Re: [PATCH V3 2/3] ARM: net: bpf_jit: make code generation less dependent on struct sk_filter.

Signed-off-by: Nicolas Schichan <redacted>
---
  arch/arm/net/bpf_jit_32.c |   46 ++++++++++++++++++++++++++++-----------------
  1 file changed, 29 insertions(+), 17 deletions(-)

diff --git a/arch/arm/net/bpf_jit_32.c b/arch/arm/net/bpf_jit_32.c
index a0bd8a7..bb66a2b 100644
--- a/arch/arm/net/bpf_jit_32.c
+++ b/arch/arm/net/bpf_jit_32.c

@@ -55,7 +55,8 @@
  #define FLAG_NEED_X_RESET	(1 << 0)

  struct jit_ctx {
-	const struct sk_filter *skf;
+	unsigned short prog_len;
+	struct sock_filter *prog_insns;
  	unsigned idx;
  	unsigned prologue_bytes;
  	int ret0_fp_idx;

@@ -131,8 +132,8 @@ static u16 saved_regs(struct jit_ctx *ctx)
  {
  	u16 ret = 0;

-	if ((ctx->skf->len > 1) ||
-	    (ctx->skf->insns[0].code == BPF_S_RET_A))
+	if ((ctx->prog_len > 1) ||
+	    (ctx->prog_insns[0].code == BPF_S_RET_A))
  		ret |= 1 << r_A;

  #ifdef CONFIG_FRAME_POINTER

@@ -181,7 +182,7 @@ static inline bool is_load_to_a(u16 inst)
  static void build_prologue(struct jit_ctx *ctx)
  {
  	u16 reg_set = saved_regs(ctx);
-	u16 first_inst = ctx->skf->insns[0].code;
+	u16 first_inst = ctx->prog_insns[0].code;
  	u16 off;

  #ifdef CONFIG_FRAME_POINTER

@@ -279,7 +280,7 @@ static u16 imm_offset(u32 k, struct jit_ctx *ctx)
  		ctx->imms[i] = k;

  	/* constants go just after the epilogue */
-	offset =  ctx->offsets[ctx->skf->len];
+	offset =  ctx->offsets[ctx->prog_len];
  	offset += ctx->prologue_bytes;
  	offset += ctx->epilogue_bytes;
  	offset += i * 4;

@@ -419,7 +420,7 @@ static inline void emit_err_ret(u8 cond, struct jit_ctx *ctx)
  		emit(ARM_MOV_R(ARM_R0, ARM_R0), ctx);
  	} else {
  		_emit(cond, ARM_MOV_I(ARM_R0, 0), ctx);
-		_emit(cond, ARM_B(b_imm(ctx->skf->len, ctx)), ctx);
+		_emit(cond, ARM_B(b_imm(ctx->prog_len, ctx)), ctx);
  	}
  }

@@ -469,14 +470,13 @@ static inline void update_on_xread(struct jit_ctx *ctx)
  static int build_body(struct jit_ctx *ctx)
  {
  	void *load_func[] = {jit_get_skb_b, jit_get_skb_h, jit_get_skb_w};
-	const struct sk_filter *prog = ctx->skf;
  	const struct sock_filter *inst;
  	unsigned i, load_order, off, condt;
  	int imm12;
  	u32 k;

-	for (i = 0; i < prog->len; i++) {
-		inst = &(prog->insns[i]);
+	for (i = 0; i < ctx->prog_len; i++) {
+		inst = &(ctx->prog_insns[i]);
  		/* K as an immediate value operand */
  		k = inst->k;

@@ -769,8 +769,8 @@ cmp_x:
  				ctx->ret0_fp_idx = i;
  			emit_mov_i(ARM_R0, k, ctx);
  b_epilogue:
-			if (i != ctx->skf->len - 1)
-				emit(ARM_B(b_imm(prog->len, ctx)), ctx);
+			if (i != ctx->prog_len - 1)
+				emit(ARM_B(b_imm(ctx->prog_len, ctx)), ctx);
  			break;
  		case BPF_S_MISC_TAX:
  			/* X = A */

@@ -858,7 +858,7 @@ b_epilogue:
  }


-void bpf_jit_compile(struct sk_filter *fp)
+static void __bpf_jit_compile(struct jit_ctx *out_ctx)
  {
  	struct jit_ctx ctx;
  	unsigned tmp_idx;

@@ -867,11 +867,10 @@ void bpf_jit_compile(struct sk_filter *fp)
  	if (!bpf_jit_enable)
  		return;

-	memset(&ctx, 0, sizeof(ctx));
-	ctx.skf		= fp;
+	ctx = *out_ctx;
  	ctx.ret0_fp_idx = -1;

-	ctx.offsets = kzalloc(4 * (ctx.skf->len + 1), GFP_KERNEL);
+	ctx.offsets = kzalloc(4 * (ctx.prog_len + 1), GFP_KERNEL);
  	if (ctx.offsets == NULL)
  		return;

@@ -921,13 +920,26 @@ void bpf_jit_compile(struct sk_filter *fp)
  		print_hex_dump(KERN_INFO, "BPF JIT code: ",
  			       DUMP_PREFIX_ADDRESS, 16, 4, ctx.target,
  			       alloc_size, false);
-
-	fp->bpf_func = (void *)ctx.target;
  out:
  	kfree(ctx.offsets);
+
+	*out_ctx = ctx;
  	return;
  }

+void bpf_jit_compile(struct sk_filter *fp)
+{
+	struct jit_ctx ctx;
+
+	memset(&ctx, 0, sizeof(ctx));
+	ctx.prog_len = fp->len;
+	ctx.prog_insns = fp->insns;
+
+	__bpf_jit_compile(&ctx);
+	if (ctx.target)
+		fp->bpf_func = (void *)ctx.target;
+}
+
  static void bpf_jit_free_worker(struct work_struct *work)
  {
  	module_free(NULL, work);