Dear Linux folks,

Building Linux v5.8-rc4-25-gbfe91da29bfad with Clang/LLD 1:11~++20200701093119+ffee8040534-1~exp1 from Debian experimental for 32-bit (`ARCH=i386`), starting Weston (Wayland) or X.Org Server results in non-working screen, and Linux shows the trace below [1].

[ 502.044997] BUG: unable to handle page fault for address: 17ec6000 [ 502.045650] #PF: supervisor write access in kernel mode [ 502.046301] #PF: error_code(0x0002) - not-present page [ 502.046956] *pde = 00000000 [ 502.047612] Oops: 0002 [#1] SMP [ 502.048269] CPU: 0 PID: 2125 Comm: Xorg.wrap Not tainted 5.8.0-rc4-00105-g4da71f1ee6263 #141 [ 502.048967] Hardware name: System manufacturer System Product Name/F2A85-M PRO, BIOS 6601 11/25/2014 [ 502.049686] EIP: __srcu_read_lock+0x11/0x20 [ 502.050413] Code: 83 e0 03 50 56 68 72 c6 99 dd 68 46 c6 99 dd e8 3a c8 fe ff 83 c4 10 eb ce 0f 1f 44 00 00 55 89 e5 8b 48 68 8b 40 7c 83 e1 01 <64> ff 04 88 f0 83 44 24 fc 00 89 c8 5d c3 90 0f 1f 44 00 00 55 89 [ 502.052027] EAX: 00000000 EBX: f36671b8 ECX: 00000000 EDX: 00000286 [ 502.052856] ESI: f3f94eb8 EDI: f3e51c00 EBP: f303dd9c ESP: f303dd9c [ 502.053695] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246 [ 502.054543] CR0: 80050033 CR2: 17ec6000 CR3: 2eea2000 CR4: 000406d0 [ 502.055402] Call Trace: [ 502.056275] drm_minor_acquire+0x6f/0x140 [drm] [ 502.057162] drm_stub_open+0x2e/0x110 [drm] [ 502.058049] chrdev_open+0xdd/0x1e0 [ 502.058937] do_dentry_open+0x21d/0x330 [ 502.059828] vfs_open+0x23/0x30 [ 502.060718] path_openat+0x947/0xd60 [ 502.061610] ? unlink_anon_vmas+0x53/0x120 [ 502.062504] do_filp_open+0x6d/0x100 [ 502.063404] ? __alloc_fd+0x73/0x140 [ 502.064305] do_sys_openat2+0x1b3/0x2a0 [ 502.065217] __ia32_sys_openat+0x90/0xb0 [ 502.066128] ? prepare_exit_to_usermode+0xa/0x20 [ 502.067046] do_fast_syscall_32+0x68/0xd0 [ 502.067970] do_SYSENTER_32+0x12/0x20 [ 502.068902] entry_SYSENTER_32+0x9f/0xf2 [ 502.069839] EIP: 0xb7ef14f9 [ 502.070764] Code: Bad RIP value. [ 502.071689] EAX: ffffffda EBX: ffffff9c ECX: bfa6a2ac EDX: 00008002 [ 502.072654] ESI: 00000000 EDI: b7ed1000 EBP: bfa6b2c8 ESP: bfa6a1c0 [ 502.073630] DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 007b EFLAGS: 00000246 [ 502.074615] Modules linked in: af_packet k10temp r8169 realtek i2c_piix4 snd_hda_codec_realtek snd_hda_codec_generic ohci_pci ohci_hcd ehci_pci snd_hda_codec_hdmi ehci_hcd radeon i2c_algo_bit snd_hda_intel ttm snd_intel_dspcfg snd_hda_codec drm_kms_helper snd_hda_core snd_pcm cfbimgblt cfbcopyarea cfbfillrect snd_timer sysimgblt syscopyarea sysfillrect snd fb_sys_fops xhci_pci xhci_hcd soundcore acpi_cpufreq drm drm_panel_orientation_quirks agpgart ipv6 nf_defrag_ipv6 [ 502.077895] CR2: 0000000017ec6000 [ 502.079050] ---[ end trace ced4517b63a6db26 ]--- [ 502.080214] EIP: __srcu_read_lock+0x11/0x20 [ 502.081392] Code: 83 e0 03 50 56 68 72 c6 99 dd 68 46 c6 99 dd e8 3a c8 fe ff 83 c4 10 eb ce 0f 1f 44 00 00 55 89 e5 8b 48 68 8b 40 7c 83 e1 01 <64> ff 04 88 f0 83 44 24 fc 00 89 c8 5d c3 90 0f 1f 44 00 00 55 89 [ 502.083891] EAX: 00000000 EBX: f36671b8 ECX: 00000000 EDX: 00000286 [ 502.085148] ESI: f3f94eb8 EDI: f3e51c00 EBP: f303dd9c ESP: f303dd9c [ 502.086406] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246 [ 502.087675] CR0: 80050033 CR2: 17ec6000 CR3: 2eea2000 CR4: 000406d0

$ dmesg | ./scripts/decodecode [ 55.784870] Code: 83 e0 03 50 56 68 ca c6 99 cf 68 9e c6 99 cf e8 3a c8 fe ff 83 c4 10 eb ce 0f 1f 44 00 00 55 89 e5 8b 48 68 8b 40 7c 83 e1 01 <64> ff 04 88 f0 83 44 24 fc 00 89 c8 5d c3 90 0f 1f 44 00 00 55 89 All code ======== 0: 83 e0 03 and $0x3,%eax 3: 50 push %eax 4: 56 push %esi 5: 68 ca c6 99 cf push $0xcf99c6ca a: 68 9e c6 99 cf push $0xcf99c69e f: e8 3a c8 fe ff call 0xfffec84e 14: 83 c4 10 add $0x10,%esp 17: eb ce jmp 0xffffffe7 19: 0f 1f 44 00 00 nopl 0x0(%eax,%eax,1) 1e: 55 push %ebp 1f: 89 e5 mov %esp,%ebp 21: 8b 48 68 mov 0x68(%eax),%ecx 24: 8b 40 7c mov 0x7c(%eax),%eax 27: 83 e1 01 and $0x1,%ecx 2a:* 64 ff 04 88 incl %fs:(%eax,%ecx,4) <-- trapping instruction 2e: f0 83 44 24 fc 00 lock addl $0x0,-0x4(%esp) 34: 89 c8 mov %ecx,%eax 36: 5d pop %ebp 37: c3 ret 38: 90 nop 39: 0f 1f 44 00 00 nopl 0x0(%eax,%eax,1) 3e: 55 push %ebp 3f: 89 .byte 0x89

Code starting with the faulting instruction

0: 64 ff 04 88 incl %fs:(%eax,%ecx,4) 4: f0 83 44 24 fc 00 lock addl $0x0,-0x4(%esp) a: 89 c8 mov %ecx,%eax c: 5d pop %ebp d: c3 ret e: 90 nop f: 0f 1f 44 00 00 nopl 0x0(%eax,%eax,1) 14: 55 push %ebp 15: 89 .byte 0x89

Kind regards,

Paul

[1]: https://github.com/ClangBuiltLinux/linux/issues/1081