[dpdk-dev] [PATCH v4 4/8] bpf: add function to dump eBPF instructions

[Stephen Hemminger <stephen@networkplumber.org>]

When debugging converted (and other) programs it is useful
to see disassembled eBPF output.

Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
---
 lib/bpf/bpf_dump.c  | 118 ++++++++++++++++++++++++++++++++++++++++++++
 lib/bpf/meson.build |   1 +
 lib/bpf/rte_bpf.h   |  14 ++++++
 lib/bpf/version.map |   1 +
 4 files changed, 134 insertions(+)
 create mode 100644 lib/bpf/bpf_dump.c

diff --git a/lib/bpf/bpf_dump.c b/lib/bpf/bpf_dump.c
new file mode 100644
index 000000000000..a6a431e64903
--- /dev/null
+++ b/lib/bpf/bpf_dump.c
@@ -0,0 +1,118 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ * Copyright (c) 2021 Stephen Hemminger
+ * Based on filter2xdp
+ * Copyright (C) 2017 Tobias Klauser
+ */
+
+#include <stdio.h>
+#include <stdint.h>
+
+#include "rte_bpf.h"
+
+#define BPF_OP_INDEX(x) (BPF_OP(x) >> 4)
+#define BPF_SIZE_INDEX(x) (BPF_SIZE(x) >> 3)
+
+static const char *const class_tbl[] = {
+	[BPF_LD] = "ld",   [BPF_LDX] = "ldx",	 [BPF_ST] = "st",
+	[BPF_STX] = "stx", [BPF_ALU] = "alu",	 [BPF_JMP] = "jmp",
+	[BPF_RET] = "ret", [BPF_MISC] = "alu64",
+};
+
+static const char *const alu_op_tbl[16] = {
+	[BPF_ADD >> 4] = "add",	   [BPF_SUB >> 4] = "sub",
+	[BPF_MUL >> 4] = "mul",	   [BPF_DIV >> 4] = "div",
+	[BPF_OR >> 4] = "or",	   [BPF_AND >> 4] = "and",
+	[BPF_LSH >> 4] = "lsh",	   [BPF_RSH >> 4] = "rsh",
+	[BPF_NEG >> 4] = "neg",	   [BPF_MOD >> 4] = "mod",
+	[BPF_XOR >> 4] = "xor",	   [EBPF_MOV >> 4] = "mov",
+	[EBPF_ARSH >> 4] = "arsh", [EBPF_END >> 4] = "endian",
+};
+
+static const char *const size_tbl[] = {
+	[BPF_W >> 3] = "w",
+	[BPF_H >> 3] = "h",
+	[BPF_B >> 3] = "b",
+	[EBPF_DW >> 3] = "dw",
+};
+
+static const char *const jump_tbl[16] = {
+	[BPF_JA >> 4] = "ja",	   [BPF_JEQ >> 4] = "jeq",
+	[BPF_JGT >> 4] = "jgt",	   [BPF_JGE >> 4] = "jge",
+	[BPF_JSET >> 4] = "jset",  [EBPF_JNE >> 4] = "jne",
+	[EBPF_JSGT >> 4] = "jsgt", [EBPF_JSGE >> 4] = "jsge",
+	[EBPF_CALL >> 4] = "call", [EBPF_EXIT >> 4] = "exit",
+};
+
+static void ebpf_dump(FILE *f, const struct ebpf_insn insn, size_t n)
+{
+	const char *op, *postfix = "";
+	uint8_t cls = BPF_CLASS(insn.code);
+
+	fprintf(f, " L%zu:\t", n);
+
+	switch (cls) {
+	default:
+		fprintf(f, "unimp 0x%x // class: %s\n", insn.code,
+			class_tbl[cls]);
+		break;
+	case BPF_ALU:
+		postfix = "32";
+		/* fall through */
+	case EBPF_ALU64:
+		op = alu_op_tbl[BPF_OP_INDEX(insn.code)];
+		if (BPF_SRC(insn.code) == BPF_X)
+			fprintf(f, "%s%s r%u, r%u\n", op, postfix, insn.dst_reg,
+				insn.src_reg);
+		else
+			fprintf(f, "%s%s r%u, #0x%x\n", op, postfix,
+				insn.dst_reg, insn.imm);
+		break;
+	case BPF_LD:
+		op = "ld";
+		postfix = size_tbl[BPF_SIZE_INDEX(insn.code)];
+		if (BPF_MODE(insn.code) == BPF_IMM)
+			fprintf(f, "%s%s r%d, #0x%x\n", op, postfix,
+				insn.dst_reg, insn.imm);
+		else if (BPF_MODE(insn.code) == BPF_ABS)
+			fprintf(f, "%s%s r%d, [%d]\n", op, postfix,
+				insn.dst_reg, insn.imm);
+		else if (BPF_MODE(insn.code) == BPF_IND)
+			fprintf(f, "%s%s r%d, [r%u + %d]\n", op, postfix,
+				insn.dst_reg, insn.src_reg, insn.imm);
+		else
+			fprintf(f, "// BUG: LD opcode 0x%02x in eBPF insns\n",
+				insn.code);
+		break;
+	case BPF_LDX:
+		op = "ldx";
+		postfix = size_tbl[BPF_SIZE_INDEX(insn.code)];
+		fprintf(f, "%s%s r%d, [r%u + %d]\n", op, postfix, insn.dst_reg,
+			insn.src_reg, insn.off);
+		break;
+#define L(pc, off) ((int)(pc) + 1 + (off))
+	case BPF_JMP:
+		op = jump_tbl[BPF_OP_INDEX(insn.code)];
+		if (op == NULL)
+			fprintf(f, "invalid jump opcode: %#x\n", insn.code);
+		else if (BPF_OP(insn.code) == BPF_JA)
+			fprintf(f, "%s L%d\n", op, L(n, insn.off));
+		else if (BPF_OP(insn.code) == EBPF_EXIT)
+			fprintf(f, "%s\n", op);
+		else
+			fprintf(f, "%s r%u, #0x%x, L%d\n", op, insn.dst_reg,
+				insn.imm, L(n, insn.off));
+		break;
+	case BPF_RET:
+		fprintf(f, "// BUG: RET opcode 0x%02x in eBPF insns\n",
+			insn.code);
+		break;
+	}
+}
+
+void rte_bpf_dump(FILE *f, const struct ebpf_insn *buf, uint32_t len)
+{
+	uint32_t i;
+
+	for (i = 0; i < len; ++i)
+		ebpf_dump(f, buf[i], i);
+}
diff --git a/lib/bpf/meson.build b/lib/bpf/meson.build
index 54f7610ae990..5b5585173aeb 100644
--- a/lib/bpf/meson.build
+++ b/lib/bpf/meson.build
@@ -2,6 +2,7 @@
 # Copyright(c) 2018 Intel Corporation
 
 sources = files('bpf.c',
+	'bpf_dump.c',
         'bpf_exec.c',
         'bpf_load.c',
         'bpf_pkt.c',
diff --git a/lib/bpf/rte_bpf.h b/lib/bpf/rte_bpf.h
index 2f23e272a376..0d0a84b130a0 100644
--- a/lib/bpf/rte_bpf.h
+++ b/lib/bpf/rte_bpf.h
@@ -198,6 +198,20 @@ rte_bpf_exec_burst(const struct rte_bpf *bpf, void *ctx[], uint64_t rc[],
 int
 rte_bpf_get_jit(const struct rte_bpf *bpf, struct rte_bpf_jit *jit);
 
+/**
+ * Dump epf instructions to a file.
+ *
+ * @param f
+ *   A pointer to a file for output
+ * @param buf
+ *   A pointer to BPF instructions
+ * @param len
+ *   Number of BPF instructions to dump.
+ */
+__rte_experimental
+void
+rte_bpf_dump(FILE *f, const struct ebpf_insn *buf, uint32_t len);
+
 #ifdef RTE_PORT_PCAP
 
 struct bpf_program;
diff --git a/lib/bpf/version.map b/lib/bpf/version.map
index 47082d5003ef..3b953f2f4592 100644
--- a/lib/bpf/version.map
+++ b/lib/bpf/version.map
@@ -19,4 +19,5 @@ EXPERIMENTAL {
 	global:
 
 	rte_bpf_convert;
+	rte_bpf_dump;
 };
-- 
2.30.2