BPF standardization

[Konstantin Ananyev]

> This was taken from how kernel converts cBPF and the prologue it generates.
> Surprising that verifier gags?

Indeed it looks strange...
Have to admit I didn't dig into how linux converter works...
Below is the patch I used to test it from DPDK UT - might be you'll spot something obvious here.  

================

Subject: [PATCH 2/2] test/bpf: call linux verifier for converted cBPF filter

To ensure DPDK/kernel compatibility for converted cBPF filters, etc.

Signed-off-by: Konstantin Ananyev <konstantin.ananyev at huawei.com>
---
 app/test/meson.build             |  1 +
 app/test/test_bpf.c              | 11 +++++++++
 app/test/test_bpf.h              | 12 ++++++++++
 app/test/test_bpf_verify_linux.c | 39 ++++++++++++++++++++++++++++++++
 4 files changed, 63 insertions(+)
 create mode 100644 app/test/test_bpf.h
 create mode 100644 app/test/test_bpf_verify_linux.c

diff --git a/app/test/meson.build b/app/test/meson.build
index e29258e6ec..d46e688db5 100644
--- a/app/test/meson.build
+++ b/app/test/meson.build
@@ -35,6 +35,7 @@ source_file_deps = {
     'test_bitops.c': [],
     'test_bitratestats.c': ['metrics', 'bitratestats', 'ethdev'] + sample_packet_forward_deps,
     'test_bpf.c': ['bpf', 'net'],
+    'test_bpf_verify_linux.c': [],
     'test_byteorder.c': [],
 #    'test_cfgfile.c': ['cfgfile'],
     'test_cksum.c': ['net'],
diff --git a/app/test/test_bpf.c b/app/test/test_bpf.c
index 7819d6aba9..749f9de20c 100644
--- a/app/test/test_bpf.c
+++ b/app/test/test_bpf.c
@@ -15,6 +15,7 @@
 #include <rte_byteorder.h>
 #include <rte_errno.h>
 #include "test.h"
+#include "test_bpf.h"
 
 #if !defined(RTE_LIB_BPF)
 
@@ -3431,10 +3432,13 @@ static const char * const sample_filters[] = {
 static int
 test_bpf_filter(pcap_t *pcap, const char *s)
 {
+	int32_t rc;
 	struct bpf_program fcode;
 	struct rte_bpf_prm *prm = NULL;
 	struct rte_bpf *bpf = NULL;
 
+	static char logbuf[UINT16_MAX + 1];
+
 	if (pcap_compile(pcap, &fcode, s, 1, PCAP_NETMASK_UNKNOWN)) {
 		printf("%s@%d: pcap_compile('%s') failed: %s;\n",
 		       __func__, __LINE__, s, pcap_geterr(pcap));
@@ -3451,6 +3455,13 @@ test_bpf_filter(pcap_t *pcap, const char *s)
 	printf("bpf convert for \"%s\" produced:\n", s);
 	rte_bpf_dump(stdout, prm->ins, prm->nb_ins);
 
+	rc = bpf_linux_verify(prm, logbuf, sizeof(logbuf));
+	printf("%s@%d: linux verifier reports: %d(%s);\n",
+		__func__, __LINE__, rc, strerror(-rc));
+	printf("linux verifier log: %s\n", logbuf);
+	if (rc != 0)
+		goto error;
+
 	bpf = rte_bpf_load(prm);
 	if (bpf == NULL) {
 		printf("%s@%d: failed to load bpf code, error=%d(%s);\n",
diff --git a/app/test/test_bpf.h b/app/test/test_bpf.h
new file mode 100644
index 0000000000..e5be2be920
--- /dev/null
+++ b/app/test/test_bpf.h
@@ -0,0 +1,12 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef _TEST_BPF_H_
+#define _TEST_BPF_H_
+
+#include <rte_bpf.h>
+
+int bpf_linux_verify(const struct rte_bpf_prm *prm, char *logbuf,
+	uint32_t lbsz);
+
+#endif
diff --git a/app/test/test_bpf_verify_linux.c b/app/test/test_bpf_verify_linux.c
new file mode 100644
index 0000000000..2a42d61fb5
--- /dev/null
+++ b/app/test/test_bpf_verify_linux.c
@@ -0,0 +1,39 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdio.h>
+#include <string.h>
+#include <stdint.h>
+#include <inttypes.h>
+#include <linux/bpf.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+
+#include "test_bpf.h"
+
+int
+bpf_linux_verify(const struct rte_bpf_prm *prm, char *logbuf, uint32_t lbsz)
+{
+	int32_t rc;
+	union bpf_attr attr;
+
+	memset(&attr, 0, sizeof(attr));
+	attr.prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
+	attr.insn_cnt = prm->nb_ins;
+	attr.insns = (uintptr_t)prm->ins;
+	attr.license = (uintptr_t)"GPL";
+	attr.log_buf = (uintptr_t)logbuf;
+	attr.log_size = lbsz;
+	attr.log_level = (logbuf == NULL) ? 0 : 3;
+
+	rc = syscall(SYS_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
+	if (rc < 0)
+		rc = -errno;
+	else {
+		/* closed fd for BPF prog */
+		close(rc);
+		rc = 0;
+	}
+
+	return rc;
+}
-- 
2.35.3