@vladimir Thanks!

Here is the output of dmesg after the segfault.

[ 91.878302] tdevmon: hooking /dev/ttyUSB0 (fops: 9174bd4c)
[ 91.878332] 8<--- cut here ---
[ 91.878347] Unable to handle kernel paging request at virtual address c0c48068
[ 91.878363] pgd = 2f6d8e2b
[ 91.878378] [c0c48068] *pgd=80000000007003, *pmd=40000000c0079d(bad)
[ 91.878421] Internal error: Oops: a0e [#1] SMP ARM
[ 91.878433] Modules linked in: exfat rfcomm cmac algif_hash aes_arm_bs crypto_simd cryptd algif_skcipher af_alg bnep hci_uart btbcm bluetooth ecdh_generic ecc snd_soc_hdmi_codec 8021q garp stp llc joydev ftdi_sio usbserial brcmfmac brcmutil v3d cfg80211 gpu_sched rfkill raspberrypi_hwmon i2c_brcmstb bcm2835_isp(C) bcm2835_v4l2(C) bcm2835_codec(C) snd_bcm2835(C) bcm2835_mmal_vchiq(C) v4l2_mem2mem videobuf2_vmalloc videobuf2_dma_contig videobuf2_memops videobuf2_v4l2 videobuf2_common videodev mc vc_sm_cma(C) vc4 rpivid_mem cec drm_kms_helper snd_soc_core snd_compress snd_pcm_dmaengine snd_pcm snd_timer snd syscopyarea sysfillrect sysimgblt fb_sys_fops nvmem_rmem uio_pdrv_genirq uio sg tdevmon(O) i2c_dev drm fuse drm_panel_orientation_quirks backlight ip_tables x_tables ipv6
[ 91.878787] CPU: 3 PID: 1116 Comm: tdevmon Tainted: G C O 5.15.32-v7l+ #1538
[ 91.878801] Hardware name: BCM2711
[ 91.878810] PC is at Hook_create+0x150/0x230 [tdevmon]
[ 91.878854] LR is at 0x0
[ 91.878863] pc : [<bf192e74>] lr : [<00000000>] psr: 40000013
[ 91.878873] sp : c2b03e70 ip : 00000020 fp : c2b03ea4
[ 91.878883] r10: 00000000 r9 : bf19a448 r8 : c341bcc8
[ 91.878891] r7 : c2b03eac r6 : c0c48030 r5 : c0c480b0 r4 : c3534180
[ 91.878901] r3 : bf1935f8 r2 : 00000000 r1 : c0c480b0 r0 : c353418c
[ 91.878910] Flags: nZcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user
[ 91.878924] Control: 30c5383d Table: 04a73b00 DAC: 55555555
[ 91.878932] Register r0 information: slab kmalloc-192 start c3534180 pointer offset 12 size 192
[ 91.878967] Register r1 information: non-slab/vmalloc memory
[ 91.878982] Register r2 information: NULL pointer
[ 91.878996] Register r3 information: 13-page vmalloc region starting at 0xbf191000 allocated at load_module+0xb94/0x2840
[ 91.879025] Register r4 information: slab kmalloc-192 start c3534180 pointer offset 0 size 192
[ 91.879057] Register r5 information: non-slab/vmalloc memory
[ 91.879070] Register r6 information: non-slab/vmalloc memory
[ 91.879082] Register r7 information: non-slab/vmalloc memory
[ 91.879095] Register r8 information: slab filp start c341bcc0 pointer offset 8
[ 91.879122] Register r9 information: 13-page vmalloc region starting at 0xbf191000 allocated at load_module+0xb94/0x2840
[ 91.879141] Register r10 information: NULL pointer
[ 91.879154] Register r11 information: non-slab/vmalloc memory
[ 91.879167] Register r12 information: non-paged memory
[ 91.879179] Process tdevmon (pid: 1116, stack limit = 0x3d367e2b)
[ 91.879190] Stack: (0xc2b03e70 to 0xc2b04000)
[ 91.879202] 3e60: 00000000 00c0079d 04400000 3391a86e
[ 91.879215] 3e80: c2b03ea4 c341bcc0 bf19a440 c341b300 c0c48030 00000000 c2b03ee4 c2b03ea8
[ 91.879226] 3ea0: bf191f04 bf192d30 c2b03ee4 00000000 bf196e98 3391a86e c2b03f34 40086d0b
[ 91.879238] 3ec0: c341b300 c4a73cc0 00000000 c341b300 be942270 00000003 c2b03f0c c2b03ee8
[ 91.879249] 3ee0: bf1929d4 bf191d50 be942270 3391a86e 40086d0b c1205048 0000000c 00000000
[ 91.879261] 3f00: c2b03fa4 c2b03f10 c046ca40 bf1928a8 ffffff9c 00000000 00000000 0005a094
[ 91.879272] 3f20: c2b02000 00000142 c2b03f94 c341b300 c045333c c04516f8 00000902 00000000
[ 91.879283] 3f40: 00000000 00000000 00000000 00000000 00000902 00000000 00000000 00000000
[ 91.879294] 3f60: 00000000 00000000 c2b03fac 3391a86e c02152e0 3391a86e b6f13500 be942270
[ 91.879306] 3f80: 0006f000 0000000c 00000036 c0200244 c2b02000 00000036 00000000 c2b03fa8
[ 91.879317] 3fa0: c0200040 c046c920 be942270 0006f000 00000003 40086d0b be942270 00000015
[ 91.879328] 3fc0: be942270 0006f000 0000000c 00000036 be942258 be9423b4 40086d0b 00000015
[ 91.879339] 3fe0: b6d8d1a0 be942224 00026298 b6d8d1ac 60000010 00000003 00000000 00000000
[ 91.879347] Backtrace:
[ 91.879359] [<bf192d24>] (Hook_create [tdevmon]) from [<bf191f04>] (Device_p_connectImpl+0x1c0/0x274 [tdevmon])
[ 91.879420] r8:00000000 r7:c0c48030 r6:c341b300 r5:bf19a440 r4:c341bcc0
[ 91.879428] [<bf191d44>] (Device_p_connectImpl [tdevmon]) from [<bf1929d4>] (Device_fop_ioctl+0x138/0x3f0 [tdevmon])
[ 91.879484] r10:00000003 r9:be942270 r8:c341b300 r7:00000000 r6:c4a73cc0 r5:c341b300
[ 91.879493] r4:40086d0b
[ 91.879501] [<bf19289c>] (Device_fop_ioctl [tdevmon]) from [<c046ca40>] (sys_ioctl+0x12c/0xa20)
[ 91.879539] r7:00000000 r6:0000000c r5:c1205048 r4:40086d0b
[ 91.879547] [<c046c914>] (sys_ioctl) from [<c0200040>] (ret_fast_syscall+0x0/0x1c)
[ 91.879564] Exception stack(0xc2b03fa8 to 0xc2b03ff0)
[ 91.879575] 3fa0: be942270 0006f000 00000003 40086d0b be942270 00000015
[ 91.879587] 3fc0: be942270 0006f000 0000000c 00000036 be942258 be9423b4 40086d0b 00000015
[ 91.879597] 3fe0: b6d8d1a0 be942224 00026298 b6d8d1ac
[ 91.879609] r10:00000036 r9:c2b02000 r8:c0200244 r7:00000036 r6:0000000c r5:0006f000
[ 91.879617] r4:be942270
[ 91.879629] Code: e284000c eb57f4d4 e30335f8 e34b3f19 (e5863038)
[ 91.879641] ---[ end trace a838db62019b3702 ]---
[ 326.926021] v3d fec00000.v3d: MMU error from client CLE (4) at 0x74a1000, pte invalid

@vladimir Yes, this does give me a segfault. This is even after I installed the new kernel module you posted in your other message.

I get this far:

Session started
Capture started on /dev/ttyUSB0

pi@raspberrypi:~ $ sudo tdevmon --version
Tibbo Device Monitor v3.3.9 (arm32)
Built on: Sep 6 2021 09:37:19

Tibbo Device Monitor kernel module (arm32) v3.3.9
Built on: Jun 3 2022 16:40:26

pi@raspberrypi:~ $ uname -a
Linux raspberrypi 5.15.32-v7l+ #1538 SMP Thu Mar 31 19:39:41 BST 2022 armv7l GNU/Linux

I'm trying to use the evaluation copy to monitor serial activity on /dev/ttyUSB0. I got the kernel module installed and ran the app and created a serial monitor session on /dev/ttyUSB0. I get the "Capture started on /dev/ttyUSB0" message when I start capture but I don't see any data displayed. I know my device is sending data because the LEDs on the USB to serial adapter are flashing. Also, my application that is using the serial port is working. Why wouldn't I see the captured data when I start capturing?

I'm running on a Raspberry Pi 4.