
/* How may s* regs do we need to preserved? */
sp_off += hweight32(ctx->flags >> SEEN_SREG_SFT) * SZREG;
if (ctx->flags & SEEN_MEM)
sp_off += 4 * BPF_MEMWORDS; /* BPF_MEMWORDS are 32-bit */
if (ctx->flags & SEEN_CALL)
sp_off += SZREG; /* Space for our ra register */
return sp_off;
}
static void build_prologue(struct jit_ctx *ctx)
{
u16 first_inst = ctx->skf->insns[0].code;
int sp_off;
/* Calculate the total offset for the stack pointer */
sp_off = get_stack_depth(ctx);
save_bpf_jit_regs(ctx, sp_off);
if (ctx->flags & SEEN_SKB)
emit_reg_move(r_skb, MIPS_R_A0, ctx);
if (ctx->flags & SEEN_SKB_DATA) {
/* Load packet length */
emit_load(r_skb_len, r_skb, offsetof(struct sk_buff, len),
ctx);
emit_load(r_tmp, r_skb, offsetof(struct sk_buff, data_len),
ctx);
/* Load the data pointer */
emit_load_ptr(r_skb_data, r_skb,
offsetof(struct sk_buff, data), ctx);
/* Load the header length */
emit_subu(r_skb_hl, r_skb_len, r_tmp, ctx);
}
if (ctx->flags & SEEN_X)
emit_jit_reg_move(r_X, r_zero, ctx);
/* Do not leak kernel data to userspace */
if ((first_inst != (BPF_RET | BPF_K)) && !(is_load_to_a(first_inst)))
emit_jit_reg_move(r_A, r_zero, ctx);
}
static void build_epilogue(struct jit_ctx *ctx)
{
unsigned int sp_off;
/* Calculate the total offset for the stack pointer */
sp_off = get_stack_depth(ctx);
restore_bpf_jit_regs(ctx, sp_off);
/* Return */
emit_jr(r_ra, ctx);
emit_nop(ctx);
}
#define CHOOSE_LOAD_FUNC(K, func) \
((int)K < 0 ? ((int)K >= SKF_LL_OFF ? func##_negative : func) : \
func##_positive)
static int build_body(struct jit_ctx *ctx)
{
const struct bpf_prog *prog = ctx->skf;
const struct sock_filter *inst;
unsigned int i, off, condt;
u32 k, b_off __maybe_unused;
u8 (*sk_load_func)(unsigned long *skb, int offset);
for (i = 0; i < prog->len; i++) {
u16 code;
inst = &(prog->insns[i]);
pr_debug("%s: code->0x%02x, jt->0x%x, jf->0x%x, k->0x%x\n",
__func__, inst->code, inst->jt, inst->jf, inst->k);
k = inst->k;
code = bpf_anc_helper(inst);
if (ctx->target == NULL)
ctx->offsets[i] = ctx->idx * 4;
switch (code) {
case BPF_LD | BPF_IMM:
/* A <- k ==> li r_A, k */
ctx->flags |= SEEN_A;
emit_load_imm(r_A, k, ctx);
break;
case BPF_LD | BPF_W | BPF_LEN:
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
/* A <- len ==> lw r_A, offset(skb) */
ctx->flags |= SEEN_SKB | SEEN_A;
off = offsetof(struct sk_buff, len);
emit_load(r_A, r_skb, off, ctx);
break;
case BPF_LD | BPF_MEM:
/* A <- M[k] ==> lw r_A, offset(M) */
ctx->flags |= SEEN_MEM | SEEN_A;
emit_load(r_A, r_M, SCRATCH_OFF(k), ctx);
break;
case BPF_LD | BPF_W | BPF_ABS:
/* A <- P[k:4] */
sk_load_func = CHOOSE_LOAD_FUNC(k, sk_load_word);
goto load;
case BPF_LD | BPF_H | BPF_ABS:
/* A <- P[k:2] */
sk_load_func = CHOOSE_LOAD_FUNC(k, sk_load_half);
goto load;
case BPF_LD | BPF_B | BPF_ABS:
/* A <- P[k:1] */
sk_load_func = CHOOSE_LOAD_FUNC(k, sk_load_byte);
load:
emit_load_imm(r_off, k, ctx);
load_common:
ctx->flags |= SEEN_CALL | SEEN_OFF |
SEEN_SKB | SEEN_A | SEEN_SKB_DATA;
emit_load_func(r_s0, (ptr)sk_load_func, ctx);
emit_reg_move(MIPS_R_A0, r_skb, ctx);
emit_jalr(MIPS_R_RA, r_s0, ctx);
/* Load second argument to delay slot */
emit_reg_move(MIPS_R_A1, r_off, ctx);
/* Check the error value */
emit_bcond(MIPS_COND_EQ, r_ret, 0, b_imm(i + 1, ctx),
ctx);
/* Load return register on DS for failures */
emit_reg_move(r_ret, r_zero, ctx);
/* Return with error */
emit_b(b_imm(prog->len, ctx), ctx);
emit_nop(ctx);
break;
case BPF_LD | BPF_W | BPF_IND:
/* A <- P[X + k:4] */
sk_load_func = sk_load_word;
goto load_ind;
case BPF_LD | BPF_H | BPF_IND:
/* A <- P[X + k:2] */
sk_load_func = sk_load_half;
goto load_ind;
case BPF_LD | BPF_B | BPF_IND:
/* A <- P[X + k:1] */
sk_load_func = sk_load_byte;
load_ind:
ctx->flags |= SEEN_OFF | SEEN_X;
emit_addiu(r_off, r_X, k, ctx);
goto load_common;
case BPF_LDX | BPF_IMM:
/* X <- k */
ctx->flags |= SEEN_X;
emit_load_imm(r_X, k, ctx);
break;
case BPF_LDX | BPF_MEM:
/* X <- M[k] */
ctx->flags |= SEEN_X | SEEN_MEM;
emit_load(r_X, r_M, SCRATCH_OFF(k), ctx);
break;
case BPF_LDX | BPF_W | BPF_LEN:
/* X <- len */
ctx->flags |= SEEN_X | SEEN_SKB;
off = offsetof(struct sk_buff, len);
emit_load(r_X, r_skb, off, ctx);
break;
case BPF_LDX | BPF_B | BPF_MSH:
/* X <- 4 * (P[k:1] & 0xf) */
ctx->flags |= SEEN_X | SEEN_CALL | SEEN_SKB;
/* Load offset to a1 */
emit_load_func(r_s0, (ptr)sk_load_byte, ctx);
/*
* This may emit two instructions so it may not fit
* in the delay slot. So use a0 in the delay slot.
*/
emit_load_imm(MIPS_R_A1, k, ctx);
emit_jalr(MIPS_R_RA, r_s0, ctx);
emit_reg_move(MIPS_R_A0, r_skb, ctx); /* delay slot */
/* Check the error value */
emit_bcond(MIPS_COND_NE, r_ret, 0,
b_imm(prog->len, ctx), ctx);
emit_reg_move(r_ret, r_zero, ctx);
/* We are good */
/* X <- P[1:K] & 0xf */
emit_andi(r_X, r_A, 0xf, ctx);
/* X << 2 */
emit_b(b_imm(i + 1, ctx), ctx);
emit_sll(r_X, r_X, 2, ctx); /* delay slot */
break;
case BPF_ST:
/* M[k] <- A */
ctx->flags |= SEEN_MEM | SEEN_A;
emit_store(r_A, r_M, SCRATCH_OFF(k), ctx);
break;
case BPF_STX:
/* M[k] <- X */
ctx->flags |= SEEN_MEM | SEEN_X;
emit_store(r_X, r_M, SCRATCH_OFF(k), ctx);
break;
case BPF_ALU | BPF_ADD | BPF_K:
/* A += K */
ctx->flags |= SEEN_A;
emit_addiu(r_A, r_A, k, ctx);
break;
case BPF_ALU | BPF_ADD | BPF_X:
/* A += X */
ctx->flags |= SEEN_A | SEEN_X;
emit_addu(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_SUB | BPF_K:
/* A -= K */
ctx->flags |= SEEN_A;
emit_addiu(r_A, r_A, -k, ctx);
break;
case BPF_ALU | BPF_SUB | BPF_X:
/* A -= X */
ctx->flags |= SEEN_A | SEEN_X;
emit_subu(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_MUL | BPF_K:
/* A *= K */
/* Load K to scratch register before MUL */
ctx->flags |= SEEN_A;
emit_load_imm(r_s0, k, ctx);
emit_mul(r_A, r_A, r_s0, ctx);
break;
case BPF_ALU | BPF_MUL | BPF_X:
/* A *= X */
ctx->flags |= SEEN_A | SEEN_X;
emit_mul(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_DIV | BPF_K:
/* A /= k */
if (k == 1)
break;
if (optimize_div(&k)) {
ctx->flags |= SEEN_A;
emit_srl(r_A, r_A, k, ctx);
break;
}
ctx->flags |= SEEN_A;
emit_load_imm(r_s0, k, ctx);
emit_div(r_A, r_s0, ctx);
break;
case BPF_ALU | BPF_MOD | BPF_K:
/* A %= k */
if (k == 1) {
ctx->flags |= SEEN_A;
emit_jit_reg_move(r_A, r_zero, ctx);
} else {
ctx->flags |= SEEN_A;
emit_load_imm(r_s0, k, ctx);
emit_mod(r_A, r_s0, ctx);
}
break;
case BPF_ALU | BPF_DIV | BPF_X:
/* A /= X */
ctx->flags |= SEEN_X | SEEN_A;
/* Check if r_X is zero */
emit_bcond(MIPS_COND_EQ, r_X, r_zero,
b_imm(prog->len, ctx), ctx);
emit_load_imm(r_ret, 0, ctx); /* delay slot */
emit_div(r_A, r_X, ctx);
break;
case BPF_ALU | BPF_MOD | BPF_X:
/* A %= X */
ctx->flags |= SEEN_X | SEEN_A;
/* Check if r_X is zero */
emit_bcond(MIPS_COND_EQ, r_X, r_zero,
b_imm(prog->len, ctx), ctx);
emit_load_imm(r_ret, 0, ctx); /* delay slot */
emit_mod(r_A, r_X, ctx);
break;
case BPF_ALU | BPF_OR | BPF_K:
/* A |= K */
ctx->flags |= SEEN_A;
emit_ori(r_A, r_A, k, ctx);
break;
case BPF_ALU | BPF_OR | BPF_X:
/* A |= X */
ctx->flags |= SEEN_A;
emit_ori(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_XOR | BPF_K:
/* A ^= k */
ctx->flags |= SEEN_A;
emit_xori(r_A, r_A, k, ctx);
break;
case BPF_ANC | SKF_AD_ALU_XOR_X:
case BPF_ALU | BPF_XOR | BPF_X:
/* A ^= X */
ctx->flags |= SEEN_A;
emit_xor(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_AND | BPF_K:
/* A &= K */
ctx->flags |= SEEN_A;
emit_andi(r_A, r_A, k, ctx);
break;
case BPF_ALU | BPF_AND | BPF_X:
/* A &= X */
ctx->flags |= SEEN_A | SEEN_X;
emit_and(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_LSH | BPF_K:
/* A <<= K */
ctx->flags |= SEEN_A;
emit_sll(r_A, r_A, k, ctx);
break;
case BPF_ALU | BPF_LSH | BPF_X:
/* A <<= X */
ctx->flags |= SEEN_A | SEEN_X;
emit_sllv(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_RSH | BPF_K:
/* A >>= K */
ctx->flags |= SEEN_A;
emit_srl(r_A, r_A, k, ctx);
break;
case BPF_ALU | BPF_RSH | BPF_X:
ctx->flags |= SEEN_A | SEEN_X;
emit_srlv(r_A, r_A, r_X, ctx);
break;
case BPF_ALU | BPF_NEG:
/* A = -A */
ctx->flags |= SEEN_A;
emit_neg(r_A, ctx);
break;
case BPF_JMP | BPF_JA:
/* pc += K */
emit_b(b_imm(i + k + 1, ctx), ctx);
emit_nop(ctx);
break;
case BPF_JMP | BPF_JEQ | BPF_K:
/* pc += ( A == K ) ? pc->jt : pc->jf */
condt = MIPS_COND_EQ | MIPS_COND_K;
goto jmp_cmp;
case BPF_JMP | BPF_JEQ | BPF_X:
ctx->flags |= SEEN_X;
/* pc += ( A == X ) ? pc->jt : pc->jf */
condt = MIPS_COND_EQ | MIPS_COND_X;
goto jmp_cmp;
case BPF_JMP | BPF_JGE | BPF_K:
/* pc += ( A >= K ) ? pc->jt : pc->jf */
condt = MIPS_COND_GE | MIPS_COND_K;
goto jmp_cmp;
case BPF_JMP | BPF_JGE | BPF_X:
ctx->flags |= SEEN_X;
/* pc += ( A >= X ) ? pc->jt : pc->jf */
condt = MIPS_COND_GE | MIPS_COND_X;
goto jmp_cmp;
case BPF_JMP | BPF_JGT | BPF_K:
/* pc += ( A > K ) ? pc->jt : pc->jf */
condt = MIPS_COND_GT | MIPS_COND_K;
goto jmp_cmp;
case BPF_JMP | BPF_JGT | BPF_X:
ctx->flags |= SEEN_X;
/* pc += ( A > X ) ? pc->jt : pc->jf */
condt = MIPS_COND_GT | MIPS_COND_X;
jmp_cmp:
/* Greater or Equal */
if ((condt & MIPS_COND_GE) ||
(condt & MIPS_COND_GT)) {
if (condt & MIPS_COND_K) { /* K */
ctx->flags |= SEEN_A;
emit_sltiu(r_s0, r_A, k, ctx);
} else { /* X */
ctx->flags |= SEEN_A |
SEEN_X;
emit_sltu(r_s0, r_A, r_X, ctx);
}
/* A < (K|X) ? r_scrach = 1 */
b_off = b_imm(i + inst->jf + 1, ctx);
emit_bcond(MIPS_COND_NE, r_s0, r_zero, b_off,
ctx);
emit_nop(ctx);
/* A > (K|X) ? scratch = 0 */
if (condt & MIPS_COND_GT) {
/* Checking for equality */
ctx->flags |= SEEN_A | SEEN_X;
if (condt & MIPS_COND_K)
emit_load_imm(r_s0, k, ctx);
else
emit_jit_reg_move(r_s0, r_X,
ctx);
b_off = b_imm(i + inst->jf + 1, ctx);
emit_bcond(MIPS_COND_EQ, r_A, r_s0,
b_off, ctx);
emit_nop(ctx);
/* Finally, A > K|X */
b_off = b_imm(i + inst->jt + 1, ctx);
emit_b(b_off, ctx);
emit_nop(ctx);
} else {
/* A >= (K|X) so jump */
b_off = b_imm(i + inst->jt + 1, ctx);
emit_b(b_off, ctx);
emit_nop(ctx);
}
} else {
/* A == K|X */
if (condt & MIPS_COND_K) { /* K */
ctx->flags |= SEEN_A;
emit_load_imm(r_s0, k, ctx);
/* jump true */
b_off = b_imm(i + inst->jt + 1, ctx);
emit_bcond(MIPS_COND_EQ, r_A, r_s0,
b_off, ctx);
emit_nop(ctx);
/* jump false */
b_off = b_imm(i + inst->jf + 1,
ctx);
emit_bcond(MIPS_COND_NE, r_A, r_s0,
b_off, ctx);
emit_nop(ctx);
} else { /* X */
/* jump true */
ctx->flags |= SEEN_A | SEEN_X;
b_off = b_imm(i + inst->jt + 1,
ctx);
emit_bcond(MIPS_COND_EQ, r_A, r_X,
b_off, ctx);
emit_nop(ctx);
/* jump false */
b_off = b_imm(i + inst->jf + 1, ctx);
emit_bcond(MIPS_COND_NE, r_A, r_X,
b_off, ctx);
emit_nop(ctx);
}
}
break;
case BPF_JMP | BPF_JSET | BPF_K:
ctx->flags |= SEEN_A;
/* pc += (A & K) ? pc -> jt : pc -> jf */
emit_load_imm(r_s1, k, ctx);
emit_and(r_s0, r_A, r_s1, ctx);
/* jump true */
b_off = b_imm(i + inst->jt + 1, ctx);
emit_bcond(MIPS_COND_NE, r_s0, r_zero, b_off, ctx);
emit_nop(ctx);
/* jump false */
b_off = b_imm(i + inst->jf + 1, ctx);
emit_b(b_off, ctx);
emit_nop(ctx);
break;
case BPF_JMP | BPF_JSET | BPF_X:
ctx->flags |= SEEN_X | SEEN_A;
/* pc += (A & X) ? pc -> jt : pc -> jf */
emit_and(r_s0, r_A, r_X, ctx);
/* jump true */
b_off = b_imm(i + inst->jt + 1, ctx);
emit_bcond(MIPS_COND_NE, r_s0, r_zero, b_off, ctx);
emit_nop(ctx);
/* jump false */
b_off = b_imm(i + inst->jf + 1, ctx);
emit_b(b_off, ctx);
emit_nop(ctx);
break;
case BPF_RET | BPF_A:
ctx->flags |= SEEN_A;
if (i != prog->len - 1)
/*
* If this is not the last instruction
* then jump to the epilogue
*/
emit_b(b_imm(prog->len, ctx), ctx);
emit_reg_move(r_ret, r_A, ctx); /* delay slot */
break;
case BPF_RET | BPF_K:
/*
* It can emit two instructions so it does not fit on
* the delay slot.
*/
emit_load_imm(r_ret, k, ctx);
if (i != prog->len - 1) {
/*
* If this is not the last instruction
* then jump to the epilogue
*/
emit_b(b_imm(prog->len, ctx), ctx);
emit_nop(ctx);
}
break;
case BPF_MISC | BPF_TAX:
/* X = A */
ctx->flags |= SEEN_X | SEEN_A;
emit_jit_reg_move(r_X, r_A, ctx);
break;
case BPF_MISC | BPF_TXA:
/* A = X */
ctx->flags |= SEEN_A | SEEN_X;
emit_jit_reg_move(r_A, r_X, ctx);
break;
/* AUX */
case BPF_ANC | SKF_AD_PROTOCOL:
/* A = ntohs(skb->protocol */
ctx->flags |= SEEN_SKB | SEEN_OFF | SEEN_A;
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
protocol) != 2);
off = offsetof(struct sk_buff, protocol);
emit_half_load(r_A, r_skb, off, ctx);
#ifdef CONFIG_CPU_LITTLE_ENDIAN
/* This needs little endian fixup */
if (cpu_has_wsbh) {
/* R2 and later have the wsbh instruction */
emit_wsbh(r_A, r_A, ctx);
} else {
/* Get first byte */
emit_andi(r_tmp_imm, r_A, 0xff, ctx);
/* Shift it */
emit_sll(r_tmp, r_tmp_imm, 8, ctx);
/* Get second byte */
emit_srl(r_tmp_imm, r_A, 8, ctx);
emit_andi(r_tmp_imm, r_tmp_imm, 0xff, ctx);
/* Put everyting together in r_A */
emit_or(r_A, r_tmp, r_tmp_imm, ctx);
}
#endif
break;
case BPF_ANC | SKF_AD_CPU:
ctx->flags |= SEEN_A | SEEN_OFF;
/* A = current_thread_info()->cpu */
BUILD_BUG_ON(FIELD_SIZEOF(struct thread_info,
cpu) != 4);
off = offsetof(struct thread_info, cpu);
/* $28/gp points to the thread_info struct */
emit_load(r_A, 28, off, ctx);
break;
case BPF_ANC | SKF_AD_IFINDEX:
/* A = skb->dev->ifindex */
ctx->flags |= SEEN_SKB | SEEN_A;
off = offsetof(struct sk_buff, dev);
/* Load *dev pointer */
emit_load_ptr(r_s0, r_skb, off, ctx);
/* error (0) in the delay slot */
emit_bcond(MIPS_COND_EQ, r_s0, r_zero,
b_imm(prog->len, ctx), ctx);
emit_reg_move(r_ret, r_zero, ctx);
BUILD_BUG_ON(FIELD_SIZEOF(struct net_device,
ifindex) != 4);
off = offsetof(struct net_device, ifindex);
emit_load(r_A, r_s0, off, ctx);
break;
case BPF_ANC | SKF_AD_MARK:
ctx->flags |= SEEN_SKB | SEEN_A;
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, mark) != 4);
off = offsetof(struct sk_buff, mark);
emit_load(r_A, r_skb, off, ctx);
break;
case BPF_ANC | SKF_AD_RXHASH:
ctx->flags |= SEEN_SKB | SEEN_A;
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, hash) != 4);
off = offsetof(struct sk_buff, hash);
emit_load(r_A, r_skb, off, ctx);
break;
case BPF_ANC | SKF_AD_VLAN_TAG:
case BPF_ANC | SKF_AD_VLAN_TAG_PRESENT:
ctx->flags |= SEEN_SKB | SEEN_A;
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
vlan_tci) != 2);
off = offsetof(struct sk_buff, vlan_tci);
emit_half_load(r_s0, r_skb, off, ctx);
if (code == (BPF_ANC | SKF_AD_VLAN_TAG)) {
emit_andi(r_A, r_s0, (u16)~VLAN_TAG_PRESENT, ctx);
} else {
emit_andi(r_A, r_s0, VLAN_TAG_PRESENT, ctx);
/* return 1 if present */
emit_sltu(r_A, r_zero, r_A, ctx);
}
break;
case BPF_ANC | SKF_AD_PKTTYPE:
ctx->flags |= SEEN_SKB;
emit_load_byte(r_tmp, r_skb, PKT_TYPE_OFFSET(), ctx);
/* Keep only the last 3 bits */
emit_andi(r_A, r_tmp, PKT_TYPE_MAX, ctx);
#ifdef __BIG_ENDIAN_BITFIELD
/* Get the actual packet type to the lower 3 bits */
emit_srl(r_A, r_A, 5, ctx);
#endif
break;
case BPF_ANC | SKF_AD_QUEUE:
ctx->flags |= SEEN_SKB | SEEN_A;
BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff,
queue_mapping) != 2);
BUILD_BUG_ON(offsetof(struct sk_buff,
queue_mapping) > 0xff);
off = offsetof(struct sk_buff, queue_mapping);
emit_half_load(r_A, r_skb, off, ctx);
break;
default:
pr_debug("%s: Unhandled opcode: 0x%02x\n", __FILE__,
inst->code);
return -1;
}
}
/* compute offsets only during the first pass */
if (ctx->target == NULL)
ctx->offsets[i] = ctx->idx * 4;
return 0;
}
int bpf_jit_enable __read_mostly;
void bpf_jit_compile(struct bpf_prog *fp)
{
struct jit_ctx ctx;
unsigned int alloc_size, tmp_idx;
if (!bpf_jit_enable)
return;
memset(&ctx, 0, sizeof(ctx));
ctx.offsets = kcalloc(fp->len, sizeof(*ctx.offsets), GFP_KERNEL);
if (ctx.offsets == NULL)
return;
ctx.skf = fp;
if (build_body(&ctx))
goto out;
tmp_idx = ctx.idx;
build_prologue(&ctx);
ctx.prologue_bytes = (ctx.idx - tmp_idx) * 4;
/* just to complete the ctx.idx count */
build_epilogue(&ctx);
alloc_size = 4 * ctx.idx;
ctx.target = module_alloc(alloc_size);
if (ctx.target == NULL)
goto out;
/* Clean it */
memset(ctx.target, 0, alloc_size);
ctx.idx = 0;
/* Generate the actual JIT code */
build_prologue(&ctx);
build_body(&ctx);
build_epilogue(&ctx);
/* Update the icache */
flush_icache_range((ptr)ctx.target, (ptr)(ctx.target + ctx.idx));
if (bpf_jit_enable > 1)
/* Dump JIT code */
bpf_jit_dump(fp->len, alloc_size, 2, ctx.target);
fp->bpf_func = (void *)ctx.target;
fp->jited = true;
out:
kfree(ctx.offsets);
}
void bpf_jit_free(struct bpf_prog *fp)
{
if (fp->jited)
module_memfree(fp->bpf_func);
bpf_prog_unlock_free(fp);
}
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