From 273c50454f646d4f425035c8f60f300ad8c2c5f3 Mon Sep 17 00:00:00 2001
From: disconnect3d <dominik.b.czarnota@gmail.com>
Date: Sat, 1 Apr 2023 15:55:11 +0200
Subject: [PATCH] Warn about untested network drivers

This commit adds detection for the driver used by the provided network
interface and if an untested one is used (like igb, for which things
halted for me) a warning is printed.

This may help users to find out that they used wrong interface or a
driver.
---
 kgdboe_io.c | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/kgdboe_io.c b/kgdboe_io.c
index 75940c7..8f193cd 100644
--- a/kgdboe_io.c
+++ b/kgdboe_io.c
@@ -1,4 +1,6 @@
 #include <linux/kgdb.h>
+#include <linux/namei.h>
+#include <linux/dcache.h>
 #include <linux/module.h>
 #include <linux/kallsyms.h>
 #include <linux/cpu.h>
@@ -161,6 +163,30 @@ int force_single_cpu_mode(void)
 	return 0;
 }
 
+
+void check_device_driver_and_warn_if_untested(const char* device_name)
+{
+	char driver_symlink[256] = {0};
+	snprintf(driver_symlink, sizeof(driver_symlink), "/sys/class/net/%s/device/driver", device_name);
+
+	struct path path;
+
+	int err = kern_path(driver_symlink, LOOKUP_FOLLOW, &path);
+
+	if (err == 0) {
+		char symlink_target[256] = {0};
+		char* ptr = d_path(&path, symlink_target, sizeof(symlink_target));
+		if (!IS_ERR(ptr)) {
+			if (strstr(ptr, "pcnet32") || strstr(ptr, "e1000") || strstr(ptr, "r8169"))
+				return;
+
+			printk(KERN_WARNING "kgdboe: WARNING: kgdboe was only tested on pcnet32, e1000 and r8169 (Detected driver: %s). Other drivers may hang.\n", ptr);
+			return;
+		}
+	}
+	printk(KERN_WARNING "kgdboe: WARNING: could not detect the driver for %s device (via readlink %s). Note that kgdboe was only tested on pcnet32, e1000 and r8169. Other drivers may hang.\n", device_name, driver_symlink);
+}
+
 int kgdboe_io_init(const char *device_name, int port, const char *local_ip, bool force_single_core)
 {
 	int err;
@@ -168,6 +194,8 @@ int kgdboe_io_init(const char *device_name, int port, const char *local_ip, bool
 
 	spin_lock_init(&exception_lock);
 
+	check_device_driver_and_warn_if_untested(device_name);
+	
 	s_pKgdboeNetpoll = netpoll_wrapper_create(device_name, port, local_ip);
 	if (!s_pKgdboeNetpoll)
 		return -EINVAL;