Thanks for quick response. Log and .config file is in attachment. KGDBoE shows no error on build and looks like it is installed successfully. In meantime I’m trying to get debug running using LPC-Link 2 probe JTAG with CMSIS-DAP firmware.

Kernel module project running on Kernel build from VisualKernel and set “Kernel type” to it (so symbols should match) throws same error. Output from debug UART on device:

kgdboe: loading out-of-tree module taints kernel.
netpoll: kgdboe: local IP 10.0.7.134
kgdboe: single-core mode enabled. Shutting down all cores except #0. This is slower, but safer.
kgdboe: you can try using multi-core mode by specifying the following argument:
	insmod kgdboe.ko force_single_core = 0
CPU1: shutdown
KGDB: Registered I/O driver kgdboe
kgdboe: Successfully initialized. Use the following gdb command to attach:
	target remote udp:10.0.7.134:31337
LinuxKernelModule1: module license 'Proprietary' taints kernel.
Disabling lock debugging due to kernel taint
LinuxKernelModule1: Hello, world!
LinuxKernelModule1: Goodbye, world!

Log is in attachment.

I have tried to change “Obtain module information via:” to “Optimized helper module”. Looks like it at least detect module in “Modules” tab and symbols tab points to correct object, but now I get error in UART debug console and module does not run. Without Optimized helper module I cannot see module in “Modules” tab (lsmod displays it correctly on device) so it is probably cause of why debugging symbols are not loaded in my previous post.

LinuxKernelModule1: module license 'Proprietary' taints kernel.
Disabling lock debugging due to kernel taint
Unhandled prefetch abort: breakpoint debug exception (0x002) at 0x7f02a16c
Internal error: : 2 [#1] PREEMPT SMP ARM
Modules linked in: LinuxKernelModule1(PO+) LinuxKernelDebugHelper(O) ov5640_camera_mipi mxc_mipi_csi evbug mx6s_capture
CPU: 1 PID: 503 Comm: insmod Tainted: P           O    4.9.67-fslc+g953c6e30c970 #23
Hardware name: Freescale i.MX7 Dual (Device Tree)
task: a8460580 task.stack: a8606000
PC is at ModuleEventCallback+0x0/0x18 [LinuxKernelDebugHelper]
LR is at ModuleNotificationCallback+0x144/0x164 [LinuxKernelDebugHelper]
pc : [<7f02a16c>]    lr : [<7f02a40c>]    psr: 600b0013
sp : a8607e30  ip : 00000000  fp : a8607e4c
r10: a8880da4  r9 : 00000000  r8 : 00000001
r7 : 00000000  r6 : 7f02e0c0  r5 : 7f02aa40  r4 : 7f02a7f4
r3 : 7f02a16c  r2 : 00000054  r1 : 5456454d  r0 : 00000001
Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 10c53c7d  Table: a887806a  DAC: 00000051
Process insmod (pid: 503, stack limit = 0xa8606210)
Stack: (0xa8607e30 to 0xa8608000)
7e20:                                     a93673c8 00000001 a8880d80 7f02e0c0
7e40: a8607e5c a8607e50 7f02a448 7f02a2d4 a8607f1c a8607e60 801b21c0 7f02a438
7e60: 7f02e0cc 00007fff 7f02e0c0 801ae804 0000f1e8 00000000 80d567d4 80d56910
7e80: 80d567fc 7f02e0cc a8607f44 7f02e0cc 80b039e0 7f02e2a4 7f02e108 024000c0
7ea0: a8607eec a8607eb0 80259170 80258fcc c0ab1000 00000000 00006c65 00000000
7ec0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
7ee0: 00000000 00000000 00000000 00000000 7fffffff 00000000 00000003 0045c378
7f00: 0000017b 80108504 a8606000 00000000 a8607fa4 a8607f20 801b260c 801b00f0
7f20: 7fffffff 00000000 00000003 a8607f38 8021e104 c0ab1000 0000f1e8 00000000
7f40: 00000000 c0ab1000 0000f1e8 c0abfbf8 c0abfa70 c0abcba4 000002c0 00000390
7f60: 00000000 00000000 00000000 00000490 00000023 00000024 0000000e 00000012
7f80: 00000008 00000000 00000000 00000000 00c7d190 00000000 00000000 a8607fa8
7fa0: 80108340 801b2564 00000000 00c7d190 00000003 0045c378 00000000 7edfdbfc
7fc0: 00000000 00c7d190 00000000 0000017b 00000002 00000002 0046ee28 00000000
7fe0: 7edfdc00 7edfdbf0 004551e7 76e7b5f2 60030030 00000003 0a746961 0000000a
[<7f02a16c>] (ModuleEventCallback [LinuxKernelDebugHelper]) from [<7f02a448>] (hook_module_load+0x1c/0x20 [LinuxKernelDebugHelper])
[<7f02a448>] (hook_module_load [LinuxKernelDebugHelper]) from [<801b21c0>] (load_module+0x20dc/0x2300)
[<801b21c0>] (load_module) from [<801b260c>] (SyS_finit_module+0xb4/0xcc)
[<801b260c>] (SyS_finit_module) from [<80108340>] (ret_fast_syscall+0x0/0x3c)
Code: e1a00004 eb487df8 e89da830 e7f001f2 (e1200171) 
---[ end trace 98d462b56ca2f876 ]---
note: insmod[503] exited with preempt_count 1

Hi,

I have tried to change to hardware breakpoints and it now breaks with SIGTRAP on first line in

/*
 * This is where the real work happens.
 *
 * Keep it uninlined to provide a reliable breakpoint target, e.g. for the gdb
 * helper command 'lx-symbols'.
 */
static noinline int do_init_module(struct module *mod)
{
	int ret = 0;
	struct mod_initfree *freeinit;

	freeinit = kmalloc(sizeof(*freeinit), GFP_KERNEL);
	if (!freeinit) {
		ret = -ENOMEM;
		goto fail;
	}
	freeinit->module_init = mod->init_layout.base;

	/*
	 * We want to find out whether @mod uses async during init.  Clear
	 * PF_USED_ASYNC.  async_schedule*() will set it.
	 */
	current->flags &= ~PF_USED_ASYNC;

	do_mod_ctors(mod);
	/* Start the module */
	if (mod->init != NULL)
		ret = do_one_initcall(mod->init);
	if (ret < 0) {
		goto fail_free_freeinit;
	}
	if (ret > 0) {
		pr_warn("%s: '%s'->init suspiciously returned %d, it should "
			"follow 0/-E convention\n"
			"%s: loading module anyway...\n",
			__func__, mod->name, ret, __func__);
		dump_stack();
	}

	/* Now it's a first class citizen! */
	mod->state = MODULE_STATE_LIVE;
	blocking_notifier_call_chain(&module_notify_list,
				     MODULE_STATE_LIVE, mod);

	/*
	 * We need to finish all async code before the module init sequence
	 * is done.  This has potential to deadlock.  For example, a newly
	 * detected block device can trigger request_module() of the
	 * default iosched from async probing task.  Once userland helper
	 * reaches here, async_synchronize_full() will wait on the async
	 * task waiting on request_module() and deadlock.
	 *
	 * This deadlock is avoided by perfomring async_synchronize_full()
	 * iff module init queued any async jobs.  This isn't a full
	 * solution as it will deadlock the same if module loading from
	 * async jobs nests more than once; however, due to the various
	 * constraints, this hack seems to be the best option for now.
	 * Please refer to the following thread for details.
	 *
	 * http://thread.gmane.org/gmane.linux.kernel/1420814
	 */
	if (!mod->async_probe_requested && (current->flags & PF_USED_ASYNC))
		async_synchronize_full();

	mutex_lock(&module_mutex);
	/* Drop initial reference. */
	module_put(mod);
	trim_init_extable(mod);
#ifdef CONFIG_KALLSYMS
	/* Switch to core kallsyms now init is done: kallsyms may be walking! */
	rcu_assign_pointer(mod->kallsyms, &mod->core_kallsyms);
#endif
	module_enable_ro(mod, true);
	mod_tree_remove_init(mod);
	disable_ro_nx(&mod->init_layout);
	module_arch_freeing_init(mod);
	mod->init_layout.base = NULL;
	mod->init_layout.size = 0;
	mod->init_layout.ro_size = 0;
	mod->init_layout.ro_after_init_size = 0;
	mod->init_layout.text_size = 0;
	/*
	 * We want to free module_init, but be aware that kallsyms may be
	 * walking this with preempt disabled.  In all the failure paths, we
	 * call synchronize_sched(), but we don't want to slow down the success
	 * path, so use actual RCU here.
	 */
	call_rcu_sched(&freeinit->rcu, do_free_init);
	mutex_unlock(&module_mutex);
	wake_up_all(&module_wq);

	return 0;

fail_free_freeinit:
	kfree(freeinit);
fail:
	/* Try to protect us from buggy refcounters. */
	mod->state = MODULE_STATE_GOING;
	synchronize_sched();
	module_put(mod);
	blocking_notifier_call_chain(&module_notify_list,
				     MODULE_STATE_GOING, mod);
	klp_module_going(mod);
	ftrace_release_mod(mod);
	free_module(mod);
	wake_up_all(&module_wq);
	return ret;
}

However I was able to start debugging with workaround correctly using J-LINK with official driver and J-Link GDB server. Next I setup Custom kernel connection on Host/Port provided by GDB server and select Before debugging, target is: Crashed/frozen in Kernel session tweaking category, because GDB server puts MCU to halted state automatically. Kernel module is not loaded automatically this way, so It must be loaded manually over SSH or from GDB session tab.

Thanks for all support.