diff --git a/sys/amd64/amd64/sigtramp.S b/sys/amd64/amd64/sigtramp.S
index 6c2895a14a0a..f951ee14c2f7 100644
--- a/sys/amd64/amd64/sigtramp.S
+++ b/sys/amd64/amd64/sigtramp.S
@@ -1,98 +1,101 @@
 /*-
  * Copyright (c) 2003 Peter Wemm <peter@freeBSD.org>
  * All rights reserved.
  *
  * Copyright (c) 2021 The FreeBSD Foundation
  *
  * Portions of this software were developed by Konstantin Belousov
  * under sponsorship from the FreeBSD Foundation.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
  * $FreeBSD$
  */
 
 #include <sys/syscall.h>
 #include <machine/asmacros.h>
 
 #include "assym.inc"
 
 	.text
 /*
  * Signal trampoline, mapped as vdso into shared page.
  */
 ENTRY(__vdso_sigcode)
 	.cfi_startproc
 	.cfi_signal_frame
 	.cfi_def_cfa	%rsp, 0
 	.cfi_offset	%rdi, SIGF_UC + UC_RDI
 	.cfi_offset	%rsi, SIGF_UC + UC_RSI
 	.cfi_offset	%rdx, SIGF_UC + UC_RDX
 	.cfi_offset	%rcx, SIGF_UC + UC_RCX
 	.cfi_offset	%r8,  SIGF_UC + UC_R8
 	.cfi_offset	%r9,  SIGF_UC + UC_R9
 	.cfi_offset	%rax, SIGF_UC + UC_RAX
 	.cfi_offset	%rbx, SIGF_UC + UC_RBX
 	.cfi_offset	%rbp, SIGF_UC + UC_RBP
 	.cfi_offset	%r10, SIGF_UC + UC_R10
 	.cfi_offset	%r11, SIGF_UC + UC_R11
 	.cfi_offset	%r12, SIGF_UC + UC_R12
 	.cfi_offset	%r13, SIGF_UC + UC_R13
 	.cfi_offset	%r14, SIGF_UC + UC_R14
 	.cfi_offset	%r15, SIGF_UC + UC_R15
 #if 0
 /*
  * Gnu as complains about %fs/%gs/%es/%ds registers offsets not being
  * multiple of 8, but gas + ld.bfd work for %cs/%ss.
  *
  * Clang IAS + ld.lld combination cannot handle any of the segment
  * registers.  Also, clang IAS does not know %rflags/%fs.base/%gs.base
  * registers names, use dwarf registers numbers from psABI directly.
+ *
+ * LLVM libunwind from stable/13 cannot parse register numbers higher
+ * than 32.  Disable %rflags, %fs.base, and %gs.base annotations.
  */	
 	.cfi_offset	%fs,  SIGF_UC + UC_FS
 	.cfi_offset	%gs,  SIGF_UC + UC_GS
 	.cfi_offset	%es,  SIGF_UC + UC_ES
 	.cfi_offset	%ds,  SIGF_UC + UC_DS
 #endif
 	.cfi_offset	%rip, SIGF_UC + UC_RIP
 #if 0
 	.cfi_offset	%cs,  SIGF_UC + UC_CS
-#endif
 	.cfi_offset	49 /* %rflags */, SIGF_UC + UC_RFLAGS
+#endif
 	.cfi_offset	%rsp, SIGF_UC + UC_RSP
 #if 0
 	.cfi_offset	%ss,  SIGF_UC + UC_SS
-#endif
 	.cfi_offset	58 /* %fs.base */, SIGF_UC + UC_FSBASE
 	.cfi_offset	59 /* %gs.base */, SIGF_UC + UC_GSBASE
+#endif
 	call	*SIGF_HANDLER(%rsp)	/* call signal handler */
 	lea	SIGF_UC(%rsp),%rdi	/* get ucontext_t */
 	pushq	$0			/* junk to fake return addr. */
 	.cfi_def_cfa	%rsp, 8
 	movq	$SYS_sigreturn,%rax
 	syscall				/* enter kernel with args */
 0:	hlt				/* trap priviliged instruction */
 	jmp	0b
 	.cfi_endproc
 END(__vdso_sigcode)
 
 	.section .note.GNU-stack,"",%progbits