label-fixup

ir.c

@@ -1,4 +1,5 @@
 #include <assert.h>
+#include <errno.h>
 #include <inttypes.h>
 #include <stdio.h>
 #include <string.h>
@@ -507,6 +508,9 @@ struct ir *ir_new(void)
 	return ir;
 }
 
+
+/* ir->bpf generation */
+
 static void ir_bpf_vreg_replace(struct ir *ir, struct vinsn *last, int reg)
 {
 	struct vinsn *vi;
@@ -525,7 +529,7 @@ static void ir_bpf_vreg_replace(struct ir *ir, struct vinsn *last, int reg)
 }
 
 
-int ir_bpf_registerize_one(struct ir *ir, struct vinsn *last)
+static int ir_bpf_registerize_one(struct ir *ir, struct vinsn *last)
 {
 	struct vinsn *vi;
 	uint16_t clean = 0x3ff;
@@ -538,7 +542,8 @@ int ir_bpf_registerize_one(struct ir *ir, struct vinsn *last)
 			clean &= ~(1 << vi->insn.src);
 		if (!(vi->insn.dst & vreg_base))
 			clean &= ~(1 << vi->insn.dst);
-		if (vi->insn.bpf.code == (BPF_JMP | BPF_CALL))
+		if ((BPF_CLASS(vi->insn.bpf.code) == BPF_JMP)
+		    && (BPF_OP(vi->insn.bpf.code) == BPF_CALL))
 			clean &= ~BPF_REG_CALLER_SAVE;
 	}
 
@@ -555,7 +560,7 @@ int ir_bpf_registerize_one(struct ir *ir, struct vinsn *last)
 	return -1;
 }
 
-int ir_bpf_registerize(struct ir *ir)
+static int ir_bpf_registerize(struct ir *ir)
 {
 	struct vinsn *vi;
 	int err = 0;
@@ -576,6 +581,50 @@ int ir_bpf_registerize(struct ir *ir)
 	return err;
 }
 
+static int ir_bpf_jmp_resolve_one(struct ir *ir, struct vinsn *jmp)
+{
+	struct vinsn *vi;
+	int off = 0;
+
+	for (vi = jmp + 1; vi < &ir->vi[ir->len - 1]; vi++) {
+		switch (vi->vitype) {
+		case VI_INSN:
+			off++;
+			break;
+		case VI_LABEL:
+			if (vi->label != jmp->insn.bpf.off)
+				break;
+
+			jmp->insn.bpf.off = off;
+			return 0;
+		default:
+			break;
+		}
+	}
+
+	return -ENOENT;
+}
+
+static int ir_bpf_jmp_resolve(struct ir *ir)
+{
+	struct vinsn *vi;
+	int err;
+
+	for (vi = ir->vi; vi < &ir->vi[ir->len - 1]; vi++) {
+		if (vi->vitype != VI_INSN)
+			continue;
+
+		if ((BPF_CLASS(vi->insn.bpf.code) == BPF_JMP)
+		    && (vi->insn.bpf.off < 0)) {
+			err = ir_bpf_jmp_resolve_one(ir, vi);
+			if (err)
+				return err;
+		}
+	}
+
+	return 0;
+}
+
 int ir_bpf_generate(struct ir *ir)
 {
 	int err;
@@ -584,5 +633,13 @@ int ir_bpf_generate(struct ir *ir)
 	if (err)
 		return err;
 
+	/* no instructions will be added/removed to the program after
+	 * this point, thus it is now safe to convert labeled jumps to
+	 * fixed offsets. */
+	
+	err = ir_bpf_jmp_resolve(ir);
+	if (err)
+		return err;
+
 	return 0;
 }