Message-ID: <axujhror2lskp3bxfslursibmlo6qwuzhc2tgfb4jea7progc3@4op6ajqu35c2>
Date: Fri, 13 Jun 2025 17:58:57 +0200
From: Luigi Leonardi <leonardi@...hat.com>
To: Michal Luczaj <mhal@...x.co>
Cc: Stefano Garzarella <sgarzare@...hat.com>, 
	virtualization@...ts.linux.dev, netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 2/3] vsock/test: Introduce get_transports()

Hi Michal,

On Wed, Jun 11, 2025 at 09:56:51PM +0200, Michal Luczaj wrote:
>Return a bitmap of registered vsock transports. As guesstimated by 
>grepping
>/proc/kallsyms (CONFIG_KALLSYMS=y) for known symbols of type `struct
>vsock_transport`, or `struct virtio_transport` in case the 
>vsock_transport
>is embedded within.
>
>Note that the way `enum transport` and `transport_ksyms[]` are defined
>triggers checkpatch.pl:
>
>util.h:11: ERROR: Macros with complex values should be enclosed in 
>parentheses
>util.h:20: ERROR: Macros with complex values should be enclosed in 
>parentheses
>util.h:20: WARNING: Argument 'symbol' is not used in function-like 
>macro
>util.h:28: WARNING: Argument 'name' is not used in function-like macro
>
>While commit 15d4734c7a58 ("checkpatch: qualify do-while-0 advice")
>suggests it is known that the ERRORs heuristics are insufficient, I can 
>not
>find many other places where preprocessor is used in this
>checkpatch-unhappy fashion. Notable exception being bcachefs, e.g.
>fs/bcachefs/alloc_background_format.h. WARNINGs regarding unused macro
>arguments seem more common, e.g. __ASM_SEL in 
>arch/x86/include/asm/asm.h.
>
>In other words, this might be unnecessarily complex. The same can be
>achieved by just telling human to keep the order:
>
>enum transport {
>	TRANSPORT_LOOPBACK = BIT(0),
>	TRANSPORT_VIRTIO = BIT(1),
>	TRANSPORT_VHOST = BIT(2),
>	TRANSPORT_VMCI = BIT(3),
>	TRANSPORT_HYPERV = BIT(4),
>	TRANSPORT_NUM = 5,
>};
>
> #define KSYM_ENTRY(sym) "d " sym "_transport"
>
>/* Keep `enum transport` order */
>static const char * const transport_ksyms[] = {
>	KSYM_ENTRY("loopback"),
>	KSYM_ENTRY("virtio"),
>	KSYM_ENTRY("vhost"),
>	KSYM_ENTRY("vmci"),
>	KSYM_ENTRY("vhs"),
>};
>
>Suggested-by: Stefano Garzarella <sgarzare@...hat.com>
>Signed-off-by: Michal Luczaj <mhal@...x.co>
>---
> tools/testing/vsock/util.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++
> tools/testing/vsock/util.h | 29 ++++++++++++++++++++++++
> 2 files changed, 85 insertions(+)
>
>diff --git a/tools/testing/vsock/util.c b/tools/testing/vsock/util.c
>index b7b3fb2221c1682ecde58cf12e2f0b0ded1cff39..803f1e075b62228c25f9dffa1eff131b8072a06a 100644
>--- a/tools/testing/vsock/util.c
>+++ b/tools/testing/vsock/util.c
>@@ -7,6 +7,7 @@
>  * Author: Stefan Hajnoczi <stefanha@...hat.com>
>  */
>
>+#include <ctype.h>
> #include <errno.h>
> #include <stdio.h>
> #include <stdint.h>
>@@ -23,6 +24,9 @@
> #include "control.h"
> #include "util.h"
>
>+#define KALLSYMS_PATH		"/proc/kallsyms"
>+#define KALLSYMS_LINE_LEN	512
>+
> /* Install signal handlers */
> void init_signals(void)
> {
>@@ -854,3 +858,55 @@ void enable_so_linger(int fd, int timeout)
> 		exit(EXIT_FAILURE);
> 	}
> }
>+
>+static int __get_transports(void)
>+{
>+	char buf[KALLSYMS_LINE_LEN];
>+	const char *ksym;
>+	int ret = 0;
>+	FILE *f;
>+
>+	f = fopen(KALLSYMS_PATH, "r");
>+	if (!f) {
>+		perror("Can't open " KALLSYMS_PATH);
>+		exit(EXIT_FAILURE);
>+	}
>+
>+	while (fgets(buf, sizeof(buf), f)) {
>+		char *match;
>+		int i;
>+
>+		assert(buf[strlen(buf) - 1] == '\n');
>+
>+		for (i = 0; i < TRANSPORT_NUM; ++i) {
>+			if (ret & BIT(i))
>+				continue;
>+
>+			/* Match should be followed by '\t' or '\n'.
>+			 * See kallsyms.c:s_show().
>+			 */
>+			ksym = transport_ksyms[i];
>+			match = strstr(buf, ksym);
>+			if (match && isspace(match[strlen(ksym)])) {
>+				ret |= BIT(i);
>+				break;
>+			}
>+		}
>+	}
>+
>+	fclose(f);
>+	return ret;
>+}
>+
>+/* Return integer with TRANSPORT_* bit set for every (known) registered vsock
>+ * transport.
>+ */
>+int get_transports(void)
>+{
>+	static int tr = -1;
>+
>+	if (tr == -1)
>+		tr = __get_transports();
>+
>+	return tr;
>+}
>diff --git a/tools/testing/vsock/util.h b/tools/testing/vsock/util.h
>index 0afe7cbae12e5194172c639ccfbeb8b81f7c25ac..71895192cc02313bf52784e2f77aa3b0c28a0c94 100644
>--- a/tools/testing/vsock/util.h
>+++ b/tools/testing/vsock/util.h
>@@ -3,8 +3,36 @@
> #define UTIL_H
>
> #include <sys/socket.h>
>+#include <linux/bitops.h>
>+#include <linux/kernel.h>
> #include <linux/vm_sockets.h>
>
>+/* All known vsock transports, see callers of vsock_core_register() */
>+#define KNOWN_TRANSPORTS(x)		\
>+	x(LOOPBACK, "loopback")		\
>+	x(VIRTIO, "virtio")		\
>+	x(VHOST, "vhost")		\
>+	x(VMCI, "vmci")			\
>+	x(HYPERV, "hvs")
>+
>+enum transport {
>+	TRANSPORT_COUNTER_BASE = __COUNTER__ + 1,
>+	#define x(name, symbol)		\
>+		TRANSPORT_##name = BIT(__COUNTER__ - TRANSPORT_COUNTER_BASE),
>+	KNOWN_TRANSPORTS(x)
>+	TRANSPORT_NUM = __COUNTER__ - TRANSPORT_COUNTER_BASE,
>+	#undef x
>+};
>+
>+static const char * const transport_ksyms[] = {
>+	#define x(name, symbol) "d " symbol "_transport",
>+	KNOWN_TRANSPORTS(x)
>+	#undef x
>+};
>+
>+static_assert(ARRAY_SIZE(transport_ksyms) == TRANSPORT_NUM);
>+static_assert(BITS_PER_TYPE(int) >= TRANSPORT_NUM);
>+
> /* Tests can either run as the client or the server */
> enum test_mode {
> 	TEST_MODE_UNSET,
>@@ -82,4 +110,5 @@ void setsockopt_timeval_check(int fd, int level, int optname,
> 			      struct timeval val, char const *errmsg);
> void enable_so_zerocopy_check(int fd);
> void enable_so_linger(int fd, int timeout);
>+int get_transports(void);
> #endif /* UTIL_H */
>
>-- 
>2.49.0
>

Checked the code and tested `get_transports()`. It works as expected!
I'm not sure about the `checkpatch.pl` errors, but code LGTM to me.

Tested-by: Luigi Leonardi <leonardi@...hat.com>
Reviewed-by: Luigi Leonardi <leonardi@...hat.com>

Thanks!
Luigi

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